fix: properly stop active downloads when pausing the queue

# Conflicts:
#	lib/constants/app_info.dart
#	lib/main.dart
#	lib/screens/local_album_screen.dart
#	lib/screens/queue_tab.dart
#	lib/screens/settings/donate_page.dart
#	lib/services/local_track_redownload_service.dart
#	pubspec.yaml

.fvmrc

@@ -0,0 +1,3 @@
+{
+  "flutter": "3.41.4"
+}

.gitattributes

@@ -0,0 +1,20 @@
+* text=auto eol=lf
+
+# Windows scripts
+*.bat text eol=crlf
+*.cmd text eol=crlf
+*.ps1 text eol=crlf
+
+# Binary files
+*.png binary
+*.jpg binary
+*.jpeg binary
+*.gif binary
+*.webp binary
+*.ico binary
+*.pdf binary
+*.zip binary
+*.jar binary
+*.aar binary
+*.keystore binary
+*.jks binary

.github/FUNDING.yml

@@ -0,0 +1,3 @@
+github: zarzet
+ko_fi: zarzet
+

.github/workflows/auto-tag.yml

@@ -15,7 +15,7 @@ jobs:
     
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 2  # Need previous commit to compare
 

.github/workflows/pages.yml

@@ -0,0 +1,44 @@
+name: Deploy to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'site/**'
+      - '.github/workflows/pages.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v4
+        with:
+          path: site
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

.github/workflows/release.yml

@@ -60,23 +60,23 @@ jobs:
           df -h
 
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Setup Java
-        uses: actions/setup-java@v4
+        uses: actions/setup-java@v5
         with:
           distribution: "temurin"
           java-version: "17"
 
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
-          go-version: "1.21"
+          go-version: "1.25.7"
           cache-dependency-path: go_backend/go.sum
 
       # Cache Gradle for faster builds
       - name: Cache Gradle
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: |
             ~/.gradle/caches
@@ -158,7 +158,7 @@ jobs:
           ls -la
 
       - name: Upload APK artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: android-apk
           path: build/app/outputs/flutter-apk/SpotiFLAC-*.apk
@@ -169,17 +169,17 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
-          go-version: "1.21"
+          go-version: "1.25.7"
           cache-dependency-path: go_backend/go.sum
 
       # Cache CocoaPods
       - name: Cache CocoaPods
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: ios/Pods
           key: pods-${{ runner.os }}-${{ hashFiles('ios/Podfile.lock') }}
@@ -194,7 +194,7 @@ jobs:
         working-directory: go_backend
         run: |
           mkdir -p ../ios/Frameworks
-          gomobile bind -target=ios -o ../ios/Frameworks/Gobackend.xcframework .
+          gomobile bind -target=ios -tags ios -o ../ios/Frameworks/Gobackend.xcframework .
         env:
           CGO_ENABLED: 1
 
@@ -249,23 +249,6 @@ jobs:
           channel: "stable"
           cache: true
 
-      # Swap pubspec for iOS build (includes ffmpeg_kit_flutter)
-      - name: Use iOS pubspec with FFmpeg plugin
-        run: |
-          cp pubspec.yaml pubspec_android_backup.yaml
-          cp pubspec_ios.yaml pubspec.yaml
-          echo "Swapped to iOS pubspec with ffmpeg_kit_flutter"
-
-      # Swap FFmpeg service for iOS
-      - name: Use iOS FFmpeg service
-        run: |
-          cp lib/services/ffmpeg_service.dart lib/services/ffmpeg_service_android.dart
-          cp build_assets/ffmpeg_service_ios.dart lib/services/ffmpeg_service.dart
-          # Update class name in the swapped file
-          sed -i '' 's/FFmpegServiceIOS/FFmpegService/g' lib/services/ffmpeg_service.dart
-          sed -i '' 's/FFmpegResultIOS/FFmpegResult/g' lib/services/ffmpeg_service.dart
-          echo "Swapped to iOS FFmpeg service"
-
       - name: Get Flutter dependencies
         run: flutter pub get
 
@@ -312,7 +295,7 @@ jobs:
           fi
 
       - name: Upload IPA artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: ios-ipa
           path: build/ios/ipa/SpotiFLAC-*.ipa
@@ -325,43 +308,33 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0  # Full history needed for git-cliff
 
-      - name: Extract changelog for version
+      - name: Generate changelog with git-cliff
         id: changelog
+        uses: orhun/git-cliff-action@v4
+        with:
+          config: cliff.toml
+          args: --latest --strip header
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          OUTPUT: /tmp/changelog.txt
+
+      - name: Show generated changelog
         run: |
-          VERSION=${{ needs.get-version.outputs.version }}
-          VERSION_NUM=${VERSION#v}  # Remove 'v' prefix
-
-          echo "Looking for version: $VERSION_NUM"
-
-          # Extract changelog section for this version using sed
-          # Find the line with version, then print until next version header or end
-          CHANGELOG=$(sed -n "/^## \[$VERSION_NUM\]/,/^## \[/{ /^## \[$VERSION_NUM\]/d; /^## \[/d; p; }" CHANGELOG.md)
-
-          # If no changelog found, use default message
-          if [ -z "$CHANGELOG" ]; then
-            echo "No changelog found for version $VERSION_NUM"
-            CHANGELOG="See CHANGELOG.md for details."
-          else
-            echo "Found changelog content"
-            # Remove trailing --- separator if present (CHANGELOG uses --- between versions)
-            CHANGELOG=$(echo "$CHANGELOG" | sed '/^---$/d')
-          fi
-
-          # Save to file for multiline support
-          echo "$CHANGELOG" > /tmp/changelog.txt
-          echo "Extracted changelog:"
+          echo "Generated changelog:"
           cat /tmp/changelog.txt
 
       - name: Download Android APK
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v7
         with:
           name: android-apk
           path: ./release
 
       - name: Download iOS IPA
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v7
         with:
           name: ios-ipa
           path: ./release
@@ -369,15 +342,22 @@ jobs:
       - name: Prepare release body
         run: |
           VERSION=${{ needs.get-version.outputs.version }}
-          cat > /tmp/release_body.txt << 'HEADER'
-          ### What's New
-          HEADER
-
-          cat /tmp/changelog.txt >> /tmp/release_body.txt
-
           REPO_OWNER="${{ github.repository_owner }}"
           REPO_NAME="${{ github.event.repository.name }}"
-          
+          CURRENT_REF=$(git rev-list -n 1 "$VERSION" 2>/dev/null || git rev-parse HEAD)
+          PREVIOUS_TAG=$(git describe --tags --abbrev=0 "${CURRENT_REF}^" 2>/dev/null || true)
+
+          # Start with git-cliff changelog, but replace its compare footer with a
+          # deterministic previous-tag lookup from git.
+          sed '/^## [0-9][0-9.[:alpha:]-]*$/d; /^\*\*Full Changelog\*\*/d' /tmp/changelog.txt > /tmp/release_body.txt
+
+          if [ -n "$PREVIOUS_TAG" ]; then
+            printf '\n**Full Changelog**: [%s...%s](https://github.com/%s/%s/compare/%s...%s)\n' \
+              "$PREVIOUS_TAG" "$VERSION" "$REPO_OWNER" "$REPO_NAME" "$PREVIOUS_TAG" "$VERSION" \
+              >> /tmp/release_body.txt
+          fi
+
+          # Append download section
           cat >> /tmp/release_body.txt << FOOTER
 
           ---
@@ -402,7 +382,7 @@ jobs:
           cat /tmp/release_body.txt
 
       - name: Create Release
-        uses: softprops/action-gh-release@v1
+        uses: softprops/action-gh-release@v2
         with:
           tag_name: ${{ needs.get-version.outputs.version }}
           name: SpotiFLAC ${{ needs.get-version.outputs.version }}
@@ -412,3 +392,185 @@ jobs:
           prerelease: ${{ needs.get-version.outputs.is_prerelease == 'true' }}
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  update-altstore:
+    runs-on: ubuntu-latest
+    needs: [get-version, build-ios, create-release]
+    if: ${{ needs.get-version.outputs.is_prerelease != 'true' }}
+    permissions:
+      contents: write
+
+    steps:
+      - name: Checkout main branch
+        uses: actions/checkout@v6
+        with:
+          ref: main
+
+      - name: Download iOS IPA
+        uses: actions/download-artifact@v7
+        with:
+          name: ios-ipa
+          path: ./release
+
+      - name: Update apps.json
+        run: |
+          VERSION="${{ needs.get-version.outputs.version }}"
+          VERSION_NUM="${VERSION#v}"
+          DATE=$(date -u +%Y-%m-%d)
+          IPA_FILE=$(find ./release -name "*ios*.ipa" | head -1)
+
+          if [ -z "$IPA_FILE" ]; then
+            echo "WARNING: IPA file not found, skipping apps.json update"
+            exit 0
+          fi
+
+          IPA_SIZE=$(stat -c%s "$IPA_FILE" 2>/dev/null || stat -f%z "$IPA_FILE")
+
+          if [ ! -f apps.json ]; then
+            echo "WARNING: apps.json not found on main, skipping"
+            exit 0
+          fi
+
+          jq --arg ver "$VERSION_NUM" \
+             --arg date "$DATE" \
+             --arg url "https://github.com/zarzet/SpotiFLAC-Mobile/releases/download/${VERSION}/SpotiFLAC-${VERSION}-ios-unsigned.ipa" \
+             --argjson size "$IPA_SIZE" \
+             '.apps[0].version = $ver | .apps[0].versionDate = $date | .apps[0].downloadURL = $url | .apps[0].size = $size' \
+             apps.json > apps.json.tmp && mv apps.json.tmp apps.json
+
+          echo "Updated apps.json:"
+          cat apps.json
+
+      - name: Commit and push
+        run: |
+          VERSION="${{ needs.get-version.outputs.version }}"
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add apps.json
+          git diff --cached --quiet && echo "No changes to commit" || \
+            (git commit -m "chore: update AltStore source to ${VERSION}" && git push)
+
+  notify-telegram:
+    runs-on: ubuntu-latest
+    needs: [get-version, create-release]
+    if: ${{ needs.get-version.outputs.is_prerelease != 'true' }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Download Android APK
+        uses: actions/download-artifact@v7
+        with:
+          name: android-apk
+          path: ./release
+
+      - name: Download iOS IPA
+        uses: actions/download-artifact@v7
+        with:
+          name: ios-ipa
+          path: ./release
+
+      - name: Generate changelog with git-cliff for Telegram
+        uses: orhun/git-cliff-action@v4
+        with:
+          config: cliff.toml
+          args: --latest --strip all
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          OUTPUT: /tmp/cliff_tg.txt
+
+      - name: Convert changelog for Telegram
+        id: changelog
+        run: |
+          if [ ! -s /tmp/cliff_tg.txt ]; then
+            echo "See release notes on GitHub for details." > /tmp/changelog.txt
+          else
+            # Convert Markdown to Telegram HTML
+            CHANGELOG=$(cat /tmp/cliff_tg.txt | \
+              sed '/^## [0-9][0-9.[:alpha:]-]*$/d' | \
+              sed '/^\*\*Full Changelog\*\*/d' | \
+              sed 's/ by \[@[^]]*\](https:\/\/github\.com\/[^)]*)//g' | \
+              sed 's/ by @[A-Za-z0-9_-]\+//g' | \
+              sed 's/\[#\([0-9]*\)\]([^)]*)/#\1/g' | \
+              sed 's/\[@\([^]]*\)\]([^)]*)/@\1/g' | \
+              sed 's/&/\&amp;/g' | \
+              sed 's/</\&lt;/g' | \
+              sed 's/>/\&gt;/g' | \
+              sed 's/\*\*\([^*]*\)\*\*/<b>\1<\/b>/g' | \
+              sed 's/^### \(.*\)$/<b>\1<\/b>/g' | \
+              sed 's/^## \(.*\)$/<b>\1<\/b>/g' | \
+              sed 's/^- /• /g')
+
+            # Truncate for Telegram 4096 char limit
+            CHANGELOG=$(echo "$CHANGELOG" | head -c 2500 | sed '$d')
+            echo "$CHANGELOG" > /tmp/changelog.txt
+          fi
+
+          echo "Telegram changelog:"
+          cat /tmp/changelog.txt
+
+      - name: Send to Telegram Channel
+        env:
+          TELEGRAM_BOT_TOKEN: ${{ secrets.TELEGRAM_BOT_TOKEN }}
+          TELEGRAM_CHANNEL_ID: ${{ secrets.TELEGRAM_CHANNEL_ID }}
+        run: |
+          VERSION=${{ needs.get-version.outputs.version }}
+          CHANGELOG=$(cat /tmp/changelog.txt)
+          
+          # Find APK files
+          ARM64_APK=$(find ./release -name "*arm64*.apk" | head -1)
+          ARM32_APK=$(find ./release -name "*arm32*.apk" | head -1)
+          
+          # Prepare message with changelog (HTML format)
+          printf '%s\n' \
+            "<b>SpotiFLAC Mobile ${VERSION} Released!</b>" \
+            "" \
+            "<b>What's New:</b>" \
+            "${CHANGELOG}" \
+            "" \
+            "<a href=\"https://github.com/${{ github.repository }}/releases/tag/${VERSION}\">View Release Notes</a>" \
+            > /tmp/telegram_message.txt
+
+          MESSAGE=$(cat /tmp/telegram_message.txt)
+
+          # Send message first (using HTML parse mode)
+          # Use --data-urlencode for proper encoding of special chars (+, &, etc.)
+          # Use || true to ensure file uploads continue even if message fails
+          curl -s -X POST "https://api.telegram.org/bot${TELEGRAM_BOT_TOKEN}/sendMessage" \
+            --data-urlencode "chat_id=${TELEGRAM_CHANNEL_ID}" \
+            --data-urlencode "text=${MESSAGE}" \
+            --data-urlencode "parse_mode=HTML" \
+            --data-urlencode "disable_web_page_preview=true" || true
+
+          # Upload arm64 APK to channel
+          if [ -f "$ARM64_APK" ]; then
+            echo "Uploading arm64 APK to Telegram..."
+            curl -s -X POST "https://api.telegram.org/bot${TELEGRAM_BOT_TOKEN}/sendDocument" \
+              -F chat_id="${TELEGRAM_CHANNEL_ID}" \
+              -F document=@"${ARM64_APK}" \
+              -F caption="SpotiFLAC ${VERSION} - arm64 (recommended)"
+          fi
+
+          # Upload arm32 APK to channel
+          if [ -f "$ARM32_APK" ]; then
+            echo "Uploading arm32 APK to Telegram..."
+            curl -s -X POST "https://api.telegram.org/bot${TELEGRAM_BOT_TOKEN}/sendDocument" \
+              -F chat_id="${TELEGRAM_CHANNEL_ID}" \
+              -F document=@"${ARM32_APK}" \
+              -F caption="SpotiFLAC ${VERSION} - arm32"
+          fi
+
+          # Upload iOS IPA to channel
+          IOS_IPA=$(find ./release -name "*ios*.ipa" | head -1)
+          if [ -f "$IOS_IPA" ]; then
+            echo "Uploading iOS IPA to Telegram..."
+            curl -s -X POST "https://api.telegram.org/bot${TELEGRAM_BOT_TOKEN}/sendDocument" \
+              -F chat_id="${TELEGRAM_CHANNEL_ID}" \
+              -F document=@"${IOS_IPA}" \
+              -F caption="SpotiFLAC ${VERSION} - iOS (unsigned, sideload required)"
+          fi
+
+          echo "Telegram notification sent!"

.gitignore

@@ -12,6 +12,9 @@ Thumbs.db
 # Kiro specs (development only)
 .kiro/
 
+# Design assets (banners, mockups)
+design/
+
 # Reference folder (development only)
 referensi/
 
@@ -64,6 +67,7 @@ AGENTS.md
 
 # Temp/misc
 nul
+network_requests.txt
 
 # Log files
 *.log
@@ -72,3 +76,7 @@ flutter_*.log
 
 # Development tools
 tool/
+.claude/settings.local.json
+
+# FVM Version Cache
+.fvm/

CODE_OF_CONDUCT.md

@@ -0,0 +1,133 @@
+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+We as members, contributors, and leaders pledge to make participation in our
+community a harassment-free experience for everyone, regardless of age, body
+size, visible or invisible disability, ethnicity, sex characteristics, gender
+identity and expression, level of experience, education, socio-economic status,
+nationality, personal appearance, race, caste, color, religion, or sexual
+identity and orientation.
+
+We pledge to act and interact in ways that contribute to an open, welcoming,
+diverse, inclusive, and healthy community.
+
+## Our Standards
+
+Examples of behavior that contributes to a positive environment for our
+community include:
+
+* Demonstrating empathy and kindness toward other people
+* Being respectful of differing opinions, viewpoints, and experiences
+* Giving and gracefully accepting constructive feedback
+* Accepting responsibility and apologizing to those affected by our mistakes,
+  and learning from the experience
+* Focusing on what is best not just for us as individuals, but for the overall
+  community
+
+Examples of unacceptable behavior include:
+
+* The use of sexualized language or imagery, and sexual attention or advances of
+  any kind
+* Trolling, insulting or derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or email address,
+  without their explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Enforcement Responsibilities
+
+Community leaders are responsible for clarifying and enforcing our standards of
+acceptable behavior and will take appropriate and fair corrective action in
+response to any behavior that they deem inappropriate, threatening, offensive,
+or harmful.
+
+Community leaders have the right and responsibility to remove, edit, or reject
+comments, commits, code, wiki edits, issues, and other contributions that are
+not aligned to this Code of Conduct, and will communicate reasons for moderation
+decisions when appropriate.
+
+## Scope
+
+This Code of Conduct applies within all community spaces, and also applies when
+an individual is officially representing the community in public spaces.
+Examples of representing our community include using an official email address,
+posting via an official social media account, or acting as an appointed
+representative at an online or offline event.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported to the community leaders responsible for enforcement at
+**[zarzet](https://github.com/zarzet)**.
+
+All complaints will be reviewed and investigated promptly and fairly.
+
+All community leaders are obligated to respect the privacy and security of the
+reporter of any incident.
+
+## Enforcement Guidelines
+
+Community leaders will follow these Community Impact Guidelines in determining
+the consequences for any action they deem in violation of this Code of Conduct:
+
+### 1. Correction
+
+**Community Impact**: Use of inappropriate language or other behavior deemed
+unprofessional or unwelcome in the community.
+
+**Consequence**: A private, written warning from community leaders, providing
+clarity around the nature of the violation and an explanation of why the
+behavior was inappropriate. A public apology may be requested.
+
+### 2. Warning
+
+**Community Impact**: A violation through a single incident or series of
+actions.
+
+**Consequence**: A warning with consequences for continued behavior. No
+interaction with the people involved, including unsolicited interaction with
+those enforcing the Code of Conduct, for a specified period of time. This
+includes avoiding interactions in community spaces as well as external channels
+like social media. Violating these terms may lead to a temporary or permanent
+ban.
+
+### 3. Temporary Ban
+
+**Community Impact**: A serious violation of community standards, including
+sustained inappropriate behavior.
+
+**Consequence**: A temporary ban from any sort of interaction or public
+communication with the community for a specified period of time. No public or
+private interaction with the people involved, including unsolicited interaction
+with those enforcing the Code of Conduct, is allowed during this period.
+Violating these terms may lead to a permanent ban.
+
+### 4. Permanent Ban
+
+**Community Impact**: Demonstrating a pattern of violation of community
+standards, including sustained inappropriate behavior, harassment of an
+individual, or aggression toward or disparagement of classes of individuals.
+
+**Consequence**: A permanent ban from any sort of public interaction within the
+community.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage],
+version 2.1, available at
+[https://www.contributor-covenant.org/version/2/1/code_of_conduct.html][v2.1].
+
+Community Impact Guidelines were inspired by
+[Mozilla's code of conduct enforcement ladder][Mozilla CoC].
+
+For answers to common questions about this code of conduct, see the FAQ at
+[https://www.contributor-covenant.org/faq][FAQ]. Translations are available at
+[https://www.contributor-covenant.org/translations][translations].
+
+[homepage]: https://www.contributor-covenant.org
+[v2.1]: https://www.contributor-covenant.org/version/2/1/code_of_conduct.html
+[Mozilla CoC]: https://github.com/mozilla/diversity
+[FAQ]: https://www.contributor-covenant.org/faq
+[translations]: https://www.contributor-covenant.org/translations

CONTRIBUTING.md

@@ -0,0 +1,282 @@
+# Contributing to SpotiFLAC
+
+First off, thank you for considering contributing to SpotiFLAC! 🎉
+
+This document provides guidelines and steps for contributing. Following these guidelines helps maintain code quality and ensures a smooth collaboration process.
+
+## Table of Contents
+
+- [Code of Conduct](#code-of-conduct)
+- [How Can I Contribute?](#how-can-i-contribute)
+  - [Reporting Bugs](#reporting-bugs)
+  - [Suggesting Features](#suggesting-features)
+  - [Code Contributions](#code-contributions)
+  - [Translations](#translations)
+- [Development Setup](#development-setup)
+- [Project Structure](#project-structure)
+- [Coding Guidelines](#coding-guidelines)
+- [Commit Guidelines](#commit-guidelines)
+- [Pull Request Process](#pull-request-process)
+
+## Code of Conduct
+
+This project and everyone participating in it is governed by our [Code of Conduct](CODE_OF_CONDUCT.md). By participating, you are expected to uphold this code. Please report unacceptable behavior to the project maintainers.
+
+## How Can I Contribute?
+
+### Reporting Bugs
+
+Before creating bug reports, please check the [existing issues](https://github.com/zarzet/SpotiFLAC-Mobile/issues) to avoid duplicates.
+
+When creating a bug report, please use the bug report template and include:
+
+- **Clear and descriptive title**
+- **Steps to reproduce** the issue
+- **Expected behavior** vs **actual behavior**
+- **Screenshots or screen recordings** if applicable
+- **Device information** (model, OS version)
+- **App version**
+- **Logs** from Settings > About > View Logs
+
+### Suggesting Features
+
+Feature requests are welcome! Please use the feature request template and:
+
+- **Check existing issues** to avoid duplicates
+- **Describe the feature** clearly
+- **Explain the use case** - why would this be useful?
+- **Consider the scope** - is this a small enhancement or a major feature?
+
+### Code Contributions
+
+1. **Fork the repository** and create your branch from `dev`
+2. **Make your changes** following our coding guidelines
+3. **Test your changes** thoroughly
+4. **Submit a pull request** to the `dev` branch
+
+### Translations
+
+We use [Crowdin](https://crowdin.com/project/spotiflac-mobile) for translations. To contribute:
+
+1. Visit our [Crowdin project](https://crowdin.com/project/spotiflac-mobile)
+2. Select your language or request a new one
+3. Start translating!
+
+Translation files are located in `lib/l10n/arb/`.
+
+## Development Setup
+
+### Prerequisites
+
+- **Flutter SDK** 3.10.0 or higher
+- **Dart SDK** 3.10.0 or higher
+- **Android Studio** or **VS Code** with Flutter extensions
+- **Git**
+
+### Getting Started
+
+1. **Clone your fork**
+   ```bash
+   git clone https://github.com/YOUR_USERNAME/SpotiFLAC-Mobile.git
+   cd SpotiFLAC-Mobile
+   ```
+
+2. **Add upstream remote**
+   ```bash
+   git remote add upstream https://github.com/zarzet/SpotiFLAC-Mobile.git
+   ```
+
+3. **Use FVM (Flutter Version: 3.38.1)**
+   ```bash
+   fvm use
+   ```
+
+4. **Install dependencies**
+   ```bash
+   flutter pub get
+   ```
+
+5. **Generate code** (for Riverpod, JSON serialization, etc.)
+   ```bash
+   dart run build_runner build --delete-conflicting-outputs
+   ```
+
+6. **Set up Go environment (Go Version: 1.25.7)**
+   ```bash
+   cd go_backend 
+   mkdir -p ../android/app/libs
+   gomobile init
+   gomobile bind -target=android -androidapi 24 -o ../android/app/libs/gobackend.aar .
+   cd ..
+   ```
+
+7. **Run the app**
+   ```bash
+   flutter run
+   ```
+
+### Building
+
+```bash
+# Debug build
+flutter build apk --debug
+
+# Release build
+flutter build apk --release
+```
+
+## Project Structure
+
+```
+lib/
+├── l10n/               # Localization files
+│   └── arb/            # ARB translation files
+├── models/             # Data models
+├── providers/          # Riverpod providers
+├── screens/            # UI screens
+│   └── settings/       # Settings sub-screens
+├── services/           # Business logic services
+├── theme/              # App theming
+├── utils/              # Utility functions
+├── widgets/            # Reusable widgets
+├── app.dart            # App configuration
+└── main.dart           # Entry point
+```
+
+## Coding Guidelines
+
+### General
+
+- Follow [Effective Dart](https://dart.dev/effective-dart) guidelines
+- Use meaningful variable and function names
+- Keep functions small and focused
+- Add comments for complex logic
+
+### Formatting
+
+- Use `dart format` before committing
+- Maximum line length: 80 characters
+- Use trailing commas for better formatting
+
+```bash
+dart format .
+```
+
+### Linting
+
+Ensure your code passes all lints:
+
+```bash
+flutter analyze
+```
+
+### State Management
+
+We use **Riverpod** for state management. Follow these patterns:
+
+```dart
+// Use code generation with riverpod_annotation
+@riverpod
+class MyNotifier extends _$MyNotifier {
+  @override
+  MyState build() => MyState();
+  
+  // Methods to update state
+}
+```
+
+### Localization
+
+All user-facing strings should be localized:
+
+```dart
+// Good
+Text(AppLocalizations.of(context)!.downloadComplete)
+
+// Bad
+Text('Download Complete')
+```
+
+To add new strings:
+1. Add the key to `lib/l10n/arb/app_en.arb`
+2. Run `flutter gen-l10n`
+
+## Commit Guidelines
+
+We follow [Conventional Commits](https://www.conventionalcommits.org/):
+
+```
+<type>(<scope>): <description>
+
+[optional body]
+
+[optional footer(s)]
+```
+
+### Types
+
+- `feat`: New feature
+- `fix`: Bug fix
+- `docs`: Documentation changes
+- `style`: Code style changes (formatting, etc.)
+- `refactor`: Code refactoring
+- `perf`: Performance improvements
+- `test`: Adding or updating tests
+- `chore`: Maintenance tasks
+
+### Examples
+
+```
+feat(download): add batch download support
+fix(ui): resolve overflow on small screens
+docs: update contributing guidelines
+chore(deps): update flutter_riverpod to 3.1.0
+```
+
+## Pull Request Process
+
+1. **Update your fork**
+   ```bash
+   git fetch upstream
+   git rebase upstream/dev
+   ```
+
+2. **Create a feature branch**
+   ```bash
+   git checkout -b feat/my-new-feature
+   ```
+
+3. **Make your changes** and commit following our guidelines
+
+4. **Push to your fork**
+   ```bash
+   git push origin feat/my-new-feature
+   ```
+
+5. **Create a Pull Request**
+   - Target the `dev` branch
+   - Fill in the PR template
+   - Link related issues
+
+6. **Address review feedback**
+   - Make requested changes
+   - Push additional commits
+   - Request re-review when ready
+
+### PR Requirements
+
+- [ ] Code follows project conventions
+- [ ] All tests pass
+- [ ] No new linting errors
+- [ ] Documentation updated (if needed)
+- [ ] Commit messages follow guidelines
+- [ ] PR description is clear and complete
+
+## Questions?
+
+If you have questions, feel free to:
+
+- Open a [Discussion](https://github.com/zarzet/SpotiFLAC-Mobile/discussions)
+- Check existing [Issues](https://github.com/zarzet/SpotiFLAC-Mobile/issues)
+
+Thank you for contributing! 💚

README.md

@@ -1,20 +1,19 @@
-[![GitHub All Releases](https://img.shields.io/github/downloads/zarzet/SpotiFLAC-Mobile/total?style=for-the-badge)](https://github.com/zarzet/SpotiFLAC-Mobile/releases)
-[![VirusTotal](https://img.shields.io/badge/VirusTotal-Safe-brightgreen?style=for-the-badge&logo=virustotal)](https://www.virustotal.com/gui/file/e1c527eacb6f5ce527af214a75aab8da060c2afc629825fff24af858439e7e6b)
-[![Crowdin](https://img.shields.io/badge/HELP%20TRANSLATE%20ON-CROWDIN-%2321252b?style=for-the-badge&logo=crowdin)](https://crowdin.com/project/spotiflac-mobile)
-
 <div align="center">
 
-<img src="icon.png" width="128" />
+<picture>
+  <source media="(prefers-color-scheme: dark)" srcset="assets/images/banner-readme-dark.png">
+  <source media="(prefers-color-scheme: light)" srcset="assets/images/banner-readme-light.png">
+  <img alt="SpotiFLAC Mobile" src="assets/images/banner-readme-light.png" width="650" height="auto">
+</picture>
 
-Download music in true lossless FLAC from Tidal, Qobuz & Amazon Music — no account required.
-
-![Android](https://img.shields.io/badge/Android-7.0%2B-3DDC84?style=for-the-badge&logo=android&logoColor=white)
-![iOS](https://img.shields.io/badge/iOS-14.0%2B-000000?style=for-the-badge&logo=apple&logoColor=white)
+<p align="center">
+  <a href="https://trendshift.io/repositories/17247">
+    <img src="https://trendshift.io/api/badge/repositories/17247" alt="zarzet%2FSpotiFLAC-Mobile | Trendshift" width="250" height="55">
+  </a>
+</p>
 
 </div>
 
-### [Download](https://github.com/zarzet/SpotiFLAC-Mobile/releases)
-
 ## Screenshots
 
 <p align="center">
@@ -24,14 +23,16 @@ Download music in true lossless FLAC from Tidal, Qobuz & Amazon Music — no acc
   <img src="assets/images/4.jpg?v=2" width="200" />
 </p>
 
-## Search Source
+<div align="center">
 
-SpotiFLAC supports multiple search sources for finding music metadata:
+[![GitHub Release](https://img.shields.io/github/v/release/zarzet/SpotiFLAC-Mobile?style=for-the-badge&logo=github)](https://github.com/zarzet/SpotiFLAC-Mobile/releases)
+[![VirusTotal](https://img.shields.io/badge/VirusTotal-Safe-brightgreen?style=for-the-badge&logo=virustotal)](https://www.virustotal.com/gui/file/63a445a956fa71ea347ad3695a62d543e14e341933326b9dbb9a15d79614ef58)
+[![Crowdin](https://img.shields.io/badge/HELP%20TRANSLATE%20ON-CROWDIN-%2321252b?style=for-the-badge&logo=crowdin)](https://crowdin.com/project/spotiflac-mobile)
 
-| Source | Setup |
-|--------|-------|
-| **Deezer** (Default) | No setup required |
-| **Extensions** | Install additional search providers from the Store |
+[![Telegram Channel](https://img.shields.io/badge/CHANNEL-2CA5E0?style=for-the-badge&logo=telegram&logoColor=white)](https://t.me/spotiflac)
+[![Telegram Community](https://img.shields.io/badge/COMMUNITY-2CA5E0?style=for-the-badge&logo=telegram&logoColor=white)](https://t.me/spotiflac_chat)
+
+</div>
 
 ## Extensions
 
@@ -39,13 +40,14 @@ Extensions allow the community to add new music sources and features without wai
 
 ### Installing Extensions
 1. Go to **Store** tab in the app
-2. Browse and install extensions with one tap
-3. Or download a `.spotiflac-ext` file and install manually via **Settings > Extensions**
-4. Configure extension settings if needed
-5. Set provider priority in **Settings > Extensions > Provider Priority**
+2. When opening the Store for the first time, you will be asked to enter an **Extension Repository URL**
+3. Browse and install extensions with one tap
+4. Or download a `.spotiflac-ext` file and install manually via **Settings > Extensions**
+5. Configure extension settings if needed
+6. Set provider priority in **Settings > Extensions > Provider Priority**
 
 ### Developing Extensions
-Want to create your own extension? Check out the [Extension Development Guide](https://zarz.moe/docs) for complete documentation.
+Want to create your own extension? Check out the [Extension Development Guide](https://zarzet.github.io/SpotiFLAC-Mobile/docs) for complete documentation.
 
 ## Other project
 
@@ -54,11 +56,14 @@ Download music in true lossless FLAC from Tidal, Qobuz & Amazon Music for Window
 
 ## FAQ
 
+**Q: Why does the Store tab ask me to enter a URL?**  
+A: Starting from version 3.8.0, SpotiFLAC uses a decentralized extension repository system — extensions are hosted on GitHub repositories rather than a built-in server, so anyone can create and host their own. Enter a repository URL in the Store tab to browse and install extensions.
+
 **Q: Why is my download failing with "Song not found"?**  
-A: The track may not be available on Tidal, Qobuz, or Amazon Music. Try enabling more download services in Settings > Download > Provider Priority, or install additional extensions from the Store.
+A: The track may not be available on the streaming services. Try enabling more download services in Settings > Download > Provider Priority, or install additional extensions like Amazon Music from the Store.
 
 **Q: Why are some tracks downloading in lower quality?**  
-A: Quality depends on what's available from the streaming service. Tidal offers up to 24-bit/192kHz, Qobuz up to 24-bit/192kHz, and Amazon up to 24-bit/48kHz. The app automatically selects the best available quality.
+A: Quality depends on what's available from the streaming service and extensions. Built-in providers: Tidal offers up to 24-bit/192kHz, Qobuz up to 24-bit/192kHz, and Deezer up to 16-bit/44.1kHz.
 
 **Q: Can I download playlists?**  
 A: Yes! Just paste the playlist URL in the search bar. The app will fetch all tracks and queue them for download.
@@ -69,19 +74,38 @@ A: The app needs permission to save downloaded files to your device. On Android
 **Q: Is this app safe?**  
 A: Yes, the app is open source and you can verify the code yourself. Each release is scanned with VirusTotal (see badge at top of README).
 
-[![Ko-fi](https://img.shields.io/badge/Ko--fi-Support%20Me-FF5E5B?style=for-the-badge&logo=ko-fi&logoColor=white)](https://ko-fi.com/zarzet)
+**Q: Why is download not working in my country?**  
+A: Some countries have restricted access to certain streaming service APIs. If downloads are failing, try using a VPN to connect through a different region.
 
-## Disclaimer
+**Q: Can I add SpotiFLAC to AltStore or SideStore?**
+A: Yes! You can add the official source to receive updates directly within the app. Just copy this link:
+https://raw.githubusercontent.com/zarzet/SpotiFLAC-Mobile/refs/heads/main/apps.json
+In AltStore/SideStore, go to the Browse tab, tap Sources at the top, then tap the + icon and paste the link.
 
-This project is for **educational and private use only**. The developer does not condone or encourage copyright infringement.
 
-**SpotiFLAC** is a third-party tool and is not affiliated with, endorsed by, or connected to Tidal, Qobuz, Amazon Music, Deezer, or any other streaming service.
+### Want to support SpotiFLAC-Mobile?
 
-The application is purely a user interface that facilitates communication between your device and existing third-party services.
+_If this software is useful and brings you value, consider supporting the project. Your support helps keep development going._
 
-You are solely responsible for:
-1. Ensuring your use of this software complies with your local laws.
-2. Reading and adhering to the Terms of Service of the respective platforms.
-3. Any legal consequences resulting from the misuse of this tool.
+[![Ko-fi](https://ko-fi.com/img/githubbutton_sm.svg)](https://ko-fi.com/zarzet)
 
-The software is provided "as is", without warranty of any kind. The author assumes no liability for any bans, damages, or legal issues arising from its use.
+## Contributors
+
+Thanks to all the amazing people who have contributed to SpotiFLAC Mobile!
+
+<a href="https://github.com/zarzet/SpotiFLAC-Mobile/graphs/contributors">
+  <img src="https://contrib.rocks/image?repo=zarzet/SpotiFLAC-Mobile" />
+</a>
+
+We also appreciate everyone who has helped with [translations on Crowdin](https://crowdin.com/project/spotiflac-mobile), reported bugs, suggested features, and spread the word about SpotiFLAC Mobile.
+
+Interested in contributing? Check out our [Contributing Guide](CONTRIBUTING.md) to get started!
+
+## API Credits
+
+[hifi-api](https://github.com/binimum/hifi-api) · [music.binimum.org](https://music.binimum.org) · [qqdl.site](https://qqdl.site) · [squid.wtf](https://squid.wtf) · [spotisaver.net](https://spotisaver.net) · [dabmusic.xyz](https://dabmusic.xyz) · [AfkarXYZ](https://github.com/afkarxyz) · [LRCLib](https://lrclib.net) · [Paxsenix](https://lyrics.paxsenix.org) · [Cobalt](https://cobalt.tools) · [qwkuns.me](https://qwkuns.me) · [SpotubeDL](https://spotubedl.com) · [Song.link](https://song.link) · [IDHS](https://github.com/sjdonado/idonthavespotify)
+
+
+> [!TIP]
+>
+> **Star Us**, You will receive all release notifications from GitHub without any delay 

android/app/build.gradle.kts

@@ -96,11 +96,13 @@ repositories {
 }
 
 dependencies {
-    coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.1.4")
+    coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.1.5")
     
     // Include all AAR and JAR files from libs folder
     implementation(fileTree(mapOf("dir" to "libs", "include" to listOf("*.jar", "*.aar"))))
     
-    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")
-    implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.7.0")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.10.2")
+    implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.10.0")
+    implementation("androidx.documentfile:documentfile:1.1.0")
+    implementation("androidx.activity:activity-ktx:1.12.3")
 }

android/app/proguard-rules.pro

@@ -5,6 +5,7 @@
 -keep class io.flutter.view.** { *; }
 -keep class io.flutter.** { *; }
 -keep class io.flutter.plugins.** { *; }
+-keep class io.flutter.embedding.** { *; }
 
 # Ignore missing Play Core classes (not used, but referenced by Flutter)
 -dontwarn com.google.android.play.core.splitcompat.**
@@ -14,13 +15,22 @@
 # Ignore missing javax.xml.stream (not used on Android)
 -dontwarn javax.xml.stream.**
 
-# Go backend (gobackend.aar)
+# Go backend (gobackend.aar) - CRITICAL for release builds
 -keep class gobackend.** { *; }
 -keep class go.** { *; }
+-keep interface gobackend.** { *; }
+-keepclassmembers class gobackend.** { *; }
+
+# Go mobile binding internals
+-keep class org.golang.** { *; }
+-dontwarn org.golang.**
 
 # FFmpeg Kit
 -keep class com.arthenica.ffmpegkit.** { *; }
 -keep class com.arthenica.smartexception.** { *; }
+# FFmpeg Kit (new fork package)
+-keep class com.antonkarpenko.ffmpegkit.** { *; }
+-keep class com.antonkarpenko.smartexception.** { *; }
 
 # Apache Tika (if used by FFmpeg)
 -dontwarn org.apache.tika.**
@@ -30,15 +40,77 @@
     native <methods>;
 }
 
-# Kotlin coroutines
+# Kotlin coroutines - expanded rules
 -keepnames class kotlinx.coroutines.internal.MainDispatcherFactory {}
 -keepnames class kotlinx.coroutines.CoroutineExceptionHandler {}
 -keepclassmembers class kotlinx.coroutines.** {
     volatile <fields>;
 }
+-keepclassmembernames class kotlinx.** {
+    volatile <fields>;
+}
+-dontwarn kotlinx.coroutines.**
+
+# Kotlin serialization
+-keepattributes RuntimeVisibleAnnotations,AnnotationDefault
+-dontwarn kotlin.**
+-keep class kotlin.** { *; }
+-keep class kotlin.Metadata { *; }
+
+# Keep MainActivity and related classes
+-keep class com.zarz.spotiflac.** { *; }
 
 # Prevent R8 from removing metadata
 -keepattributes *Annotation*
 -keepattributes SourceFile,LineNumberTable
 -keepattributes Signature
 -keepattributes Exceptions
+-keepattributes InnerClasses
+-keepattributes EnclosingMethod
+
+# JSON parsing (used by Go backend responses)
+-keep class org.json.** { *; }
+
+# Shared Preferences
+-keep class androidx.datastore.** { *; }
+-dontwarn androidx.datastore.**
+
+# Flutter Plugins - CRITICAL: Prevent R8 from removing plugin implementations
+# Path Provider
+-keep class io.flutter.plugins.pathprovider.** { *; }
+-keep class dev.flutter.pigeon.** { *; }
+
+# Local Notifications
+-keep class com.dexterous.** { *; }
+-keep class com.dexterous.flutterlocalnotifications.** { *; }
+
+# Receive Sharing Intent
+-keep class com.kasem.receive_sharing_intent.** { *; }
+
+# Permission Handler
+-keep class com.baseflow.permissionhandler.** { *; }
+
+# File Picker
+-keep class com.mr.flutter.plugin.filepicker.** { *; }
+
+# URL Launcher
+-keep class io.flutter.plugins.urllauncher.** { *; }
+
+# Share Plus
+-keep class dev.fluttercommunity.plus.share.** { *; }
+
+# Device Info Plus
+-keep class dev.fluttercommunity.plus.device_info.** { *; }
+
+# Open File
+-keep class com.crazecoder.openfile.** { *; }
+
+# Sqflite
+-keep class com.tekartik.sqflite.** { *; }
+
+# Dynamic Color
+-keep class io.material.** { *; }
+
+# Keep all Flutter plugin registrants
+-keep class io.flutter.plugins.GeneratedPluginRegistrant { *; }
+-keep class ** extends io.flutter.embedding.engine.plugins.FlutterPlugin { *; }

android/app/src/main/AndroidManifest.xml

@@ -12,6 +12,7 @@
     <uses-permission android:name="android.permission.READ_MEDIA_AUDIO" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_DATA_SYNC" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
@@ -20,9 +21,10 @@
         android:label="SpotiFLAC"
         android:name="${applicationName}"
         android:icon="@mipmap/ic_launcher"
-        android:requestLegacyExternalStorage="true"
-        android:usesCleartextTraffic="true"
-        android:enableOnBackInvokedCallback="true">
+        android:usesCleartextTraffic="false"
+        android:networkSecurityConfig="@xml/network_security_config"
+        android:enableOnBackInvokedCallback="true"
+        android:localeConfig="@xml/locale_config">
 
         <activity
             android:name=".MainActivity"
@@ -43,7 +45,7 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
 
-            <!-- Handle Spotify URL sharing -->
+            <!-- Handle music URL sharing (Spotify, Deezer, Tidal, YT Music) -->
             <intent-filter>
                 <action android:name="android.intent.action.SEND" />
                 <category android:name="android.intent.category.DEFAULT" />
@@ -57,6 +59,33 @@
                 <category android:name="android.intent.category.BROWSABLE" />
                 <data android:scheme="https" android:host="open.spotify.com" />
             </intent-filter>
+
+            <!-- Handle Deezer deep links -->
+            <intent-filter android:autoVerify="true">
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="https" android:host="www.deezer.com" />
+                <data android:scheme="https" android:host="deezer.com" />
+                <data android:scheme="https" android:host="deezer.page.link" />
+            </intent-filter>
+
+            <!-- Handle Tidal deep links -->
+            <intent-filter android:autoVerify="true">
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="https" android:host="tidal.com" />
+                <data android:scheme="https" android:host="listen.tidal.com" />
+            </intent-filter>
+
+            <!-- Handle YouTube Music deep links -->
+            <intent-filter android:autoVerify="true">
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="https" android:host="music.youtube.com" />
+            </intent-filter>
         </activity>
 
         <!-- Download Service -->
@@ -65,6 +94,24 @@
             android:exported="false"
             android:foregroundServiceType="dataSync" />
 
+        <!-- Audio playback service for media notification / background audio -->
+        <service
+            android:name="com.ryanheise.audioservice.AudioService"
+            android:exported="true"
+            android:foregroundServiceType="mediaPlayback">
+            <intent-filter>
+                <action android:name="android.media.browse.MediaBrowserService" />
+            </intent-filter>
+        </service>
+
+        <receiver
+            android:name="com.ryanheise.audioservice.MediaButtonReceiver"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MEDIA_BUTTON" />
+            </intent-filter>
+        </receiver>
+
         <!-- flutter_local_notifications receivers -->
         <receiver android:exported="false" android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationReceiver" />
         <receiver android:exported="false" android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationBootReceiver">

android/app/src/main/kotlin/com/zarz/spotiflac/DownloadService.kt

@@ -115,10 +115,8 @@ class DownloadService : Service() {
      * We must call stopSelf() within a few seconds to avoid a crash.
      */
     override fun onTimeout(startId: Int, fgsType: Int) {
-        // Log the timeout for debugging
         android.util.Log.w("DownloadService", "Foreground service timeout reached (6 hours limit). Stopping service.")
         
-        // Gracefully stop the service
         stopForegroundService()
     }
     

android/app/src/main/res/values/colors.xml

@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <color name="ic_launcher_background">#1a1a2e</color>
+    <color name="ic_launcher_background">#000000</color>
 </resources>

android/app/src/main/res/xml/locale_config.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<locale-config xmlns:android="http://schemas.android.com/apk/res/android">
+    <locale android:name="en" />
+    <locale android:name="ru" />
+    <locale android:name="es-ES" />
+    <locale android:name="id" />
+    <locale android:name="pt-PT" />
+    <locale android:name="ja" />
+    <locale android:name="tr" />
+    <locale android:name="de" />
+    <locale android:name="fr" />
+    <locale android:name="hi" />
+    <locale android:name="ko" />
+    <locale android:name="nl" />
+    <locale android:name="zh" />
+</locale-config>

android/app/src/main/res/xml/network_security_config.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<network-security-config>
+    <base-config cleartextTrafficPermitted="false" />
+
+    <!-- Allow local loopback cleartext for FFmpeg live decrypt tunnel only. -->
+    <domain-config cleartextTrafficPermitted="true">
+        <domain includeSubdomains="true">localhost</domain>
+        <domain includeSubdomains="true">127.0.0.1</domain>
+    </domain-config>
+</network-security-config>

android/build.gradle.kts

@@ -22,7 +22,7 @@ subprojects {
             }
             
             // Add desugaring dependency to all Android subprojects
-            project.dependencies.add("coreLibraryDesugaring", "com.android.tools:desugar_jdk_libs:2.1.4")
+            project.dependencies.add("coreLibraryDesugaring", "com.android.tools:desugar_jdk_libs:2.1.5")
         }
         
         tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {

android/gradle.properties

@@ -1,2 +1,2 @@
-org.gradle.jvmargs=-Xmx8G -XX:MaxMetaspaceSize=4G -XX:ReservedCodeCacheSize=512m -XX:+HeapDumpOnOutOfMemoryError
+org.gradle.jvmargs=-Xmx4G -XX:MaxMetaspaceSize=2G -XX:ReservedCodeCacheSize=256m -XX:+HeapDumpOnOutOfMemoryError
 android.useAndroidX=true

android/gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.14-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.3.1-all.zip

android/settings.gradle.kts

@@ -19,8 +19,8 @@ pluginManagement {
 
 plugins {
     id("dev.flutter.flutter-plugin-loader") version "1.0.0"
-    id("com.android.application") version "8.11.1" apply false
-    id("org.jetbrains.kotlin.android") version "2.3.0" apply false
+    id("com.android.application") version "8.13.2" apply false
+    id("org.jetbrains.kotlin.android") version "2.2.21" apply false
 }
 
 include(":app")

apps.json

@@ -0,0 +1,18 @@
+{
+  "name": "SpotiFLAC Source",
+  "identifier": "com.zarzet.spotiflac.source",
+  "subtitle": "FLAC Downloader for iOS",
+  "apps": [
+    {
+      "name": "SpotiFLAC",
+      "bundleIdentifier": "com.zarzet.spotiflac",
+      "developerName": "zarzet",
+      "version": "3.8.6",
+      "versionDate": "2026-03-16",
+      "downloadURL": "https://github.com/zarzet/SpotiFLAC-Mobile/releases/download/v3.8.6/SpotiFLAC-v3.8.6-ios-unsigned.ipa",
+      "localizedDescription": "Mobile version of SpotiFLAC written in Flutter. Download Tracks in true FLAC from Tidal, Qobuz, & Amazon Music.",
+      "iconURL": "https://raw.githubusercontent.com/zarzet/SpotiFLAC-Mobile/main/assets/images/logo.png",
+      "size": 33676960
+    }
+  ]
+}

build_assets/ffmpeg_service_ios.dart

@@ -1,335 +0,0 @@
-import 'dart:io';
-import 'package:ffmpeg_kit_flutter_new_audio/ffmpeg_kit.dart';
-import 'package:ffmpeg_kit_flutter_new_audio/return_code.dart';
-import 'package:spotiflac_android/utils/logger.dart';
-
-final _log = AppLogger('FFmpeg');
-
-/// FFmpeg service for iOS using ffmpeg_kit_flutter plugin
-class FFmpegServiceIOS {
-  /// Execute FFmpeg command and return result
-  static Future<FFmpegResultIOS> _execute(String command) async {
-    try {
-      final session = await FFmpegKit.execute(command);
-      final returnCode = await session.getReturnCode();
-      final output = await session.getOutput() ?? '';
-      return FFmpegResultIOS(
-        success: ReturnCode.isSuccess(returnCode),
-        returnCode: returnCode?.getValue() ?? -1,
-        output: output,
-      );
-    } catch (e) {
-      _log.e('FFmpeg execute error: $e');
-      return FFmpegResultIOS(success: false, returnCode: -1, output: e.toString());
-    }
-  }
-
-  /// Convert M4A (DASH segments) to FLAC
-  static Future<String?> convertM4aToFlac(String inputPath) async {
-    final outputPath = inputPath.replaceAll('.m4a', '.flac');
-    final command = '-i "$inputPath" -c:a flac -compression_level 8 "$outputPath" -y';
-    final result = await _execute(command);
-
-    if (result.success) {
-      try {
-        await File(inputPath).delete();
-      } catch (_) {}
-      return outputPath;
-    }
-
-    _log.e('M4A to FLAC conversion failed: ${result.output}');
-    return null;
-  }
-
-  /// Convert FLAC to MP3
-  /// If deleteOriginal is true, deletes the FLAC file after conversion
-  static Future<String?> convertFlacToMp3(
-    String inputPath, {
-    String bitrate = '320k',
-    bool deleteOriginal = true,
-  }) async {
-    // Convert in same folder, just change extension
-    final outputPath = inputPath.replaceAll('.flac', '.mp3');
-
-    final command = '-i "$inputPath" -codec:a libmp3lame -b:a $bitrate -map 0:a -map_metadata 0 -id3v2_version 3 "$outputPath" -y';
-    final result = await _execute(command);
-
-    if (result.success) {
-      // Delete original FLAC if requested
-      if (deleteOriginal) {
-        try {
-          await File(inputPath).delete();
-        } catch (_) {}
-      }
-      return outputPath;
-    }
-    _log.e('FLAC to MP3 conversion failed: ${result.output}');
-    return null;
-  }
-
-  /// Convert FLAC to M4A
-  static Future<String?> convertFlacToM4a(String inputPath, {String codec = 'aac', String bitrate = '256k'}) async {
-    final dir = File(inputPath).parent.path;
-    final baseName = inputPath.split(Platform.pathSeparator).last.replaceAll('.flac', '');
-    final outputDir = '$dir${Platform.pathSeparator}M4A';
-    await Directory(outputDir).create(recursive: true);
-    final outputPath = '$outputDir${Platform.pathSeparator}$baseName.m4a';
-
-    String command;
-    if (codec == 'alac') {
-      command = '-i "$inputPath" -codec:a alac -map 0:a -map_metadata 0 "$outputPath" -y';
-    } else {
-      command = '-i "$inputPath" -codec:a aac -b:a $bitrate -map 0:a -map_metadata 0 "$outputPath" -y';
-    }
-
-    final result = await _execute(command);
-    if (result.success) return outputPath;
-    _log.e('FLAC to M4A conversion failed: ${result.output}');
-    return null;
-  }
-
-  /// Embed cover art to FLAC file
-  static Future<String?> embedCover(String flacPath, String coverPath) async {
-    final tempOutput = '$flacPath.tmp';
-    final command = '-i "$flacPath" -i "$coverPath" -map 0:a -map 1:0 -c copy -metadata:s:v title="Album cover" -metadata:s:v comment="Cover (front)" -disposition:v attached_pic "$tempOutput" -y';
-
-    final result = await _execute(command);
-
-    if (result.success) {
-      try {
-        await File(flacPath).delete();
-        await File(tempOutput).rename(flacPath);
-        return flacPath;
-      } catch (e) {
-        _log.e('Failed to replace file after cover embed: $e');
-        return null;
-      }
-    }
-
-    try {
-      final tempFile = File(tempOutput);
-      if (await tempFile.exists()) await tempFile.delete();
-    } catch (_) {}
-
-    _log.e('Cover embed failed: ${result.output}');
-    return null;
-  }
-
-  /// Embed metadata and cover art to FLAC file
-  /// Returns the file path on success, null on failure
-  static Future<String?> embedMetadata({
-    required String flacPath,
-    String? coverPath,
-    Map<String, String>? metadata,
-  }) async {
-    final tempOutput = '$flacPath.tmp';
-    
-    // Construct command
-    final StringBuffer cmdBuffer = StringBuffer();
-    cmdBuffer.write('-i "$flacPath" ');
-    
-    // Add cover input if available
-    if (coverPath != null) {
-      cmdBuffer.write('-i "$coverPath" ');
-    }
-    
-    // Map audio stream
-    cmdBuffer.write('-map 0:a ');
-    
-    // Map cover stream if available
-    if (coverPath != null) {
-      cmdBuffer.write('-map 1:0 ');
-      cmdBuffer.write('-c:v copy ');
-      cmdBuffer.write('-disposition:v attached_pic ');
-      cmdBuffer.write('-metadata:s:v title="Album cover" ');
-      cmdBuffer.write('-metadata:s:v comment="Cover (front)" ');
-    }
-    
-    // Copy audio codec (don't re-encode)
-    cmdBuffer.write('-c:a copy ');
-    
-    // Add text metadata
-    if (metadata != null) {
-      metadata.forEach((key, value) {
-        // Sanitize value: escape double quotes
-        final sanitizedValue = value.replaceAll('"', '\\"');
-        cmdBuffer.write('-metadata $key="$sanitizedValue" ');
-      });
-    }
-    
-    cmdBuffer.write('"$tempOutput" -y');
-    
-    final command = cmdBuffer.toString();
-    _log.d('Executing FFmpeg command: $command');
-
-    final result = await _execute(command);
-
-    if (result.success) {
-      try {
-        await File(flacPath).delete();
-        await File(tempOutput).rename(flacPath);
-        return flacPath;
-      } catch (e) {
-        _log.e('Failed to replace file after metadata embed: $e');
-        return null;
-      }
-    }
-
-    // Clean up temp file if exists
-    try {
-      final tempFile = File(tempOutput);
-      if (await tempFile.exists()) {
-        await tempFile.delete();
-      }
-    } catch (_) {}
-
-    _log.e('Metadata/Cover embed failed: ${result.output}');
-    return null;
-  }
-
-  /// Embed metadata and cover art to MP3 file using ID3v2 tags
-  /// Returns the file path on success, null on failure
-  static Future<String?> embedMetadataToMp3({
-    required String mp3Path,
-    String? coverPath,
-    Map<String, String>? metadata,
-  }) async {
-    final tempOutput = '$mp3Path.tmp';
-    
-    final StringBuffer cmdBuffer = StringBuffer();
-    cmdBuffer.write('-i "$mp3Path" ');
-    
-    if (coverPath != null) {
-      cmdBuffer.write('-i "$coverPath" ');
-    }
-    
-    cmdBuffer.write('-map 0:a ');
-    
-    if (coverPath != null) {
-      cmdBuffer.write('-map 1:0 ');
-      cmdBuffer.write('-c:v:0 copy ');
-      cmdBuffer.write('-id3v2_version 3 ');
-      cmdBuffer.write('-metadata:s:v title="Album cover" ');
-      cmdBuffer.write('-metadata:s:v comment="Cover (front)" ');
-    }
-    
-    cmdBuffer.write('-c:a copy ');
-    
-    if (metadata != null) {
-      // Convert FLAC/Vorbis tags to ID3v2 tags for MP3
-      final id3Metadata = _convertToId3Tags(metadata);
-      id3Metadata.forEach((key, value) {
-        final sanitizedValue = value.replaceAll('"', '\\"');
-        cmdBuffer.write('-metadata $key="$sanitizedValue" ');
-      });
-    }
-    
-    cmdBuffer.write('-id3v2_version 3 "$tempOutput" -y');
-    
-    final command = cmdBuffer.toString();
-    _log.d('Executing FFmpeg MP3 embed command: $command');
-
-    final result = await _execute(command);
-
-    if (result.success) {
-      try {
-        await File(mp3Path).delete();
-        await File(tempOutput).rename(mp3Path);
-        _log.d('MP3 metadata embedded successfully');
-        return mp3Path;
-      } catch (e) {
-        _log.e('Failed to replace MP3 file after metadata embed: $e');
-        return null;
-      }
-    }
-
-    try {
-      final tempFile = File(tempOutput);
-      if (await tempFile.exists()) {
-        await tempFile.delete();
-      }
-    } catch (_) {}
-
-    _log.e('MP3 Metadata/Cover embed failed: ${result.output}');
-    return null;
-  }
-
-  /// Convert FLAC/Vorbis comment tags to ID3v2 compatible tags
-  static Map<String, String> _convertToId3Tags(Map<String, String> vorbisMetadata) {
-    final id3Map = <String, String>{};
-    
-    for (final entry in vorbisMetadata.entries) {
-      final key = entry.key.toUpperCase();
-      final value = entry.value;
-      
-      // Map Vorbis comments to ID3v2 frame names
-      switch (key) {
-        case 'TITLE':
-          id3Map['title'] = value;
-          break;
-        case 'ARTIST':
-          id3Map['artist'] = value;
-          break;
-        case 'ALBUM':
-          id3Map['album'] = value;
-          break;
-        case 'ALBUMARTIST':
-          id3Map['album_artist'] = value;
-          break;
-        case 'TRACKNUMBER':
-        case 'TRACK':
-          id3Map['track'] = value;
-          break;
-        case 'DISCNUMBER':
-        case 'DISC':
-          id3Map['disc'] = value;
-          break;
-        case 'DATE':
-        case 'YEAR':
-          id3Map['date'] = value;
-          break;
-        case 'ISRC':
-          id3Map['TSRC'] = value; // ID3v2 ISRC frame
-          break;
-        case 'LYRICS':
-        case 'UNSYNCEDLYRICS':
-          id3Map['lyrics'] = value;
-          break;
-        default:
-          // Pass through other tags as-is
-          id3Map[key.toLowerCase()] = value;
-      }
-    }
-    
-    return id3Map;
-  }
-
-  /// Check if FFmpeg is available
-  static Future<bool> isAvailable() async {
-    try {
-      final session = await FFmpegKit.execute('-version');
-      final returnCode = await session.getReturnCode();
-      return ReturnCode.isSuccess(returnCode);
-    } catch (e) {
-      return false;
-    }
-  }
-
-  /// Get FFmpeg version info
-  static Future<String?> getVersion() async {
-    try {
-      final session = await FFmpegKit.execute('-version');
-      return await session.getOutput();
-    } catch (e) {
-      return null;
-    }
-  }
-}
-
-class FFmpegResultIOS {
-  final bool success;
-  final int returnCode;
-  final String output;
-
-  FFmpegResultIOS({required this.success, required this.returnCode, required this.output});
-}

cliff.toml

@@ -0,0 +1,103 @@
+# git-cliff configuration for SpotiFLAC Mobile
+# https://git-cliff.org/docs/configuration
+
+[changelog]
+# Template for the changelog body
+body = """
+{%- macro remote_url() -%}
+  https://github.com/zarzet/SpotiFLAC-Mobile
+{%- endmacro -%}
+
+{% if version %}\
+    ## {{ version | trim_start_matches(pat="v") }}
+{% else %}\
+    ## Unreleased
+{% endif %}\
+
+{% for group, commits in commits | group_by(attribute="group") %}
+    ### {{ group | striptags | trim | upper_first }}
+    {% for commit in commits %}
+        - {% if commit.scope %}**{{ commit.scope }}**: {% endif %}\
+            {{ commit.message | upper_first }}\
+            {% if commit.github.pr_number %} \
+                ([#{{ commit.github.pr_number }}]({{ self::remote_url() }}/pull/{{ commit.github.pr_number }}))\
+            {% endif %}\
+            {%- if commit.github.username and commit.github.username != "zarzet" %} by [@{{ commit.github.username }}](https://github.com/{{ commit.github.username }}){%- endif %}
+    {%- endfor %}
+{% endfor %}
+
+{%- if github.contributors | filter(attribute="is_first_time", value=true) | length != 0 %}
+
+  ### New Contributors
+{%- for contributor in github.contributors | filter(attribute="is_first_time", value=true) %}
+  * @{{ contributor.username }} made their first contribution
+    {%- if contributor.pr_number %} in \
+      [#{{ contributor.pr_number }}]({{ self::remote_url() }}/pull/{{ contributor.pr_number }}) \
+    {%- endif %}
+{%- endfor %}
+{%- endif -%}
+
+{% if version %}
+    {% if previous.version %}
+      **Full Changelog**: [{{ previous.version }}...{{ version }}]({{ self::remote_url() }}/compare/{{ previous.version }}...{{ version }})
+    {% endif %}
+{% else -%}
+    {% raw %}\n{% endraw %}
+{% endif %}
+"""
+# Remove leading and trailing whitespace
+trim = true
+
+[git]
+# Parse conventional commits
+conventional_commits = true
+filter_unconventional = true
+
+# Process each line of a commit as an individual commit
+split_commits = false
+
+# Regex for preprocessing the commit messages
+commit_preprocessors = [
+  # Strip conventional commit prefix for cleaner messages
+  # (group header already shows the type)
+]
+
+# Regex for parsing and grouping commits
+commit_parsers = [
+  # Skip noise: translation commits from Crowdin
+  { message = "^New translations", skip = true },
+  { message = "^Update source file", skip = true },
+  # Skip merge commits
+  { message = "^Merge", skip = true },
+  # Skip version bump commits
+  { message = "^v\\d+", skip = true },
+  { message = "^chore: update VirusTotal", skip = true },
+
+  # Group by conventional commit type
+  { message = "^feat", group = "<!-- 0 -->New Features" },
+  { message = "^fix", group = "<!-- 1 -->Bug Fixes" },
+  { message = "^perf", group = "<!-- 2 -->Performance" },
+  { message = "^refactor", group = "<!-- 3 -->Refactoring" },
+  { message = "^doc", group = "<!-- 4 -->Documentation" },
+  { message = "^style", group = "<!-- 5 -->Styling" },
+  { message = "^test", group = "<!-- 6 -->Testing" },
+  { message = "^chore\\(deps\\)", group = "<!-- 7 -->Dependencies" },
+  { message = "^chore\\(l10n\\)", skip = true },
+  { message = "^chore|^ci", group = "<!-- 8 -->Chores" },
+]
+
+# Protect breaking changes from being skipped
+protect_breaking_commits = true
+
+# Filter out commits by matching patterns
+filter_commits = false
+
+# Tag pattern for version detection
+tag_pattern = "v[0-9].*"
+
+# Sort commits by newest first
+sort_commits = "newest"
+
+[remote.github]
+owner = "zarzet"
+repo = "SpotiFLAC-Mobile"

go_backend/amazon.go

@@ -1,637 +0,0 @@
-package gobackend
-
-import (
-	"bufio"
-	"context"
-	"encoding/base64"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"io"
-	"net/http"
-	"net/url"
-	"os"
-	"path/filepath"
-	"strings"
-	"sync"
-	"time"
-)
-
-// AmazonDownloader handles Amazon Music downloads using DoubleDouble service (same as PC)
-type AmazonDownloader struct {
-	client           *http.Client
-	regions          []string  // us, eu regions for DoubleDouble service
-	lastAPICallTime  time.Time // Rate limiting: track last API call
-	apiCallCount     int       // Rate limiting: counter per minute
-	apiCallResetTime time.Time // Rate limiting: reset time
-}
-
-var (
-	globalAmazonDownloader *AmazonDownloader
-	amazonDownloaderOnce   sync.Once
-	amazonRateLimitMu      sync.Mutex
-)
-
-// DoubleDoubleSubmitResponse is the response from DoubleDouble submit endpoint
-type DoubleDoubleSubmitResponse struct {
-	Success bool   `json:"success"`
-	ID      string `json:"id"`
-}
-
-// DoubleDoubleStatusResponse is the response from DoubleDouble status endpoint
-type DoubleDoubleStatusResponse struct {
-	Status         string `json:"status"`
-	FriendlyStatus string `json:"friendlyStatus"`
-	URL            string `json:"url"`
-	Current        struct {
-		Name   string `json:"name"`
-		Artist string `json:"artist"`
-	} `json:"current"`
-}
-
-// amazonArtistsMatch checks if the artist names are similar enough
-func amazonArtistsMatch(expectedArtist, foundArtist string) bool {
-	normExpected := strings.ToLower(strings.TrimSpace(expectedArtist))
-	normFound := strings.ToLower(strings.TrimSpace(foundArtist))
-
-	if normExpected == normFound {
-		return true
-	}
-
-	if strings.Contains(normExpected, normFound) || strings.Contains(normFound, normExpected) {
-		return true
-	}
-
-	expectedFirst := strings.Split(normExpected, ",")[0]
-	expectedFirst = strings.Split(expectedFirst, " feat")[0]
-	expectedFirst = strings.Split(expectedFirst, " ft.")[0]
-	expectedFirst = strings.TrimSpace(expectedFirst)
-
-	foundFirst := strings.Split(normFound, ",")[0]
-	foundFirst = strings.Split(foundFirst, " feat")[0]
-	foundFirst = strings.Split(foundFirst, " ft.")[0]
-	foundFirst = strings.TrimSpace(foundFirst)
-
-	if expectedFirst == foundFirst {
-		return true
-	}
-
-	if strings.Contains(expectedFirst, foundFirst) || strings.Contains(foundFirst, expectedFirst) {
-		return true
-	}
-
-	expectedASCII := amazonIsASCIIString(expectedArtist)
-	foundASCII := amazonIsASCIIString(foundArtist)
-	if expectedASCII != foundASCII {
-		GoLog("[Amazon] Artist names in different scripts, assuming match: '%s' vs '%s'\n", expectedArtist, foundArtist)
-		return true
-	}
-
-	return false
-}
-
-// amazonIsASCIIString checks if a string contains only ASCII characters
-func amazonIsASCIIString(s string) bool {
-	for _, r := range s {
-		if r > 127 {
-			return false
-		}
-	}
-	return true
-}
-
-// NewAmazonDownloader creates a new Amazon downloader (returns singleton for connection reuse)
-func NewAmazonDownloader() *AmazonDownloader {
-	amazonDownloaderOnce.Do(func() {
-		globalAmazonDownloader = &AmazonDownloader{
-			client:           NewHTTPClientWithTimeout(120 * time.Second), // 120s timeout like PC
-			regions:          []string{"us", "eu"},                        // Same regions as PC
-			apiCallResetTime: time.Now(),
-		}
-	})
-	return globalAmazonDownloader
-}
-
-// waitForRateLimit implements rate limiting similar to PC version
-// Max 9 requests per minute with 7 second delay between requests
-func (a *AmazonDownloader) waitForRateLimit() {
-	amazonRateLimitMu.Lock()
-	defer amazonRateLimitMu.Unlock()
-
-	now := time.Now()
-
-	if now.Sub(a.apiCallResetTime) >= time.Minute {
-		a.apiCallCount = 0
-		a.apiCallResetTime = now
-	}
-
-	// If we've hit the limit (9 requests per minute), wait until next minute
-	if a.apiCallCount >= 9 {
-		waitTime := time.Minute - now.Sub(a.apiCallResetTime)
-		if waitTime > 0 {
-			GoLog("[Amazon] Rate limit reached, waiting %v...\n", waitTime.Round(time.Second))
-			time.Sleep(waitTime)
-			a.apiCallCount = 0
-			a.apiCallResetTime = time.Now()
-		}
-	}
-
-	// Add delay between requests (7 seconds like PC version)
-	if !a.lastAPICallTime.IsZero() {
-		timeSinceLastCall := now.Sub(a.lastAPICallTime)
-		minDelay := 7 * time.Second
-		if timeSinceLastCall < minDelay {
-			waitTime := minDelay - timeSinceLastCall
-			GoLog("[Amazon] Rate limiting: waiting %v...\n", waitTime.Round(time.Second))
-			time.Sleep(waitTime)
-		}
-	}
-
-	a.lastAPICallTime = time.Now()
-	a.apiCallCount++
-}
-
-// GetAvailableAPIs returns list of available DoubleDouble regions
-// Uses same service as PC version (doubledouble.top)
-func (a *AmazonDownloader) GetAvailableAPIs() []string {
-	// DoubleDouble service regions (same as PC)
-	// Format: https://{region}.doubledouble.top
-	var apis []string
-	for _, region := range a.regions {
-		apis = append(apis, fmt.Sprintf("https://%s.doubledouble.top", region))
-	}
-	return apis
-}
-
-// downloadFromDoubleDoubleService downloads a track using DoubleDouble service (same as PC)
-// This uses submit → poll → download mechanism
-// Internal function - not exported to gomobile
-func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, _ string) (string, string, string, error) {
-	var lastError error
-
-	for _, region := range a.regions {
-		GoLog("[Amazon] Trying region: %s...\n", region)
-
-		serviceBase, _ := base64.StdEncoding.DecodeString("aHR0cHM6Ly8=")               // https://
-		serviceDomain, _ := base64.StdEncoding.DecodeString("LmRvdWJsZWRvdWJsZS50b3A=") // .doubledouble.top
-		baseURL := fmt.Sprintf("%s%s%s", string(serviceBase), region, string(serviceDomain))
-
-		// Step 1: Submit download request with rate limiting
-		encodedURL := url.QueryEscape(amazonURL)
-		submitURL := fmt.Sprintf("%s/dl?url=%s", baseURL, encodedURL)
-
-		// Apply rate limiting before request (like PC version)
-		a.waitForRateLimit()
-
-		req, err := http.NewRequest("GET", submitURL, nil)
-		if err != nil {
-			lastError = fmt.Errorf("failed to create request: %w", err)
-			continue
-		}
-
-		req.Header.Set("User-Agent", getRandomUserAgent())
-
-		fmt.Println("[Amazon] Submitting download request...")
-
-		// Retry logic for 429 errors (like PC version: 3 retries with 15s wait)
-		var resp *http.Response
-		maxRetries := 3
-		for retry := 0; retry < maxRetries; retry++ {
-			resp, err = a.client.Do(req)
-			if err != nil {
-				lastError = fmt.Errorf("failed to submit request: %w", err)
-				break
-			}
-
-			if resp.StatusCode == 429 { // Too Many Requests
-				resp.Body.Close()
-				if retry < maxRetries-1 {
-					waitTime := 15 * time.Second
-					GoLog("[Amazon] Rate limited (429), waiting %v before retry %d/%d...\n", waitTime, retry+2, maxRetries)
-					time.Sleep(waitTime)
-					continue
-				}
-				lastError = fmt.Errorf("API rate limit exceeded after %d retries", maxRetries)
-				break
-			}
-
-			if resp.StatusCode != 200 {
-				resp.Body.Close()
-				lastError = fmt.Errorf("submit failed with status %d", resp.StatusCode)
-				break
-			}
-
-			// Success - break retry loop
-			break
-		}
-
-		if err != nil || lastError != nil {
-			if resp != nil {
-				resp.Body.Close()
-			}
-			continue
-		}
-
-		var submitResp DoubleDoubleSubmitResponse
-		if err := json.NewDecoder(resp.Body).Decode(&submitResp); err != nil {
-			resp.Body.Close()
-			lastError = fmt.Errorf("failed to decode submit response: %w", err)
-			continue
-		}
-		resp.Body.Close()
-
-		if !submitResp.Success || submitResp.ID == "" {
-			lastError = fmt.Errorf("submit request failed")
-			continue
-		}
-
-		downloadID := submitResp.ID
-		GoLog("[Amazon] Download ID: %s\n", downloadID)
-
-		// Step 2: Poll for completion
-		statusURL := fmt.Sprintf("%s/dl/%s", baseURL, downloadID)
-		fmt.Println("[Amazon] Waiting for download to complete...")
-
-		maxWait := 300 * time.Second // 5 minutes max wait
-		elapsed := time.Duration(0)
-		pollInterval := 3 * time.Second
-
-		for elapsed < maxWait {
-			time.Sleep(pollInterval)
-			elapsed += pollInterval
-
-			statusReq, err := http.NewRequest("GET", statusURL, nil)
-			if err != nil {
-				continue
-			}
-
-			statusReq.Header.Set("User-Agent", getRandomUserAgent())
-
-			statusResp, err := a.client.Do(statusReq)
-			if err != nil {
-				fmt.Printf("\r[Amazon] Status check failed, retrying...")
-				continue
-			}
-
-			if statusResp.StatusCode != 200 {
-				statusResp.Body.Close()
-				fmt.Printf("\r[Amazon] Status check failed (status %d), retrying...", statusResp.StatusCode)
-				continue
-			}
-
-			var status DoubleDoubleStatusResponse
-			if err := json.NewDecoder(statusResp.Body).Decode(&status); err != nil {
-				statusResp.Body.Close()
-				fmt.Printf("\r[Amazon] Invalid JSON response, retrying...")
-				continue
-			}
-			statusResp.Body.Close()
-
-			if status.Status == "done" {
-				fmt.Println("\n[Amazon] Download ready!")
-
-				fileURL := status.URL
-				if strings.HasPrefix(fileURL, "./") {
-					fileURL = fmt.Sprintf("%s/%s", baseURL, fileURL[2:])
-				} else if strings.HasPrefix(fileURL, "/") {
-					fileURL = fmt.Sprintf("%s%s", baseURL, fileURL)
-				}
-
-				trackName := status.Current.Name
-				artist := status.Current.Artist
-
-				GoLog("[Amazon] Downloading: %s - %s\n", artist, trackName)
-				return fileURL, trackName, artist, nil
-
-			} else if status.Status == "error" {
-				errorMsg := status.FriendlyStatus
-				if errorMsg == "" {
-					errorMsg = "Unknown error"
-				}
-				lastError = fmt.Errorf("processing failed: %s", errorMsg)
-				break
-			} else {
-				// Still processing
-				friendlyStatus := status.FriendlyStatus
-				if friendlyStatus == "" {
-					friendlyStatus = status.Status
-				}
-				fmt.Printf("\r[Amazon] %s...", friendlyStatus)
-			}
-		}
-
-		if elapsed >= maxWait {
-			lastError = fmt.Errorf("download timeout")
-			fmt.Printf("\n[Amazon] Error with %s region: %v\n", region, lastError)
-			continue
-		}
-
-		if lastError != nil {
-			fmt.Printf("\n[Amazon] Error with %s region: %v\n", region, lastError)
-		}
-	}
-
-	return "", "", "", fmt.Errorf("all regions failed. Last error: %v", lastError)
-}
-
-// DownloadFile downloads a file from URL with User-Agent and progress tracking
-func (a *AmazonDownloader) DownloadFile(downloadURL, outputPath, itemID string) error {
-	ctx := context.Background()
-
-	// Initialize item progress (required for all downloads)
-	if itemID != "" {
-		StartItemProgress(itemID)
-		defer CompleteItemProgress(itemID)
-		ctx = initDownloadCancel(itemID)
-		defer clearDownloadCancel(itemID)
-	}
-
-	if isDownloadCancelled(itemID) {
-		return ErrDownloadCancelled
-	}
-
-	req, err := http.NewRequestWithContext(ctx, "GET", downloadURL, nil)
-	if err != nil {
-		return fmt.Errorf("failed to create request: %w", err)
-	}
-
-	req.Header.Set("User-Agent", getRandomUserAgent())
-
-	resp, err := a.client.Do(req)
-	if err != nil {
-		if isDownloadCancelled(itemID) {
-			return ErrDownloadCancelled
-		}
-		return err
-	}
-	defer resp.Body.Close()
-
-	if resp.StatusCode != 200 {
-		return fmt.Errorf("download failed: HTTP %d", resp.StatusCode)
-	}
-
-	expectedSize := resp.ContentLength
-	if expectedSize > 0 && itemID != "" {
-		SetItemBytesTotal(itemID, expectedSize)
-	}
-
-	out, err := os.Create(outputPath)
-	if err != nil {
-		return err
-	}
-
-	bufWriter := bufio.NewWriterSize(out, 256*1024)
-
-	var written int64
-	if itemID != "" {
-		pw := NewItemProgressWriter(bufWriter, itemID)
-		written, err = io.Copy(pw, resp.Body)
-	} else {
-		written, err = io.Copy(bufWriter, resp.Body)
-	}
-
-	// Flush buffer before checking for errors
-	flushErr := bufWriter.Flush()
-	closeErr := out.Close()
-
-	if err != nil {
-		os.Remove(outputPath)
-		if isDownloadCancelled(itemID) {
-			return ErrDownloadCancelled
-		}
-		return fmt.Errorf("download interrupted: %w", err)
-	}
-	if flushErr != nil {
-		os.Remove(outputPath)
-		return fmt.Errorf("failed to flush buffer: %w", flushErr)
-	}
-	if closeErr != nil {
-		os.Remove(outputPath)
-		return fmt.Errorf("failed to close file: %w", closeErr)
-	}
-
-	// Verify file size if Content-Length was provided
-	if expectedSize > 0 && written != expectedSize {
-		os.Remove(outputPath)
-		return fmt.Errorf("incomplete download: expected %d bytes, got %d bytes", expectedSize, written)
-	}
-
-	fmt.Printf("\r[Amazon] Downloaded: %.2f MB (Complete)\n", float64(written)/(1024*1024))
-	return nil
-}
-
-// AmazonDownloadResult contains download result with quality info
-type AmazonDownloadResult struct {
-	FilePath    string
-	BitDepth    int
-	SampleRate  int
-	Title       string
-	Artist      string
-	Album       string
-	ReleaseDate string
-	TrackNumber int
-	DiscNumber  int
-	ISRC        string
-}
-
-// downloadFromAmazon downloads a track using the request parameters
-// Uses DoubleDouble service (same as PC version)
-func downloadFromAmazon(req DownloadRequest) (AmazonDownloadResult, error) {
-	downloader := NewAmazonDownloader()
-
-	if existingFile, exists := checkISRCExistsInternal(req.OutputDir, req.ISRC); exists {
-		return AmazonDownloadResult{FilePath: "EXISTS:" + existingFile}, nil
-	}
-
-	songlink := NewSongLinkClient()
-	var availability *TrackAvailability
-	var err error
-
-	if strings.HasPrefix(req.SpotifyID, "deezer:") {
-		deezerID := strings.TrimPrefix(req.SpotifyID, "deezer:")
-		GoLog("[Amazon] Using Deezer ID for SongLink lookup: %s\n", deezerID)
-		availability, err = songlink.CheckAvailabilityFromDeezer(deezerID)
-	} else if req.SpotifyID != "" {
-		availability, err = songlink.CheckTrackAvailability(req.SpotifyID, req.ISRC)
-	} else {
-		return AmazonDownloadResult{}, fmt.Errorf("no valid Spotify or Deezer ID provided for Amazon lookup")
-	}
-
-	if err != nil {
-		return AmazonDownloadResult{}, fmt.Errorf("failed to check Amazon availability via SongLink: %w", err)
-	}
-
-	if !availability.Amazon || availability.AmazonURL == "" {
-		return AmazonDownloadResult{}, fmt.Errorf("track not available on Amazon Music (SongLink returned no Amazon URL)")
-	}
-
-	if req.OutputDir != "." {
-		if err := os.MkdirAll(req.OutputDir, 0755); err != nil {
-			return AmazonDownloadResult{}, fmt.Errorf("failed to create output directory: %w", err)
-		}
-	}
-
-	// Download using DoubleDouble service (same as PC)
-	downloadURL, trackName, artistName, err := downloader.downloadFromDoubleDoubleService(availability.AmazonURL, req.OutputDir)
-	if err != nil {
-		return AmazonDownloadResult{}, fmt.Errorf("failed to get download URL: %w", err)
-	}
-
-	// Verify artist matches
-	if artistName != "" && !amazonArtistsMatch(req.ArtistName, artistName) {
-		GoLog("[Amazon] Artist mismatch: expected '%s', got '%s'. Rejecting.\n", req.ArtistName, artistName)
-		return AmazonDownloadResult{}, fmt.Errorf("artist mismatch: expected '%s', got '%s'", req.ArtistName, artistName)
-	}
-
-	GoLog("[Amazon] Match found: '%s' by '%s'\n", trackName, artistName)
-
-	filename := buildFilenameFromTemplate(req.FilenameFormat, map[string]interface{}{
-		"title":  req.TrackName,
-		"artist": req.ArtistName,
-		"album":  req.AlbumName,
-		"track":  req.TrackNumber,
-		"year":   extractYear(req.ReleaseDate),
-		"disc":   req.DiscNumber,
-	})
-	filename = sanitizeFilename(filename) + ".flac"
-	outputPath := filepath.Join(req.OutputDir, filename)
-
-	if fileInfo, statErr := os.Stat(outputPath); statErr == nil && fileInfo.Size() > 0 {
-		return AmazonDownloadResult{FilePath: "EXISTS:" + outputPath}, nil
-	}
-
-	// START PARALLEL: Fetch cover and lyrics while downloading audio
-	var parallelResult *ParallelDownloadResult
-	parallelDone := make(chan struct{})
-	go func() {
-		defer close(parallelDone)
-		parallelResult = FetchCoverAndLyricsParallel(
-			req.CoverURL,
-			req.EmbedMaxQualityCover,
-			req.SpotifyID,
-			req.TrackName,
-			req.ArtistName,
-			req.EmbedLyrics,
-			int64(req.DurationMS),
-		)
-	}()
-
-	// Download audio file with item ID for progress tracking
-	if err := downloader.DownloadFile(downloadURL, outputPath, req.ItemID); err != nil {
-		if errors.Is(err, ErrDownloadCancelled) {
-			return AmazonDownloadResult{}, ErrDownloadCancelled
-		}
-		return AmazonDownloadResult{}, fmt.Errorf("download failed: %w", err)
-	}
-
-	// Wait for parallel operations to complete
-	<-parallelDone
-
-	if req.ItemID != "" {
-		SetItemProgress(req.ItemID, 1.0, 0, 0)
-		SetItemFinalizing(req.ItemID)
-	}
-
-	// Log track info from DoubleDouble (for debugging)
-	if trackName != "" && artistName != "" {
-		GoLog("[Amazon] DoubleDouble returned: %s - %s\n", artistName, trackName)
-	}
-
-	existingMeta, metaErr := ReadMetadata(outputPath)
-	actualTrackNum := req.TrackNumber
-	actualDiscNum := req.DiscNumber
-
-	if metaErr == nil && existingMeta != nil {
-		if existingMeta.TrackNumber > 0 && (req.TrackNumber == 0 || req.TrackNumber == 1) {
-			actualTrackNum = existingMeta.TrackNumber
-			GoLog("[Amazon] Using track number from file: %d (request had: %d)\n", actualTrackNum, req.TrackNumber)
-		}
-		if existingMeta.DiscNumber > 0 && (req.DiscNumber == 0 || req.DiscNumber == 1) {
-			actualDiscNum = existingMeta.DiscNumber
-			GoLog("[Amazon] Using disc number from file: %d (request had: %d)\n", actualDiscNum, req.DiscNumber)
-		}
-	}
-
-	// Embed metadata using Spotify data (more accurate than DoubleDouble)
-	// But preserve track/disc numbers from file if they were better
-	metadata := Metadata{
-		Title:       req.TrackName,
-		Artist:      req.ArtistName,
-		Album:       req.AlbumName,
-		AlbumArtist: req.AlbumArtist,
-		Date:        req.ReleaseDate,
-		TrackNumber: actualTrackNum,
-		TotalTracks: req.TotalTracks,
-		DiscNumber:  actualDiscNum,
-		ISRC:        req.ISRC,
-		Genre:       req.Genre,     // From Deezer album metadata
-		Label:       req.Label,     // From Deezer album metadata
-		Copyright:   req.Copyright, // From Deezer album metadata
-	}
-
-	// Use cover data from parallel fetch
-	var coverData []byte
-	if parallelResult != nil && parallelResult.CoverData != nil {
-		coverData = parallelResult.CoverData
-		GoLog("[Amazon] Using parallel-fetched cover (%d bytes)\n", len(coverData))
-	}
-
-	if err := EmbedMetadataWithCoverData(outputPath, metadata, coverData); err != nil {
-		fmt.Printf("Warning: failed to embed metadata: %v\n", err)
-	}
-
-	// Embed lyrics from parallel fetch
-	if req.EmbedLyrics && parallelResult != nil && parallelResult.LyricsLRC != "" {
-		GoLog("[Amazon] Embedding parallel-fetched lyrics (%d lines)...\n", len(parallelResult.LyricsData.Lines))
-		if embedErr := EmbedLyrics(outputPath, parallelResult.LyricsLRC); embedErr != nil {
-			GoLog("[Amazon] Warning: failed to embed lyrics: %v\n", embedErr)
-		} else {
-			fmt.Println("[Amazon] Lyrics embedded successfully")
-		}
-	} else if req.EmbedLyrics {
-		fmt.Println("[Amazon] No lyrics available from parallel fetch")
-	}
-
-	fmt.Println("[Amazon] ✓ Downloaded successfully from Amazon Music")
-
-	quality, err := GetAudioQuality(outputPath)
-	if err != nil {
-		GoLog("[Amazon] Warning: couldn't read quality from file: %v\n", err)
-	} else {
-		GoLog("[Amazon] Actual quality: %d-bit/%dHz\n", quality.BitDepth, quality.SampleRate)
-	}
-
-	finalMeta, metaReadErr := ReadMetadata(outputPath)
-	if metaReadErr == nil && finalMeta != nil {
-		GoLog("[Amazon] Final metadata from file - Track: %d, Disc: %d, Date: %s\n",
-			finalMeta.TrackNumber, finalMeta.DiscNumber, finalMeta.Date)
-		actualTrackNum = finalMeta.TrackNumber
-		actualDiscNum = finalMeta.DiscNumber
-		if finalMeta.Date != "" {
-			req.ReleaseDate = finalMeta.Date
-		}
-	}
-
-	// Add to ISRC index for fast duplicate checking
-	AddToISRCIndex(req.OutputDir, req.ISRC, outputPath)
-
-	bitDepth := 0
-	sampleRate := 0
-	if err == nil {
-		bitDepth = quality.BitDepth
-		sampleRate = quality.SampleRate
-	}
-
-	return AmazonDownloadResult{
-		FilePath:    outputPath,
-		BitDepth:    bitDepth,
-		SampleRate:  sampleRate,
-		Title:       req.TrackName,
-		Artist:      req.ArtistName,
-		Album:       req.AlbumName,
-		ReleaseDate: req.ReleaseDate,
-		TrackNumber: actualTrackNum,
-		DiscNumber:  actualDiscNum,
-		ISRC:        req.ISRC,
-	}, nil
-}

go_backend/cover.go

@@ -8,18 +8,15 @@ import (
 	"strings"
 )
 
-// Spotify image size codes (same as PC version)
 const (
-	spotifySize300 = "ab67616d00001e02" // 300x300 (small)
-	spotifySize640 = "ab67616d0000b273" // 640x640 (medium)
-	spotifySizeMax = "ab67616d000082c1" // Max resolution (~2000x2000)
+	spotifySize300 = "ab67616d00001e02"
+	spotifySize640 = "ab67616d0000b273"
+	spotifySizeMax = "ab67616d000082c1"
 )
 
 // Deezer CDN supports these sizes: 56, 250, 500, 1000, 1400, 1800
 var deezerSizeRegex = regexp.MustCompile(`/(\d+)x(\d+)-\d+-\d+-\d+-\d+\.jpg$`)
 
-// convertSmallToMedium upgrades 300x300 cover URL to 640x640
-// Same logic as PC version for consistency
 func convertSmallToMedium(imageURL string) string {
 	if strings.Contains(imageURL, spotifySize300) {
 		return strings.Replace(imageURL, spotifySize300, spotifySize640, 1)
@@ -27,8 +24,6 @@ func convertSmallToMedium(imageURL string) string {
 	return imageURL
 }
 
-// downloadCoverToMemory downloads cover art and returns as bytes (no file creation)
-// This avoids file permission issues on Android
 func downloadCoverToMemory(coverURL string, maxQuality bool) ([]byte, error) {
 	if coverURL == "" {
 		return nil, fmt.Errorf("no cover URL provided")
@@ -90,8 +85,6 @@ func downloadCoverToMemory(coverURL string, maxQuality bool) ([]byte, error) {
 	return data, nil
 }
 
-// upgradeToMaxQuality upgrades cover URL to maximum quality
-// Supports both Spotify and Deezer CDNs
 func upgradeToMaxQuality(coverURL string) string {
 	// Spotify CDN upgrade
 	if strings.Contains(coverURL, spotifySize640) {
@@ -106,15 +99,11 @@ func upgradeToMaxQuality(coverURL string) string {
 	return coverURL
 }
 
-// upgradeDeezerCover upgrades Deezer cover URL to maximum quality (1800x1800)
-// Deezer CDN format: https://cdn-images.dzcdn.net/images/cover/{hash}/{size}x{size}-000000-80-0-0.jpg
-// Available sizes: 56, 250, 500, 1000, 1400, 1800
 func upgradeDeezerCover(coverURL string) string {
 	if !strings.Contains(coverURL, "cdn-images.dzcdn.net") {
 		return coverURL
 	}
 
-	// Replace any size pattern with 1800x1800
 	upgraded := deezerSizeRegex.ReplaceAllString(coverURL, "/1800x1800-000000-80-0-0.jpg")
 	if upgraded != coverURL {
 		GoLog("[Cover] Deezer: upgraded to 1800x1800")
@@ -122,7 +111,6 @@ func upgradeDeezerCover(coverURL string) string {
 	return upgraded
 }
 
-// GetCoverFromSpotify gets cover URL from Spotify metadata
 func GetCoverFromSpotify(imageURL string, maxQuality bool) string {
 	if imageURL == "" {
 		return ""

go_backend/cue_parser.go

@@ -0,0 +1,590 @@
+package gobackend
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// CueSheet represents a parsed .cue file
+type CueSheet struct {
+	// Album-level metadata
+	Performer string     `json:"performer"`
+	Title     string     `json:"title"`
+	FileName  string     `json:"file_name"`
+	FileType  string     `json:"file_type"` // WAVE, FLAC, MP3, AIFF, etc.
+	Genre     string     `json:"genre,omitempty"`
+	Date      string     `json:"date,omitempty"`
+	Comment   string     `json:"comment,omitempty"`
+	Composer  string     `json:"composer,omitempty"`
+	Tracks    []CueTrack `json:"tracks"`
+}
+
+// CueTrack represents a single track in a cue sheet
+type CueTrack struct {
+	Number    int    `json:"number"`
+	Title     string `json:"title"`
+	Performer string `json:"performer"`
+	ISRC      string `json:"isrc,omitempty"`
+	Composer  string `json:"composer,omitempty"`
+	// Index positions in seconds (fractional)
+	StartTime float64 `json:"start_time"` // INDEX 01 in seconds
+	PreGap    float64 `json:"pre_gap"`    // INDEX 00 in seconds (or -1 if not present)
+}
+
+// CueSplitInfo represents the information needed to split a CUE+audio file
+type CueSplitInfo struct {
+	CuePath   string          `json:"cue_path"`
+	AudioPath string          `json:"audio_path"`
+	Album     string          `json:"album"`
+	Artist    string          `json:"artist"`
+	Genre     string          `json:"genre,omitempty"`
+	Date      string          `json:"date,omitempty"`
+	Tracks    []CueSplitTrack `json:"tracks"`
+}
+
+// CueSplitTrack has the FFmpeg split parameters for a single track
+type CueSplitTrack struct {
+	Number   int     `json:"number"`
+	Title    string  `json:"title"`
+	Artist   string  `json:"artist"`
+	ISRC     string  `json:"isrc,omitempty"`
+	Composer string  `json:"composer,omitempty"`
+	StartSec float64 `json:"start_sec"`
+	EndSec   float64 `json:"end_sec"` // -1 means until end of file
+}
+
+var (
+	reRemCommand = regexp.MustCompile(`^REM\s+(\S+)\s+(.+)$`)
+	reQuoted     = regexp.MustCompile(`"([^"]*)"`)
+)
+
+// ParseCueFile parses a .cue file and returns a CueSheet
+func ParseCueFile(cuePath string) (*CueSheet, error) {
+	f, err := os.Open(cuePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open cue file: %w", err)
+	}
+	defer f.Close()
+
+	sheet := &CueSheet{}
+	var currentTrack *CueTrack
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" {
+			continue
+		}
+
+		// Handle BOM at start of file
+		if strings.HasPrefix(line, "\xef\xbb\xbf") {
+			line = strings.TrimPrefix(line, "\xef\xbb\xbf")
+			line = strings.TrimSpace(line)
+		}
+
+		upper := strings.ToUpper(line)
+
+		// REM commands (album-level metadata)
+		if strings.HasPrefix(upper, "REM ") {
+			matches := reRemCommand.FindStringSubmatch(line)
+			if len(matches) == 3 {
+				key := strings.ToUpper(matches[1])
+				value := unquoteCue(matches[2])
+				switch key {
+				case "GENRE":
+					sheet.Genre = value
+				case "DATE":
+					sheet.Date = value
+				case "COMMENT":
+					sheet.Comment = value
+				case "COMPOSER":
+					if currentTrack != nil {
+						currentTrack.Composer = value
+					} else {
+						sheet.Composer = value
+					}
+				}
+			}
+			continue
+		}
+
+		if strings.HasPrefix(upper, "PERFORMER ") {
+			value := unquoteCue(line[len("PERFORMER "):])
+			if currentTrack != nil {
+				currentTrack.Performer = value
+			} else {
+				sheet.Performer = value
+			}
+			continue
+		}
+
+		if strings.HasPrefix(upper, "TITLE ") {
+			value := unquoteCue(line[len("TITLE "):])
+			if currentTrack != nil {
+				currentTrack.Title = value
+			} else {
+				sheet.Title = value
+			}
+			continue
+		}
+
+		if strings.HasPrefix(upper, "FILE ") {
+			rest := line[len("FILE "):]
+			// Extract filename and type
+			// Format: FILE "filename.flac" WAVE
+			// or: FILE filename.flac WAVE
+			fname, ftype := parseCueFileLine(rest)
+			sheet.FileName = fname
+			sheet.FileType = ftype
+			continue
+		}
+
+		if strings.HasPrefix(upper, "TRACK ") {
+			// Save previous track
+			if currentTrack != nil {
+				sheet.Tracks = append(sheet.Tracks, *currentTrack)
+			}
+
+			parts := strings.Fields(line)
+			trackNum := 0
+			if len(parts) >= 2 {
+				trackNum, _ = strconv.Atoi(parts[1])
+			}
+
+			currentTrack = &CueTrack{
+				Number: trackNum,
+				PreGap: -1,
+			}
+			continue
+		}
+
+		if strings.HasPrefix(upper, "INDEX ") && currentTrack != nil {
+			parts := strings.Fields(line)
+			if len(parts) >= 3 {
+				indexNum, _ := strconv.Atoi(parts[1])
+				timeSec := parseCueTimestamp(parts[2])
+				switch indexNum {
+				case 0:
+					currentTrack.PreGap = timeSec
+				case 1:
+					currentTrack.StartTime = timeSec
+				}
+			}
+			continue
+		}
+
+		if strings.HasPrefix(upper, "ISRC ") && currentTrack != nil {
+			currentTrack.ISRC = strings.TrimSpace(line[len("ISRC "):])
+			continue
+		}
+
+		// SONGWRITER (used as composer sometimes)
+		if strings.HasPrefix(upper, "SONGWRITER ") {
+			value := unquoteCue(line[len("SONGWRITER "):])
+			if currentTrack != nil {
+				currentTrack.Composer = value
+			} else {
+				sheet.Composer = value
+			}
+			continue
+		}
+	}
+
+	// Don't forget the last track
+	if currentTrack != nil {
+		sheet.Tracks = append(sheet.Tracks, *currentTrack)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("error reading cue file: %w", err)
+	}
+
+	if len(sheet.Tracks) == 0 {
+		return nil, fmt.Errorf("no tracks found in cue file")
+	}
+
+	return sheet, nil
+}
+
+// parseCueTimestamp converts MM:SS:FF (frames at 75fps) to seconds
+func parseCueTimestamp(ts string) float64 {
+	parts := strings.Split(ts, ":")
+	if len(parts) != 3 {
+		return 0
+	}
+
+	minutes, _ := strconv.Atoi(parts[0])
+	seconds, _ := strconv.Atoi(parts[1])
+	frames, _ := strconv.Atoi(parts[2])
+
+	return float64(minutes)*60 + float64(seconds) + float64(frames)/75.0
+}
+
+// formatCueTimestamp converts seconds to HH:MM:SS.mmm format for FFmpeg
+func formatCueTimestamp(seconds float64) string {
+	if seconds < 0 {
+		return "0"
+	}
+	hours := int(seconds) / 3600
+	mins := (int(seconds) % 3600) / 60
+	secs := seconds - float64(hours*3600) - float64(mins*60)
+	return fmt.Sprintf("%02d:%02d:%06.3f", hours, mins, secs)
+}
+
+// unquoteCue removes surrounding quotes from a CUE value
+func unquoteCue(s string) string {
+	s = strings.TrimSpace(s)
+	if matches := reQuoted.FindStringSubmatch(s); len(matches) == 2 {
+		return matches[1]
+	}
+	return s
+}
+
+// parseCueFileLine parses the FILE command's filename and type
+func parseCueFileLine(rest string) (string, string) {
+	rest = strings.TrimSpace(rest)
+
+	var filename, ftype string
+
+	if strings.HasPrefix(rest, "\"") {
+		// Quoted filename
+		endQuote := strings.Index(rest[1:], "\"")
+		if endQuote >= 0 {
+			filename = rest[1 : endQuote+1]
+			remaining := strings.TrimSpace(rest[endQuote+2:])
+			ftype = remaining
+		} else {
+			filename = rest
+		}
+	} else {
+		// Unquoted filename - last word is the type
+		parts := strings.Fields(rest)
+		if len(parts) >= 2 {
+			ftype = parts[len(parts)-1]
+			filename = strings.Join(parts[:len(parts)-1], " ")
+		} else if len(parts) == 1 {
+			filename = parts[0]
+		}
+	}
+
+	return filename, strings.TrimSpace(ftype)
+}
+
+// ResolveCueAudioPath finds the actual audio file referenced by a .cue sheet.
+// It checks relative to the cue file's directory.
+func ResolveCueAudioPath(cuePath string, cueFileName string) string {
+	cueDir := filepath.Dir(cuePath)
+
+	// 1. Try the exact filename from the .cue
+	candidate := filepath.Join(cueDir, cueFileName)
+	if _, err := os.Stat(candidate); err == nil {
+		return candidate
+	}
+
+	// 2. Try common case variations
+	baseName := strings.TrimSuffix(cueFileName, filepath.Ext(cueFileName))
+	commonExts := []string{".flac", ".wav", ".ape", ".mp3", ".ogg", ".wv", ".m4a"}
+	for _, ext := range commonExts {
+		candidate = filepath.Join(cueDir, baseName+ext)
+		if _, err := os.Stat(candidate); err == nil {
+			return candidate
+		}
+		// Try uppercase ext
+		candidate = filepath.Join(cueDir, baseName+strings.ToUpper(ext))
+		if _, err := os.Stat(candidate); err == nil {
+			return candidate
+		}
+	}
+
+	// 3. Try to find any audio file with the same base name as the .cue file
+	cueBase := strings.TrimSuffix(filepath.Base(cuePath), filepath.Ext(cuePath))
+	for _, ext := range commonExts {
+		candidate = filepath.Join(cueDir, cueBase+ext)
+		if _, err := os.Stat(candidate); err == nil {
+			return candidate
+		}
+	}
+
+	// 4. If there's only one audio file in the directory, use that
+	entries, err := os.ReadDir(cueDir)
+	if err == nil {
+		audioExts := map[string]bool{
+			".flac": true, ".wav": true, ".ape": true, ".mp3": true,
+			".ogg": true, ".wv": true, ".m4a": true, ".aiff": true,
+		}
+		var audioFiles []string
+		for _, entry := range entries {
+			if entry.IsDir() {
+				continue
+			}
+			ext := strings.ToLower(filepath.Ext(entry.Name()))
+			if audioExts[ext] {
+				audioFiles = append(audioFiles, filepath.Join(cueDir, entry.Name()))
+			}
+		}
+		if len(audioFiles) == 1 {
+			return audioFiles[0]
+		}
+	}
+
+	return ""
+}
+
+// BuildCueSplitInfo creates the split information from a parsed CUE sheet.
+// This is returned to the Dart side so FFmpeg can perform the splitting.
+// audioDir, if non-empty, overrides the directory for audio file resolution.
+func BuildCueSplitInfo(cuePath string, sheet *CueSheet, audioDir string) (*CueSplitInfo, error) {
+	resolveDir := cuePath
+	if audioDir != "" {
+		// Create a virtual path in audioDir so ResolveCueAudioPath looks there
+		resolveDir = filepath.Join(audioDir, filepath.Base(cuePath))
+	}
+	audioPath := ResolveCueAudioPath(resolveDir, sheet.FileName)
+	if audioPath == "" {
+		return nil, fmt.Errorf("audio file not found for cue sheet: %s (referenced: %s)", cuePath, sheet.FileName)
+	}
+
+	info := &CueSplitInfo{
+		CuePath:   cuePath,
+		AudioPath: audioPath,
+		Album:     sheet.Title,
+		Artist:    sheet.Performer,
+		Genre:     sheet.Genre,
+		Date:      sheet.Date,
+	}
+
+	for i, track := range sheet.Tracks {
+		performer := track.Performer
+		if performer == "" {
+			performer = sheet.Performer
+		}
+
+		composer := track.Composer
+		if composer == "" {
+			composer = sheet.Composer
+		}
+
+		// End time is the start of the next track, or -1 for the last track
+		endSec := float64(-1)
+		if i+1 < len(sheet.Tracks) {
+			nextTrack := sheet.Tracks[i+1]
+			// Use pre-gap of next track if available, otherwise its start time
+			if nextTrack.PreGap >= 0 {
+				endSec = nextTrack.PreGap
+			} else {
+				endSec = nextTrack.StartTime
+			}
+		}
+
+		info.Tracks = append(info.Tracks, CueSplitTrack{
+			Number:   track.Number,
+			Title:    track.Title,
+			Artist:   performer,
+			ISRC:     track.ISRC,
+			Composer: composer,
+			StartSec: track.StartTime,
+			EndSec:   endSec,
+		})
+	}
+
+	return info, nil
+}
+
+// ParseCueFileJSON parses a .cue file and returns JSON with split info.
+// This is the main entry point called from Dart via the platform bridge.
+// audioDir, if non-empty, overrides the directory used for resolving the
+// referenced audio file (useful when the .cue was copied to a temp dir
+// but the audio still lives in the original location, e.g. SAF).
+func ParseCueFileJSON(cuePath string, audioDir string) (string, error) {
+	sheet, err := ParseCueFile(cuePath)
+	if err != nil {
+		return "", fmt.Errorf("failed to parse cue file: %w", err)
+	}
+
+	info, err := BuildCueSplitInfo(cuePath, sheet, audioDir)
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(info)
+	if err != nil {
+		return "", fmt.Errorf("failed to marshal cue split info: %w", err)
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ScanCueFileForLibrary parses a .cue file and returns multiple LibraryScanResult
+// entries, one per track. This is used by the library scanner to populate the
+// library with individual track entries from a single CUE+FLAC album.
+func ScanCueFileForLibrary(cuePath string, scanTime string) ([]LibraryScanResult, error) {
+	sheet, err := ParseCueFile(cuePath)
+	if err != nil {
+		return nil, err
+	}
+	audioPath, err := resolveCueAudioPathForLibrary(cuePath, sheet, "")
+	if err != nil {
+		return nil, err
+	}
+	return scanCueSheetForLibrary(cuePath, sheet, audioPath, "", 0, scanTime)
+}
+
+// ScanCueFileForLibraryExt is like ScanCueFileForLibrary but with extra parameters
+// for SAF (Storage Access Framework) scenarios:
+//   - audioDir: if non-empty, overrides the directory used to find the audio file
+//   - virtualPathPrefix: if non-empty, used instead of cuePath as the base for
+//     virtual file paths (e.g. a content:// URI). IDs are also based on this.
+//   - fileModTime: if > 0, used as the FileModTime for all results instead of
+//     stat-ing the cuePath on disk (useful when the real file lives behind SAF)
+func ScanCueFileForLibraryExt(cuePath, audioDir, virtualPathPrefix string, fileModTime int64, scanTime string) ([]LibraryScanResult, error) {
+	sheet, err := ParseCueFile(cuePath)
+	if err != nil {
+		return nil, err
+	}
+	audioPath, err := resolveCueAudioPathForLibrary(cuePath, sheet, audioDir)
+	if err != nil {
+		return nil, err
+	}
+	return scanCueSheetForLibrary(cuePath, sheet, audioPath, virtualPathPrefix, fileModTime, scanTime)
+}
+
+func resolveCueAudioPathForLibrary(cuePath string, sheet *CueSheet, audioDir string) (string, error) {
+	if sheet == nil {
+		return "", fmt.Errorf("cue sheet is nil for %s", cuePath)
+	}
+	resolveBase := cuePath
+	if audioDir != "" {
+		resolveBase = filepath.Join(audioDir, filepath.Base(cuePath))
+	}
+	audioPath := ResolveCueAudioPath(resolveBase, sheet.FileName)
+	if audioPath == "" {
+		return "", fmt.Errorf("audio file not found for cue: %s (referenced: %s)", cuePath, sheet.FileName)
+	}
+	return audioPath, nil
+}
+
+func scanCueSheetForLibrary(cuePath string, sheet *CueSheet, audioPath, virtualPathPrefix string, fileModTime int64, scanTime string) ([]LibraryScanResult, error) {
+	if sheet == nil {
+		return nil, fmt.Errorf("cue sheet is nil for %s", cuePath)
+	}
+
+	// Try to get quality info from the audio file
+	var bitDepth, sampleRate int
+	var totalDurationSec float64
+	audioExt := strings.ToLower(filepath.Ext(audioPath))
+	switch audioExt {
+	case ".flac":
+		quality, qErr := GetAudioQuality(audioPath)
+		if qErr == nil {
+			bitDepth = quality.BitDepth
+			sampleRate = quality.SampleRate
+			if quality.SampleRate > 0 && quality.TotalSamples > 0 {
+				totalDurationSec = float64(quality.TotalSamples) / float64(quality.SampleRate)
+			}
+		}
+	case ".mp3":
+		quality, qErr := GetMP3Quality(audioPath)
+		if qErr == nil {
+			sampleRate = quality.SampleRate
+			totalDurationSec = float64(quality.Duration)
+		}
+	}
+
+	// Extract cover from audio file for all tracks
+	var coverPath string
+	libraryCoverCacheMu.RLock()
+	coverCacheDir := libraryCoverCacheDir
+	libraryCoverCacheMu.RUnlock()
+	if coverCacheDir != "" {
+		cp, err := SaveCoverToCache(audioPath, coverCacheDir)
+		if err == nil && cp != "" {
+			coverPath = cp
+		}
+	}
+
+	// Determine the base path for virtual paths and IDs
+	pathBase := cuePath
+	if virtualPathPrefix != "" {
+		pathBase = virtualPathPrefix
+	}
+
+	// Determine fileModTime
+	modTime := fileModTime
+	if modTime <= 0 {
+		if info, err := os.Stat(cuePath); err == nil {
+			modTime = info.ModTime().UnixMilli()
+		}
+	}
+
+	var results []LibraryScanResult
+	for i, track := range sheet.Tracks {
+		performer := track.Performer
+		if performer == "" {
+			performer = sheet.Performer
+		}
+		if performer == "" {
+			performer = "Unknown Artist"
+		}
+
+		title := track.Title
+		if title == "" {
+			title = fmt.Sprintf("Track %02d", track.Number)
+		}
+
+		album := sheet.Title
+		if album == "" {
+			album = "Unknown Album"
+		}
+
+		// Calculate duration for this track
+		var duration int
+		if i+1 < len(sheet.Tracks) {
+			nextStart := sheet.Tracks[i+1].StartTime
+			if sheet.Tracks[i+1].PreGap >= 0 {
+				nextStart = sheet.Tracks[i+1].PreGap
+			}
+			duration = int(nextStart - track.StartTime)
+		} else if totalDurationSec > 0 {
+			duration = int(totalDurationSec - track.StartTime)
+		}
+
+		id := generateLibraryID(fmt.Sprintf("%s#track%d", pathBase, track.Number))
+
+		// Use a virtual file path that includes the track number to ensure
+		// uniqueness in the database (file_path has a UNIQUE constraint).
+		// Format: /path/to/album.cue#track01 or content://...album.cue#track01
+		virtualFilePath := fmt.Sprintf("%s#track%02d", pathBase, track.Number)
+
+		result := LibraryScanResult{
+			ID:          id,
+			TrackName:   title,
+			ArtistName:  performer,
+			AlbumName:   album,
+			AlbumArtist: sheet.Performer,
+			FilePath:    virtualFilePath,
+			CoverPath:   coverPath,
+			ScannedAt:   scanTime,
+			ISRC:        track.ISRC,
+			TrackNumber: track.Number,
+			DiscNumber:  1,
+			Duration:    duration,
+			ReleaseDate: sheet.Date,
+			BitDepth:    bitDepth,
+			SampleRate:  sampleRate,
+			Genre:       sheet.Genre,
+			Format:      "cue+" + strings.TrimPrefix(audioExt, "."),
+		}
+
+		result.FileModTime = modTime
+
+		results = append(results, result)
+	}
+
+	return results, nil
+}

go_backend/deezer_download.go

@@ -0,0 +1,606 @@
+package gobackend
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+const deezerYoinkifyURL = "https://yoinkify.lol/api/download"
+const deezerMusicDLURL = "https://www.musicdl.me/api/download"
+
+type YoinkifyRequest struct {
+	URL         string `json:"url"`
+	Format      string `json:"format"`
+	GenreSource string `json:"genreSource"`
+}
+
+type DeezerDownloadResult struct {
+	FilePath    string
+	BitDepth    int
+	SampleRate  int
+	Title       string
+	Artist      string
+	Album       string
+	ReleaseDate string
+	TrackNumber int
+	DiscNumber  int
+	ISRC        string
+	LyricsLRC   string
+}
+
+func resolveSpotifyURLForYoinkify(req DownloadRequest) (string, error) {
+	rawSpotify := strings.TrimSpace(req.SpotifyID)
+	if rawSpotify != "" {
+		if isLikelySpotifyTrackID(rawSpotify) {
+			return fmt.Sprintf("https://open.spotify.com/track/%s", rawSpotify), nil
+		}
+
+		if parsed, err := parseSpotifyURI(rawSpotify); err == nil && parsed.Type == "track" && parsed.ID != "" {
+			return fmt.Sprintf("https://open.spotify.com/track/%s", parsed.ID), nil
+		}
+	}
+
+	deezerID := strings.TrimSpace(req.DeezerID)
+	if deezerID == "" {
+		if prefixed, found := strings.CutPrefix(rawSpotify, "deezer:"); found {
+			deezerID = strings.TrimSpace(prefixed)
+		}
+	}
+
+	if deezerID != "" {
+		songlink := NewSongLinkClient()
+		spotifyID, err := songlink.GetSpotifyIDFromDeezer(deezerID)
+		if err != nil {
+			return "", fmt.Errorf("failed to map deezer:%s to Spotify ID: %w", deezerID, err)
+		}
+		spotifyID = strings.TrimSpace(spotifyID)
+		if spotifyID == "" {
+			return "", fmt.Errorf("SongLink returned empty Spotify ID for deezer:%s", deezerID)
+		}
+		return fmt.Sprintf("https://open.spotify.com/track/%s", spotifyID), nil
+	}
+
+	return "", fmt.Errorf("missing Spotify track ID for Deezer Yoinkify")
+}
+
+func isLikelySpotifyTrackID(value string) bool {
+	if len(value) != 22 {
+		return false
+	}
+	for _, r := range value {
+		switch {
+		case r >= 'A' && r <= 'Z':
+		case r >= 'a' && r <= 'z':
+		case r >= '0' && r <= '9':
+		default:
+			return false
+		}
+	}
+	return true
+}
+
+func (c *DeezerClient) DownloadFromYoinkify(spotifyURL, outputPath string, outputFD int, itemID string) error {
+	payload := YoinkifyRequest{
+		URL:         spotifyURL,
+		Format:      "flac",
+		GenreSource: "spotify",
+	}
+
+	jsonData, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("failed to encode Yoinkify request: %w", err)
+	}
+
+	ctx := context.Background()
+	if itemID != "" {
+		StartItemProgress(itemID)
+		defer CompleteItemProgress(itemID)
+		ctx = initDownloadCancel(itemID)
+		defer clearDownloadCancel(itemID)
+	}
+
+	if isDownloadCancelled(itemID) {
+		return ErrDownloadCancelled
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, deezerYoinkifyURL, bytes.NewBuffer(jsonData))
+	if err != nil {
+		return fmt.Errorf("failed to create Yoinkify request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Accept", "*/*")
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := GetDownloadClient().Do(req)
+	if err != nil {
+		if isDownloadCancelled(itemID) {
+			return ErrDownloadCancelled
+		}
+		return fmt.Errorf("failed to call Yoinkify: %w", err)
+	}
+	defer resp.Body.Close()
+
+	contentType := strings.ToLower(strings.TrimSpace(resp.Header.Get("Content-Type")))
+	if resp.StatusCode != http.StatusOK {
+		bodyBytes, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
+		bodyText := strings.TrimSpace(string(bodyBytes))
+		if bodyText != "" {
+			return fmt.Errorf("Yoinkify returned status %d: %s", resp.StatusCode, bodyText)
+		}
+		return fmt.Errorf("Yoinkify returned status %d", resp.StatusCode)
+	}
+
+	if strings.Contains(contentType, "application/json") {
+		bodyBytes, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
+		bodyText := strings.TrimSpace(string(bodyBytes))
+		if bodyText == "" {
+			bodyText = "empty JSON payload"
+		}
+		return fmt.Errorf("Yoinkify returned JSON instead of audio: %s", bodyText)
+	}
+
+	expectedSize := resp.ContentLength
+	if expectedSize > 0 && itemID != "" {
+		SetItemBytesTotal(itemID, expectedSize)
+	}
+
+	out, err := openOutputForWrite(outputPath, outputFD)
+	if err != nil {
+		return err
+	}
+
+	bufWriter := bufio.NewWriterSize(out, 256*1024)
+	var written int64
+	if itemID != "" {
+		pw := NewItemProgressWriter(bufWriter, itemID)
+		written, err = io.Copy(pw, resp.Body)
+	} else {
+		written, err = io.Copy(bufWriter, resp.Body)
+	}
+
+	flushErr := bufWriter.Flush()
+	closeErr := out.Close()
+
+	if err != nil {
+		cleanupOutputOnError(outputPath, outputFD)
+		if isDownloadCancelled(itemID) {
+			return ErrDownloadCancelled
+		}
+		return fmt.Errorf("download interrupted: %w", err)
+	}
+	if flushErr != nil {
+		cleanupOutputOnError(outputPath, outputFD)
+		return fmt.Errorf("failed to flush output: %w", flushErr)
+	}
+	if closeErr != nil {
+		cleanupOutputOnError(outputPath, outputFD)
+		return fmt.Errorf("failed to close output: %w", closeErr)
+	}
+
+	if expectedSize > 0 && written != expectedSize {
+		cleanupOutputOnError(outputPath, outputFD)
+		return fmt.Errorf("incomplete download: expected %d bytes, got %d bytes", expectedSize, written)
+	}
+
+	GoLog("[Deezer] Downloaded via Yoinkify: %.2f MB\n", float64(written)/(1024*1024))
+	return nil
+}
+
+func resolveDeezerTrackURL(req DownloadRequest) (string, error) {
+	deezerID := strings.TrimSpace(req.DeezerID)
+	if deezerID == "" {
+		if prefixed, found := strings.CutPrefix(strings.TrimSpace(req.SpotifyID), "deezer:"); found {
+			deezerID = strings.TrimSpace(prefixed)
+		}
+	}
+	if deezerID != "" {
+		trackURL := fmt.Sprintf("https://www.deezer.com/track/%s", deezerID)
+		if err := verifyDeezerTrack(req, deezerID); err != nil {
+			GoLog("[Deezer] Direct ID %s verification failed: %v\n", deezerID, err)
+			// Don't reject direct IDs from request payload — they're presumably correct.
+		}
+		return trackURL, nil
+	}
+
+	// Try SongLink
+	spotifyID := strings.TrimSpace(req.SpotifyID)
+	if spotifyID != "" && isLikelySpotifyTrackID(spotifyID) {
+		songlink := NewSongLinkClient()
+		availability, err := songlink.CheckTrackAvailability(spotifyID, "")
+		if err == nil && availability.Deezer && availability.DeezerURL != "" {
+			resolvedID := extractDeezerIDFromURL(availability.DeezerURL)
+			if resolvedID != "" {
+				if verifyErr := verifyDeezerTrack(req, resolvedID); verifyErr != nil {
+					GoLog("[Deezer] SongLink ID %s rejected: %v\n", resolvedID, verifyErr)
+					// Fall through to ISRC search instead of using wrong track.
+				} else {
+					return availability.DeezerURL, nil
+				}
+			} else {
+				return availability.DeezerURL, nil
+			}
+		}
+	}
+
+	// Try ISRC
+	isrc := strings.TrimSpace(req.ISRC)
+	if isrc != "" {
+		ctx, cancel := context.WithTimeout(context.Background(), SongLinkTimeout)
+		defer cancel()
+		track, err := GetDeezerClient().SearchByISRC(ctx, isrc)
+		if err == nil && track != nil {
+			resolvedID := songLinkExtractDeezerTrackID(track)
+			if resolvedID != "" {
+				if verifyErr := verifyDeezerTrack(req, resolvedID); verifyErr != nil {
+					GoLog("[Deezer] ISRC-resolved ID %s rejected: %v\n", resolvedID, verifyErr)
+					return "", fmt.Errorf("deezer track resolved via ISRC does not match: %w", verifyErr)
+				}
+				return fmt.Sprintf("https://www.deezer.com/track/%s", resolvedID), nil
+			}
+		}
+	}
+
+	return "", fmt.Errorf("could not resolve Deezer track URL")
+}
+
+func verifyDeezerTrack(req DownloadRequest, deezerID string) error {
+	ctx, cancel := context.WithTimeout(context.Background(), SongLinkTimeout)
+	defer cancel()
+	trackResp, err := GetDeezerClient().GetTrack(ctx, deezerID)
+	if err != nil {
+		return nil // Can't verify — don't block the download.
+	}
+	resolved := resolvedTrackInfo{
+		Title:      trackResp.Track.Name,
+		ArtistName: trackResp.Track.Artists,
+		Duration:   trackResp.Track.DurationMS / 1000,
+	}
+	if !trackMatchesRequest(req, resolved, "Deezer") {
+		return fmt.Errorf("expected '%s - %s', got '%s - %s'",
+			req.ArtistName, req.TrackName, resolved.ArtistName, resolved.Title)
+	}
+	GoLog("[Deezer] Track %s verified: '%s - %s' ✓\n", deezerID, resolved.ArtistName, resolved.Title)
+	return nil
+}
+
+type deezerMusicDLRequest struct {
+	Platform string `json:"platform"`
+	URL      string `json:"url"`
+}
+
+func (c *DeezerClient) GetMusicDLDownloadURL(deezerTrackURL string) (string, error) {
+	payload := deezerMusicDLRequest{
+		Platform: "deezer",
+		URL:      deezerTrackURL,
+	}
+	jsonData, err := json.Marshal(payload)
+	if err != nil {
+		return "", fmt.Errorf("failed to encode MusicDL request: %w", err)
+	}
+
+	req, err := http.NewRequest(http.MethodPost, deezerMusicDLURL, bytes.NewReader(jsonData))
+	if err != nil {
+		return "", fmt.Errorf("failed to create MusicDL request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-Debug-Key", getQobuzDebugKey())
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("MusicDL request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 64*1024))
+	if err != nil {
+		return "", fmt.Errorf("failed to read MusicDL response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("MusicDL returned HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(body)))
+	}
+
+	var raw map[string]any
+	if err := json.Unmarshal(body, &raw); err != nil {
+		return "", fmt.Errorf("invalid MusicDL JSON: %w", err)
+	}
+
+	if errMsg, ok := raw["error"].(string); ok && strings.TrimSpace(errMsg) != "" {
+		return "", fmt.Errorf("MusicDL error: %s", errMsg)
+	}
+
+	// Try various response fields for download URL
+	for _, key := range []string{"download_url", "url", "link"} {
+		if urlVal, ok := raw[key].(string); ok && strings.TrimSpace(urlVal) != "" {
+			return strings.TrimSpace(urlVal), nil
+		}
+	}
+	if data, ok := raw["data"].(map[string]any); ok {
+		for _, key := range []string{"download_url", "url", "link"} {
+			if urlVal, ok := data[key].(string); ok && strings.TrimSpace(urlVal) != "" {
+				return strings.TrimSpace(urlVal), nil
+			}
+		}
+	}
+
+	return "", fmt.Errorf("no download URL found in MusicDL response")
+}
+
+func (c *DeezerClient) DownloadFromMusicDL(deezerTrackURL, outputPath string, outputFD int, itemID string) error {
+	GoLog("[Deezer] Resolving download URL via MusicDL for: %s\n", deezerTrackURL)
+
+	downloadURL, err := c.GetMusicDLDownloadURL(deezerTrackURL)
+	if err != nil {
+		return err
+	}
+	GoLog("[Deezer] MusicDL returned download URL, starting download...\n")
+
+	ctx := context.Background()
+	if itemID != "" {
+		StartItemProgress(itemID)
+		defer CompleteItemProgress(itemID)
+		ctx = initDownloadCancel(itemID)
+		defer clearDownloadCancel(itemID)
+	}
+
+	if isDownloadCancelled(itemID) {
+		return ErrDownloadCancelled
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "GET", downloadURL, nil)
+	if err != nil {
+		return fmt.Errorf("failed to create download request: %w", err)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := GetDownloadClient().Do(req)
+	if err != nil {
+		if isDownloadCancelled(itemID) {
+			return ErrDownloadCancelled
+		}
+		return fmt.Errorf("download request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("download returned HTTP %d", resp.StatusCode)
+	}
+
+	expectedSize := resp.ContentLength
+	if expectedSize > 0 && itemID != "" {
+		SetItemBytesTotal(itemID, expectedSize)
+	}
+
+	out, err := openOutputForWrite(outputPath, outputFD)
+	if err != nil {
+		return err
+	}
+
+	bufWriter := bufio.NewWriterSize(out, 256*1024)
+	var written int64
+	if itemID != "" {
+		pw := NewItemProgressWriter(bufWriter, itemID)
+		written, err = io.Copy(pw, resp.Body)
+	} else {
+		written, err = io.Copy(bufWriter, resp.Body)
+	}
+
+	flushErr := bufWriter.Flush()
+	closeErr := out.Close()
+
+	if err != nil {
+		cleanupOutputOnError(outputPath, outputFD)
+		if isDownloadCancelled(itemID) {
+			return ErrDownloadCancelled
+		}
+		return fmt.Errorf("download interrupted: %w", err)
+	}
+	if flushErr != nil {
+		cleanupOutputOnError(outputPath, outputFD)
+		return fmt.Errorf("failed to flush output: %w", flushErr)
+	}
+	if closeErr != nil {
+		cleanupOutputOnError(outputPath, outputFD)
+		return fmt.Errorf("failed to close output: %w", closeErr)
+	}
+
+	if expectedSize > 0 && written != expectedSize {
+		cleanupOutputOnError(outputPath, outputFD)
+		return fmt.Errorf("incomplete download: expected %d bytes, got %d bytes", expectedSize, written)
+	}
+
+	GoLog("[Deezer] Downloaded via MusicDL: %.2f MB\n", float64(written)/(1024*1024))
+	return nil
+}
+
+func downloadFromDeezer(req DownloadRequest) (DeezerDownloadResult, error) {
+	deezerClient := GetDeezerClient()
+	isSafOutput := isFDOutput(req.OutputFD) || strings.TrimSpace(req.OutputPath) != ""
+
+	if !isSafOutput {
+		if existingFile, exists := checkISRCExistsInternal(req.OutputDir, req.ISRC); exists {
+			return DeezerDownloadResult{FilePath: "EXISTS:" + existingFile}, nil
+		}
+	}
+
+	filename := buildFilenameFromTemplate(req.FilenameFormat, map[string]interface{}{
+		"title":  req.TrackName,
+		"artist": req.ArtistName,
+		"album":  req.AlbumName,
+		"track":  req.TrackNumber,
+		"year":   extractYear(req.ReleaseDate),
+		"date":   req.ReleaseDate,
+		"disc":   req.DiscNumber,
+	})
+
+	var outputPath string
+	if isSafOutput {
+		outputPath = strings.TrimSpace(req.OutputPath)
+		if outputPath == "" && isFDOutput(req.OutputFD) {
+			outputPath = fmt.Sprintf("/proc/self/fd/%d", req.OutputFD)
+		}
+	} else {
+		filename = sanitizeFilename(filename) + ".flac"
+		outputPath = filepath.Join(req.OutputDir, filename)
+		if fileInfo, statErr := os.Stat(outputPath); statErr == nil && fileInfo.Size() > 0 {
+			return DeezerDownloadResult{FilePath: "EXISTS:" + outputPath}, nil
+		}
+	}
+
+	var parallelResult *ParallelDownloadResult
+	parallelDone := make(chan struct{})
+	go func() {
+		defer close(parallelDone)
+		coverURL := req.CoverURL
+		embedLyrics := req.EmbedLyrics
+		if !req.EmbedMetadata {
+			coverURL = ""
+			embedLyrics = false
+		}
+		parallelResult = FetchCoverAndLyricsParallel(
+			coverURL,
+			req.EmbedMaxQualityCover,
+			req.SpotifyID,
+			req.TrackName,
+			req.ArtistName,
+			embedLyrics,
+			int64(req.DurationMS),
+		)
+	}()
+
+	// Try MusicDL first (better quality), fallback to Yoinkify
+	var downloadErr error
+	deezerTrackURL, deezerURLErr := resolveDeezerTrackURL(req)
+	if deezerURLErr == nil {
+		GoLog("[Deezer] Trying MusicDL for: %s\n", deezerTrackURL)
+		downloadErr = deezerClient.DownloadFromMusicDL(deezerTrackURL, outputPath, req.OutputFD, req.ItemID)
+		if downloadErr != nil {
+			if errors.Is(downloadErr, ErrDownloadCancelled) {
+				return DeezerDownloadResult{}, ErrDownloadCancelled
+			}
+			GoLog("[Deezer] MusicDL failed: %v, falling back to Yoinkify\n", downloadErr)
+		}
+	} else {
+		GoLog("[Deezer] Could not resolve Deezer URL: %v, using Yoinkify directly\n", deezerURLErr)
+	}
+
+	if downloadErr != nil || deezerURLErr != nil {
+		spotifyURL, err := resolveSpotifyURLForYoinkify(req)
+		if err != nil {
+			if deezerURLErr != nil {
+				return DeezerDownloadResult{}, fmt.Errorf(
+					"deezer download failed: direct Deezer resolution error: %v; Yoinkify fallback error: %w",
+					deezerURLErr,
+					err,
+				)
+			}
+			return DeezerDownloadResult{}, err
+		}
+		downloadErr = deezerClient.DownloadFromYoinkify(spotifyURL, outputPath, req.OutputFD, req.ItemID)
+		if downloadErr != nil {
+			if errors.Is(downloadErr, ErrDownloadCancelled) {
+				return DeezerDownloadResult{}, ErrDownloadCancelled
+			}
+			return DeezerDownloadResult{}, fmt.Errorf("deezer download failed (MusicDL + Yoinkify): %w", downloadErr)
+		}
+	}
+
+	<-parallelDone
+
+	if req.ItemID != "" {
+		SetItemProgress(req.ItemID, 1.0, 0, 0)
+		SetItemFinalizing(req.ItemID)
+	}
+
+	metadata := Metadata{
+		Title:       req.TrackName,
+		Artist:      req.ArtistName,
+		Album:       req.AlbumName,
+		AlbumArtist: req.AlbumArtist,
+		Date:        req.ReleaseDate,
+		TrackNumber: req.TrackNumber,
+		TotalTracks: req.TotalTracks,
+		DiscNumber:  req.DiscNumber,
+		ISRC:        req.ISRC,
+		Genre:       req.Genre,
+		Label:       req.Label,
+		Copyright:   req.Copyright,
+	}
+
+	var coverData []byte
+	if parallelResult != nil && parallelResult.CoverData != nil {
+		coverData = parallelResult.CoverData
+	}
+
+	if isSafOutput || !req.EmbedMetadata {
+		if !req.EmbedMetadata {
+			GoLog("[Deezer] Metadata embedding disabled by settings, skipping in-backend metadata/lyrics embedding\n")
+		} else {
+			GoLog("[Deezer] SAF output detected - skipping in-backend metadata/lyrics embedding (handled in Flutter)\n")
+		}
+	} else {
+		if err := EmbedMetadataWithCoverData(outputPath, metadata, coverData); err != nil {
+			GoLog("[Deezer] Warning: failed to embed metadata: %v\n", err)
+		}
+
+		if req.EmbedLyrics && parallelResult != nil && parallelResult.LyricsLRC != "" {
+			lyricsMode := req.LyricsMode
+			if lyricsMode == "" {
+				lyricsMode = "embed"
+			}
+
+			if lyricsMode == "external" || lyricsMode == "both" {
+				if lrcPath, lrcErr := SaveLRCFile(outputPath, parallelResult.LyricsLRC); lrcErr != nil {
+					GoLog("[Deezer] Warning: failed to save LRC file: %v\n", lrcErr)
+				} else {
+					GoLog("[Deezer] LRC file saved: %s\n", lrcPath)
+				}
+			}
+
+			if lyricsMode == "embed" || lyricsMode == "both" {
+				if embedErr := EmbedLyrics(outputPath, parallelResult.LyricsLRC); embedErr != nil {
+					GoLog("[Deezer] Warning: failed to embed lyrics: %v\n", embedErr)
+				}
+			}
+		}
+	}
+
+	if !isSafOutput {
+		AddToISRCIndex(req.OutputDir, req.ISRC, outputPath)
+	}
+
+	bitDepth, sampleRate := 0, 0
+	if quality, qErr := GetAudioQuality(outputPath); qErr == nil {
+		bitDepth = quality.BitDepth
+		sampleRate = quality.SampleRate
+	}
+
+	lyricsLRC := ""
+	if req.EmbedMetadata && req.EmbedLyrics && parallelResult != nil && parallelResult.LyricsLRC != "" {
+		lyricsLRC = parallelResult.LyricsLRC
+	}
+
+	return DeezerDownloadResult{
+		FilePath:    outputPath,
+		BitDepth:    bitDepth,
+		SampleRate:  sampleRate,
+		Title:       req.TrackName,
+		Artist:      req.ArtistName,
+		Album:       req.AlbumName,
+		ReleaseDate: req.ReleaseDate,
+		TrackNumber: req.TrackNumber,
+		DiscNumber:  req.DiscNumber,
+		ISRC:        req.ISRC,
+		LyricsLRC:   lyricsLRC,
+	}, nil
+}

go_backend/duplicate.go

@@ -10,7 +10,6 @@ import (
 	"time"
 )
 
-// ISRCIndex holds a cached map of ISRC -> file path for fast duplicate checking
 type ISRCIndex struct {
 	index     map[string]string // ISRC (uppercase) -> file path
 	outputDir string
@@ -25,8 +24,6 @@ var (
 	isrcIndexTTL     = 5 * time.Minute
 )
 
-// GetISRCIndex returns or builds an ISRC index for the given directory
-// Uses per-directory mutex to prevent concurrent builds (race condition fix)
 func GetISRCIndex(outputDir string) *ISRCIndex {
 	// Fast path: check cache first
 	isrcIndexCacheMu.RLock()
@@ -37,7 +34,6 @@ func GetISRCIndex(outputDir string) *ISRCIndex {
 		return idx
 	}
 
-	// Slow path: need to build index
 	// Use per-directory mutex to prevent multiple goroutines from building simultaneously
 	buildLock, _ := isrcBuildingMu.LoadOrStore(outputDir, &sync.Mutex{})
 	mu := buildLock.(*sync.Mutex)
@@ -56,7 +52,6 @@ func GetISRCIndex(outputDir string) *ISRCIndex {
 	return buildISRCIndex(outputDir)
 }
 
-// buildISRCIndex scans a directory and builds a map of ISRC -> file path
 func buildISRCIndex(outputDir string) *ISRCIndex {
 	idx := &ISRCIndex{
 		index:     make(map[string]string),
@@ -91,7 +86,7 @@ func buildISRCIndex(outputDir string) *ISRCIndex {
 		return nil
 	})
 
-	fmt.Printf("[ISRCIndex] Built index for %s: %d files in %v\n", 
+	fmt.Printf("[ISRCIndex] Built index for %s: %d files in %v\n",
 		outputDir, fileCount, time.Since(startTime).Round(time.Millisecond))
 
 	isrcIndexCacheMu.Lock()
@@ -113,7 +108,6 @@ func (idx *ISRCIndex) lookup(isrc string) (string, bool) {
 	return path, exists
 }
 
-// remove deletes an ISRC entry from the index (internal use)
 func (idx *ISRCIndex) remove(isrc string) {
 	if isrc == "" {
 		return
@@ -125,14 +119,11 @@ func (idx *ISRCIndex) remove(isrc string) {
 	delete(idx.index, strings.ToUpper(isrc))
 }
 
-// Lookup checks if an ISRC exists in the index (gomobile compatible)
-// Returns filepath if found, empty string if not found
 func (idx *ISRCIndex) Lookup(isrc string) (string, error) {
 	path, _ := idx.lookup(isrc)
 	return path, nil
 }
 
-// Add adds a new ISRC to the index (call after successful download)
 func (idx *ISRCIndex) Add(isrc, filePath string) {
 	if isrc == "" || filePath == "" {
 		return
@@ -144,21 +135,17 @@ func (idx *ISRCIndex) Add(isrc, filePath string) {
 	idx.index[strings.ToUpper(isrc)] = filePath
 }
 
-// InvalidateCache clears the ISRC index cache for a directory
 func InvalidateISRCCache(outputDir string) {
 	isrcIndexCacheMu.Lock()
 	delete(isrcIndexCache, outputDir)
 	isrcIndexCacheMu.Unlock()
 }
 
-// checkISRCExistsInternal checks if a file with the given ISRC exists (internal use)
-// Uses ISRC index for fast lookup
 func checkISRCExistsInternal(outputDir, isrc string) (string, bool) {
 	if isrc == "" || outputDir == "" {
 		return "", false
 	}
 
-	// Use index for fast lookup
 	idx := GetISRCIndex(outputDir)
 	filePath, exists := idx.lookup(isrc)
 	if !exists {
@@ -174,14 +161,11 @@ func checkISRCExistsInternal(outputDir, isrc string) (string, bool) {
 	return filePath, true
 }
 
-// CheckISRCExists is the exported version for gomobile (returns string, error)
-// Returns the filepath if exists, empty string if not
 func CheckISRCExists(outputDir, isrc string) (string, error) {
 	filepath, _ := checkISRCExistsInternal(outputDir, isrc)
 	return filepath, nil
 }
 
-// CheckFileExists checks if a file with the given name exists
 func CheckFileExists(filePath string) bool {
 	info, err := os.Stat(filePath)
 	if err != nil {
@@ -190,7 +174,6 @@ func CheckFileExists(filePath string) bool {
 	return !info.IsDir() && info.Size() > 0
 }
 
-// FileExistenceResult represents the result of checking if a file exists
 type FileExistenceResult struct {
 	ISRC       string `json:"isrc"`
 	Exists     bool   `json:"exists"`
@@ -199,9 +182,6 @@ type FileExistenceResult struct {
 	ArtistName string `json:"artist_name,omitempty"`
 }
 
-// CheckFilesExistParallel checks if multiple files exist in parallel
-// It builds an ISRC index from the output directory once, then checks all tracks against it
-// Same implementation as PC version for consistency
 func CheckFilesExistParallel(outputDir string, tracksJSON string) (string, error) {
 	var tracks []struct {
 		ISRC       string `json:"isrc"`
@@ -254,8 +234,6 @@ func CheckFilesExistParallel(outputDir string, tracksJSON string) (string, error
 	return string(resultJSON), nil
 }
 
-// PreBuildISRCIndex pre-builds the ISRC index for a directory
-// Call this when app starts or when entering album/playlist screen
 func PreBuildISRCIndex(outputDir string) error {
 	if outputDir == "" {
 		return fmt.Errorf("output directory is required")
@@ -265,8 +243,6 @@ func PreBuildISRCIndex(outputDir string) error {
 	return nil
 }
 
-// AddToISRCIndex adds a new file to the ISRC index after successful download
-// This avoids rebuilding the entire index
 func AddToISRCIndex(outputDir, isrc, filePath string) {
 	if outputDir == "" || isrc == "" || filePath == "" {
 		return

go_backend/exports_deezer_metadata_test.go

@@ -0,0 +1,59 @@
+package gobackend
+
+import "testing"
+
+func TestBuildDeezerExtendedMetadataResultHandlesNil(t *testing.T) {
+	result := buildDeezerExtendedMetadataResult(nil)
+
+	if result["genre"] != "" {
+		t.Fatalf("expected empty genre, got %q", result["genre"])
+	}
+	if result["label"] != "" {
+		t.Fatalf("expected empty label, got %q", result["label"])
+	}
+	if result["copyright"] != "" {
+		t.Fatalf("expected empty copyright, got %q", result["copyright"])
+	}
+}
+
+func TestBuildDeezerExtendedMetadataResultIncludesCopyright(t *testing.T) {
+	result := buildDeezerExtendedMetadataResult(&AlbumExtendedMetadata{
+		Genre:     "Rock",
+		Label:     "EMI",
+		Copyright: "(C) Queen",
+	})
+
+	if result["genre"] != "Rock" {
+		t.Fatalf("unexpected genre: %q", result["genre"])
+	}
+	if result["label"] != "EMI" {
+		t.Fatalf("unexpected label: %q", result["label"])
+	}
+	if result["copyright"] != "(C) Queen" {
+		t.Fatalf("unexpected copyright: %q", result["copyright"])
+	}
+}
+
+func TestBuildDeezerISRCSearchResultAddsCompatibilityIDs(t *testing.T) {
+	result := buildDeezerISRCSearchResult(&TrackMetadata{
+		SpotifyID:   "deezer:3135556",
+		Name:        "Love Of My Life",
+		Artists:     "Queen",
+		AlbumName:   "A Night at the Opera",
+		ISRC:        "GBUM71029604",
+		ReleaseDate: "1975-11-21",
+	})
+
+	if result["spotify_id"] != "deezer:3135556" {
+		t.Fatalf("unexpected spotify_id: %v", result["spotify_id"])
+	}
+	if result["id"] != "3135556" {
+		t.Fatalf("unexpected id: %v", result["id"])
+	}
+	if result["track_id"] != "3135556" {
+		t.Fatalf("unexpected track_id: %v", result["track_id"])
+	}
+	if result["success"] != true {
+		t.Fatalf("expected success=true, got %v", result["success"])
+	}
+}

go_backend/exports_test.go

@@ -0,0 +1,86 @@
+package gobackend
+
+import "testing"
+
+func TestBuildDownloadSuccessResponsePrefersRequestedAlbumMetadata(t *testing.T) {
+	req := DownloadRequest{
+		TrackName:   "Bonus Track",
+		ArtistName:  "Artist",
+		AlbumName:   "Album (Deluxe)",
+		AlbumArtist: "Artist",
+		ReleaseDate: "2024-01-01",
+		TrackNumber: 14,
+		DiscNumber:  1,
+		ISRC:        "REQ123",
+		CoverURL:    "https://example.com/cover.jpg",
+		Genre:       "Pop",
+		Label:       "Label",
+		Copyright:   "Copyright",
+	}
+
+	result := DownloadResult{
+		Title:       "Bonus Track",
+		Artist:      "Artist",
+		Album:       "Album",
+		ReleaseDate: "2023-12-01",
+		TrackNumber: 2,
+		DiscNumber:  9,
+		ISRC:        "RES456",
+	}
+
+	resp := buildDownloadSuccessResponse(
+		req,
+		result,
+		"tidal",
+		"ok",
+		"/tmp/test.flac",
+		false,
+	)
+
+	if resp.Album != req.AlbumName {
+		t.Fatalf("album = %q, want %q", resp.Album, req.AlbumName)
+	}
+	if resp.ReleaseDate != req.ReleaseDate {
+		t.Fatalf("release date = %q, want %q", resp.ReleaseDate, req.ReleaseDate)
+	}
+	if resp.TrackNumber != req.TrackNumber {
+		t.Fatalf("track number = %d, want %d", resp.TrackNumber, req.TrackNumber)
+	}
+	if resp.DiscNumber != req.DiscNumber {
+		t.Fatalf("disc number = %d, want %d", resp.DiscNumber, req.DiscNumber)
+	}
+	if resp.Artist != result.Artist {
+		t.Fatalf("artist = %q, want provider artist %q", resp.Artist, result.Artist)
+	}
+	if resp.ISRC != result.ISRC {
+		t.Fatalf("isrc = %q, want provider isrc %q", resp.ISRC, result.ISRC)
+	}
+}
+
+func TestPreferredReleaseMetadataPrefersRequestValues(t *testing.T) {
+	album, releaseDate, trackNumber, discNumber := preferredReleaseMetadata(
+		DownloadRequest{
+			AlbumName:   "Album (Deluxe Edition)",
+			ReleaseDate: "2024-01-01",
+			TrackNumber: 13,
+			DiscNumber:  2,
+		},
+		"Album",
+		"2023-01-01",
+		3,
+		1,
+	)
+
+	if album != "Album (Deluxe Edition)" {
+		t.Fatalf("album = %q", album)
+	}
+	if releaseDate != "2024-01-01" {
+		t.Fatalf("release date = %q", releaseDate)
+	}
+	if trackNumber != 13 {
+		t.Fatalf("track number = %d", trackNumber)
+	}
+	if discNumber != 2 {
+		t.Fatalf("disc number = %d", discNumber)
+	}
+}

go_backend/extension_manager.go

@@ -1,4 +1,3 @@
-// Package gobackend provides extension management functionality
 package gobackend
 
 import (
@@ -15,8 +14,6 @@ import (
 	"github.com/dop251/goja"
 )
 
-// compareVersions compares two semantic version strings
-// Returns: -1 if v1 < v2, 0 if v1 == v2, 1 if v1 > v2
 func compareVersions(v1, v2 string) int {
 	parts1 := strings.Split(strings.TrimPrefix(v1, "v"), ".")
 	parts2 := strings.Split(strings.TrimPrefix(v2, "v"), ".")
@@ -46,24 +43,24 @@ func compareVersions(v1, v2 string) int {
 	return 0
 }
 
-// LoadedExtension represents an extension that has been loaded into memory
 type LoadedExtension struct {
 	ID        string             `json:"id"`
 	Manifest  *ExtensionManifest `json:"manifest"`
 	VM        *goja.Runtime      `json:"-"`
-	Enabled   bool               `json:"enabled"`
-	Error     string             `json:"error,omitempty"`
-	DataDir   string             `json:"data_dir"`
-	SourceDir string             `json:"source_dir"`
-	IconPath  string             `json:"icon_path"`
+	VMMu      sync.Mutex         `json:"-"`
+	runtime   *ExtensionRuntime
+	Enabled   bool   `json:"enabled"`
+	Error     string `json:"error,omitempty"`
+	DataDir   string `json:"data_dir"`
+	SourceDir string `json:"source_dir"`
+	IconPath  string `json:"icon_path"`
 }
 
-// ExtensionManager manages all loaded extensions
 type ExtensionManager struct {
 	mu            sync.RWMutex
 	extensions    map[string]*LoadedExtension
-	extensionsDir string // Base directory for extensions
-	dataDir       string // Base directory for extension data
+	extensionsDir string
+	dataDir       string
 }
 
 var (
@@ -71,7 +68,6 @@ var (
 	globalExtManagerOnce sync.Once
 )
 
-// GetExtensionManager returns the global extension manager instance
 func GetExtensionManager() *ExtensionManager {
 	globalExtManagerOnce.Do(func() {
 		globalExtManager = &ExtensionManager{
@@ -81,7 +77,6 @@ func GetExtensionManager() *ExtensionManager {
 	return globalExtManager
 }
 
-// SetDirectories sets the extensions and data directories
 func (m *ExtensionManager) SetDirectories(extensionsDir, dataDir string) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -99,14 +94,11 @@ func (m *ExtensionManager) SetDirectories(extensionsDir, dataDir string) error {
 	return nil
 }
 
-// LoadExtensionFromFile loads an extension from a .spotiflac-ext file
 func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtension, error) {
-	// Validate file extension
 	if !strings.HasSuffix(strings.ToLower(filePath), ".spotiflac-ext") {
 		return nil, fmt.Errorf("Invalid file format. Please select a .spotiflac-ext file")
 	}
 
-	// Open the zip file
 	zipReader, err := zip.OpenReader(filePath)
 	if err != nil {
 		return nil, fmt.Errorf("Cannot open extension file. The file may be corrupted or not a valid extension package")
@@ -159,7 +151,6 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 	if exists {
 		versionCompare := compareVersions(manifest.Version, existingVersion)
 		if versionCompare > 0 {
-			// This is an upgrade - call UpgradeExtension
 			return m.UpgradeExtension(filePath)
 		} else if versionCompare == 0 {
 			return nil, fmt.Errorf("Extension '%s' v%s is already installed", existingDisplayName, existingVersion)
@@ -180,14 +171,11 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 		return nil, fmt.Errorf("failed to create extension directory: %w", err)
 	}
 
-	// Extract all files (preserving directory structure)
 	for _, file := range zipReader.File {
 		if file.FileInfo().IsDir() {
 			continue
 		}
 
-		// Preserve relative path within the zip (support subdirectories)
-		// Clean the path to prevent path traversal attacks
 		relPath := filepath.Clean(file.Name)
 		if strings.HasPrefix(relPath, "..") || filepath.IsAbs(relPath) {
 			GoLog("[Extension] Skipping unsafe path in archive: %s\n", file.Name)
@@ -232,7 +220,6 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 		SourceDir: extDir,
 	}
 
-	// Initialize Goja VM
 	if err := m.initializeVM(ext); err != nil {
 		ext.Error = err.Error()
 		ext.Enabled = false
@@ -245,7 +232,6 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 	return ext, nil
 }
 
-// initializeVM creates and initializes the Goja VM for an extension
 func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
 	vm := goja.New()
 	ext.VM = vm
@@ -257,6 +243,7 @@ func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
 	}
 
 	runtime := NewExtensionRuntime(ext)
+	ext.runtime = runtime
 	runtime.RegisterAPIs(vm)
 	runtime.RegisterGoBackendAPIs(vm)
 
@@ -280,13 +267,11 @@ func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
 		return goja.Undefined()
 	})
 
-	// Run the extension code
 	_, err = vm.RunString(string(jsCode))
 	if err != nil {
 		return fmt.Errorf("failed to execute extension code: %w", err)
 	}
 
-	// Verify extension was registered
 	if registeredExtension == nil || goja.IsUndefined(registeredExtension) {
 		return fmt.Errorf("extension did not call registerExtension()")
 	}
@@ -294,7 +279,6 @@ func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
 	return nil
 }
 
-// UnloadExtension unloads an extension by ID
 func (m *ExtensionManager) UnloadExtension(extensionID string) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -304,9 +288,7 @@ func (m *ExtensionManager) UnloadExtension(extensionID string) error {
 		return fmt.Errorf("Extension not found")
 	}
 
-	// Call cleanup if VM is initialized
 	if ext.VM != nil {
-		// Try to call cleanup function
 		cleanup, err := ext.VM.RunString("typeof extension !== 'undefined' && typeof extension.cleanup === 'function' ? extension.cleanup() : null")
 		if err != nil {
 			GoLog("[Extension] Error calling cleanup for %s: %v\n", extensionID, err)
@@ -314,16 +296,20 @@ func (m *ExtensionManager) UnloadExtension(extensionID string) error {
 			GoLog("[Extension] Cleanup called for %s\n", extensionID)
 		}
 	}
+	if ext.runtime != nil {
+		if err := ext.runtime.flushStorageNow(); err != nil {
+			GoLog("[Extension] Failed to flush storage for %s: %v\n", extensionID, err)
+		}
+		ext.runtime.closeStorageFlusher()
+		ext.runtime = nil
+	}
 
-	// Remove from registry
 	delete(m.extensions, extensionID)
 	GoLog("[Extension] Unloaded extension: %s\n", extensionID)
 
 	return nil
 }
 
-// GetExtension returns a loaded extension by ID
-// Returns error if extension not found (gomobile compatible)
 func (m *ExtensionManager) GetExtension(extensionID string) (*LoadedExtension, error) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
@@ -335,7 +321,6 @@ func (m *ExtensionManager) GetExtension(extensionID string) (*LoadedExtension, e
 	return ext, nil
 }
 
-// GetAllExtensions returns all loaded extensions
 func (m *ExtensionManager) GetAllExtensions() []*LoadedExtension {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
@@ -347,7 +332,6 @@ func (m *ExtensionManager) GetAllExtensions() []*LoadedExtension {
 	return result
 }
 
-// SetExtensionEnabled enables or disables an extension
 func (m *ExtensionManager) SetExtensionEnabled(extensionID string, enabled bool) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -360,7 +344,6 @@ func (m *ExtensionManager) SetExtensionEnabled(extensionID string, enabled bool)
 	ext.Enabled = enabled
 	GoLog("[Extension] %s %s\n", extensionID, map[bool]string{true: "enabled", false: "disabled"}[enabled])
 
-	// Persist enabled state to settings store
 	store := GetExtensionSettingsStore()
 	if err := store.Set(extensionID, "_enabled", enabled); err != nil {
 		GoLog("[Extension] Failed to persist enabled state for %s: %v\n", extensionID, err)
@@ -369,7 +352,6 @@ func (m *ExtensionManager) SetExtensionEnabled(extensionID string, enabled bool)
 	return nil
 }
 
-// LoadExtensionsFromDirectory scans a directory and loads all valid extensions
 func (m *ExtensionManager) LoadExtensionsFromDirectory(dirPath string) ([]string, []error) {
 	var loaded []string
 	var errors []error
@@ -408,7 +390,6 @@ func (m *ExtensionManager) LoadExtensionsFromDirectory(dirPath string) ([]string
 	return loaded, errors
 }
 
-// loadExtensionFromDirectory loads an extension from an already extracted directory
 func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedExtension, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -419,7 +400,6 @@ func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedEx
 		return nil, fmt.Errorf("failed to read manifest.json: %w", err)
 	}
 
-	// Parse and validate manifest
 	manifest, err := ParseManifest(manifestData)
 	if err != nil {
 		return nil, fmt.Errorf("Invalid extension manifest: %w", err)
@@ -448,7 +428,6 @@ func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedEx
 		SourceDir: dirPath,
 	}
 
-	// Restore enabled state from settings store
 	store := GetExtensionSettingsStore()
 	if enabledVal, err := store.Get(manifest.Name, "_enabled"); err == nil {
 		if enabled, ok := enabledVal.(bool); ok {
@@ -457,7 +436,6 @@ func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedEx
 		}
 	}
 
-	// Initialize Goja VM
 	if err := m.initializeVM(ext); err != nil {
 		ext.Error = err.Error()
 		ext.Enabled = false
@@ -470,42 +448,31 @@ func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedEx
 	return ext, nil
 }
 
-// RemoveExtension completely removes an extension (unload + delete files)
 func (m *ExtensionManager) RemoveExtension(extensionID string) error {
 	ext, err := m.GetExtension(extensionID)
 	if err != nil {
 		return err
 	}
 
-	// Unload first
 	if err := m.UnloadExtension(extensionID); err != nil {
 		return err
 	}
 
-	// Remove source directory
 	if ext.SourceDir != "" {
 		if err := os.RemoveAll(ext.SourceDir); err != nil {
 			GoLog("[Extension] Warning: failed to remove source dir: %v\n", err)
 		}
 	}
 
-	// Optionally remove data directory (keep for now to preserve settings)
-	// if ext.DataDir != "" {
-	//     os.RemoveAll(ext.DataDir)
-	// }
-
 	return nil
 }
 
-// UpgradeExtension upgrades an existing extension from a new package file
 // Only allows upgrades (new version > current version), not downgrades
 func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension, error) {
-	// Validate file extension
 	if !strings.HasSuffix(strings.ToLower(filePath), ".spotiflac-ext") {
 		return nil, fmt.Errorf("Invalid file format. Please select a .spotiflac-ext file")
 	}
 
-	// Open the zip file
 	zipReader, err := zip.OpenReader(filePath)
 	if err != nil {
 		return nil, fmt.Errorf("Cannot open extension file. The file may be corrupted or not a valid extension package")
@@ -553,7 +520,6 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 		return nil, fmt.Errorf("Extension '%s' is not installed. Use install instead of upgrade.", newManifest.DisplayName)
 	}
 
-	// Compare versions - only allow upgrade, not downgrade
 	versionCompare := compareVersions(newManifest.Version, existing.Manifest.Version)
 	if versionCompare < 0 {
 		return nil, fmt.Errorf("Cannot downgrade extension. Current version: %s, New version: %s", existing.Manifest.Version, newManifest.Version)
@@ -564,16 +530,12 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 
 	GoLog("[Extension] Upgrading %s from v%s to v%s\n", newManifest.DisplayName, existing.Manifest.Version, newManifest.Version)
 
-	// Save data directory path and enabled state (we want to preserve them)
 	extDataDir := existing.DataDir
 	extDir := existing.SourceDir
 	wasEnabled := existing.Enabled
 
-	// Cleanup and unload existing extension
-	m.CleanupExtension(existing.ID)
 	m.UnloadExtension(existing.ID)
 
-	// Remove old source files but keep data directory
 	if extDir != "" {
 		if err := os.RemoveAll(extDir); err != nil {
 			GoLog("[Extension] Warning: failed to remove old source dir: %v\n", err)
@@ -628,7 +590,6 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 		SourceDir: extDir,
 	}
 
-	// Initialize Goja VM
 	if err := m.initializeVM(ext); err != nil {
 		ext.Error = err.Error()
 		ext.Enabled = false
@@ -644,7 +605,6 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 	return ext, nil
 }
 
-// ExtensionUpgradeInfo holds information about extension upgrade check
 type ExtensionUpgradeInfo struct {
 	ExtensionID    string `json:"extension_id"`
 	CurrentVersion string `json:"current_version"`
@@ -653,16 +613,13 @@ type ExtensionUpgradeInfo struct {
 	IsInstalled    bool   `json:"is_installed"`
 }
 
-// checkExtensionUpgradeInternal checks if a package file is an upgrade for an existing extension
-// Internal function that returns struct
 func (m *ExtensionManager) checkExtensionUpgradeInternal(filePath string) (*ExtensionUpgradeInfo, error) {
-	// Validate file extension
 	if !strings.HasSuffix(strings.ToLower(filePath), ".spotiflac-ext") {
-		return nil, fmt.Errorf("Invalid file format")
+		return nil, fmt.Errorf("Invalid file format. Please select a .spotiflac-ext file")
 	}
 
-	// Open the zip file
 	zipReader, err := zip.OpenReader(filePath)
+
 	if err != nil {
 		return nil, fmt.Errorf("Cannot open extension file")
 	}
@@ -705,7 +662,6 @@ func (m *ExtensionManager) checkExtensionUpgradeInternal(filePath string) (*Exte
 	}
 
 	if !exists {
-		// Not installed - this is a new install, not upgrade
 		info.CurrentVersion = ""
 		info.CanUpgrade = false
 	} else {
@@ -716,7 +672,6 @@ func (m *ExtensionManager) checkExtensionUpgradeInternal(filePath string) (*Exte
 	return info, nil
 }
 
-// CheckExtensionUpgradeJSON checks if a package file is an upgrade and returns JSON
 func (m *ExtensionManager) CheckExtensionUpgradeJSON(filePath string) (string, error) {
 	info, err := m.checkExtensionUpgradeInternal(filePath)
 	if err != nil {
@@ -731,32 +686,33 @@ func (m *ExtensionManager) CheckExtensionUpgradeJSON(filePath string) (string, e
 	return string(jsonBytes), nil
 }
 
-// GetInstalledExtensionsJSON returns all extensions as JSON for Flutter
 func (m *ExtensionManager) GetInstalledExtensionsJSON() (string, error) {
 	extensions := m.GetAllExtensions()
 
 	type ExtensionInfo struct {
-		ID                     string                `json:"id"`
-		Name                   string                `json:"name"`
-		DisplayName            string                `json:"display_name"`
-		Version                string                `json:"version"`
-		Author                 string                `json:"author"`
-		Description            string                `json:"description"`
-		Homepage               string                `json:"homepage,omitempty"`
-		IconPath               string                `json:"icon_path,omitempty"`
-		Types                  []ExtensionType       `json:"types"`
-		Enabled                bool                  `json:"enabled"`
-		Status                 string                `json:"status"`
-		Error                  string                `json:"error_message,omitempty"`
-		Settings               []ExtensionSetting    `json:"settings,omitempty"`
-		QualityOptions         []QualityOption       `json:"quality_options,omitempty"`
-		Permissions            []string              `json:"permissions"`
-		HasMetadataProvider    bool                  `json:"has_metadata_provider"`
-		HasDownloadProvider    bool                  `json:"has_download_provider"`
-		SkipMetadataEnrichment bool                  `json:"skip_metadata_enrichment"`
-		SearchBehavior         *SearchBehaviorConfig `json:"search_behavior,omitempty"`
-		TrackMatching          *TrackMatchingConfig  `json:"track_matching,omitempty"`
-		PostProcessing         *PostProcessingConfig `json:"post_processing,omitempty"`
+		ID                     string                 `json:"id"`
+		Name                   string                 `json:"name"`
+		DisplayName            string                 `json:"display_name"`
+		Version                string                 `json:"version"`
+		Author                 string                 `json:"author"`
+		Description            string                 `json:"description"`
+		Homepage               string                 `json:"homepage,omitempty"`
+		IconPath               string                 `json:"icon_path,omitempty"`
+		Types                  []ExtensionType        `json:"types"`
+		Enabled                bool                   `json:"enabled"`
+		Status                 string                 `json:"status"`
+		Error                  string                 `json:"error_message,omitempty"`
+		Settings               []ExtensionSetting     `json:"settings,omitempty"`
+		QualityOptions         []QualityOption        `json:"quality_options,omitempty"`
+		Permissions            []string               `json:"permissions"`
+		HasMetadataProvider    bool                   `json:"has_metadata_provider"`
+		HasDownloadProvider    bool                   `json:"has_download_provider"`
+		HasLyricsProvider      bool                   `json:"has_lyrics_provider"`
+		SkipMetadataEnrichment bool                   `json:"skip_metadata_enrichment"`
+		SearchBehavior         *SearchBehaviorConfig  `json:"search_behavior,omitempty"`
+		TrackMatching          *TrackMatchingConfig   `json:"track_matching,omitempty"`
+		PostProcessing         *PostProcessingConfig  `json:"post_processing,omitempty"`
+		Capabilities           map[string]interface{} `json:"capabilities,omitempty"`
 	}
 
 	infos := make([]ExtensionInfo, len(extensions))
@@ -769,7 +725,6 @@ func (m *ExtensionManager) GetInstalledExtensionsJSON() (string, error) {
 			permissions = append(permissions, "storage:enabled")
 		}
 
-		// Determine status
 		status := "loaded"
 		if ext.Error != "" {
 			status = "error"
@@ -809,10 +764,12 @@ func (m *ExtensionManager) GetInstalledExtensionsJSON() (string, error) {
 			Permissions:            permissions,
 			HasMetadataProvider:    ext.Manifest.IsMetadataProvider(),
 			HasDownloadProvider:    ext.Manifest.IsDownloadProvider(),
+			HasLyricsProvider:      ext.Manifest.IsLyricsProvider(),
 			SkipMetadataEnrichment: ext.Manifest.SkipMetadataEnrichment,
 			SearchBehavior:         ext.Manifest.SearchBehavior,
 			TrackMatching:          ext.Manifest.TrackMatching,
 			PostProcessing:         ext.Manifest.PostProcessing,
+			Capabilities:           ext.Manifest.Capabilities,
 		}
 	}
 
@@ -824,9 +781,6 @@ func (m *ExtensionManager) GetInstalledExtensionsJSON() (string, error) {
 	return string(jsonBytes), nil
 }
 
-// ==================== Extension Lifecycle ====================
-
-// InitializeExtension calls the extension's initialize method with settings
 func (m *ExtensionManager) InitializeExtension(extensionID string, settings map[string]interface{}) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -888,7 +842,6 @@ func (m *ExtensionManager) InitializeExtension(extensionID string, settings map[
 	return nil
 }
 
-// CleanupExtension calls the extension's cleanup method
 func (m *ExtensionManager) CleanupExtension(extensionID string) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -899,10 +852,9 @@ func (m *ExtensionManager) CleanupExtension(extensionID string) error {
 	}
 
 	if ext.VM == nil {
-		return nil // No VM, nothing to cleanup
+		return nil
 	}
 
-	// Call cleanup function
 	script := `
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.cleanup === 'function') {
@@ -941,7 +893,6 @@ func (m *ExtensionManager) CleanupExtension(extensionID string) error {
 	return nil
 }
 
-// UnloadAllExtensions unloads all extensions gracefully
 func (m *ExtensionManager) UnloadAllExtensions() {
 	m.mu.Lock()
 	extensionIDs := make([]string, 0, len(m.extensions))
@@ -951,17 +902,12 @@ func (m *ExtensionManager) UnloadAllExtensions() {
 	m.mu.Unlock()
 
 	for _, id := range extensionIDs {
-		// Call cleanup first
-		m.CleanupExtension(id)
-		// Then unload
 		m.UnloadExtension(id)
 	}
 
 	GoLog("[Extension] All extensions unloaded\n")
 }
 
-// InvokeAction calls a custom action function on an extension (e.g., for button settings)
-// The function is called as extension.<actionName>() and can return a result
 func (m *ExtensionManager) InvokeAction(extensionID string, actionName string) (map[string]interface{}, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -979,7 +925,6 @@ func (m *ExtensionManager) InvokeAction(extensionID string, actionName string) (
 		return nil, fmt.Errorf("extension is disabled")
 	}
 
-	// Call the action function on the extension object
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.%s === 'function') {

go_backend/extension_manifest.go

@@ -1,4 +1,3 @@
-// Package gobackend provides extension manifest parsing and validation
 package gobackend
 
 import (
@@ -7,15 +6,14 @@ import (
 	"strings"
 )
 
-// ExtensionType represents the type of extension
 type ExtensionType string
 
 const (
 	ExtensionTypeMetadataProvider ExtensionType = "metadata_provider"
 	ExtensionTypeDownloadProvider ExtensionType = "download_provider"
+	ExtensionTypeLyricsProvider   ExtensionType = "lyrics_provider"
 )
 
-// SettingType represents the type of a setting field
 type SettingType string
 
 const (
@@ -26,14 +24,12 @@ const (
 	SettingTypeButton SettingType = "button" // Action button that calls a JS function
 )
 
-// ExtensionPermissions defines what resources an extension can access
 type ExtensionPermissions struct {
-	Network []string `json:"network"` // List of allowed domains
-	Storage bool     `json:"storage"` // Whether extension can use storage API
-	File    bool     `json:"file"`    // Whether extension can use file API
+	Network []string `json:"network"`
+	Storage bool     `json:"storage"`
+	File    bool     `json:"file"`
 }
 
-// ExtensionSetting defines a configurable setting for an extension
 type ExtensionSetting struct {
 	Key         string      `json:"key"`
 	Type        SettingType `json:"type"`
@@ -42,19 +38,17 @@ type ExtensionSetting struct {
 	Required    bool        `json:"required,omitempty"`
 	Secret      bool        `json:"secret,omitempty"`
 	Default     interface{} `json:"default,omitempty"`
-	Options     []string    `json:"options,omitempty"` // For select type
-	Action      string      `json:"action,omitempty"`  // For button type: JS function name to call (e.g., "startLogin")
+	Options     []string    `json:"options,omitempty"`
+	Action      string      `json:"action,omitempty"`
 }
 
-// QualityOption represents a quality option for download providers
 type QualityOption struct {
-	ID          string                   `json:"id"`                 // Unique identifier (e.g., "mp3_320", "opus_128")
-	Label       string                   `json:"label"`              // Display name (e.g., "MP3 320kbps")
-	Description string                   `json:"description"`        // Optional description (e.g., "Best quality MP3")
-	Settings    []QualitySpecificSetting `json:"settings,omitempty"` // Quality-specific settings
+	ID          string                   `json:"id"`
+	Label       string                   `json:"label"`
+	Description string                   `json:"description"`
+	Settings    []QualitySpecificSetting `json:"settings,omitempty"`
 }
 
-// QualitySpecificSetting represents a setting that's specific to a quality option
 type QualitySpecificSetting struct {
 	Key         string      `json:"key"`
 	Type        SettingType `json:"type"`
@@ -63,71 +57,72 @@ type QualitySpecificSetting struct {
 	Required    bool        `json:"required,omitempty"`
 	Secret      bool        `json:"secret,omitempty"`
 	Default     interface{} `json:"default,omitempty"`
-	Options     []string    `json:"options,omitempty"` // For select type
+	Options     []string    `json:"options,omitempty"`
+}
+
+type SearchFilter struct {
+	ID    string `json:"id"`
+	Label string `json:"label,omitempty"`
+	Icon  string `json:"icon,omitempty"`
 }
 
-// SearchBehaviorConfig defines custom search behavior for an extension
 type SearchBehaviorConfig struct {
-	Enabled         bool   `json:"enabled"`                   // Whether extension provides custom search
-	Placeholder     string `json:"placeholder,omitempty"`     // Placeholder text for search box
-	Primary         bool   `json:"primary,omitempty"`         // If true, show as primary search tab
-	Icon            string `json:"icon,omitempty"`            // Icon for search tab
-	ThumbnailRatio  string `json:"thumbnailRatio,omitempty"`  // Thumbnail aspect ratio: "square" (1:1), "wide" (16:9), "portrait" (2:3)
-	ThumbnailWidth  int    `json:"thumbnailWidth,omitempty"`  // Custom thumbnail width in pixels
-	ThumbnailHeight int    `json:"thumbnailHeight,omitempty"` // Custom thumbnail height in pixels
+	Enabled         bool           `json:"enabled"`
+	Placeholder     string         `json:"placeholder,omitempty"`
+	Primary         bool           `json:"primary,omitempty"`
+	Icon            string         `json:"icon,omitempty"`
+	ThumbnailRatio  string         `json:"thumbnailRatio,omitempty"`
+	ThumbnailWidth  int            `json:"thumbnailWidth,omitempty"`
+	ThumbnailHeight int            `json:"thumbnailHeight,omitempty"`
+	Filters         []SearchFilter `json:"filters,omitempty"`
 }
 
-// URLHandlerConfig defines custom URL handling for an extension
 type URLHandlerConfig struct {
-	Enabled  bool     `json:"enabled"`            // Whether extension handles URLs
-	Patterns []string `json:"patterns,omitempty"` // URL patterns to match (e.g., "music.youtube.com", "soundcloud.com")
+	Enabled  bool     `json:"enabled"`
+	Patterns []string `json:"patterns,omitempty"`
 }
 
-// TrackMatchingConfig defines custom track matching behavior
 type TrackMatchingConfig struct {
-	CustomMatching    bool   `json:"customMatching"`              // Whether extension handles matching
-	Strategy          string `json:"strategy,omitempty"`          // "isrc", "name", "duration", "custom"
-	DurationTolerance int    `json:"durationTolerance,omitempty"` // Tolerance in seconds for duration matching
+	CustomMatching    bool   `json:"customMatching"`
+	Strategy          string `json:"strategy,omitempty"`
+	DurationTolerance int    `json:"durationTolerance,omitempty"`
 }
 
-// PostProcessingHook defines a post-processing hook
 type PostProcessingHook struct {
-	ID               string   `json:"id"`                         // Unique identifier
-	Name             string   `json:"name"`                       // Display name
-	Description      string   `json:"description,omitempty"`      // Description
-	DefaultEnabled   bool     `json:"defaultEnabled,omitempty"`   // Whether enabled by default
-	SupportedFormats []string `json:"supportedFormats,omitempty"` // Supported file formats (e.g., ["flac", "mp3"])
+	ID               string   `json:"id"`
+	Name             string   `json:"name"`
+	Description      string   `json:"description,omitempty"`
+	DefaultEnabled   bool     `json:"defaultEnabled,omitempty"`
+	SupportedFormats []string `json:"supportedFormats,omitempty"`
 }
 
-// PostProcessingConfig defines post-processing capabilities
 type PostProcessingConfig struct {
-	Enabled bool                 `json:"enabled"`         // Whether extension provides post-processing
-	Hooks   []PostProcessingHook `json:"hooks,omitempty"` // Available hooks
+	Enabled bool                 `json:"enabled"`
+	Hooks   []PostProcessingHook `json:"hooks,omitempty"`
 }
 
-// ExtensionManifest represents the manifest.json of an extension
 type ExtensionManifest struct {
-	Name                   string                `json:"name"`
-	DisplayName            string                `json:"displayName"`
-	Version                string                `json:"version"`
-	Author                 string                `json:"author"`
-	Description            string                `json:"description"`
-	Homepage               string                `json:"homepage,omitempty"`
-	Icon                   string                `json:"icon,omitempty"` // Icon filename (e.g., "icon.png")
-	Types                  []ExtensionType       `json:"type"`
-	Permissions            ExtensionPermissions  `json:"permissions"`
-	Settings               []ExtensionSetting    `json:"settings,omitempty"`
-	QualityOptions         []QualityOption       `json:"qualityOptions,omitempty"` // Custom quality options for download providers
-	MinAppVersion          string                `json:"minAppVersion,omitempty"`
-	SkipMetadataEnrichment bool                  `json:"skipMetadataEnrichment,omitempty"` // If true, don't enrich metadata from Deezer/Spotify
-	SkipBuiltInFallback    bool                  `json:"skipBuiltInFallback,omitempty"`    // If true, don't fallback to built-in providers (tidal/qobuz/amazon)
-	SearchBehavior         *SearchBehaviorConfig `json:"searchBehavior,omitempty"`         // Custom search behavior
-	URLHandler             *URLHandlerConfig     `json:"urlHandler,omitempty"`             // Custom URL handling
-	TrackMatching          *TrackMatchingConfig  `json:"trackMatching,omitempty"`          // Custom track matching
-	PostProcessing         *PostProcessingConfig `json:"postProcessing,omitempty"`         // Post-processing hooks
+	Name                   string                 `json:"name"`
+	DisplayName            string                 `json:"displayName"`
+	Version                string                 `json:"version"`
+	Author                 string                 `json:"author"`
+	Description            string                 `json:"description"`
+	Homepage               string                 `json:"homepage,omitempty"`
+	Icon                   string                 `json:"icon,omitempty"`
+	Types                  []ExtensionType        `json:"type"`
+	Permissions            ExtensionPermissions   `json:"permissions"`
+	Settings               []ExtensionSetting     `json:"settings,omitempty"`
+	QualityOptions         []QualityOption        `json:"qualityOptions,omitempty"`
+	MinAppVersion          string                 `json:"minAppVersion,omitempty"`
+	SkipMetadataEnrichment bool                   `json:"skipMetadataEnrichment,omitempty"`
+	SkipBuiltInFallback    bool                   `json:"skipBuiltInFallback,omitempty"`
+	SearchBehavior         *SearchBehaviorConfig  `json:"searchBehavior,omitempty"`
+	URLHandler             *URLHandlerConfig      `json:"urlHandler,omitempty"`
+	TrackMatching          *TrackMatchingConfig   `json:"trackMatching,omitempty"`
+	PostProcessing         *PostProcessingConfig  `json:"postProcessing,omitempty"`
+	Capabilities           map[string]interface{} `json:"capabilities,omitempty"`
 }
 
-// ManifestValidationError represents a validation error in the manifest
 type ManifestValidationError struct {
 	Field   string
 	Message string
@@ -137,7 +132,6 @@ func (e *ManifestValidationError) Error() string {
 	return fmt.Sprintf("manifest validation error: %s - %s", e.Field, e.Message)
 }
 
-// ParseManifest parses and validates a manifest from JSON bytes
 func ParseManifest(data []byte) (*ExtensionManifest, error) {
 	var manifest ExtensionManifest
 	if err := json.Unmarshal(data, &manifest); err != nil {
@@ -151,9 +145,7 @@ func ParseManifest(data []byte) (*ExtensionManifest, error) {
 	return &manifest, nil
 }
 
-// Validate checks if the manifest has all required fields and valid values
 func (m *ExtensionManifest) Validate() error {
-	// Check required fields
 	if strings.TrimSpace(m.Name) == "" {
 		return &ManifestValidationError{Field: "name", Message: "name is required"}
 	}
@@ -174,17 +166,15 @@ func (m *ExtensionManifest) Validate() error {
 		return &ManifestValidationError{Field: "type", Message: "at least one type is required"}
 	}
 
-	// Validate extension types
 	for _, t := range m.Types {
-		if t != ExtensionTypeMetadataProvider && t != ExtensionTypeDownloadProvider {
+		if t != ExtensionTypeMetadataProvider && t != ExtensionTypeDownloadProvider && t != ExtensionTypeLyricsProvider {
 			return &ManifestValidationError{
 				Field:   "type",
-				Message: fmt.Sprintf("invalid extension type: %s (must be 'metadata_provider' or 'download_provider')", t),
+				Message: fmt.Sprintf("invalid extension type: %s (must be 'metadata_provider', 'download_provider', or 'lyrics_provider')", t),
 			}
 		}
 	}
 
-	// Validate settings if present
 	for i, setting := range m.Settings {
 		if strings.TrimSpace(setting.Key) == "" {
 			return &ManifestValidationError{
@@ -200,21 +190,6 @@ func (m *ExtensionManifest) Validate() error {
 			}
 		}
 
-		// Validate setting type
-		validTypes := map[SettingType]bool{
-			SettingTypeString: true,
-			SettingTypeNumber: true,
-			SettingTypeBool:   true,
-			SettingTypeSelect: true,
-			SettingTypeButton: true,
-		}
-		if !validTypes[setting.Type] {
-			return &ManifestValidationError{
-				Field:   fmt.Sprintf("settings[%d].type", i),
-				Message: fmt.Sprintf("invalid setting type: %s", setting.Type),
-			}
-		}
-
 		// Select type requires options
 		if setting.Type == SettingTypeSelect && len(setting.Options) == 0 {
 			return &ManifestValidationError{
@@ -223,7 +198,6 @@ func (m *ExtensionManifest) Validate() error {
 			}
 		}
 
-		// Button type requires action
 		if setting.Type == SettingTypeButton && setting.Action == "" {
 			return &ManifestValidationError{
 				Field:   fmt.Sprintf("settings[%d].action", i),
@@ -235,7 +209,6 @@ func (m *ExtensionManifest) Validate() error {
 	return nil
 }
 
-// HasType checks if the extension has a specific type
 func (m *ExtensionManifest) HasType(t ExtensionType) bool {
 	for _, et := range m.Types {
 		if et == t {
@@ -245,17 +218,18 @@ func (m *ExtensionManifest) HasType(t ExtensionType) bool {
 	return false
 }
 
-// IsMetadataProvider returns true if extension provides metadata
 func (m *ExtensionManifest) IsMetadataProvider() bool {
 	return m.HasType(ExtensionTypeMetadataProvider)
 }
 
-// IsDownloadProvider returns true if extension provides downloads
 func (m *ExtensionManifest) IsDownloadProvider() bool {
 	return m.HasType(ExtensionTypeDownloadProvider)
 }
 
-// IsDomainAllowed checks if a domain is in the allowed network permissions
+func (m *ExtensionManifest) IsLyricsProvider() bool {
+	return m.HasType(ExtensionTypeLyricsProvider)
+}
+
 func (m *ExtensionManifest) IsDomainAllowed(domain string) bool {
 	domain = strings.ToLower(strings.TrimSpace(domain))
 	for _, allowed := range m.Permissions.Network {
@@ -265,7 +239,7 @@ func (m *ExtensionManifest) IsDomainAllowed(domain string) bool {
 		}
 		// Support wildcard subdomains (e.g., *.example.com)
 		if strings.HasPrefix(allowed, "*.") {
-			suffix := allowed[1:] // Remove the *
+			suffix := allowed[1:]
 			if strings.HasSuffix(domain, suffix) {
 				return true
 			}
@@ -274,37 +248,30 @@ func (m *ExtensionManifest) IsDomainAllowed(domain string) bool {
 	return false
 }
 
-// HasCustomSearch returns true if extension provides custom search
 func (m *ExtensionManifest) HasCustomSearch() bool {
 	return m.SearchBehavior != nil && m.SearchBehavior.Enabled
 }
 
-// HasCustomMatching returns true if extension provides custom track matching
 func (m *ExtensionManifest) HasCustomMatching() bool {
 	return m.TrackMatching != nil && m.TrackMatching.CustomMatching
 }
 
-// HasPostProcessing returns true if extension provides post-processing
 func (m *ExtensionManifest) HasPostProcessing() bool {
 	return m.PostProcessing != nil && m.PostProcessing.Enabled
 }
 
-// HasURLHandler returns true if extension handles custom URLs
 func (m *ExtensionManifest) HasURLHandler() bool {
 	return m.URLHandler != nil && m.URLHandler.Enabled && len(m.URLHandler.Patterns) > 0
 }
 
-// MatchesURL checks if a URL matches any of the extension's URL patterns
 func (m *ExtensionManifest) MatchesURL(urlStr string) bool {
 	if !m.HasURLHandler() {
 		return false
 	}
 
-	// Parse URL to get host
 	urlStr = strings.ToLower(strings.TrimSpace(urlStr))
 	for _, pattern := range m.URLHandler.Patterns {
 		pattern = strings.ToLower(strings.TrimSpace(pattern))
-		// Check if URL contains the pattern (host match)
 		if strings.Contains(urlStr, pattern) {
 			return true
 		}
@@ -312,7 +279,6 @@ func (m *ExtensionManifest) MatchesURL(urlStr string) bool {
 	return false
 }
 
-// GetPostProcessingHooks returns all post-processing hooks
 func (m *ExtensionManifest) GetPostProcessingHooks() []PostProcessingHook {
 	if m.PostProcessing == nil {
 		return nil
@@ -320,7 +286,6 @@ func (m *ExtensionManifest) GetPostProcessingHooks() []PostProcessingHook {
 	return m.PostProcessing.Hooks
 }
 
-// ToJSON serializes the manifest to JSON
 func (m *ExtensionManifest) ToJSON() ([]byte, error) {
 	return json.Marshal(m)
 }

go_backend/extension_providers_test.go

@@ -0,0 +1,68 @@
+package gobackend
+
+import "testing"
+
+func TestSetMetadataProviderPriorityAddsBuiltIns(t *testing.T) {
+	original := GetMetadataProviderPriority()
+	defer SetMetadataProviderPriority(original)
+
+	SetMetadataProviderPriority([]string{"tidal"})
+	got := GetMetadataProviderPriority()
+	want := []string{"tidal", "deezer", "qobuz"}
+	if len(got) != len(want) {
+		t.Fatalf("unexpected priority length: got %v want %v", got, want)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("unexpected priority at %d: got %v want %v", i, got, want)
+		}
+	}
+}
+
+func TestSearchTracksWithMetadataProvidersUsesPriorityAndDedupes(t *testing.T) {
+	originalPriority := GetMetadataProviderPriority()
+	originalSearch := searchBuiltInMetadataTracksFunc
+	defer func() {
+		SetMetadataProviderPriority(originalPriority)
+		searchBuiltInMetadataTracksFunc = originalSearch
+	}()
+
+	SetMetadataProviderPriority([]string{"qobuz", "tidal", "deezer"})
+
+	var calls []string
+	searchBuiltInMetadataTracksFunc = func(providerID, query string, limit int) ([]ExtTrackMetadata, error) {
+		calls = append(calls, providerID)
+		switch providerID {
+		case "qobuz":
+			return []ExtTrackMetadata{
+				{ProviderID: "qobuz", SpotifyID: "qobuz:1", ISRC: "AAA111", Name: "First"},
+			}, nil
+		case "tidal":
+			return []ExtTrackMetadata{
+				{ProviderID: "tidal", SpotifyID: "tidal:2", ISRC: "AAA111", Name: "Duplicate"},
+				{ProviderID: "tidal", SpotifyID: "tidal:3", ISRC: "BBB222", Name: "Second"},
+			}, nil
+		case "deezer":
+			return []ExtTrackMetadata{
+				{ProviderID: "deezer", SpotifyID: "deezer:4", ISRC: "CCC333", Name: "Third"},
+			}, nil
+		default:
+			return nil, nil
+		}
+	}
+
+	manager := GetExtensionManager()
+	tracks, err := manager.SearchTracksWithMetadataProviders("query", 3, false)
+	if err != nil {
+		t.Fatalf("SearchTracksWithMetadataProviders returned error: %v", err)
+	}
+	if len(tracks) != 3 {
+		t.Fatalf("unexpected track count: got %d want 3", len(tracks))
+	}
+	if tracks[0].ProviderID != "qobuz" || tracks[1].ProviderID != "tidal" || tracks[2].ProviderID != "deezer" {
+		t.Fatalf("unexpected track provider order: %+v", tracks)
+	}
+	if len(calls) != 3 || calls[0] != "qobuz" || calls[1] != "tidal" || calls[2] != "deezer" {
+		t.Fatalf("unexpected provider call order: %v", calls)
+	}
+}

go_backend/extension_runtime.go

@@ -1,9 +1,11 @@
-// Package gobackend provides extension runtime with sandboxed execution
 package gobackend
 
 import (
+	"fmt"
+	"net"
 	"net/http"
 	"net/url"
+	"strings"
 	"sync"
 	"time"
 
@@ -17,7 +19,6 @@ var (
 	extensionAuthStateMu sync.RWMutex
 )
 
-// ExtensionAuthState holds auth state for an extension
 type ExtensionAuthState struct {
 	PendingAuthURL  string
 	AuthCode        string
@@ -25,12 +26,10 @@ type ExtensionAuthState struct {
 	RefreshToken    string
 	ExpiresAt       time.Time
 	IsAuthenticated bool
-	// PKCE support
-	PKCEVerifier  string
-	PKCEChallenge string
+	PKCEVerifier    string
+	PKCEChallenge   string
 }
 
-// PendingAuthRequest holds a pending OAuth request that needs Flutter to open URL
 type PendingAuthRequest struct {
 	ExtensionID string
 	AuthURL     string
@@ -42,7 +41,6 @@ var (
 	pendingAuthRequestsMu sync.RWMutex
 )
 
-// GetPendingAuthRequest returns pending auth request for an extension (called from Flutter)
 func GetPendingAuthRequest(extensionID string) *PendingAuthRequest {
 	pendingAuthRequestsMu.RLock()
 	defer pendingAuthRequestsMu.RUnlock()
@@ -55,7 +53,6 @@ func ClearPendingAuthRequest(extensionID string) {
 	delete(pendingAuthRequests, extensionID)
 }
 
-// SetExtensionAuthCode sets auth code for an extension (called from Flutter after OAuth callback)
 func SetExtensionAuthCode(extensionID string, authCode string) {
 	extensionAuthStateMu.Lock()
 	defer extensionAuthStateMu.Unlock()
@@ -68,7 +65,6 @@ func SetExtensionAuthCode(extensionID string, authCode string) {
 	state.AuthCode = authCode
 }
 
-// SetExtensionTokens sets access/refresh tokens for an extension
 func SetExtensionTokens(extensionID string, accessToken, refreshToken string, expiresAt time.Time) {
 	extensionAuthStateMu.Lock()
 	defer extensionAuthStateMu.Unlock()
@@ -84,7 +80,6 @@ func SetExtensionTokens(extensionID string, accessToken, refreshToken string, ex
 	state.IsAuthenticated = accessToken != ""
 }
 
-// ExtensionRuntime provides sandboxed APIs for extensions
 type ExtensionRuntime struct {
 	extensionID string
 	manifest    *ExtensionManifest
@@ -93,50 +88,88 @@ type ExtensionRuntime struct {
 	cookieJar   http.CookieJar
 	dataDir     string
 	vm          *goja.Runtime
+
+	storageMu      sync.RWMutex
+	storageCache   map[string]interface{}
+	storageLoaded  bool
+	storageDirty   bool
+	storageClosed  bool
+	storageTimer   *time.Timer
+	storageWriteMu sync.Mutex
+
+	credentialsMu     sync.RWMutex
+	credentialsCache  map[string]interface{}
+	credentialsLoaded bool
+	storageFlushDelay time.Duration
 }
 
-// NewExtensionRuntime creates a new runtime for an extension
+type privateIPCacheEntry struct {
+	isPrivate bool
+	expiresAt time.Time
+}
+
+const (
+	privateIPCacheTTL      = 5 * time.Minute
+	privateIPErrorCacheTTL = 30 * time.Second
+	maxPrivateIPCacheSize  = 1024
+)
+
+var (
+	privateIPCache   = make(map[string]privateIPCacheEntry)
+	privateIPCacheMu sync.RWMutex
+)
+
 func NewExtensionRuntime(ext *LoadedExtension) *ExtensionRuntime {
 	jar, _ := newSimpleCookieJar()
 
 	runtime := &ExtensionRuntime{
-		extensionID: ext.ID,
-		manifest:    ext.Manifest,
-		settings:    make(map[string]interface{}),
-		cookieJar:   jar,
-		dataDir:     ext.DataDir,
-		vm:          ext.VM,
+		extensionID:       ext.ID,
+		manifest:          ext.Manifest,
+		settings:          make(map[string]interface{}),
+		cookieJar:         jar,
+		dataDir:           ext.DataDir,
+		vm:                ext.VM,
+		storageFlushDelay: defaultStorageFlushDelay,
 	}
 
-	// Create HTTP client with redirect validation to prevent SSRF via open redirect
+	// Extension sandbox enforces HTTPS-only domains. Do not apply global
+	// allow_http scheme downgrade here, because some extension APIs (e.g.
+	// spotify-web) will redirect http -> https and can end up in 301 loops.
+	// We still reuse sharedTransport so insecure TLS compatibility mode remains effective.
 	client := &http.Client{
-		Timeout: 30 * time.Second,
-		Jar:     jar,
-		CheckRedirect: func(req *http.Request, via []*http.Request) error {
-			// Validate redirect target domain against allowed domains
-			domain := req.URL.Hostname()
-			if !ext.Manifest.IsDomainAllowed(domain) {
-				GoLog("[Extension:%s] Redirect blocked: domain '%s' not in allowed list\n", ext.ID, domain)
-				return &RedirectBlockedError{Domain: domain}
-			}
-			// Also block redirects to private/local networks (SSRF protection)
-			if isPrivateIP(domain) {
-				GoLog("[Extension:%s] Redirect blocked: private IP '%s'\n", ext.ID, domain)
-				return &RedirectBlockedError{Domain: domain, IsPrivate: true}
-			}
-			// Default redirect limit (10)
-			if len(via) >= 10 {
-				return http.ErrUseLastResponse
-			}
-			return nil
-		},
+		Transport: sharedTransport,
+		Timeout:   30 * time.Second,
+		Jar:       jar,
+	}
+	client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
+		if req.URL.Scheme != "https" {
+			GoLog("[Extension:%s] Redirect blocked: non-https scheme '%s'\n", ext.ID, req.URL.Scheme)
+			return fmt.Errorf("redirect blocked: only https is allowed")
+		}
+
+		domain := req.URL.Hostname()
+		if domain == "" {
+			GoLog("[Extension:%s] Redirect blocked: missing hostname\n", ext.ID)
+			return fmt.Errorf("redirect blocked: hostname is required")
+		}
+		if !ext.Manifest.IsDomainAllowed(domain) {
+			GoLog("[Extension:%s] Redirect blocked: domain '%s' not in allowed list\n", ext.ID, domain)
+			return &RedirectBlockedError{Domain: domain}
+		}
+		if isPrivateIP(domain) {
+			GoLog("[Extension:%s] Redirect blocked: private IP '%s'\n", ext.ID, domain)
+			return &RedirectBlockedError{Domain: domain, IsPrivate: true}
+		}
+		if len(via) >= 10 {
+			return http.ErrUseLastResponse
+		}
+		return nil
 	}
 	runtime.httpClient = client
 
 	return runtime
 }
 
-// RedirectBlockedError is returned when a redirect is blocked due to domain validation
 type RedirectBlockedError struct {
 	Domain    string
 	IsPrivate bool
@@ -149,41 +182,102 @@ func (e *RedirectBlockedError) Error() string {
 	return "redirect blocked: domain '" + e.Domain + "' not in allowed list"
 }
 
-// isPrivateIP checks if a hostname resolves to a private/local IP address
 func isPrivateIP(host string) bool {
-	// Block common private network patterns
-	// This is a simple check - for production, consider DNS resolution
-	privatePatterns := []string{
-		"localhost",
-		"127.",
-		"10.",
-		"172.16.", "172.17.", "172.18.", "172.19.",
-		"172.20.", "172.21.", "172.22.", "172.23.",
-		"172.24.", "172.25.", "172.26.", "172.27.",
-		"172.28.", "172.29.", "172.30.", "172.31.",
-		"192.168.",
-		"169.254.", // Link-local
-		"::1",      // IPv6 localhost
-		"fc00:",    // IPv6 private
-		"fe80:",    // IPv6 link-local
+	hostLower := strings.ToLower(strings.TrimSpace(host))
+	if hostLower == "" {
+		return false
 	}
 
-	hostLower := host
-	for _, pattern := range privatePatterns {
-		if hostLower == pattern || len(hostLower) > len(pattern) && hostLower[:len(pattern)] == pattern {
-			return true
-		}
-	}
-
-	// Also block .local domains
-	if len(host) > 6 && host[len(host)-6:] == ".local" {
+	if hostLower == "localhost" || strings.HasSuffix(hostLower, ".local") {
 		return true
 	}
 
+	if ip := net.ParseIP(hostLower); ip != nil {
+		return isPrivateIPAddr(ip)
+	}
+
+	if cached, ok := getPrivateIPCache(hostLower); ok {
+		return cached
+	}
+
+	ips, err := net.LookupIP(hostLower)
+	if err != nil {
+		setPrivateIPCache(hostLower, false, privateIPErrorCacheTTL)
+		return false
+	}
+
+	isPrivate := false
+	for _, ip := range ips {
+		if isPrivateIPAddr(ip) {
+			isPrivate = true
+			break
+		}
+	}
+
+	setPrivateIPCache(hostLower, isPrivate, privateIPCacheTTL)
+	return isPrivate
+}
+
+func getPrivateIPCache(host string) (bool, bool) {
+	now := time.Now()
+
+	privateIPCacheMu.RLock()
+	entry, exists := privateIPCache[host]
+	privateIPCacheMu.RUnlock()
+	if !exists {
+		return false, false
+	}
+
+	if now.Before(entry.expiresAt) {
+		return entry.isPrivate, true
+	}
+
+	privateIPCacheMu.Lock()
+	delete(privateIPCache, host)
+	privateIPCacheMu.Unlock()
+	return false, false
+}
+
+func setPrivateIPCache(host string, isPrivate bool, ttl time.Duration) {
+	expiresAt := time.Now().Add(ttl)
+
+	privateIPCacheMu.Lock()
+	if len(privateIPCache) >= maxPrivateIPCacheSize {
+		now := time.Now()
+		for key, entry := range privateIPCache {
+			if now.After(entry.expiresAt) {
+				delete(privateIPCache, key)
+			}
+		}
+		if len(privateIPCache) >= maxPrivateIPCacheSize {
+			privateIPCache = make(map[string]privateIPCacheEntry)
+		}
+	}
+	privateIPCache[host] = privateIPCacheEntry{
+		isPrivate: isPrivate,
+		expiresAt: expiresAt,
+	}
+	privateIPCacheMu.Unlock()
+}
+
+func isPrivateIPAddr(ip net.IP) bool {
+	if ip == nil {
+		return false
+	}
+	if ip.IsLoopback() ||
+		ip.IsPrivate() ||
+		ip.IsLinkLocalUnicast() ||
+		ip.IsLinkLocalMulticast() ||
+		ip.IsMulticast() ||
+		ip.IsUnspecified() {
+		return true
+	}
+	if !ip.IsGlobalUnicast() {
+		return true
+	}
 	return false
 }
 
-// simpleCookieJar is a simple in-memory cookie jar
 type simpleCookieJar struct {
 	cookies map[string][]*http.Cookie
 	mu      sync.RWMutex
@@ -208,34 +302,29 @@ func (j *simpleCookieJar) Cookies(u *url.URL) []*http.Cookie {
 	return j.cookies[u.Host]
 }
 
-// SetSettings updates the runtime settings
 func (r *ExtensionRuntime) SetSettings(settings map[string]interface{}) {
 	r.settings = settings
 }
 
-// RegisterAPIs registers all sandboxed APIs to the Goja VM
 func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
 	r.vm = vm
 
-	// HTTP client (sandboxed to allowed domains)
 	httpObj := vm.NewObject()
 	httpObj.Set("get", r.httpGet)
 	httpObj.Set("post", r.httpPost)
 	httpObj.Set("put", r.httpPut)
 	httpObj.Set("delete", r.httpDelete)
 	httpObj.Set("patch", r.httpPatch)
-	httpObj.Set("request", r.httpRequest) // Generic HTTP request (GET, POST, PUT, DELETE, etc.)
+	httpObj.Set("request", r.httpRequest)
 	httpObj.Set("clearCookies", r.httpClearCookies)
 	vm.Set("http", httpObj)
 
-	// Storage API
 	storageObj := vm.NewObject()
 	storageObj.Set("get", r.storageGet)
 	storageObj.Set("set", r.storageSet)
 	storageObj.Set("remove", r.storageRemove)
 	vm.Set("storage", storageObj)
 
-	// Secure Credentials API (encrypted storage for sensitive data)
 	credentialsObj := vm.NewObject()
 	credentialsObj.Set("store", r.credentialsStore)
 	credentialsObj.Set("get", r.credentialsGet)
@@ -243,7 +332,6 @@ func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
 	credentialsObj.Set("has", r.credentialsHas)
 	vm.Set("credentials", credentialsObj)
 
-	// Auth API (for OAuth and other auth flows)
 	authObj := vm.NewObject()
 	authObj.Set("openAuthUrl", r.authOpenUrl)
 	authObj.Set("getAuthCode", r.authGetCode)
@@ -251,14 +339,12 @@ func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
 	authObj.Set("clearAuth", r.authClear)
 	authObj.Set("isAuthenticated", r.authIsAuthenticated)
 	authObj.Set("getTokens", r.authGetTokens)
-	// PKCE support
 	authObj.Set("generatePKCE", r.authGeneratePKCE)
 	authObj.Set("getPKCE", r.authGetPKCE)
 	authObj.Set("startOAuthWithPKCE", r.authStartOAuthWithPKCE)
 	authObj.Set("exchangeCodeWithPKCE", r.authExchangeCodeWithPKCE)
 	vm.Set("auth", authObj)
 
-	// File operations (sandboxed)
 	fileObj := vm.NewObject()
 	fileObj.Set("download", r.fileDownload)
 	fileObj.Set("exists", r.fileExists)
@@ -270,21 +356,18 @@ func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
 	fileObj.Set("getSize", r.fileGetSize)
 	vm.Set("file", fileObj)
 
-	// FFmpeg API (for post-processing)
 	ffmpegObj := vm.NewObject()
 	ffmpegObj.Set("execute", r.ffmpegExecute)
 	ffmpegObj.Set("getInfo", r.ffmpegGetInfo)
 	ffmpegObj.Set("convert", r.ffmpegConvert)
 	vm.Set("ffmpeg", ffmpegObj)
 
-	// Track matching API
 	matchingObj := vm.NewObject()
 	matchingObj.Set("compareStrings", r.matchingCompareStrings)
 	matchingObj.Set("compareDuration", r.matchingCompareDuration)
 	matchingObj.Set("normalizeString", r.matchingNormalizeString)
 	vm.Set("matching", matchingObj)
 
-	// Utilities
 	utilsObj := vm.NewObject()
 	utilsObj.Set("base64Encode", r.base64Encode)
 	utilsObj.Set("base64Decode", r.base64Decode)
@@ -295,13 +378,12 @@ func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
 	utilsObj.Set("hmacSHA1", r.hmacSHA1)
 	utilsObj.Set("parseJSON", r.parseJSON)
 	utilsObj.Set("stringifyJSON", r.stringifyJSON)
-	// Crypto utilities for developers
 	utilsObj.Set("encrypt", r.cryptoEncrypt)
 	utilsObj.Set("decrypt", r.cryptoDecrypt)
 	utilsObj.Set("generateKey", r.cryptoGenerateKey)
+	utilsObj.Set("randomUserAgent", r.randomUserAgent)
 	vm.Set("utils", utilsObj)
 
-	// Log object (already set in extension_manager.go, but we can enhance it)
 	logObj := vm.NewObject()
 	logObj.Set("debug", r.logDebug)
 	logObj.Set("info", r.logInfo)
@@ -309,27 +391,18 @@ func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
 	logObj.Set("error", r.logError)
 	vm.Set("log", logObj)
 
-	// Go backend functions
 	gobackendObj := vm.NewObject()
 	gobackendObj.Set("sanitizeFilename", r.sanitizeFilenameWrapper)
 	vm.Set("gobackend", gobackendObj)
 
-	// ==================== Browser-like Polyfills ====================
-	// These make porting browser/Node.js libraries easier
-
-	// Global fetch() - Promise-style HTTP API (browser-compatible)
 	vm.Set("fetch", r.fetchPolyfill)
 
-	// Global atob/btoa - Base64 encoding (browser-compatible)
 	vm.Set("atob", r.atobPolyfill)
 	vm.Set("btoa", r.btoaPolyfill)
 
-	// TextEncoder/TextDecoder constructors
 	r.registerTextEncoderDecoder(vm)
 
-	// URL class for URL parsing
 	r.registerURLClass(vm)
 
-	// JSON global (browser-compatible)
 	r.registerJSONGlobal(vm)
 }

go_backend/extension_runtime_auth.go

@@ -1,4 +1,3 @@
-// Package gobackend provides Auth API and PKCE support for extension runtime
 package gobackend
 
 import (
@@ -16,9 +15,43 @@ import (
 	"github.com/dop251/goja"
 )
 
-// ==================== Auth API (OAuth Support) ====================
+func validateExtensionAuthURL(urlStr string) error {
+	parsed, err := url.Parse(urlStr)
+	if err != nil {
+		return fmt.Errorf("invalid auth URL: %w", err)
+	}
+
+	if parsed.Scheme != "https" {
+		return fmt.Errorf("invalid auth URL: only https is allowed")
+	}
+
+	host := parsed.Hostname()
+	if host == "" {
+		return fmt.Errorf("invalid auth URL: hostname is required")
+	}
+
+	if parsed.User != nil {
+		return fmt.Errorf("invalid auth URL: embedded credentials are not allowed")
+	}
+
+	if isPrivateIP(host) {
+		return fmt.Errorf("invalid auth URL: private/local network is not allowed")
+	}
+
+	return nil
+}
+
+func summarizeURLForLog(urlStr string) string {
+	parsed, err := url.Parse(urlStr)
+	if err != nil {
+		return urlStr
+	}
+	if parsed.Host == "" {
+		return parsed.Scheme + "://"
+	}
+	return fmt.Sprintf("%s://%s%s", parsed.Scheme, parsed.Host, parsed.Path)
+}
 
-// authOpenUrl requests Flutter to open an OAuth URL
 func (r *ExtensionRuntime) authOpenUrl(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -33,7 +66,13 @@ func (r *ExtensionRuntime) authOpenUrl(call goja.FunctionCall) goja.Value {
 		callbackURL = call.Arguments[1].String()
 	}
 
-	// Store pending auth request for Flutter to pick up
+	if err := validateExtensionAuthURL(authURL); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
 	pendingAuthRequestsMu.Lock()
 	pendingAuthRequests[r.extensionID] = &PendingAuthRequest{
 		ExtensionID: r.extensionID,
@@ -42,7 +81,6 @@ func (r *ExtensionRuntime) authOpenUrl(call goja.FunctionCall) goja.Value {
 	}
 	pendingAuthRequestsMu.Unlock()
 
-	// Update auth state
 	extensionAuthStateMu.Lock()
 	state, exists := extensionAuthState[r.extensionID]
 	if !exists {
@@ -50,10 +88,10 @@ func (r *ExtensionRuntime) authOpenUrl(call goja.FunctionCall) goja.Value {
 		extensionAuthState[r.extensionID] = state
 	}
 	state.PendingAuthURL = authURL
-	state.AuthCode = "" // Clear any previous auth code
+	state.AuthCode = ""
 	extensionAuthStateMu.Unlock()
 
-	GoLog("[Extension:%s] Auth URL requested: %s\n", r.extensionID, authURL)
+	GoLog("[Extension:%s] Auth URL requested: %s\n", r.extensionID, summarizeURLForLog(authURL))
 
 	return r.vm.ToValue(map[string]interface{}{
 		"success": true,
@@ -61,7 +99,6 @@ func (r *ExtensionRuntime) authOpenUrl(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// authGetCode gets the auth code (set by Flutter after OAuth callback)
 func (r *ExtensionRuntime) authGetCode(call goja.FunctionCall) goja.Value {
 	extensionAuthStateMu.RLock()
 	defer extensionAuthStateMu.RUnlock()
@@ -74,13 +111,11 @@ func (r *ExtensionRuntime) authGetCode(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(state.AuthCode)
 }
 
-// authSetCode sets auth code and tokens (can be called by extension after token exchange)
 func (r *ExtensionRuntime) authSetCode(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(false)
 	}
 
-	// Can accept either just auth code or an object with tokens
 	arg := call.Arguments[0].Export()
 
 	extensionAuthStateMu.Lock()
@@ -114,7 +149,6 @@ func (r *ExtensionRuntime) authSetCode(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(true)
 }
 
-// authClear clears all auth state for the extension
 func (r *ExtensionRuntime) authClear(call goja.FunctionCall) goja.Value {
 	extensionAuthStateMu.Lock()
 	delete(extensionAuthState, r.extensionID)
@@ -128,7 +162,6 @@ func (r *ExtensionRuntime) authClear(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(true)
 }
 
-// authIsAuthenticated checks if extension has valid auth
 func (r *ExtensionRuntime) authIsAuthenticated(call goja.FunctionCall) goja.Value {
 	extensionAuthStateMu.RLock()
 	defer extensionAuthStateMu.RUnlock()
@@ -138,7 +171,6 @@ func (r *ExtensionRuntime) authIsAuthenticated(call goja.FunctionCall) goja.Valu
 		return r.vm.ToValue(false)
 	}
 
-	// Check if token is expired
 	if state.IsAuthenticated && !state.ExpiresAt.IsZero() && time.Now().After(state.ExpiresAt) {
 		return r.vm.ToValue(false)
 	}
@@ -146,7 +178,6 @@ func (r *ExtensionRuntime) authIsAuthenticated(call goja.FunctionCall) goja.Valu
 	return r.vm.ToValue(state.IsAuthenticated)
 }
 
-// authGetTokens returns current tokens (for extension to use in API calls)
 func (r *ExtensionRuntime) authGetTokens(call goja.FunctionCall) goja.Value {
 	extensionAuthStateMu.RLock()
 	defer extensionAuthStateMu.RUnlock()
@@ -170,9 +201,6 @@ func (r *ExtensionRuntime) authGetTokens(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(result)
 }
 
-// ==================== PKCE Support ====================
-
-// generatePKCEVerifier generates a cryptographically random code verifier
 // Length should be between 43-128 characters (RFC 7636)
 func generatePKCEVerifier(length int) (string, error) {
 	if length < 43 {
@@ -182,16 +210,13 @@ func generatePKCEVerifier(length int) (string, error) {
 		length = 128
 	}
 
-	// Generate random bytes
 	bytes := make([]byte, length)
 	if _, err := rand.Read(bytes); err != nil {
 		return "", err
 	}
 
-	// Use base64url encoding without padding (RFC 7636 compliant)
 	verifier := base64.RawURLEncoding.EncodeToString(bytes)
 
-	// Trim to exact length
 	if len(verifier) > length {
 		verifier = verifier[:length]
 	}
@@ -199,17 +224,13 @@ func generatePKCEVerifier(length int) (string, error) {
 	return verifier, nil
 }
 
-// generatePKCEChallenge generates a code challenge from verifier using S256 method
 func generatePKCEChallenge(verifier string) string {
 	hash := sha256.Sum256([]byte(verifier))
 	// Base64url encode without padding (RFC 7636)
 	return base64.RawURLEncoding.EncodeToString(hash[:])
 }
 
-// authGeneratePKCE generates a PKCE code verifier and challenge pair
-// Returns: { verifier: string, challenge: string, method: "S256" }
 func (r *ExtensionRuntime) authGeneratePKCE(call goja.FunctionCall) goja.Value {
-	// Default length is 64 characters
 	length := 64
 	if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
 		if l, ok := call.Arguments[0].Export().(float64); ok && l >= 43 && l <= 128 {
@@ -227,7 +248,6 @@ func (r *ExtensionRuntime) authGeneratePKCE(call goja.FunctionCall) goja.Value {
 
 	challenge := generatePKCEChallenge(verifier)
 
-	// Store in auth state for later use
 	extensionAuthStateMu.Lock()
 	state, exists := extensionAuthState[r.extensionID]
 	if !exists {
@@ -247,7 +267,6 @@ func (r *ExtensionRuntime) authGeneratePKCE(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// authGetPKCE returns the current PKCE verifier and challenge (if generated)
 func (r *ExtensionRuntime) authGetPKCE(call goja.FunctionCall) goja.Value {
 	extensionAuthStateMu.RLock()
 	defer extensionAuthStateMu.RUnlock()
@@ -264,9 +283,7 @@ func (r *ExtensionRuntime) authGetPKCE(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// authStartOAuthWithPKCE is a high-level helper that generates PKCE and opens OAuth URL
 // config: { authUrl, clientId, redirectUri, scope, extraParams }
-// Returns: { success, authUrl, pkce: { verifier, challenge } }
 func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -284,7 +301,6 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 		})
 	}
 
-	// Required fields
 	authURL, _ := config["authUrl"].(string)
 	clientID, _ := config["clientId"].(string)
 	redirectURI, _ := config["redirectUri"].(string)
@@ -295,12 +311,16 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 			"error":   "authUrl, clientId, and redirectUri are required",
 		})
 	}
+	if err := validateExtensionAuthURL(authURL); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
 
-	// Optional fields
 	scope, _ := config["scope"].(string)
 	extraParams, _ := config["extraParams"].(map[string]interface{})
 
-	// Generate PKCE
 	verifier, err := generatePKCEVerifier(64)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -310,7 +330,6 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 	}
 	challenge := generatePKCEChallenge(verifier)
 
-	// Store PKCE in auth state
 	extensionAuthStateMu.Lock()
 	state, exists := extensionAuthState[r.extensionID]
 	if !exists {
@@ -319,10 +338,9 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 	}
 	state.PKCEVerifier = verifier
 	state.PKCEChallenge = challenge
-	state.AuthCode = "" // Clear any previous auth code
+	state.AuthCode = ""
 	extensionAuthStateMu.Unlock()
 
-	// Build OAuth URL with PKCE parameters
 	parsedURL, err := url.Parse(authURL)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -342,7 +360,6 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 		query.Set("scope", scope)
 	}
 
-	// Add extra params
 	for k, v := range extraParams {
 		query.Set(k, fmt.Sprintf("%v", v))
 	}
@@ -350,7 +367,6 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 	parsedURL.RawQuery = query.Encode()
 	fullAuthURL := parsedURL.String()
 
-	// Store pending auth request for Flutter
 	pendingAuthRequestsMu.Lock()
 	pendingAuthRequests[r.extensionID] = &PendingAuthRequest{
 		ExtensionID: r.extensionID,
@@ -359,7 +375,7 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 	}
 	pendingAuthRequestsMu.Unlock()
 
-	GoLog("[Extension:%s] PKCE OAuth started: %s\n", r.extensionID, fullAuthURL)
+	GoLog("[Extension:%s] PKCE OAuth started: %s\n", r.extensionID, summarizeURLForLog(fullAuthURL))
 
 	return r.vm.ToValue(map[string]interface{}{
 		"success": true,
@@ -372,9 +388,7 @@ func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.V
 	})
 }
 
-// authExchangeCodeWithPKCE exchanges auth code for tokens using PKCE
 // config: { tokenUrl, clientId, redirectUri, code, extraParams }
-// Uses the stored PKCE verifier automatically
 func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -392,7 +406,6 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 		})
 	}
 
-	// Required fields
 	tokenURL, _ := config["tokenUrl"].(string)
 	clientID, _ := config["clientId"].(string)
 	redirectURI, _ := config["redirectUri"].(string)
@@ -405,7 +418,6 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 		})
 	}
 
-	// Get stored PKCE verifier
 	extensionAuthStateMu.RLock()
 	state, exists := extensionAuthState[r.extensionID]
 	var verifier string
@@ -421,7 +433,6 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 		})
 	}
 
-	// Validate domain
 	if err := r.validateDomain(tokenURL); err != nil {
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
@@ -429,7 +440,6 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 		})
 	}
 
-	// Build token request body
 	formData := url.Values{}
 	formData.Set("grant_type", "authorization_code")
 	formData.Set("client_id", clientID)
@@ -439,14 +449,12 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 		formData.Set("redirect_uri", redirectURI)
 	}
 
-	// Add extra params
 	if extraParams, ok := config["extraParams"].(map[string]interface{}); ok {
 		for k, v := range extraParams {
 			formData.Set(k, fmt.Sprintf("%v", v))
 		}
 	}
 
-	// Make token request
 	req, err := http.NewRequest("POST", tokenURL, strings.NewReader(formData.Encode()))
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -474,18 +482,20 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 			"error":   err.Error(),
 		})
 	}
+	bodyPreview := sanitizeSensitiveLogText(string(body))
+	if len(bodyPreview) > 1000 {
+		bodyPreview = bodyPreview[:1000] + "...[truncated]"
+	}
 
-	// Parse response
 	var tokenResp map[string]interface{}
 	if err := json.Unmarshal(body, &tokenResp); err != nil {
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
 			"error":   fmt.Sprintf("failed to parse token response: %v", err),
-			"body":    string(body),
+			"body":    bodyPreview,
 		})
 	}
 
-	// Check for error in response
 	if errMsg, ok := tokenResp["error"].(string); ok {
 		errDesc, _ := tokenResp["error_description"].(string)
 		return r.vm.ToValue(map[string]interface{}{
@@ -495,7 +505,6 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 		})
 	}
 
-	// Extract tokens
 	accessToken, _ := tokenResp["access_token"].(string)
 	refreshToken, _ := tokenResp["refresh_token"].(string)
 	expiresIn, _ := tokenResp["expires_in"].(float64)
@@ -504,11 +513,10 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
 			"error":   "no access_token in response",
-			"body":    string(body),
+			"body":    bodyPreview,
 		})
 	}
 
-	// Store tokens in auth state
 	extensionAuthStateMu.Lock()
 	state, exists = extensionAuthState[r.extensionID]
 	if !exists {
@@ -521,14 +529,12 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 	if expiresIn > 0 {
 		state.ExpiresAt = time.Now().Add(time.Duration(expiresIn) * time.Second)
 	}
-	// Clear PKCE after successful exchange
 	state.PKCEVerifier = ""
 	state.PKCEChallenge = ""
 	extensionAuthStateMu.Unlock()
 
 	GoLog("[Extension:%s] PKCE token exchange successful\n", r.extensionID)
 
-	// Return full token response
 	result := map[string]interface{}{
 		"success":       true,
 		"access_token":  accessToken,
@@ -538,7 +544,6 @@ func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja
 	if expiresIn > 0 {
 		result["expires_in"] = expiresIn
 	}
-	// Include any additional fields from response
 	if scope, ok := tokenResp["scope"].(string); ok {
 		result["scope"] = scope
 	}

go_backend/extension_runtime_ffmpeg.go

@@ -1,4 +1,3 @@
-// Package gobackend provides FFmpeg API for extension runtime
 package gobackend
 
 import (
@@ -10,9 +9,7 @@ import (
 	"github.com/dop251/goja"
 )
 
-// ==================== FFmpeg API (Post-Processing) ====================
-
-// FFmpegCommand holds a pending FFmpeg command for Flutter to execute
+// FFmpegCommand holds a pending FFmpeg command for Flutter to execute.
 type FFmpegCommand struct {
 	ExtensionID string
 	Command     string
@@ -24,21 +21,18 @@ type FFmpegCommand struct {
 	Output      string
 }
 
-// Global FFmpeg command queue
 var (
 	ffmpegCommands   = make(map[string]*FFmpegCommand)
 	ffmpegCommandsMu sync.RWMutex
 	ffmpegCommandID  int64
 )
 
-// GetPendingFFmpegCommand returns a pending FFmpeg command (called from Flutter)
 func GetPendingFFmpegCommand(commandID string) *FFmpegCommand {
 	ffmpegCommandsMu.RLock()
 	defer ffmpegCommandsMu.RUnlock()
 	return ffmpegCommands[commandID]
 }
 
-// SetFFmpegCommandResult sets the result of an FFmpeg command (called from Flutter)
 func SetFFmpegCommandResult(commandID string, success bool, output, errorMsg string) {
 	ffmpegCommandsMu.Lock()
 	defer ffmpegCommandsMu.Unlock()
@@ -50,14 +44,12 @@ func SetFFmpegCommandResult(commandID string, success bool, output, errorMsg str
 	}
 }
 
-// ClearFFmpegCommand removes a completed FFmpeg command
 func ClearFFmpegCommand(commandID string) {
 	ffmpegCommandsMu.Lock()
 	defer ffmpegCommandsMu.Unlock()
 	delete(ffmpegCommands, commandID)
 }
 
-// ffmpegExecute queues an FFmpeg command for execution by Flutter
 func (r *ExtensionRuntime) ffmpegExecute(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -68,7 +60,6 @@ func (r *ExtensionRuntime) ffmpegExecute(call goja.FunctionCall) goja.Value {
 
 	command := call.Arguments[0].String()
 
-	// Generate unique command ID
 	ffmpegCommandsMu.Lock()
 	ffmpegCommandID++
 	cmdID := fmt.Sprintf("%s_%d", r.extensionID, ffmpegCommandID)
@@ -81,7 +72,6 @@ func (r *ExtensionRuntime) ffmpegExecute(call goja.FunctionCall) goja.Value {
 
 	GoLog("[Extension:%s] FFmpeg command queued: %s\n", r.extensionID, cmdID)
 
-	// Wait for completion (with timeout)
 	timeout := 5 * time.Minute
 	start := time.Now()
 	for {
@@ -101,7 +91,6 @@ func (r *ExtensionRuntime) ffmpegExecute(call goja.FunctionCall) goja.Value {
 			}
 			ffmpegCommandsMu.RUnlock()
 
-			// Cleanup
 			ClearFFmpegCommand(cmdID)
 			return r.vm.ToValue(result)
 		}
@@ -118,7 +107,6 @@ func (r *ExtensionRuntime) ffmpegExecute(call goja.FunctionCall) goja.Value {
 	}
 }
 
-// ffmpegGetInfo gets audio file information using FFprobe
 func (r *ExtensionRuntime) ffmpegGetInfo(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -129,7 +117,6 @@ func (r *ExtensionRuntime) ffmpegGetInfo(call goja.FunctionCall) goja.Value {
 
 	filePath := call.Arguments[0].String()
 
-	// Use Go's built-in audio quality function
 	quality, err := GetAudioQuality(filePath)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -147,7 +134,6 @@ func (r *ExtensionRuntime) ffmpegGetInfo(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// ffmpegConvert is a helper for common conversion operations
 func (r *ExtensionRuntime) ffmpegConvert(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -159,7 +145,6 @@ func (r *ExtensionRuntime) ffmpegConvert(call goja.FunctionCall) goja.Value {
 	inputPath := call.Arguments[0].String()
 	outputPath := call.Arguments[1].String()
 
-	// Get options if provided
 	options := map[string]interface{}{}
 	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
 		if opts, ok := call.Arguments[2].Export().(map[string]interface{}); ok {
@@ -167,36 +152,29 @@ func (r *ExtensionRuntime) ffmpegConvert(call goja.FunctionCall) goja.Value {
 		}
 	}
 
-	// Build FFmpeg command
 	var cmdParts []string
 	cmdParts = append(cmdParts, "-i", fmt.Sprintf("%q", inputPath))
 
-	// Audio codec
 	if codec, ok := options["codec"].(string); ok {
 		cmdParts = append(cmdParts, "-c:a", codec)
 	}
 
-	// Bitrate
 	if bitrate, ok := options["bitrate"].(string); ok {
 		cmdParts = append(cmdParts, "-b:a", bitrate)
 	}
 
-	// Sample rate
 	if sampleRate, ok := options["sample_rate"].(float64); ok {
 		cmdParts = append(cmdParts, "-ar", fmt.Sprintf("%d", int(sampleRate)))
 	}
 
-	// Channels
 	if channels, ok := options["channels"].(float64); ok {
 		cmdParts = append(cmdParts, "-ac", fmt.Sprintf("%d", int(channels)))
 	}
 
-	// Overwrite output
 	cmdParts = append(cmdParts, "-y", fmt.Sprintf("%q", outputPath))
 
 	command := strings.Join(cmdParts, " ")
 
-	// Execute via ffmpegExecute
 	execCall := goja.FunctionCall{
 		Arguments: []goja.Value{r.vm.ToValue(command)},
 	}

go_backend/extension_runtime_file.go

@@ -1,4 +1,3 @@
-// Package gobackend provides File API for extension runtime
 package gobackend
 
 import (
@@ -13,16 +12,11 @@ import (
 	"github.com/dop251/goja"
 )
 
-// ==================== File API (Sandboxed) ====================
-
-// List of allowed directories for file operations (set by Go backend for download operations)
 var (
 	allowedDownloadDirs   []string
 	allowedDownloadDirsMu sync.RWMutex
 )
 
-// SetAllowedDownloadDirs sets the list of directories where extensions can write files
-// This should be called by the Go backend when setting up download paths
 func SetAllowedDownloadDirs(dirs []string) {
 	allowedDownloadDirsMu.Lock()
 	defer allowedDownloadDirsMu.Unlock()
@@ -30,7 +24,6 @@ func SetAllowedDownloadDirs(dirs []string) {
 	GoLog("[Extension] Allowed download directories set: %v\n", dirs)
 }
 
-// AddAllowedDownloadDir adds a directory to the allowed list
 func AddAllowedDownloadDir(dir string) {
 	allowedDownloadDirsMu.Lock()
 	defer allowedDownloadDirsMu.Unlock()
@@ -40,68 +33,79 @@ func AddAllowedDownloadDir(dir string) {
 	}
 }
 
-// isPathInAllowedDirs checks if an absolute path is within any allowed directory
 func isPathInAllowedDirs(absPath string) bool {
 	allowedDownloadDirsMu.RLock()
 	defer allowedDownloadDirsMu.RUnlock()
 
 	for _, allowedDir := range allowedDownloadDirs {
-		if strings.HasPrefix(absPath, allowedDir) {
+		if isPathWithinBase(allowedDir, absPath) {
 			return true
 		}
 	}
 	return false
 }
 
-// validatePath checks if the path is within the extension's sandbox
-// Security: Absolute paths are BLOCKED unless they're in allowed download directories
-// Extensions should use relative paths for their own data storage
+func isPathWithinBase(baseDir, targetPath string) bool {
+	baseAbs, err := filepath.Abs(baseDir)
+	if err != nil {
+		return false
+	}
+	targetAbs, err := filepath.Abs(targetPath)
+	if err != nil {
+		return false
+	}
+
+	rel, err := filepath.Rel(baseAbs, targetAbs)
+	if err != nil {
+		return false
+	}
+	rel = filepath.Clean(rel)
+	if rel == "." {
+		return true
+	}
+
+	prefix := ".." + string(filepath.Separator)
+	if rel == ".." || strings.HasPrefix(rel, prefix) {
+		return false
+	}
+	return true
+}
+
 func (r *ExtensionRuntime) validatePath(path string) (string, error) {
-	// Check if extension has file permission
 	if !r.manifest.Permissions.File {
 		return "", fmt.Errorf("file access denied: extension does not have 'file' permission")
 	}
 
-	// Clean and resolve the path
 	cleanPath := filepath.Clean(path)
 
-	// SECURITY: Block absolute paths by default
-	// Only allow if path is in explicitly allowed download directories
 	if filepath.IsAbs(cleanPath) {
 		absPath, err := filepath.Abs(cleanPath)
 		if err != nil {
 			return "", fmt.Errorf("invalid path: %w", err)
 		}
 
-		// Check if path is in allowed download directories
 		if isPathInAllowedDirs(absPath) {
 			return absPath, nil
 		}
 
-		// Block all other absolute paths
 		return "", fmt.Errorf("file access denied: absolute paths are not allowed. Use relative paths within extension sandbox")
 	}
 
-	// For relative paths, join with data directory (extension's sandbox)
 	fullPath := filepath.Join(r.dataDir, cleanPath)
 
-	// Resolve to absolute path
 	absPath, err := filepath.Abs(fullPath)
 	if err != nil {
 		return "", fmt.Errorf("invalid path: %w", err)
 	}
 
-	// Ensure path is within data directory (prevent path traversal)
 	absDataDir, _ := filepath.Abs(r.dataDir)
-	if !strings.HasPrefix(absPath, absDataDir) {
+	if !isPathWithinBase(absDataDir, absPath) {
 		return "", fmt.Errorf("file access denied: path '%s' is outside sandbox", path)
 	}
 
 	return absPath, nil
 }
 
-// fileDownload downloads a file from URL to the specified path
-// Supports progress callback via options.onProgress
 func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -113,7 +117,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 	urlStr := call.Arguments[0].String()
 	outputPath := call.Arguments[1].String()
 
-	// Validate domain
 	if err := r.validateDomain(urlStr); err != nil {
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
@@ -121,7 +124,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Validate output path (allows absolute paths for download queue)
 	fullPath, err := r.validatePath(outputPath)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -130,20 +132,17 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Get options if provided
 	var onProgress goja.Callable
 	var headers map[string]string
 	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
 		optionsObj := call.Arguments[2].Export()
 		if opts, ok := optionsObj.(map[string]interface{}); ok {
-			// Extract headers
 			if h, ok := opts["headers"].(map[string]interface{}); ok {
 				headers = make(map[string]string)
 				for k, v := range h {
 					headers[k] = fmt.Sprintf("%v", v)
 				}
 			}
-			// Extract onProgress callback
 			if progressVal, ok := opts["onProgress"]; ok {
 				if callable, ok := goja.AssertFunction(r.vm.ToValue(progressVal)); ok {
 					onProgress = callable
@@ -152,7 +151,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 		}
 	}
 
-	// Create directory if needed
 	dir := filepath.Dir(fullPath)
 	if err := os.MkdirAll(dir, 0755); err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -161,7 +159,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Create HTTP request
 	req, err := http.NewRequest("GET", urlStr, nil)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -170,7 +167,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Set headers
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}
@@ -178,7 +174,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 		req.Header.Set("User-Agent", "SpotiFLAC-Extension/1.0")
 	}
 
-	// Download file
 	resp, err := r.httpClient.Do(req)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -195,7 +190,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Create output file
 	out, err := os.Create(fullPath)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -205,12 +199,10 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 	}
 	defer out.Close()
 
-	// Get content length for progress
 	contentLength := resp.ContentLength
 
-	// Copy content with progress reporting
 	var written int64
-	buf := make([]byte, 32*1024) // 32KB buffer
+	buf := make([]byte, 32*1024)
 	for {
 		nr, er := resp.Body.Read(buf)
 		if nr > 0 {
@@ -235,7 +227,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 				})
 			}
 
-			// Report progress
 			if onProgress != nil && contentLength > 0 {
 				_, _ = onProgress(goja.Undefined(), r.vm.ToValue(written), r.vm.ToValue(contentLength))
 			}
@@ -260,7 +251,6 @@ func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// fileExists checks if a file exists in the sandbox
 func (r *ExtensionRuntime) fileExists(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(false)
@@ -276,7 +266,6 @@ func (r *ExtensionRuntime) fileExists(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(err == nil)
 }
 
-// fileDelete deletes a file in the sandbox
 func (r *ExtensionRuntime) fileDelete(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -306,7 +295,6 @@ func (r *ExtensionRuntime) fileDelete(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// fileRead reads a file from the sandbox
 func (r *ExtensionRuntime) fileRead(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -338,7 +326,6 @@ func (r *ExtensionRuntime) fileRead(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// fileWrite writes data to a file in the sandbox
 func (r *ExtensionRuntime) fileWrite(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -358,7 +345,6 @@ func (r *ExtensionRuntime) fileWrite(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Create directory if needed
 	dir := filepath.Dir(fullPath)
 	if err := os.MkdirAll(dir, 0755); err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -380,7 +366,6 @@ func (r *ExtensionRuntime) fileWrite(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// fileCopy copies a file within the sandbox
 func (r *ExtensionRuntime) fileCopy(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -408,16 +393,15 @@ func (r *ExtensionRuntime) fileCopy(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Read source file
-	data, err := os.ReadFile(fullSrc)
+	srcFile, err := os.Open(fullSrc)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
 			"error":   fmt.Sprintf("failed to read source: %v", err),
 		})
 	}
+	defer srcFile.Close()
 
-	// Create destination directory if needed
 	dir := filepath.Dir(fullDst)
 	if err := os.MkdirAll(dir, 0755); err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -426,11 +410,26 @@ func (r *ExtensionRuntime) fileCopy(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Write to destination
-	if err := os.WriteFile(fullDst, data, 0644); err != nil {
+	dstFile, err := os.OpenFile(fullDst, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
+	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
-			"error":   fmt.Sprintf("failed to write destination: %v", err),
+			"error":   fmt.Sprintf("failed to open destination: %v", err),
+		})
+	}
+
+	if _, err := io.Copy(dstFile, srcFile); err != nil {
+		_ = dstFile.Close()
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to copy file: %v", err),
+		})
+	}
+
+	if err := dstFile.Close(); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to finalize destination: %v", err),
 		})
 	}
 
@@ -440,7 +439,6 @@ func (r *ExtensionRuntime) fileCopy(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// fileMove moves/renames a file within the sandbox
 func (r *ExtensionRuntime) fileMove(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -468,7 +466,6 @@ func (r *ExtensionRuntime) fileMove(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Create destination directory if needed
 	dir := filepath.Dir(fullDst)
 	if err := os.MkdirAll(dir, 0755); err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -490,7 +487,6 @@ func (r *ExtensionRuntime) fileMove(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// fileGetSize returns the size of a file in bytes
 func (r *ExtensionRuntime) fileGetSize(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{

go_backend/extension_runtime_http.go

@@ -1,4 +1,3 @@
-// Package gobackend provides HTTP API for extension runtime
 package gobackend
 
 import (
@@ -12,25 +11,33 @@ import (
 	"github.com/dop251/goja"
 )
 
-// ==================== HTTP API (Sandboxed) ====================
-
-// HTTPResponse represents the response from an HTTP request
 type HTTPResponse struct {
 	StatusCode int               `json:"statusCode"`
 	Body       string            `json:"body"`
 	Headers    map[string]string `json:"headers"`
 }
 
-// validateDomain checks if the domain is allowed by the extension's permissions
 func (r *ExtensionRuntime) validateDomain(urlStr string) error {
 	parsed, err := url.Parse(urlStr)
 	if err != nil {
 		return fmt.Errorf("invalid URL: %w", err)
 	}
 
-	domain := parsed.Hostname()
+	if parsed.Scheme == "" {
+		return fmt.Errorf("invalid URL: scheme is required")
+	}
+	if parsed.Scheme != "https" {
+		return fmt.Errorf("network access denied: only https is allowed")
+	}
+	if parsed.User != nil {
+		return fmt.Errorf("invalid URL: embedded credentials are not allowed")
+	}
+
+	domain := parsed.Hostname()
+	if domain == "" {
+		return fmt.Errorf("invalid URL: hostname is required")
+	}
 
-	// Block private/local network access (SSRF protection)
 	if isPrivateIP(domain) {
 		return fmt.Errorf("network access denied: private/local network '%s' not allowed", domain)
 	}
@@ -42,7 +49,6 @@ func (r *ExtensionRuntime) validateDomain(urlStr string) error {
 	return nil
 }
 
-// httpGet performs a GET request (sandboxed)
 func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -52,7 +58,6 @@ func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
 
 	urlStr := call.Arguments[0].String()
 
-	// Validate domain
 	if err := r.validateDomain(urlStr); err != nil {
 		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
 		return r.vm.ToValue(map[string]interface{}{
@@ -60,7 +65,6 @@ func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Get headers if provided
 	headers := make(map[string]string)
 	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
 		headersObj := call.Arguments[1].Export()
@@ -71,7 +75,6 @@ func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
 		}
 	}
 
-	// Create request
 	req, err := http.NewRequest("GET", urlStr, nil)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -79,16 +82,14 @@ func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Set headers - user headers first
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}
-	// Only set default User-Agent if not provided by extension
+
 	if req.Header.Get("User-Agent") == "" {
 		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
 	}
 
-	// Execute request
 	resp, err := r.httpClient.Do(req)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -97,7 +98,6 @@ func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
 	}
 	defer resp.Body.Close()
 
-	// Read body
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -105,26 +105,24 @@ func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Extract response headers - return all values as arrays for multi-value headers (cookies, etc.)
 	respHeaders := make(map[string]interface{})
 	for k, v := range resp.Header {
 		if len(v) == 1 {
 			respHeaders[k] = v[0]
 		} else {
-			respHeaders[k] = v // Return as array if multiple values
+			respHeaders[k] = v
 		}
 	}
 
 	return r.vm.ToValue(map[string]interface{}{
 		"statusCode": resp.StatusCode,
-		"status":     resp.StatusCode, // Alias for convenience
+		"status":     resp.StatusCode,
 		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
 		"body":       string(body),
 		"headers":    respHeaders,
 	})
 }
 
-// httpPost performs a POST request (sandboxed)
 func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -134,7 +132,6 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 
 	urlStr := call.Arguments[0].String()
 
-	// Validate domain
 	if err := r.validateDomain(urlStr); err != nil {
 		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
 		return r.vm.ToValue(map[string]interface{}{
@@ -142,7 +139,6 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Get body if provided - support both string and object
 	var bodyStr string
 	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
 		bodyArg := call.Arguments[1].Export()
@@ -150,7 +146,6 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 		case string:
 			bodyStr = v
 		case map[string]interface{}, []interface{}:
-			// Auto-stringify objects and arrays to JSON
 			jsonBytes, err := json.Marshal(v)
 			if err != nil {
 				return r.vm.ToValue(map[string]interface{}{
@@ -159,12 +154,10 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 			}
 			bodyStr = string(jsonBytes)
 		default:
-			// Fallback to string conversion
 			bodyStr = call.Arguments[1].String()
 		}
 	}
 
-	// Get headers if provided
 	headers := make(map[string]string)
 	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
 		headersObj := call.Arguments[2].Export()
@@ -175,7 +168,6 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 		}
 	}
 
-	// Create request
 	req, err := http.NewRequest("POST", urlStr, strings.NewReader(bodyStr))
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -183,11 +175,10 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Set headers - user headers first
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}
-	// Only set defaults if not provided by extension
+
 	if req.Header.Get("User-Agent") == "" {
 		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
 	}
@@ -195,7 +186,6 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 		req.Header.Set("Content-Type", "application/json")
 	}
 
-	// Execute request
 	resp, err := r.httpClient.Do(req)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -204,7 +194,6 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 	}
 	defer resp.Body.Close()
 
-	// Read body
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -212,27 +201,24 @@ func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Extract response headers - return all values as arrays for multi-value headers
 	respHeaders := make(map[string]interface{})
 	for k, v := range resp.Header {
 		if len(v) == 1 {
 			respHeaders[k] = v[0]
 		} else {
-			respHeaders[k] = v // Return as array if multiple values
+			respHeaders[k] = v
 		}
 	}
 
 	return r.vm.ToValue(map[string]interface{}{
 		"statusCode": resp.StatusCode,
-		"status":     resp.StatusCode, // Alias for convenience
+		"status":     resp.StatusCode,
 		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
 		"body":       string(body),
 		"headers":    respHeaders,
 	})
 }
 
-// httpRequest performs a generic HTTP request (GET, POST, PUT, DELETE, etc.)
-// Usage: http.request(url, options) where options = { method, body, headers }
 func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -242,7 +228,6 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 
 	urlStr := call.Arguments[0].String()
 
-	// Validate domain
 	if err := r.validateDomain(urlStr); err != nil {
 		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
 		return r.vm.ToValue(map[string]interface{}{
@@ -250,27 +235,22 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Default options
 	method := "GET"
 	var bodyStr string
 	headers := make(map[string]string)
 
-	// Parse options if provided
 	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
 		optionsObj := call.Arguments[1].Export()
 		if opts, ok := optionsObj.(map[string]interface{}); ok {
-			// Get method
 			if m, ok := opts["method"].(string); ok {
 				method = strings.ToUpper(m)
 			}
 
-			// Get body - support both string and object
 			if bodyArg, ok := opts["body"]; ok && bodyArg != nil {
 				switch v := bodyArg.(type) {
 				case string:
 					bodyStr = v
 				case map[string]interface{}, []interface{}:
-					// Auto-stringify objects and arrays to JSON
 					jsonBytes, err := json.Marshal(v)
 					if err != nil {
 						return r.vm.ToValue(map[string]interface{}{
@@ -283,7 +263,6 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 				}
 			}
 
-			// Get headers
 			if h, ok := opts["headers"].(map[string]interface{}); ok {
 				for k, v := range h {
 					headers[k] = fmt.Sprintf("%v", v)
@@ -292,7 +271,6 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 		}
 	}
 
-	// Create request
 	var reqBody io.Reader
 	if bodyStr != "" {
 		reqBody = strings.NewReader(bodyStr)
@@ -305,11 +283,10 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Set headers - user headers first
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}
-	// Only set defaults if not provided by extension
+
 	if req.Header.Get("User-Agent") == "" {
 		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
 	}
@@ -317,7 +294,6 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 		req.Header.Set("Content-Type", "application/json")
 	}
 
-	// Execute request
 	resp, err := r.httpClient.Do(req)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -326,7 +302,6 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 	}
 	defer resp.Body.Close()
 
-	// Read body
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -334,43 +309,36 @@ func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Extract response headers - return all values as arrays for multi-value headers
 	respHeaders := make(map[string]interface{})
 	for k, v := range resp.Header {
 		if len(v) == 1 {
 			respHeaders[k] = v[0]
 		} else {
-			respHeaders[k] = v // Return as array if multiple values
+			respHeaders[k] = v
 		}
 	}
 
-	// Return response with helper properties
 	return r.vm.ToValue(map[string]interface{}{
 		"statusCode": resp.StatusCode,
-		"status":     resp.StatusCode, // Alias for convenience
+		"status":     resp.StatusCode,
 		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
 		"body":       string(body),
 		"headers":    respHeaders,
 	})
 }
 
-// httpPut performs a PUT request (shortcut for http.request with method: "PUT")
 func (r *ExtensionRuntime) httpPut(call goja.FunctionCall) goja.Value {
 	return r.httpMethodShortcut("PUT", call)
 }
 
-// httpDelete performs a DELETE request (shortcut for http.request with method: "DELETE")
 func (r *ExtensionRuntime) httpDelete(call goja.FunctionCall) goja.Value {
 	return r.httpMethodShortcut("DELETE", call)
 }
 
-// httpPatch performs a PATCH request (shortcut for http.request with method: "PATCH")
 func (r *ExtensionRuntime) httpPatch(call goja.FunctionCall) goja.Value {
 	return r.httpMethodShortcut("PATCH", call)
 }
 
-// httpMethodShortcut is a helper for PUT/DELETE/PATCH shortcuts
-// Signature: http.put(url, body, headers) / http.delete(url, headers) / http.patch(url, body, headers)
 func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -380,7 +348,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 
 	urlStr := call.Arguments[0].String()
 
-	// Validate domain
 	if err := r.validateDomain(urlStr); err != nil {
 		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
 		return r.vm.ToValue(map[string]interface{}{
@@ -391,9 +358,7 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 	var bodyStr string
 	headers := make(map[string]string)
 
-	// For DELETE, second arg is headers; for PUT/PATCH, second arg is body
 	if method == "DELETE" {
-		// http.delete(url, headers)
 		if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
 			headersObj := call.Arguments[1].Export()
 			if h, ok := headersObj.(map[string]interface{}); ok {
@@ -403,7 +368,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 			}
 		}
 	} else {
-		// http.put(url, body, headers) / http.patch(url, body, headers)
 		if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
 			bodyArg := call.Arguments[1].Export()
 			switch v := bodyArg.(type) {
@@ -432,7 +396,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 		}
 	}
 
-	// Create request
 	var reqBody io.Reader
 	if bodyStr != "" {
 		reqBody = strings.NewReader(bodyStr)
@@ -445,7 +408,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 		})
 	}
 
-	// Set headers - user headers first
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}
@@ -456,7 +418,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 		req.Header.Set("Content-Type", "application/json")
 	}
 
-	// Execute request
 	resp, err := r.httpClient.Do(req)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -465,7 +426,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 	}
 	defer resp.Body.Close()
 
-	// Read body
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
@@ -473,7 +433,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 		})
 	}
 
-	// Extract response headers
 	respHeaders := make(map[string]interface{})
 	for k, v := range resp.Header {
 		if len(v) == 1 {
@@ -492,7 +451,6 @@ func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionC
 	})
 }
 
-// httpClearCookies clears all cookies for this extension
 func (r *ExtensionRuntime) httpClearCookies(call goja.FunctionCall) goja.Value {
 	if jar, ok := r.cookieJar.(*simpleCookieJar); ok {
 		jar.mu.Lock()

go_backend/extension_runtime_matching.go

@@ -1,4 +1,3 @@
-// Package gobackend provides Track Matching API for extension runtime
 package gobackend
 
 import (
@@ -7,9 +6,6 @@ import (
 	"github.com/dop251/goja"
 )
 
-// ==================== Track Matching API ====================
-
-// matchingCompareStrings compares two strings with fuzzy matching
 func (r *ExtensionRuntime) matchingCompareStrings(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(0.0)
@@ -22,12 +18,10 @@ func (r *ExtensionRuntime) matchingCompareStrings(call goja.FunctionCall) goja.V
 		return r.vm.ToValue(1.0)
 	}
 
-	// Calculate Levenshtein distance-based similarity
 	similarity := calculateStringSimilarity(str1, str2)
 	return r.vm.ToValue(similarity)
 }
 
-// matchingCompareDuration compares two durations with tolerance
 func (r *ExtensionRuntime) matchingCompareDuration(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(false)
@@ -36,8 +30,7 @@ func (r *ExtensionRuntime) matchingCompareDuration(call goja.FunctionCall) goja.
 	dur1 := int(call.Arguments[0].ToInteger())
 	dur2 := int(call.Arguments[1].ToInteger())
 
-	// Default tolerance: 3 seconds
-	tolerance := 3000 // milliseconds
+	tolerance := 3000
 	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) {
 		tolerance = int(call.Arguments[2].ToInteger())
 	}
@@ -50,7 +43,6 @@ func (r *ExtensionRuntime) matchingCompareDuration(call goja.FunctionCall) goja.
 	return r.vm.ToValue(diff <= tolerance)
 }
 
-// matchingNormalizeString normalizes a string for comparison
 func (r *ExtensionRuntime) matchingNormalizeString(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -61,7 +53,6 @@ func (r *ExtensionRuntime) matchingNormalizeString(call goja.FunctionCall) goja.
 	return r.vm.ToValue(normalized)
 }
 
-// calculateStringSimilarity calculates similarity between two strings (0-1)
 func calculateStringSimilarity(s1, s2 string) float64 {
 	if len(s1) == 0 && len(s2) == 0 {
 		return 1.0
@@ -70,7 +61,6 @@ func calculateStringSimilarity(s1, s2 string) float64 {
 		return 0.0
 	}
 
-	// Use Levenshtein distance
 	distance := levenshteinDistance(s1, s2)
 	maxLen := len(s1)
 	if len(s2) > maxLen {
@@ -80,7 +70,6 @@ func calculateStringSimilarity(s1, s2 string) float64 {
 	return 1.0 - float64(distance)/float64(maxLen)
 }
 
-// levenshteinDistance calculates the Levenshtein distance between two strings
 func levenshteinDistance(s1, s2 string) int {
 	if len(s1) == 0 {
 		return len(s2)
@@ -89,7 +78,6 @@ func levenshteinDistance(s1, s2 string) int {
 		return len(s1)
 	}
 
-	// Create matrix
 	matrix := make([][]int, len(s1)+1)
 	for i := range matrix {
 		matrix[i] = make([]int, len(s2)+1)
@@ -99,7 +87,6 @@ func levenshteinDistance(s1, s2 string) int {
 		matrix[0][j] = j
 	}
 
-	// Fill matrix
 	for i := 1; i <= len(s1); i++ {
 		for j := 1; j <= len(s2); j++ {
 			cost := 1
@@ -107,9 +94,9 @@ func levenshteinDistance(s1, s2 string) int {
 				cost = 0
 			}
 			matrix[i][j] = min(
-				matrix[i-1][j]+1,      // deletion
-				matrix[i][j-1]+1,      // insertion
-				matrix[i-1][j-1]+cost, // substitution
+				matrix[i-1][j]+1,
+				matrix[i][j-1]+1,
+				matrix[i-1][j-1]+cost,
 			)
 		}
 	}
@@ -117,12 +104,9 @@ func levenshteinDistance(s1, s2 string) int {
 	return matrix[len(s1)][len(s2)]
 }
 
-// normalizeStringForMatching normalizes a string for comparison
 func normalizeStringForMatching(s string) string {
-	// Convert to lowercase
 	s = strings.ToLower(s)
 
-	// Remove common suffixes/prefixes
 	suffixes := []string{
 		" (remastered)", " (remaster)", " - remastered", " - remaster",
 		" (deluxe)", " (deluxe edition)", " - deluxe", " - deluxe edition",
@@ -136,7 +120,6 @@ func normalizeStringForMatching(s string) string {
 		}
 	}
 
-	// Remove special characters
 	var result strings.Builder
 	for _, r := range s {
 		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == ' ' {
@@ -144,7 +127,6 @@ func normalizeStringForMatching(s string) string {
 		}
 	}
 
-	// Collapse multiple spaces
 	s = strings.Join(strings.Fields(result.String()), " ")
 
 	return strings.TrimSpace(s)

go_backend/extension_runtime_polyfills.go

@@ -1,4 +1,3 @@
-// Package gobackend provides Browser-like Polyfills for extension runtime
 package gobackend
 
 import (
@@ -13,26 +12,21 @@ import (
 	"github.com/dop251/goja"
 )
 
-// ==================== Browser-like Polyfills ====================
 // These polyfills make porting browser/Node.js libraries easier
-// without compromising sandbox security
+// without compromising sandbox security.
 
-// fetchPolyfill implements browser-compatible fetch() API
-// Returns a Promise-like object with json(), text() methods
+// Returns a Promise-like object with json(), text() methods.
 func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.createFetchError("URL is required")
 	}
 
 	urlStr := call.Arguments[0].String()
-
-	// Validate domain
 	if err := r.validateDomain(urlStr); err != nil {
 		GoLog("[Extension:%s] fetch blocked: %v\n", r.extensionID, err)
 		return r.createFetchError(err.Error())
 	}
 
-	// Parse options
 	method := "GET"
 	var bodyStr string
 	headers := make(map[string]string)
@@ -40,7 +34,6 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
 		optionsObj := call.Arguments[1].Export()
 		if opts, ok := optionsObj.(map[string]interface{}); ok {
-			// Method
 			if m, ok := opts["method"].(string); ok {
 				method = strings.ToUpper(m)
 			}
@@ -61,7 +54,6 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 				}
 			}
 
-			// Headers
 			if h, ok := opts["headers"]; ok && h != nil {
 				switch hv := h.(type) {
 				case map[string]interface{}:
@@ -73,7 +65,6 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 		}
 	}
 
-	// Create HTTP request
 	var reqBody io.Reader
 	if bodyStr != "" {
 		reqBody = strings.NewReader(bodyStr)
@@ -84,11 +75,9 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 		return r.createFetchError(err.Error())
 	}
 
-	// Set headers - user headers first
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}
-	// Set defaults if not provided
 	if req.Header.Get("User-Agent") == "" {
 		req.Header.Set("User-Agent", "SpotiFLAC-Extension/1.0")
 	}
@@ -96,20 +85,17 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 		req.Header.Set("Content-Type", "application/json")
 	}
 
-	// Execute request
 	resp, err := r.httpClient.Do(req)
 	if err != nil {
 		return r.createFetchError(err.Error())
 	}
 	defer resp.Body.Close()
 
-	// Read body
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return r.createFetchError(err.Error())
 	}
 
-	// Extract response headers
 	respHeaders := make(map[string]interface{})
 	for k, v := range resp.Header {
 		if len(v) == 1 {
@@ -119,7 +105,6 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 		}
 	}
 
-	// Create Response object (browser-compatible)
 	responseObj := r.vm.NewObject()
 	responseObj.Set("ok", resp.StatusCode >= 200 && resp.StatusCode < 300)
 	responseObj.Set("status", resp.StatusCode)
@@ -127,15 +112,12 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 	responseObj.Set("headers", respHeaders)
 	responseObj.Set("url", urlStr)
 
-	// Store body for methods
 	bodyString := string(body)
 
-	// text() method - returns body as string
 	responseObj.Set("text", func(call goja.FunctionCall) goja.Value {
 		return r.vm.ToValue(bodyString)
 	})
 
-	// json() method - parses body as JSON
 	responseObj.Set("json", func(call goja.FunctionCall) goja.Value {
 		var result interface{}
 		if err := json.Unmarshal(body, &result); err != nil {
@@ -145,9 +127,7 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 		return r.vm.ToValue(result)
 	})
 
-	// arrayBuffer() method - returns body as array (simplified)
 	responseObj.Set("arrayBuffer", func(call goja.FunctionCall) goja.Value {
-		// Return as array of bytes
 		byteArray := make([]interface{}, len(body))
 		for i, b := range body {
 			byteArray[i] = int(b)
@@ -158,7 +138,6 @@ func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
 	return responseObj
 }
 
-// createFetchError creates a fetch error response
 func (r *ExtensionRuntime) createFetchError(message string) goja.Value {
 	errorObj := r.vm.NewObject()
 	errorObj.Set("ok", false)
@@ -174,7 +153,6 @@ func (r *ExtensionRuntime) createFetchError(message string) goja.Value {
 	return errorObj
 }
 
-// atobPolyfill implements browser atob() - decode base64 to string
 func (r *ExtensionRuntime) atobPolyfill(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -182,7 +160,6 @@ func (r *ExtensionRuntime) atobPolyfill(call goja.FunctionCall) goja.Value {
 	input := call.Arguments[0].String()
 	decoded, err := base64.StdEncoding.DecodeString(input)
 	if err != nil {
-		// Try URL-safe base64
 		decoded, err = base64.URLEncoding.DecodeString(input)
 		if err != nil {
 			GoLog("[Extension:%s] atob decode error: %v\n", r.extensionID, err)
@@ -192,7 +169,6 @@ func (r *ExtensionRuntime) atobPolyfill(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(string(decoded))
 }
 
-// btoaPolyfill implements browser btoa() - encode string to base64
 func (r *ExtensionRuntime) btoaPolyfill(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -201,14 +177,11 @@ func (r *ExtensionRuntime) btoaPolyfill(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(base64.StdEncoding.EncodeToString([]byte(input)))
 }
 
-// registerTextEncoderDecoder registers TextEncoder and TextDecoder classes
 func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
-	// TextEncoder constructor
 	vm.Set("TextEncoder", func(call goja.ConstructorCall) *goja.Object {
 		encoder := call.This
 		encoder.Set("encoding", "utf-8")
 
-		// encode() method - string to Uint8Array
 		encoder.Set("encode", func(call goja.FunctionCall) goja.Value {
 			if len(call.Arguments) < 1 {
 				return vm.ToValue([]byte{})
@@ -216,7 +189,6 @@ func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
 			input := call.Arguments[0].String()
 			bytes := []byte(input)
 
-			// Return as array (Uint8Array-like)
 			result := make([]interface{}, len(bytes))
 			for i, b := range bytes {
 				result[i] = int(b)
@@ -224,7 +196,6 @@ func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
 			return vm.ToValue(result)
 		})
 
-		// encodeInto() method
 		encoder.Set("encodeInto", func(call goja.FunctionCall) goja.Value {
 			// Simplified implementation
 			if len(call.Arguments) < 2 {
@@ -240,11 +211,9 @@ func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
 		return nil
 	})
 
-	// TextDecoder constructor
 	vm.Set("TextDecoder", func(call goja.ConstructorCall) *goja.Object {
 		decoder := call.This
 
-		// Get encoding from arguments (default: utf-8)
 		encoding := "utf-8"
 		if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
 			encoding = call.Arguments[0].String()
@@ -253,13 +222,11 @@ func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
 		decoder.Set("fatal", false)
 		decoder.Set("ignoreBOM", false)
 
-		// decode() method - Uint8Array to string
 		decoder.Set("decode", func(call goja.FunctionCall) goja.Value {
 			if len(call.Arguments) < 1 {
 				return vm.ToValue("")
 			}
 
-			// Handle different input types
 			input := call.Arguments[0].Export()
 			var bytes []byte
 
@@ -279,7 +246,6 @@ func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
 					}
 				}
 			case string:
-				// Already a string, just return it
 				return vm.ToValue(v)
 			default:
 				return vm.ToValue("")
@@ -292,7 +258,6 @@ func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
 	})
 }
 
-// registerURLClass registers the URL class for URL parsing
 func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
 	vm.Set("URL", func(call goja.ConstructorCall) *goja.Object {
 		urlObj := call.This
@@ -304,7 +269,6 @@ func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
 
 		urlStr := call.Arguments[0].String()
 
-		// Handle relative URLs with base
 		if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) {
 			baseStr := call.Arguments[1].String()
 			baseURL, err := url.Parse(baseStr)
@@ -322,7 +286,6 @@ func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
 			return nil
 		}
 
-		// Set URL properties
 		urlObj.Set("href", parsed.String())
 		urlObj.Set("protocol", parsed.Scheme+":")
 		urlObj.Set("host", parsed.Host)
@@ -342,10 +305,9 @@ func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
 		password, _ := parsed.User.Password()
 		urlObj.Set("password", password)
 
-		// searchParams object
-		searchParams := vm.NewObject()
 		queryValues := parsed.Query()
 
+		searchParams := vm.NewObject()
 		searchParams.Set("get", func(call goja.FunctionCall) goja.Value {
 			if len(call.Arguments) < 1 {
 				return goja.Null()
@@ -379,12 +341,10 @@ func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
 
 		urlObj.Set("searchParams", searchParams)
 
-		// toString method
 		urlObj.Set("toString", func(call goja.FunctionCall) goja.Value {
 			return vm.ToValue(parsed.String())
 		})
 
-		// toJSON method
 		urlObj.Set("toJSON", func(call goja.FunctionCall) goja.Value {
 			return vm.ToValue(parsed.String())
 		})
@@ -392,17 +352,14 @@ func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
 		return nil
 	})
 
-	// URLSearchParams constructor
 	vm.Set("URLSearchParams", func(call goja.ConstructorCall) *goja.Object {
 		paramsObj := call.This
 		values := url.Values{}
 
-		// Parse initial value if provided
 		if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
 			init := call.Arguments[0].Export()
 			switch v := init.(type) {
 			case string:
-				// Parse query string
 				parsed, _ := url.ParseQuery(strings.TrimPrefix(v, "?"))
 				values = parsed
 			case map[string]interface{}:
@@ -465,13 +422,8 @@ func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
 	})
 }
 
-// registerJSONGlobal ensures JSON global is properly set up
+// JSON is already built-in to Goja; this ensures a fallback exists.
 func (r *ExtensionRuntime) registerJSONGlobal(vm *goja.Runtime) {
-	// JSON is already built-in to Goja, but we can enhance it
-	// This ensures JSON.parse and JSON.stringify work as expected
-
-	// The built-in JSON object should already work, but let's verify
-	// and add any missing functionality if needed
 	jsonScript := `
 		if (typeof JSON === 'undefined') {
 			var JSON = {

go_backend/extension_runtime_storage.go

@@ -1,4 +1,3 @@
-// Package gobackend provides Storage and Credentials API for extension runtime
 package gobackend
 
 import (
@@ -11,48 +10,164 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"reflect"
+	"time"
 
 	"github.com/dop251/goja"
 )
 
-// ==================== Storage API ====================
+const (
+	defaultStorageFlushDelay = 400 * time.Millisecond
+	storageFlushRetryDelay   = 2 * time.Second
+)
 
-// getStoragePath returns the path to the extension's storage file
 func (r *ExtensionRuntime) getStoragePath() string {
 	return filepath.Join(r.dataDir, "storage.json")
 }
 
-// loadStorage loads the storage data from disk
-func (r *ExtensionRuntime) loadStorage() (map[string]interface{}, error) {
+func cloneInterfaceMap(src map[string]interface{}) map[string]interface{} {
+	if len(src) == 0 {
+		return make(map[string]interface{})
+	}
+	dst := make(map[string]interface{}, len(src))
+	for k, v := range src {
+		dst[k] = v
+	}
+	return dst
+}
+
+func (r *ExtensionRuntime) ensureStorageLoaded() error {
+	r.storageMu.RLock()
+	if r.storageLoaded {
+		r.storageMu.RUnlock()
+		return nil
+	}
+	r.storageMu.RUnlock()
+
+	r.storageMu.Lock()
+	defer r.storageMu.Unlock()
+	if r.storageLoaded {
+		return nil
+	}
+
 	storagePath := r.getStoragePath()
 	data, err := os.ReadFile(storagePath)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return make(map[string]interface{}), nil
+			r.storageCache = make(map[string]interface{})
+			r.storageLoaded = true
+			return nil
 		}
-		return nil, err
+		return err
 	}
 
 	var storage map[string]interface{}
 	if err := json.Unmarshal(data, &storage); err != nil {
+		return err
+	}
+	if storage == nil {
+		storage = make(map[string]interface{})
+	}
+
+	r.storageCache = storage
+	r.storageLoaded = true
+	return nil
+}
+
+func (r *ExtensionRuntime) loadStorage() (map[string]interface{}, error) {
+	if err := r.ensureStorageLoaded(); err != nil {
 		return nil, err
 	}
 
-	return storage, nil
+	r.storageMu.RLock()
+	defer r.storageMu.RUnlock()
+	return cloneInterfaceMap(r.storageCache), nil
 }
 
-// saveStorage saves the storage data to disk
-func (r *ExtensionRuntime) saveStorage(storage map[string]interface{}) error {
-	storagePath := r.getStoragePath()
-	data, err := json.MarshalIndent(storage, "", "  ")
+func (r *ExtensionRuntime) queueStorageFlushLocked(delay time.Duration) {
+	if r.storageClosed {
+		return
+	}
+	if r.storageTimer != nil {
+		return
+	}
+	r.storageTimer = time.AfterFunc(delay, r.flushStorageDirtyAsync)
+}
+
+func (r *ExtensionRuntime) persistStorageSnapshot(storage map[string]interface{}) error {
+	data, err := json.Marshal(storage)
 	if err != nil {
 		return err
 	}
 
-	return os.WriteFile(storagePath, data, 0644)
+	r.storageWriteMu.Lock()
+	defer r.storageWriteMu.Unlock()
+
+	return os.WriteFile(r.getStoragePath(), data, 0600)
+}
+
+func (r *ExtensionRuntime) flushStorageDirtyAsync() {
+	if err := r.flushStorageDirty(); err != nil {
+		GoLog("[Extension:%s] Storage flush error: %v\n", r.extensionID, err)
+	}
+}
+
+func (r *ExtensionRuntime) flushStorageDirty() error {
+	r.storageMu.Lock()
+	if r.storageClosed {
+		r.storageTimer = nil
+		r.storageMu.Unlock()
+		return nil
+	}
+	if !r.storageDirty {
+		r.storageTimer = nil
+		r.storageMu.Unlock()
+		return nil
+	}
+	snapshot := cloneInterfaceMap(r.storageCache)
+	r.storageDirty = false
+	r.storageTimer = nil
+	r.storageMu.Unlock()
+
+	if err := r.persistStorageSnapshot(snapshot); err != nil {
+		r.storageMu.Lock()
+		r.storageDirty = true
+		r.queueStorageFlushLocked(storageFlushRetryDelay)
+		r.storageMu.Unlock()
+		return err
+	}
+
+	return nil
+}
+
+func (r *ExtensionRuntime) flushStorageNow() error {
+	r.storageMu.Lock()
+	if r.storageTimer != nil {
+		r.storageTimer.Stop()
+		r.storageTimer = nil
+	}
+	if !r.storageLoaded || r.storageClosed {
+		r.storageMu.Unlock()
+		return nil
+	}
+	snapshot := cloneInterfaceMap(r.storageCache)
+	r.storageDirty = false
+	r.storageMu.Unlock()
+
+	return r.persistStorageSnapshot(snapshot)
+}
+
+func (r *ExtensionRuntime) closeStorageFlusher() {
+	r.storageMu.Lock()
+	r.storageClosed = true
+	r.storageDirty = false
+	if r.storageTimer != nil {
+		r.storageTimer.Stop()
+		r.storageTimer = nil
+	}
+	r.storageMu.Unlock()
 }
 
-// storageGet retrieves a value from storage
 func (r *ExtensionRuntime) storageGet(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return goja.Undefined()
@@ -60,15 +175,15 @@ func (r *ExtensionRuntime) storageGet(call goja.FunctionCall) goja.Value {
 
 	key := call.Arguments[0].String()
 
-	storage, err := r.loadStorage()
-	if err != nil {
+	if err := r.ensureStorageLoaded(); err != nil {
 		GoLog("[Extension:%s] Storage load error: %v\n", r.extensionID, err)
 		return goja.Undefined()
 	}
 
-	value, exists := storage[key]
+	r.storageMu.RLock()
+	value, exists := r.storageCache[key]
+	r.storageMu.RUnlock()
 	if !exists {
-		// Return default value if provided
 		if len(call.Arguments) > 1 {
 			return call.Arguments[1]
 		}
@@ -78,7 +193,6 @@ func (r *ExtensionRuntime) storageGet(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(value)
 }
 
-// storageSet stores a value in storage
 func (r *ExtensionRuntime) storageSet(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(false)
@@ -87,23 +201,30 @@ func (r *ExtensionRuntime) storageSet(call goja.FunctionCall) goja.Value {
 	key := call.Arguments[0].String()
 	value := call.Arguments[1].Export()
 
-	storage, err := r.loadStorage()
-	if err != nil {
+	if err := r.ensureStorageLoaded(); err != nil {
 		GoLog("[Extension:%s] Storage load error: %v\n", r.extensionID, err)
 		return r.vm.ToValue(false)
 	}
 
-	storage[key] = value
-
-	if err := r.saveStorage(storage); err != nil {
-		GoLog("[Extension:%s] Storage save error: %v\n", r.extensionID, err)
+	r.storageMu.Lock()
+	if r.storageClosed {
+		r.storageMu.Unlock()
 		return r.vm.ToValue(false)
 	}
+	if existing, exists := r.storageCache[key]; exists {
+		if reflect.DeepEqual(existing, value) {
+			r.storageMu.Unlock()
+			return r.vm.ToValue(true)
+		}
+	}
+	r.storageCache[key] = value
+	r.storageDirty = true
+	r.queueStorageFlushLocked(r.storageFlushDelay)
+	r.storageMu.Unlock()
 
 	return r.vm.ToValue(true)
 }
 
-// storageRemove removes a value from storage
 func (r *ExtensionRuntime) storageRemove(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(false)
@@ -111,51 +232,49 @@ func (r *ExtensionRuntime) storageRemove(call goja.FunctionCall) goja.Value {
 
 	key := call.Arguments[0].String()
 
-	storage, err := r.loadStorage()
-	if err != nil {
+	if err := r.ensureStorageLoaded(); err != nil {
 		GoLog("[Extension:%s] Storage load error: %v\n", r.extensionID, err)
 		return r.vm.ToValue(false)
 	}
 
-	delete(storage, key)
-
-	if err := r.saveStorage(storage); err != nil {
-		GoLog("[Extension:%s] Storage save error: %v\n", r.extensionID, err)
+	r.storageMu.Lock()
+	if r.storageClosed {
+		r.storageMu.Unlock()
 		return r.vm.ToValue(false)
 	}
+	if _, exists := r.storageCache[key]; !exists {
+		r.storageMu.Unlock()
+		return r.vm.ToValue(true)
+	}
+	delete(r.storageCache, key)
+	r.storageDirty = true
+	r.queueStorageFlushLocked(r.storageFlushDelay)
+	r.storageMu.Unlock()
 
 	return r.vm.ToValue(true)
 }
 
-// ==================== Credentials API (Encrypted Storage) ====================
-
-// getCredentialsPath returns the path to the extension's encrypted credentials file
 func (r *ExtensionRuntime) getCredentialsPath() string {
 	return filepath.Join(r.dataDir, ".credentials.enc")
 }
 
-// getSaltPath returns the path to the extension's encryption salt file
 func (r *ExtensionRuntime) getSaltPath() string {
 	return filepath.Join(r.dataDir, ".cred_salt")
 }
 
-// getOrCreateSalt gets existing salt or creates a new random one
 func (r *ExtensionRuntime) getOrCreateSalt() ([]byte, error) {
 	saltPath := r.getSaltPath()
 
-	// Try to read existing salt
 	salt, err := os.ReadFile(saltPath)
 	if err == nil && len(salt) == 32 {
 		return salt, nil
 	}
 
-	// Generate new random salt (32 bytes)
 	salt = make([]byte, 32)
 	if _, err := io.ReadFull(rand.Reader, salt); err != nil {
 		return nil, fmt.Errorf("failed to generate salt: %w", err)
 	}
 
-	// Save salt to file
 	if err := os.WriteFile(saltPath, salt, 0600); err != nil {
 		return nil, fmt.Errorf("failed to save salt: %w", err)
 	}
@@ -163,58 +282,80 @@ func (r *ExtensionRuntime) getOrCreateSalt() ([]byte, error) {
 	return salt, nil
 }
 
-// getEncryptionKey derives an encryption key from extension ID + random salt
 func (r *ExtensionRuntime) getEncryptionKey() ([]byte, error) {
-	// Get or create per-installation random salt
 	salt, err := r.getOrCreateSalt()
 	if err != nil {
 		return nil, err
 	}
 
-	// Combine extension ID + random salt for key derivation
-	// This makes each installation unique, preventing mass decryption attacks
 	combined := append([]byte(r.extensionID), salt...)
 	hash := sha256.Sum256(combined)
 	return hash[:], nil
 }
 
-// loadCredentials loads and decrypts credentials from disk
-func (r *ExtensionRuntime) loadCredentials() (map[string]interface{}, error) {
+func (r *ExtensionRuntime) ensureCredentialsLoaded() error {
+	r.credentialsMu.RLock()
+	if r.credentialsLoaded {
+		r.credentialsMu.RUnlock()
+		return nil
+	}
+	r.credentialsMu.RUnlock()
+
+	r.credentialsMu.Lock()
+	defer r.credentialsMu.Unlock()
+	if r.credentialsLoaded {
+		return nil
+	}
+
 	credPath := r.getCredentialsPath()
 	data, err := os.ReadFile(credPath)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return make(map[string]interface{}), nil
+			r.credentialsCache = make(map[string]interface{})
+			r.credentialsLoaded = true
+			return nil
 		}
-		return nil, err
+		return err
 	}
 
-	// Decrypt the data
 	key, err := r.getEncryptionKey()
 	if err != nil {
-		return nil, fmt.Errorf("failed to get encryption key: %w", err)
+		return fmt.Errorf("failed to get encryption key: %w", err)
 	}
 	decrypted, err := decryptAES(data, key)
 	if err != nil {
-		return nil, fmt.Errorf("failed to decrypt credentials: %w", err)
+		return fmt.Errorf("failed to decrypt credentials: %w", err)
 	}
 
 	var creds map[string]interface{}
 	if err := json.Unmarshal(decrypted, &creds); err != nil {
+		return err
+	}
+	if creds == nil {
+		creds = make(map[string]interface{})
+	}
+
+	r.credentialsCache = creds
+	r.credentialsLoaded = true
+	return nil
+}
+
+func (r *ExtensionRuntime) loadCredentials() (map[string]interface{}, error) {
+	if err := r.ensureCredentialsLoaded(); err != nil {
 		return nil, err
 	}
 
-	return creds, nil
+	r.credentialsMu.RLock()
+	defer r.credentialsMu.RUnlock()
+	return cloneInterfaceMap(r.credentialsCache), nil
 }
 
-// saveCredentials encrypts and saves credentials to disk
 func (r *ExtensionRuntime) saveCredentials(creds map[string]interface{}) error {
 	data, err := json.Marshal(creds)
 	if err != nil {
 		return err
 	}
 
-	// Encrypt the data
 	key, err := r.getEncryptionKey()
 	if err != nil {
 		return fmt.Errorf("failed to get encryption key: %w", err)
@@ -225,10 +366,17 @@ func (r *ExtensionRuntime) saveCredentials(creds map[string]interface{}) error {
 	}
 
 	credPath := r.getCredentialsPath()
-	return os.WriteFile(credPath, encrypted, 0600) // Restrictive permissions
+	if err := os.WriteFile(credPath, encrypted, 0600); err != nil {
+		return err
+	}
+
+	r.credentialsMu.Lock()
+	r.credentialsCache = cloneInterfaceMap(creds)
+	r.credentialsLoaded = true
+	r.credentialsMu.Unlock()
+	return nil
 }
 
-// credentialsStore stores an encrypted credential
 func (r *ExtensionRuntime) credentialsStore(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -240,8 +388,7 @@ func (r *ExtensionRuntime) credentialsStore(call goja.FunctionCall) goja.Value {
 	key := call.Arguments[0].String()
 	value := call.Arguments[1].Export()
 
-	creds, err := r.loadCredentials()
-	if err != nil {
+	if err := r.ensureCredentialsLoaded(); err != nil {
 		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
@@ -249,9 +396,12 @@ func (r *ExtensionRuntime) credentialsStore(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	creds[key] = value
+	r.credentialsMu.RLock()
+	nextCreds := cloneInterfaceMap(r.credentialsCache)
+	r.credentialsMu.RUnlock()
+	nextCreds[key] = value
 
-	if err := r.saveCredentials(creds); err != nil {
+	if err := r.saveCredentials(nextCreds); err != nil {
 		GoLog("[Extension:%s] Credentials save error: %v\n", r.extensionID, err)
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
@@ -264,7 +414,6 @@ func (r *ExtensionRuntime) credentialsStore(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// credentialsGet retrieves a decrypted credential
 func (r *ExtensionRuntime) credentialsGet(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return goja.Undefined()
@@ -272,15 +421,15 @@ func (r *ExtensionRuntime) credentialsGet(call goja.FunctionCall) goja.Value {
 
 	key := call.Arguments[0].String()
 
-	creds, err := r.loadCredentials()
-	if err != nil {
+	if err := r.ensureCredentialsLoaded(); err != nil {
 		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
 		return goja.Undefined()
 	}
 
-	value, exists := creds[key]
+	r.credentialsMu.RLock()
+	value, exists := r.credentialsCache[key]
+	r.credentialsMu.RUnlock()
 	if !exists {
-		// Return default value if provided
 		if len(call.Arguments) > 1 {
 			return call.Arguments[1]
 		}
@@ -290,7 +439,6 @@ func (r *ExtensionRuntime) credentialsGet(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(value)
 }
 
-// credentialsRemove removes a credential
 func (r *ExtensionRuntime) credentialsRemove(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(false)
@@ -298,15 +446,17 @@ func (r *ExtensionRuntime) credentialsRemove(call goja.FunctionCall) goja.Value
 
 	key := call.Arguments[0].String()
 
-	creds, err := r.loadCredentials()
-	if err != nil {
+	if err := r.ensureCredentialsLoaded(); err != nil {
 		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
 		return r.vm.ToValue(false)
 	}
 
-	delete(creds, key)
+	r.credentialsMu.RLock()
+	nextCreds := cloneInterfaceMap(r.credentialsCache)
+	r.credentialsMu.RUnlock()
+	delete(nextCreds, key)
 
-	if err := r.saveCredentials(creds); err != nil {
+	if err := r.saveCredentials(nextCreds); err != nil {
 		GoLog("[Extension:%s] Credentials save error: %v\n", r.extensionID, err)
 		return r.vm.ToValue(false)
 	}
@@ -314,7 +464,6 @@ func (r *ExtensionRuntime) credentialsRemove(call goja.FunctionCall) goja.Value
 	return r.vm.ToValue(true)
 }
 
-// credentialsHas checks if a credential exists
 func (r *ExtensionRuntime) credentialsHas(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue(false)
@@ -322,18 +471,16 @@ func (r *ExtensionRuntime) credentialsHas(call goja.FunctionCall) goja.Value {
 
 	key := call.Arguments[0].String()
 
-	creds, err := r.loadCredentials()
-	if err != nil {
+	if err := r.ensureCredentialsLoaded(); err != nil {
 		return r.vm.ToValue(false)
 	}
 
-	_, exists := creds[key]
+	r.credentialsMu.RLock()
+	_, exists := r.credentialsCache[key]
+	r.credentialsMu.RUnlock()
 	return r.vm.ToValue(exists)
 }
 
-// ==================== Crypto Utilities ====================
-
-// encryptAES encrypts data using AES-GCM
 func encryptAES(plaintext []byte, key []byte) ([]byte, error) {
 	block, err := aes.NewCipher(key)
 	if err != nil {
@@ -354,7 +501,6 @@ func encryptAES(plaintext []byte, key []byte) ([]byte, error) {
 	return ciphertext, nil
 }
 
-// decryptAES decrypts data using AES-GCM
 func decryptAES(ciphertext []byte, key []byte) ([]byte, error) {
 	block, err := aes.NewCipher(key)
 	if err != nil {

go_backend/extension_runtime_storage_test.go

@@ -0,0 +1,120 @@
+package gobackend
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+func setStorageValue(t *testing.T, runtime *ExtensionRuntime, key string, value interface{}) {
+	t.Helper()
+	result := runtime.storageSet(goja.FunctionCall{
+		Arguments: []goja.Value{
+			runtime.vm.ToValue(key),
+			runtime.vm.ToValue(value),
+		},
+	})
+	if !result.ToBoolean() {
+		t.Fatalf("storage.set(%q) returned false", key)
+	}
+}
+
+func readStorageMap(t *testing.T, storagePath string) map[string]interface{} {
+	t.Helper()
+	data, err := os.ReadFile(storagePath)
+	if err != nil {
+		t.Fatalf("failed to read storage file: %v", err)
+	}
+
+	var parsed map[string]interface{}
+	if err := json.Unmarshal(data, &parsed); err != nil {
+		t.Fatalf("failed to unmarshal storage file: %v", err)
+	}
+	return parsed
+}
+
+func TestExtensionRuntimeStorage_DebouncedWriteCompactJSON(t *testing.T) {
+	ext := &LoadedExtension{
+		ID: "storage-test",
+		Manifest: &ExtensionManifest{
+			Name: "storage-test",
+		},
+		DataDir: t.TempDir(),
+	}
+
+	runtime := NewExtensionRuntime(ext)
+	runtime.storageFlushDelay = 25 * time.Millisecond
+	runtime.RegisterAPIs(goja.New())
+
+	setStorageValue(t, runtime, "k1", "v1")
+	setStorageValue(t, runtime, "k2", 2)
+
+	storagePath := filepath.Join(ext.DataDir, "storage.json")
+	deadline := time.Now().Add(1500 * time.Millisecond)
+
+	var raw []byte
+	for time.Now().Before(deadline) {
+		data, err := os.ReadFile(storagePath)
+		if err == nil {
+			raw = data
+			break
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	if len(raw) == 0 {
+		t.Fatalf("storage.json was not written within timeout")
+	}
+
+	var parsed map[string]interface{}
+	if err := json.Unmarshal(raw, &parsed); err != nil {
+		t.Fatalf("failed to unmarshal storage file: %v", err)
+	}
+	if parsed["k1"] != "v1" {
+		t.Fatalf("expected k1=v1, got %v", parsed["k1"])
+	}
+	if parsed["k2"] != float64(2) {
+		t.Fatalf("expected k2=2, got %v", parsed["k2"])
+	}
+	if bytes.Contains(raw, []byte("\n")) {
+		t.Fatalf("expected compact JSON without indentation, got: %q", string(raw))
+	}
+}
+
+func TestUnloadExtension_FlushesPendingStorage(t *testing.T) {
+	ext := &LoadedExtension{
+		ID: "unload-storage-test",
+		Manifest: &ExtensionManifest{
+			Name: "unload-storage-test",
+		},
+		DataDir: t.TempDir(),
+		VM:      goja.New(),
+	}
+
+	runtime := NewExtensionRuntime(ext)
+	runtime.storageFlushDelay = time.Hour
+	runtime.RegisterAPIs(ext.VM)
+	ext.runtime = runtime
+
+	manager := &ExtensionManager{
+		extensions: map[string]*LoadedExtension{
+			ext.ID: ext,
+		},
+	}
+
+	setStorageValue(t, runtime, "persist_on_unload", true)
+
+	if err := manager.UnloadExtension(ext.ID); err != nil {
+		t.Fatalf("UnloadExtension failed: %v", err)
+	}
+
+	storagePath := filepath.Join(ext.DataDir, "storage.json")
+	parsed := readStorageMap(t, storagePath)
+	if parsed["persist_on_unload"] != true {
+		t.Fatalf("expected pending storage value to be flushed on unload, got %v", parsed["persist_on_unload"])
+	}
+}

go_backend/extension_runtime_utils.go

@@ -1,4 +1,3 @@
-// Package gobackend provides Utility functions for extension runtime
 package gobackend
 
 import (
@@ -12,13 +11,11 @@ import (
 	"encoding/json"
 	"fmt"
 	"strings"
+	"time"
 
 	"github.com/dop251/goja"
 )
 
-// ==================== Utility Functions ====================
-
-// base64Encode encodes a string to base64
 func (r *ExtensionRuntime) base64Encode(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -27,7 +24,6 @@ func (r *ExtensionRuntime) base64Encode(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(base64.StdEncoding.EncodeToString([]byte(input)))
 }
 
-// base64Decode decodes a base64 string
 func (r *ExtensionRuntime) base64Decode(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -40,7 +36,6 @@ func (r *ExtensionRuntime) base64Decode(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(string(decoded))
 }
 
-// md5Hash computes MD5 hash of a string
 func (r *ExtensionRuntime) md5Hash(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -50,7 +45,6 @@ func (r *ExtensionRuntime) md5Hash(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(hex.EncodeToString(hash[:]))
 }
 
-// sha256Hash computes SHA256 hash of a string
 func (r *ExtensionRuntime) sha256Hash(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -60,7 +54,6 @@ func (r *ExtensionRuntime) sha256Hash(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(hex.EncodeToString(hash[:]))
 }
 
-// hmacSHA256 computes HMAC-SHA256 of a message with a key
 func (r *ExtensionRuntime) hmacSHA256(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue("")
@@ -73,7 +66,6 @@ func (r *ExtensionRuntime) hmacSHA256(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(hex.EncodeToString(mac.Sum(nil)))
 }
 
-// hmacSHA256Base64 computes HMAC-SHA256 and returns base64 encoded result
 func (r *ExtensionRuntime) hmacSHA256Base64(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue("")
@@ -86,15 +78,11 @@ func (r *ExtensionRuntime) hmacSHA256Base64(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(base64.StdEncoding.EncodeToString(mac.Sum(nil)))
 }
 
-// hmacSHA1 computes HMAC-SHA1 of a message with a key (for TOTP)
-// Arguments: message (string or array of bytes), key (string or array of bytes)
-// Returns: array of bytes (for TOTP dynamic truncation)
 func (r *ExtensionRuntime) hmacSHA1(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue([]byte{})
 	}
 
-	// Get key - can be string or array of bytes
 	var keyBytes []byte
 	keyArg := call.Arguments[0].Export()
 	switch k := keyArg.(type) {
@@ -113,7 +101,6 @@ func (r *ExtensionRuntime) hmacSHA1(call goja.FunctionCall) goja.Value {
 		return r.vm.ToValue([]byte{})
 	}
 
-	// Get message - can be string or array of bytes
 	var msgBytes []byte
 	msgArg := call.Arguments[1].Export()
 	switch m := msgArg.(type) {
@@ -136,7 +123,6 @@ func (r *ExtensionRuntime) hmacSHA1(call goja.FunctionCall) goja.Value {
 	mac.Write(msgBytes)
 	result := mac.Sum(nil)
 
-	// Convert to array of numbers for JavaScript
 	jsArray := make([]interface{}, len(result))
 	for i, b := range result {
 		jsArray[i] = int(b)
@@ -144,7 +130,6 @@ func (r *ExtensionRuntime) hmacSHA1(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(jsArray)
 }
 
-// parseJSON parses a JSON string
 func (r *ExtensionRuntime) parseJSON(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return goja.Undefined()
@@ -160,7 +145,6 @@ func (r *ExtensionRuntime) parseJSON(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(result)
 }
 
-// stringifyJSON converts a value to JSON string
 func (r *ExtensionRuntime) stringifyJSON(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -176,9 +160,6 @@ func (r *ExtensionRuntime) stringifyJSON(call goja.FunctionCall) goja.Value {
 	return r.vm.ToValue(string(data))
 }
 
-// ==================== Crypto Utilities for Extensions ====================
-
-// cryptoEncrypt encrypts a string using AES-GCM (for extension use)
 func (r *ExtensionRuntime) cryptoEncrypt(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -190,7 +171,6 @@ func (r *ExtensionRuntime) cryptoEncrypt(call goja.FunctionCall) goja.Value {
 	plaintext := call.Arguments[0].String()
 	keyStr := call.Arguments[1].String()
 
-	// Derive 32-byte key from provided key string
 	keyHash := sha256.Sum256([]byte(keyStr))
 
 	encrypted, err := encryptAES([]byte(plaintext), keyHash[:])
@@ -207,7 +187,6 @@ func (r *ExtensionRuntime) cryptoEncrypt(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// cryptoDecrypt decrypts a string using AES-GCM (for extension use)
 func (r *ExtensionRuntime) cryptoDecrypt(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 2 {
 		return r.vm.ToValue(map[string]interface{}{
@@ -227,14 +206,13 @@ func (r *ExtensionRuntime) cryptoDecrypt(call goja.FunctionCall) goja.Value {
 		})
 	}
 
-	// Derive 32-byte key from provided key string
 	keyHash := sha256.Sum256([]byte(keyStr))
 
 	decrypted, err := decryptAES(ciphertext, keyHash[:])
 	if err != nil {
 		return r.vm.ToValue(map[string]interface{}{
 			"success": false,
-			"error":   err.Error(),
+			"error":   "invalid base64 ciphertext",
 		})
 	}
 
@@ -244,9 +222,8 @@ func (r *ExtensionRuntime) cryptoDecrypt(call goja.FunctionCall) goja.Value {
 	})
 }
 
-// cryptoGenerateKey generates a random encryption key
 func (r *ExtensionRuntime) cryptoGenerateKey(call goja.FunctionCall) goja.Value {
-	length := 32 // Default 256-bit key
+	length := 32
 	if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
 		if l, ok := call.Arguments[0].Export().(float64); ok {
 			length = int(l)
@@ -268,7 +245,9 @@ func (r *ExtensionRuntime) cryptoGenerateKey(call goja.FunctionCall) goja.Value
 	})
 }
 
-// ==================== Logging Functions ====================
+func (r *ExtensionRuntime) randomUserAgent(call goja.FunctionCall) goja.Value {
+	return r.vm.ToValue(getRandomUserAgent())
+}
 
 func (r *ExtensionRuntime) logDebug(call goja.FunctionCall) goja.Value {
 	msg := r.formatLogArgs(call.Arguments)
@@ -302,8 +281,6 @@ func (r *ExtensionRuntime) formatLogArgs(args []goja.Value) string {
 	return strings.Join(parts, " ")
 }
 
-// ==================== Go Backend Wrappers ====================
-
 func (r *ExtensionRuntime) sanitizeFilenameWrapper(call goja.FunctionCall) goja.Value {
 	if len(call.Arguments) < 1 {
 		return r.vm.ToValue("")
@@ -312,7 +289,6 @@ func (r *ExtensionRuntime) sanitizeFilenameWrapper(call goja.FunctionCall) goja.
 	return r.vm.ToValue(sanitizeFilename(input))
 }
 
-// RegisterGoBackendAPIs adds more Go backend functions to the VM
 func (r *ExtensionRuntime) RegisterGoBackendAPIs(vm *goja.Runtime) {
 	gobackendObj := vm.Get("gobackend")
 	if gobackendObj == nil || goja.IsUndefined(gobackendObj) {
@@ -322,7 +298,6 @@ func (r *ExtensionRuntime) RegisterGoBackendAPIs(vm *goja.Runtime) {
 
 	obj := gobackendObj.(*goja.Object)
 
-	// Expose sanitizeFilename
 	obj.Set("sanitizeFilename", func(call goja.FunctionCall) goja.Value {
 		if len(call.Arguments) < 1 {
 			return vm.ToValue("")
@@ -330,7 +305,6 @@ func (r *ExtensionRuntime) RegisterGoBackendAPIs(vm *goja.Runtime) {
 		return vm.ToValue(sanitizeFilename(call.Arguments[0].String()))
 	})
 
-	// Expose getAudioQuality
 	obj.Set("getAudioQuality", func(call goja.FunctionCall) goja.Value {
 		if len(call.Arguments) < 1 {
 			return vm.ToValue(map[string]interface{}{
@@ -353,7 +327,6 @@ func (r *ExtensionRuntime) RegisterGoBackendAPIs(vm *goja.Runtime) {
 		})
 	})
 
-	// Expose buildFilename
 	obj.Set("buildFilename", func(call goja.FunctionCall) goja.Value {
 		if len(call.Arguments) < 2 {
 			return vm.ToValue("")
@@ -369,4 +342,23 @@ func (r *ExtensionRuntime) RegisterGoBackendAPIs(vm *goja.Runtime) {
 
 		return vm.ToValue(buildFilenameFromTemplate(template, metadata))
 	})
+
+	obj.Set("getLocalTime", func(call goja.FunctionCall) goja.Value {
+		now := time.Now()
+		_, offsetSeconds := now.Zone()
+		offsetMinutes := offsetSeconds / 60
+
+		return vm.ToValue(map[string]interface{}{
+			"year":          now.Year(),
+			"month":         int(now.Month()),
+			"day":           now.Day(),
+			"hour":          now.Hour(),
+			"minute":        now.Minute(),
+			"second":        now.Second(),
+			"weekday":       int(now.Weekday()),
+			"offsetMinutes": -offsetMinutes, // JS convention: negative for east of UTC
+			"timezone":      now.Location().String(),
+			"timestamp":     now.Unix(),
+		})
+	})
 }

go_backend/extension_settings.go

@@ -1,4 +1,3 @@
-// Package gobackend provides extension settings storage
 package gobackend
 
 import (
@@ -9,20 +8,17 @@ import (
 	"sync"
 )
 
-// ExtensionSettingsStore manages settings for all extensions
 type ExtensionSettingsStore struct {
 	mu       sync.RWMutex
 	dataDir  string
 	settings map[string]map[string]interface{} // extensionID -> settings
 }
 
-// Global settings store
 var (
 	globalSettingsStore     *ExtensionSettingsStore
 	globalSettingsStoreOnce sync.Once
 )
 
-// GetExtensionSettingsStore returns the global settings store
 func GetExtensionSettingsStore() *ExtensionSettingsStore {
 	globalSettingsStoreOnce.Do(func() {
 		globalSettingsStore = &ExtensionSettingsStore{
@@ -32,7 +28,6 @@ func GetExtensionSettingsStore() *ExtensionSettingsStore {
 	return globalSettingsStore
 }
 
-// SetDataDir sets the data directory for settings storage
 func (s *ExtensionSettingsStore) SetDataDir(dataDir string) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -42,16 +37,13 @@ func (s *ExtensionSettingsStore) SetDataDir(dataDir string) error {
 		return fmt.Errorf("failed to create settings directory: %w", err)
 	}
 
-	// Load all existing settings
 	return s.loadAllSettings()
 }
 
-// getSettingsPath returns the path to an extension's settings file
 func (s *ExtensionSettingsStore) getSettingsPath(extensionID string) string {
 	return filepath.Join(s.dataDir, extensionID, "settings.json")
 }
 
-// loadAllSettings loads settings for all extensions from disk
 func (s *ExtensionSettingsStore) loadAllSettings() error {
 	entries, err := os.ReadDir(s.dataDir)
 	if err != nil {
@@ -76,7 +68,6 @@ func (s *ExtensionSettingsStore) loadAllSettings() error {
 	return nil
 }
 
-// loadSettings loads settings for a specific extension
 func (s *ExtensionSettingsStore) loadSettings(extensionID string) (map[string]interface{}, error) {
 	settingsPath := s.getSettingsPath(extensionID)
 	data, err := os.ReadFile(settingsPath)
@@ -95,11 +86,9 @@ func (s *ExtensionSettingsStore) loadSettings(extensionID string) (map[string]in
 	return settings, nil
 }
 
-// saveSettings saves settings for a specific extension
 func (s *ExtensionSettingsStore) saveSettings(extensionID string, settings map[string]interface{}) error {
 	settingsPath := s.getSettingsPath(extensionID)
 
-	// Create directory if needed
 	dir := filepath.Dir(settingsPath)
 	if err := os.MkdirAll(dir, 0755); err != nil {
 		return err
@@ -113,8 +102,6 @@ func (s *ExtensionSettingsStore) saveSettings(extensionID string, settings map[s
 	return os.WriteFile(settingsPath, data, 0644)
 }
 
-// Get retrieves a setting value for an extension
-// Returns error if extension or key not found (gomobile compatible)
 func (s *ExtensionSettingsStore) Get(extensionID, key string) (interface{}, error) {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
@@ -131,7 +118,6 @@ func (s *ExtensionSettingsStore) Get(extensionID, key string) (interface{}, erro
 	return value, nil
 }
 
-// GetAll retrieves all settings for an extension
 func (s *ExtensionSettingsStore) GetAll(extensionID string) map[string]interface{} {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
@@ -141,7 +127,6 @@ func (s *ExtensionSettingsStore) GetAll(extensionID string) map[string]interface
 		return make(map[string]interface{})
 	}
 
-	// Return a copy
 	result := make(map[string]interface{})
 	for k, v := range extSettings {
 		result[k] = v
@@ -149,7 +134,6 @@ func (s *ExtensionSettingsStore) GetAll(extensionID string) map[string]interface
 	return result
 }
 
-// Set stores a setting value for an extension
 func (s *ExtensionSettingsStore) Set(extensionID, key string, value interface{}) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -160,22 +144,18 @@ func (s *ExtensionSettingsStore) Set(extensionID, key string, value interface{})
 
 	s.settings[extensionID][key] = value
 
-	// Persist to disk
 	return s.saveSettings(extensionID, s.settings[extensionID])
 }
 
-// SetAll stores all settings for an extension
 func (s *ExtensionSettingsStore) SetAll(extensionID string, settings map[string]interface{}) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
 	s.settings[extensionID] = settings
 
-	// Persist to disk
 	return s.saveSettings(extensionID, settings)
 }
 
-// Remove removes a setting for an extension
 func (s *ExtensionSettingsStore) Remove(extensionID, key string) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -187,18 +167,15 @@ func (s *ExtensionSettingsStore) Remove(extensionID, key string) error {
 
 	delete(extSettings, key)
 
-	// Persist to disk
 	return s.saveSettings(extensionID, extSettings)
 }
 
-// RemoveAll removes all settings for an extension
 func (s *ExtensionSettingsStore) RemoveAll(extensionID string) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
 	delete(s.settings, extensionID)
 
-	// Remove settings file
 	settingsPath := s.getSettingsPath(extensionID)
 	if err := os.Remove(settingsPath); err != nil && !os.IsNotExist(err) {
 		return err
@@ -207,7 +184,6 @@ func (s *ExtensionSettingsStore) RemoveAll(extensionID string) error {
 	return nil
 }
 
-// GetAllExtensionSettings returns settings for all extensions as JSON
 func (s *ExtensionSettingsStore) GetAllExtensionSettingsJSON() (string, error) {
 	s.mu.RLock()
 	defer s.mu.RUnlock()

go_backend/extension_store.go

@@ -5,13 +5,14 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 	"time"
 )
 
-// Extension categories
 const (
 	CategoryMetadata    = "metadata"
 	CategoryDownload    = "download"
@@ -20,29 +21,26 @@ const (
 	CategoryIntegration = "integration"
 )
 
-// StoreExtension represents an extension in the store
 type StoreExtension struct {
-	ID            string   `json:"id"`
-	Name          string   `json:"name"`
-	DisplayName   string   `json:"display_name,omitempty"`
-	Version       string   `json:"version"`
-	Author        string   `json:"author"`
-	Description   string   `json:"description"`
-	DownloadURL   string   `json:"download_url,omitempty"`
-	IconURL       string   `json:"icon_url,omitempty"`
-	Category      string   `json:"category"`
-	Tags          []string `json:"tags,omitempty"`
-	Downloads     int      `json:"downloads"`
-	UpdatedAt     string   `json:"updated_at"`
-	MinAppVersion string   `json:"min_app_version,omitempty"`
-	// Alternative camelCase fields (for flexibility)
-	DisplayNameAlt   string `json:"displayName,omitempty"`
-	DownloadURLAlt   string `json:"downloadUrl,omitempty"`
-	IconURLAlt       string `json:"iconUrl,omitempty"`
-	MinAppVersionAlt string `json:"minAppVersion,omitempty"`
+	ID               string   `json:"id"`
+	Name             string   `json:"name"`
+	DisplayName      string   `json:"display_name,omitempty"`
+	Version          string   `json:"version"`
+	Author           string   `json:"author"`
+	Description      string   `json:"description"`
+	DownloadURL      string   `json:"download_url,omitempty"`
+	IconURL          string   `json:"icon_url,omitempty"`
+	Category         string   `json:"category"`
+	Tags             []string `json:"tags,omitempty"`
+	Downloads        int      `json:"downloads"`
+	UpdatedAt        string   `json:"updated_at"`
+	MinAppVersion    string   `json:"min_app_version,omitempty"`
+	DisplayNameAlt   string   `json:"displayName,omitempty"`
+	DownloadURLAlt   string   `json:"downloadUrl,omitempty"`
+	IconURLAlt       string   `json:"iconUrl,omitempty"`
+	MinAppVersionAlt string   `json:"minAppVersion,omitempty"`
 }
 
-// getDisplayName returns display name, falling back to name (private to avoid gomobile conflict)
 func (e *StoreExtension) getDisplayName() string {
 	if e.DisplayName != "" {
 		return e.DisplayName
@@ -53,7 +51,6 @@ func (e *StoreExtension) getDisplayName() string {
 	return e.Name
 }
 
-// getDownloadURL returns download URL from either field (private to avoid gomobile conflict)
 func (e *StoreExtension) getDownloadURL() string {
 	if e.DownloadURL != "" {
 		return e.DownloadURL
@@ -61,7 +58,6 @@ func (e *StoreExtension) getDownloadURL() string {
 	return e.DownloadURLAlt
 }
 
-// getIconURL returns icon URL from either field (private to avoid gomobile conflict)
 func (e *StoreExtension) getIconURL() string {
 	if e.IconURL != "" {
 		return e.IconURL
@@ -69,7 +65,6 @@ func (e *StoreExtension) getIconURL() string {
 	return e.IconURLAlt
 }
 
-// getMinAppVersion returns min app version from either field (private to avoid gomobile conflict)
 func (e *StoreExtension) getMinAppVersion() string {
 	if e.MinAppVersion != "" {
 		return e.MinAppVersion
@@ -77,14 +72,12 @@ func (e *StoreExtension) getMinAppVersion() string {
 	return e.MinAppVersionAlt
 }
 
-// StoreRegistry represents the extension registry
 type StoreRegistry struct {
 	Version    int              `json:"version"`
 	UpdatedAt  string           `json:"updated_at"`
 	Extensions []StoreExtension `json:"extensions"`
 }
 
-// StoreExtensionResponse is the normalized response sent to Flutter
 type StoreExtensionResponse struct {
 	ID               string   `json:"id"`
 	Name             string   `json:"name"`
@@ -104,7 +97,6 @@ type StoreExtensionResponse struct {
 	HasUpdate        bool     `json:"has_update"`
 }
 
-// ToResponse converts StoreExtension to normalized response
 func (e *StoreExtension) ToResponse() StoreExtensionResponse {
 	return StoreExtensionResponse{
 		ID:            e.ID,
@@ -123,7 +115,6 @@ func (e *StoreExtension) ToResponse() StoreExtensionResponse {
 	}
 }
 
-// ExtensionStore manages the extension store
 type ExtensionStore struct {
 	registryURL string
 	cacheDir    string
@@ -139,36 +130,61 @@ var (
 )
 
 const (
-	defaultRegistryURL = "https://raw.githubusercontent.com/zarzet/SpotiFLAC-Extension/main/registry.json"
-	cacheTTL           = 30 * time.Minute
-	cacheFileName      = "store_cache.json"
+	cacheTTL      = 30 * time.Minute
+	cacheFileName = "store_cache.json"
 )
 
-// InitExtensionStore initializes the extension store
 func InitExtensionStore(cacheDir string) *ExtensionStore {
 	extensionStoreMu.Lock()
 	defer extensionStoreMu.Unlock()
 
 	if extensionStore == nil {
 		extensionStore = &ExtensionStore{
-			registryURL: defaultRegistryURL,
+			registryURL: "", // No default - user must provide a registry URL
 			cacheDir:    cacheDir,
 			cacheTTL:    cacheTTL,
 		}
-		// Try to load from disk cache
 		extensionStore.loadDiskCache()
 	}
 	return extensionStore
 }
 
-// GetExtensionStore returns the singleton store instance
+// SetRegistryURL updates the registry URL and clears the in-memory cache
+// so the next fetch will use the new URL. Disk cache is also cleared.
+func (s *ExtensionStore) SetRegistryURL(registryURL string) {
+	s.cacheMu.Lock()
+	defer s.cacheMu.Unlock()
+
+	if s.registryURL == registryURL {
+		return
+	}
+
+	s.registryURL = registryURL
+	s.cache = nil
+	s.cacheTime = time.Time{}
+
+	// Clear disk cache since it's from a different registry
+	if s.cacheDir != "" {
+		cachePath := filepath.Join(s.cacheDir, cacheFileName)
+		os.Remove(cachePath)
+	}
+
+	LogInfo("ExtensionStore", "Registry URL updated to: %s", registryURL)
+}
+
+// GetRegistryURL returns the currently configured registry URL.
+func (s *ExtensionStore) GetRegistryURL() string {
+	s.cacheMu.RLock()
+	defer s.cacheMu.RUnlock()
+	return s.registryURL
+}
+
 func GetExtensionStore() *ExtensionStore {
 	extensionStoreMu.Lock()
 	defer extensionStoreMu.Unlock()
 	return extensionStore
 }
 
-// loadDiskCache loads cached registry from disk
 func (s *ExtensionStore) loadDiskCache() {
 	if s.cacheDir == "" {
 		return
@@ -194,7 +210,6 @@ func (s *ExtensionStore) loadDiskCache() {
 	LogDebug("ExtensionStore", "Loaded %d extensions from disk cache", len(s.cache.Extensions))
 }
 
-// saveDiskCache saves registry to disk cache
 func (s *ExtensionStore) saveDiskCache() {
 	if s.cacheDir == "" || s.cache == nil {
 		return
@@ -217,23 +232,29 @@ func (s *ExtensionStore) saveDiskCache() {
 	os.WriteFile(cachePath, data, 0644)
 }
 
-// FetchRegistry fetches the extension registry from GitHub
 func (s *ExtensionStore) FetchRegistry(forceRefresh bool) (*StoreRegistry, error) {
 	s.cacheMu.Lock()
 	defer s.cacheMu.Unlock()
 
-	// Return cached if valid and not forcing refresh
+	// Check if a registry URL has been configured
+	if s.registryURL == "" {
+		return nil, fmt.Errorf("no registry URL configured. Please add a repository URL first")
+	}
+
 	if !forceRefresh && s.cache != nil && time.Since(s.cacheTime) < s.cacheTTL {
 		LogDebug("ExtensionStore", "Using cached registry (%d extensions)", len(s.cache.Extensions))
 		return s.cache, nil
 	}
 
+	if err := requireHTTPSURL(s.registryURL, "registry"); err != nil {
+		return nil, err
+	}
+
 	LogInfo("ExtensionStore", "Fetching registry from %s", s.registryURL)
 
-	client := &http.Client{Timeout: 30 * time.Second}
+	client := NewHTTPClientWithTimeout(30 * time.Second)
 	resp, err := client.Get(s.registryURL)
 	if err != nil {
-		// Return cached data if available on network error
 		if s.cache != nil {
 			LogWarn("ExtensionStore", "Network error, using cached registry: %v", err)
 			return s.cache, nil
@@ -268,7 +289,6 @@ func (s *ExtensionStore) FetchRegistry(forceRefresh bool) (*StoreRegistry, error
 	return &registry, nil
 }
 
-// GetExtensionsWithStatus returns extensions with installation status
 func (s *ExtensionStore) GetExtensionsWithStatus() ([]StoreExtensionResponse, error) {
 	registry, err := s.FetchRegistry(false)
 	if err != nil {
@@ -300,7 +320,6 @@ func (s *ExtensionStore) GetExtensionsWithStatus() ([]StoreExtensionResponse, er
 	return result, nil
 }
 
-// DownloadExtension downloads an extension package to the specified path
 func (s *ExtensionStore) DownloadExtension(extensionID string, destPath string) error {
 	registry, err := s.FetchRegistry(false)
 	if err != nil {
@@ -319,9 +338,13 @@ func (s *ExtensionStore) DownloadExtension(extensionID string, destPath string)
 		return fmt.Errorf("extension %s not found in store", extensionID)
 	}
 
+	if err := requireHTTPSURL(ext.getDownloadURL(), "extension download"); err != nil {
+		return err
+	}
+
 	LogInfo("ExtensionStore", "Downloading %s from %s", ext.getDisplayName(), ext.getDownloadURL())
 
-	client := &http.Client{Timeout: 5 * time.Minute}
+	client := NewHTTPClientWithTimeout(5 * time.Minute)
 	resp, err := client.Get(ext.getDownloadURL())
 	if err != nil {
 		return fmt.Errorf("failed to download: %w", err)
@@ -332,7 +355,6 @@ func (s *ExtensionStore) DownloadExtension(extensionID string, destPath string)
 		return fmt.Errorf("download returned HTTP %d", resp.StatusCode)
 	}
 
-	// Create destination file
 	out, err := os.Create(destPath)
 	if err != nil {
 		return fmt.Errorf("failed to create file: %w", err)
@@ -349,7 +371,95 @@ func (s *ExtensionStore) DownloadExtension(extensionID string, destPath string)
 	return nil
 }
 
-// GetCategories returns all available categories
+// ResolveRegistryURL normalises a user-supplied URL into a direct registry.json URL.
+//
+// Accepted formats:
+//   - https://raw.githubusercontent.com/owner/repo/<branch>/registry.json  → returned as-is
+//   - https://github.com/owner/repo  (with optional trailing path / .git)  → resolved via
+//     the GitHub API to discover the default branch, then converted to the raw URL
+//   - Any other HTTPS URL  → returned as-is (assumed to be a direct link)
+func ResolveRegistryURL(input string) (string, error) {
+	input = strings.TrimSpace(input)
+	if input == "" {
+		return "", fmt.Errorf("registry URL is empty")
+	}
+
+	// Already a fully-qualified raw URL – keep it.
+	if strings.Contains(input, "raw.githubusercontent.com") {
+		return input, nil
+	}
+
+	// Try to match https://github.com/<owner>/<repo>[/...]
+	const ghPrefix = "https://github.com/"
+	if !strings.HasPrefix(input, ghPrefix) {
+		// Also accept http:// and upgrade silently.
+		const ghPrefixHTTP = "http://github.com/"
+		if strings.HasPrefix(input, ghPrefixHTTP) {
+			input = "https://github.com/" + input[len(ghPrefixHTTP):]
+		} else {
+			// Not a GitHub URL – return as-is.
+			return input, nil
+		}
+	}
+
+	path := input[len(ghPrefix):]
+	parts := strings.SplitN(path, "/", 3) // owner, repo, [rest]
+	if len(parts) < 2 || parts[0] == "" || parts[1] == "" {
+		return "", fmt.Errorf("invalid GitHub URL: expected github.com/<owner>/<repo>")
+	}
+	owner := parts[0]
+	repo := strings.TrimSuffix(parts[1], ".git")
+
+	branch := resolveGitHubDefaultBranch(owner, repo)
+
+	resolved := fmt.Sprintf("https://raw.githubusercontent.com/%s/%s/%s/registry.json", owner, repo, branch)
+	LogInfo("ExtensionStore", "Resolved %s → %s (branch: %s)", input, resolved, branch)
+	return resolved, nil
+}
+
+// resolveGitHubDefaultBranch calls the GitHub API to discover the repository's
+// default branch.  Falls back to "main" on any error.
+func resolveGitHubDefaultBranch(owner, repo string) string {
+	apiURL := fmt.Sprintf("https://api.github.com/repos/%s/%s", owner, repo)
+	client := NewHTTPClientWithTimeout(10 * time.Second)
+
+	resp, err := client.Get(apiURL)
+	if err != nil {
+		LogWarn("ExtensionStore", "GitHub API request failed for %s/%s: %v – falling back to main", owner, repo, err)
+		return "main"
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		LogWarn("ExtensionStore", "GitHub API returned %d for %s/%s – falling back to main", resp.StatusCode, owner, repo)
+		return "main"
+	}
+
+	var info struct {
+		DefaultBranch string `json:"default_branch"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&info); err != nil || info.DefaultBranch == "" {
+		LogWarn("ExtensionStore", "Could not parse default_branch for %s/%s – falling back to main", owner, repo)
+		return "main"
+	}
+
+	return info.DefaultBranch
+}
+
+func requireHTTPSURL(rawURL string, context string) error {
+	if rawURL == "" {
+		return fmt.Errorf("%s URL is empty", context)
+	}
+	parsed, err := url.Parse(rawURL)
+	if err != nil || parsed.Host == "" {
+		return fmt.Errorf("%s URL is invalid: %s", context, rawURL)
+	}
+	if parsed.Scheme != "https" {
+		return fmt.Errorf("%s URL must use https: %s", context, rawURL)
+	}
+	return nil
+}
+
 func (s *ExtensionStore) GetCategories() []string {
 	return []string{
 		CategoryMetadata,
@@ -360,7 +470,6 @@ func (s *ExtensionStore) GetCategories() []string {
 	}
 }
 
-// SearchExtensions searches extensions by query
 func (s *ExtensionStore) SearchExtensions(query string, category string) ([]StoreExtensionResponse, error) {
 	extensions, err := s.GetExtensionsWithStatus()
 	if err != nil {
@@ -375,12 +484,10 @@ func (s *ExtensionStore) SearchExtensions(query string, category string) ([]Stor
 	queryLower := toLower(query)
 
 	for _, ext := range extensions {
-		// Filter by category
 		if category != "" && ext.Category != category {
 			continue
 		}
 
-		// Filter by query
 		if query != "" {
 			if !containsIgnoreCase(ext.Name, queryLower) &&
 				!containsIgnoreCase(ext.DisplayName, queryLower) &&
@@ -406,7 +513,6 @@ func (s *ExtensionStore) SearchExtensions(query string, category string) ([]Stor
 	return result, nil
 }
 
-// ClearCache clears the in-memory and disk cache
 func (s *ExtensionStore) ClearCache() {
 	s.cacheMu.Lock()
 	defer s.cacheMu.Unlock()
@@ -422,7 +528,6 @@ func (s *ExtensionStore) ClearCache() {
 	LogInfo("ExtensionStore", "Cache cleared")
 }
 
-// Helper: case-insensitive contains
 func containsIgnoreCase(s, substr string) bool {
 	return containsStr(toLower(s), substr)
 }

go_backend/extension_test.go

@@ -112,7 +112,6 @@ func TestExtensionRuntime_NetworkSandbox(t *testing.T) {
 
 	runtime := NewExtensionRuntime(ext)
 
-	// Test allowed domains
 	if err := runtime.validateDomain("https://api.allowed.com/path"); err != nil {
 		t.Errorf("Expected api.allowed.com to be allowed, got error: %v", err)
 	}
@@ -121,7 +120,6 @@ func TestExtensionRuntime_NetworkSandbox(t *testing.T) {
 		t.Errorf("Expected sub.wildcard.com to be allowed (wildcard), got error: %v", err)
 	}
 
-	// Test blocked domains
 	if err := runtime.validateDomain("https://blocked.com/path"); err == nil {
 		t.Error("Expected blocked.com to be denied")
 	}
@@ -139,7 +137,7 @@ func TestExtensionRuntime_FileSandbox(t *testing.T) {
 		Manifest: &ExtensionManifest{
 			Name: "test-ext",
 			Permissions: ExtensionPermissions{
-				File: true, // Enable file permission for test
+				File: true,
 			},
 		},
 		DataDir: tempDir,
@@ -147,7 +145,6 @@ func TestExtensionRuntime_FileSandbox(t *testing.T) {
 
 	runtime := NewExtensionRuntime(ext)
 
-	// Test valid path within sandbox
 	validPath, err := runtime.validatePath("test.txt")
 	if err != nil {
 		t.Errorf("Expected relative path to be valid, got error: %v", err)
@@ -156,13 +153,11 @@ func TestExtensionRuntime_FileSandbox(t *testing.T) {
 		t.Error("Expected non-empty path")
 	}
 
-	// Test path traversal attack
 	_, err = runtime.validatePath("../../../etc/passwd")
 	if err == nil {
 		t.Error("Expected path traversal to be blocked")
 	}
 
-	// Test nested path within sandbox (should be allowed)
 	nestedPath, err := runtime.validatePath("subdir/file.txt")
 	if err != nil {
 		t.Errorf("Expected nested path to be valid, got error: %v", err)
@@ -171,26 +166,23 @@ func TestExtensionRuntime_FileSandbox(t *testing.T) {
 		t.Error("Expected non-empty nested path")
 	}
 
-	// Test absolute path should be blocked (security fix)
-	// Use platform-appropriate absolute path
 	var absPath string
 	if filepath.IsAbs("C:\\Windows\\System32") {
-		absPath = "C:\\Windows\\System32\\test.txt" // Windows
+		absPath = "C:\\Windows\\System32\\test.txt"
 	} else {
-		absPath = "/etc/passwd" // Unix
+		absPath = "/etc/passwd"
 	}
 	_, err = runtime.validatePath(absPath)
 	if err == nil {
 		t.Error("Expected absolute path to be blocked")
 	}
 
-	// Test that extension without file permission is blocked
 	extNoFile := &LoadedExtension{
 		ID: "test-ext-no-file",
 		Manifest: &ExtensionManifest{
 			Name: "test-ext-no-file",
 			Permissions: ExtensionPermissions{
-				File: false, // No file permission
+				File: false,
 			},
 		},
 		DataDir: tempDir,
@@ -215,7 +207,6 @@ func TestExtensionRuntime_UtilityFunctions(t *testing.T) {
 	vm := goja.New()
 	runtime.RegisterAPIs(vm)
 
-	// Test base64 encode/decode
 	result, err := vm.RunString(`utils.base64Encode("hello")`)
 	if err != nil {
 		t.Fatalf("base64Encode failed: %v", err)
@@ -232,7 +223,6 @@ func TestExtensionRuntime_UtilityFunctions(t *testing.T) {
 		t.Errorf("Expected 'hello', got '%s'", result.String())
 	}
 
-	// Test MD5
 	result, err = vm.RunString(`utils.md5("hello")`)
 	if err != nil {
 		t.Fatalf("md5 failed: %v", err)
@@ -241,7 +231,6 @@ func TestExtensionRuntime_UtilityFunctions(t *testing.T) {
 		t.Errorf("Expected '5d41402abc4b2a76b9719d911017c592', got '%s'", result.String())
 	}
 
-	// Test JSON parse/stringify
 	result, err = vm.RunString(`utils.stringifyJSON({name: "test", value: 123})`)
 	if err != nil {
 		t.Fatalf("stringifyJSON failed: %v", err)
@@ -267,7 +256,6 @@ func TestExtensionRuntime_SSRFProtection(t *testing.T) {
 
 	runtime := NewExtensionRuntime(ext)
 
-	// Test that private IPs are blocked (SSRF protection)
 	privateIPs := []string{
 		"http://localhost/admin",
 		"http://127.0.0.1/admin",
@@ -285,7 +273,6 @@ func TestExtensionRuntime_SSRFProtection(t *testing.T) {
 		}
 	}
 
-	// Test that allowed public domain still works
 	if err := runtime.validateDomain("https://api.example.com/path"); err != nil {
 		t.Errorf("Expected api.example.com to be allowed, got error: %v", err)
 	}
@@ -296,7 +283,6 @@ func TestIsPrivateIP(t *testing.T) {
 		host     string
 		expected bool
 	}{
-		// Private IPs should be blocked
 		{"localhost", true},
 		{"127.0.0.1", true},
 		{"127.0.0.2", true},
@@ -306,18 +292,17 @@ func TestIsPrivateIP(t *testing.T) {
 		{"172.31.255.255", true},
 		{"192.168.0.1", true},
 		{"192.168.255.255", true},
-		{"169.254.169.254", true}, // AWS metadata
+		{"169.254.169.254", true},
 		{"router.local", true},
 		{"mydevice.local", true},
 
-		// Public IPs should be allowed
 		{"8.8.8.8", false},
 		{"1.1.1.1", false},
 		{"api.example.com", false},
 		{"google.com", false},
-		{"172.15.0.1", false},  // Just outside 172.16-31 range
-		{"172.32.0.1", false},  // Just outside 172.16-31 range
-		{"192.167.0.1", false}, // Not 192.168.x.x
+		{"172.15.0.1", false},
+		{"172.32.0.1", false},
+		{"192.167.0.1", false},
 	}
 
 	for _, tt := range tests {

go_backend/extension_timeout.go

@@ -1,16 +1,15 @@
-// Package gobackend provides timeout execution for extension JS code
 package gobackend
 
 import (
 	"context"
 	"fmt"
+	"runtime/debug"
 	"sync"
 	"time"
 
 	"github.com/dop251/goja"
 )
 
-// JSExecutionError represents an error during JS execution
 type JSExecutionError struct {
 	Message   string
 	IsTimeout bool
@@ -20,8 +19,6 @@ func (e *JSExecutionError) Error() string {
 	return e.Message
 }
 
-// RunWithTimeout executes JavaScript code with a timeout
-// Returns the result value and any error (including timeout)
 func RunWithTimeout(vm *goja.Runtime, script string, timeout time.Duration) (goja.Value, error) {
 	if timeout <= 0 {
 		timeout = DefaultJSTimeout
@@ -30,22 +27,18 @@ func RunWithTimeout(vm *goja.Runtime, script string, timeout time.Duration) (goj
 	ctx, cancel := context.WithTimeout(context.Background(), timeout)
 	defer cancel()
 
-	// Channel to receive result
 	type result struct {
 		value goja.Value
 		err   error
 	}
 	resultCh := make(chan result, 1)
 
-	// Track if we've interrupted
 	var interrupted bool
 	var interruptMu sync.Mutex
 
-	// Run script in goroutine
 	go func() {
 		defer func() {
 			if r := recover(); r != nil {
-				// Check if this was our interrupt
 				interruptMu.Lock()
 				wasInterrupted := interrupted
 				interruptMu.Unlock()
@@ -56,6 +49,7 @@ func RunWithTimeout(vm *goja.Runtime, script string, timeout time.Duration) (goj
 						IsTimeout: true,
 					}}
 				} else {
+					GoLog("[ExtensionRuntime] panic during JS execution: %v\n%s\n", r, string(debug.Stack()))
 					resultCh <- result{nil, fmt.Errorf("panic during execution: %v", r)}
 				}
 			}
@@ -65,22 +59,18 @@ func RunWithTimeout(vm *goja.Runtime, script string, timeout time.Duration) (goj
 		resultCh <- result{val, err}
 	}()
 
-	// Wait for result or timeout
 	select {
 	case res := <-resultCh:
 		return res.value, res.err
 	case <-ctx.Done():
-		// Timeout - interrupt the VM
 		interruptMu.Lock()
 		interrupted = true
 		interruptMu.Unlock()
 
 		vm.Interrupt("execution timeout")
 
-		// Wait a bit for the goroutine to finish
 		select {
 		case res := <-resultCh:
-			// If we got a result after interrupt, it might be the timeout error
 			if res.err != nil {
 				return nil, res.err
 			}
@@ -89,7 +79,6 @@ func RunWithTimeout(vm *goja.Runtime, script string, timeout time.Duration) (goj
 				IsTimeout: true,
 			}
 		case <-time.After(1 * time.Second):
-			// Force return timeout error
 			return nil, &JSExecutionError{
 				Message:   "execution timeout exceeded (force)",
 				IsTimeout: true,
@@ -109,7 +98,6 @@ func RunWithTimeoutAndRecover(vm *goja.Runtime, script string, timeout time.Dura
 	return result, err
 }
 
-// IsTimeoutError checks if an error is a timeout error
 func IsTimeoutError(err error) bool {
 	if jsErr, ok := err.(*JSExecutionError); ok {
 		return jsErr.IsTimeout

go_backend/filename.go

@@ -3,77 +3,156 @@ package gobackend
 import (
 	"fmt"
 	"regexp"
+	"strconv"
 	"strings"
+	"time"
 )
 
-// Invalid filename characters for Android/Windows/Linux
-var invalidChars = regexp.MustCompile(`[<>:"/\\|?*\x00-\x1f]`)
+var (
+	invalidChars                   = regexp.MustCompile(`[<>:"/\\|?*\x00-\x1f]`)
+	multiUnderscore                = regexp.MustCompile(`_+`)
+	formattedNumberPlaceholderExpr = regexp.MustCompile(`\{(track|disc):([0-9]+)\}`)
+	dateFormatPlaceholderExpr      = regexp.MustCompile(`\{date:([^{}]+)\}`)
+	yearPattern                    = regexp.MustCompile(`\d{4}`)
+)
 
-// sanitizeFilename removes invalid characters from filename
 func sanitizeFilename(filename string) string {
 	sanitized := invalidChars.ReplaceAllString(filename, "_")
-	
+
 	sanitized = strings.TrimSpace(sanitized)
 	sanitized = strings.Trim(sanitized, ".")
-	
-	multiUnderscore := regexp.MustCompile(`_+`)
+
 	sanitized = multiUnderscore.ReplaceAllString(sanitized, "_")
-	
+
 	if len(sanitized) > 200 {
 		sanitized = sanitized[:200]
 	}
-	
+
 	if sanitized == "" {
 		sanitized = "untitled"
 	}
-	
+
 	return sanitized
 }
 
-// buildFilenameFromTemplate builds a filename from template and metadata
 func buildFilenameFromTemplate(template string, metadata map[string]interface{}) string {
 	if template == "" {
 		template = "{artist} - {title}"
 	}
-	
-	result := template
-	
-	placeholders := map[string]string{
-		"{title}":  getString(metadata, "title"),
-		"{artist}": getString(metadata, "artist"),
-		"{album}":  getString(metadata, "album"),
-		"{track}":  formatTrackNumber(getInt(metadata, "track")),
-		"{year}":   getString(metadata, "year"),
-		"{disc}":   formatDiscNumber(getInt(metadata, "disc")),
+
+	result := replaceFormattedNumberPlaceholders(template, metadata)
+	result = replaceDateFormatPlaceholders(result, metadata)
+
+	dateValue := getDateValue(metadata)
+	yearValue := getString(metadata, "year")
+	if yearValue == "" {
+		yearValue = extractYear(dateValue)
 	}
-	
+
+	placeholders := map[string]string{
+		"{title}":     getString(metadata, "title"),
+		"{artist}":    getString(metadata, "artist"),
+		"{album}":     getString(metadata, "album"),
+		"{track}":     formatTrackNumber(getInt(metadata, "track")),
+		"{track_raw}": formatRawNumber(getInt(metadata, "track")),
+		"{year}":      yearValue,
+		"{date}":      dateValue,
+		"{disc}":      formatDiscNumber(getInt(metadata, "disc")),
+		"{disc_raw}":  formatRawNumber(getInt(metadata, "disc")),
+	}
+
 	for placeholder, value := range placeholders {
 		result = strings.ReplaceAll(result, placeholder, value)
 	}
-	
+
 	return result
 }
 
+func replaceFormattedNumberPlaceholders(template string, metadata map[string]interface{}) string {
+	return formattedNumberPlaceholderExpr.ReplaceAllStringFunc(template, func(match string) string {
+		parts := formattedNumberPlaceholderExpr.FindStringSubmatch(match)
+		if len(parts) != 3 {
+			return ""
+		}
+
+		number := getInt(metadata, parts[1])
+		width, err := strconv.Atoi(parts[2])
+		if err != nil {
+			return ""
+		}
+
+		return formatNumberWithWidth(number, width)
+	})
+}
+
+func replaceDateFormatPlaceholders(template string, metadata map[string]interface{}) string {
+	return dateFormatPlaceholderExpr.ReplaceAllStringFunc(template, func(match string) string {
+		parts := dateFormatPlaceholderExpr.FindStringSubmatch(match)
+		if len(parts) != 2 {
+			return ""
+		}
+
+		return formatDateWithPattern(getDateValue(metadata), parts[1])
+	})
+}
+
+func getDateValue(metadata map[string]interface{}) string {
+	date := getString(metadata, "date")
+	if date != "" {
+		return date
+	}
+
+	releaseDate := getString(metadata, "release_date")
+	if releaseDate != "" {
+		return releaseDate
+	}
+
+	return getString(metadata, "year")
+}
+
 func getString(m map[string]interface{}, key string) string {
 	if v, ok := m[key]; ok {
-		if s, ok := v.(string); ok {
-			return strings.TrimSpace(s)
+		switch value := v.(type) {
+		case string:
+			return strings.TrimSpace(value)
+		case int:
+			return strconv.Itoa(value)
+		case int64:
+			return strconv.FormatInt(value, 10)
+		case float64:
+			return strconv.Itoa(int(value))
 		}
 	}
 	return ""
 }
 
 func getInt(m map[string]interface{}, key string) int {
-	if v, ok := m[key]; ok {
-		switch n := v.(type) {
-		case int:
-			return n
-		case int64:
-			return int(n)
-		case float64:
-			return int(n)
+	candidateKeys := []string{key}
+	switch key {
+	case "track":
+		candidateKeys = append(candidateKeys, "track_number")
+	case "disc":
+		candidateKeys = append(candidateKeys, "disc_number")
+	}
+
+	for _, candidate := range candidateKeys {
+		if v, ok := m[candidate]; ok {
+			switch n := v.(type) {
+			case int:
+				return n
+			case int64:
+				return int(n)
+			case float64:
+				return int(n)
+			case string:
+				parsed, err := strconv.Atoi(strings.TrimSpace(n))
+				if err == nil {
+					return parsed
+				}
+			}
 		}
 	}
+
 	return 0
 }
 
@@ -91,7 +170,129 @@ func formatDiscNumber(n int) string {
 	return fmt.Sprintf("%d", n)
 }
 
-// extractYear extracts year from date string (YYYY-MM-DD or YYYY)
+func formatRawNumber(n int) string {
+	if n <= 0 {
+		return ""
+	}
+	return fmt.Sprintf("%d", n)
+}
+
+func formatNumberWithWidth(n int, width int) string {
+	if n <= 0 || width <= 0 {
+		return ""
+	}
+	if width <= 1 {
+		return formatRawNumber(n)
+	}
+	return fmt.Sprintf("%0*d", width, n)
+}
+
+func formatDateWithPattern(rawDate string, strftimePattern string) string {
+	if rawDate == "" || strftimePattern == "" {
+		return ""
+	}
+
+	parsedDate, ok := parseMetadataDate(rawDate)
+	if !ok {
+		return ""
+	}
+
+	goLayout := convertStrftimeToGoLayout(strftimePattern)
+	if goLayout == "" {
+		return ""
+	}
+
+	return parsedDate.Format(goLayout)
+}
+
+func parseMetadataDate(rawDate string) (time.Time, bool) {
+	clean := strings.TrimSpace(rawDate)
+	if clean == "" {
+		return time.Time{}, false
+	}
+
+	layouts := []string{
+		time.RFC3339Nano,
+		time.RFC3339,
+		"2006-01-02",
+		"2006-01",
+		"2006",
+		"2006/01/02",
+		"2006/01",
+		"2006.01.02",
+		"2006.01",
+	}
+
+	for _, layout := range layouts {
+		parsed, err := time.Parse(layout, clean)
+		if err == nil {
+			return parsed, true
+		}
+	}
+
+	if len(clean) >= 10 {
+		parsed, err := time.Parse("2006-01-02", clean[:10])
+		if err == nil {
+			return parsed, true
+		}
+	}
+
+	yearMatch := yearPattern.FindString(clean)
+	if yearMatch == "" {
+		return time.Time{}, false
+	}
+
+	year, err := strconv.Atoi(yearMatch)
+	if err != nil || year <= 0 {
+		return time.Time{}, false
+	}
+
+	return time.Date(year, time.January, 1, 0, 0, 0, 0, time.UTC), true
+}
+
+func convertStrftimeToGoLayout(pattern string) string {
+	if pattern == "" {
+		return ""
+	}
+
+	var builder strings.Builder
+	for i := 0; i < len(pattern); i++ {
+		ch := pattern[i]
+		if ch != '%' {
+			builder.WriteByte(ch)
+			continue
+		}
+
+		if i+1 >= len(pattern) {
+			builder.WriteByte('%')
+			break
+		}
+
+		i++
+		switch pattern[i] {
+		case 'Y':
+			builder.WriteString("2006")
+		case 'y':
+			builder.WriteString("06")
+		case 'm':
+			builder.WriteString("01")
+		case 'd':
+			builder.WriteString("02")
+		case 'b':
+			builder.WriteString("Jan")
+		case 'B':
+			builder.WriteString("January")
+		case '%':
+			builder.WriteByte('%')
+		default:
+			builder.WriteByte('%')
+			builder.WriteByte(pattern[i])
+		}
+	}
+
+	return builder.String()
+}
+
 func extractYear(date string) string {
 	if len(date) >= 4 {
 		return date[:4]

go_backend/filename_test.go

@@ -0,0 +1,85 @@
+package gobackend
+
+import "testing"
+
+func TestBuildFilenameFromTemplate_WithRawTrackAndDisc(t *testing.T) {
+	metadata := map[string]interface{}{
+		"title":  "Song Name",
+		"artist": "Artist Name",
+		"album":  "Album Name",
+		"track":  1,
+		"disc":   2,
+		"year":   "2025",
+	}
+
+	formatted := buildFilenameFromTemplate(
+		"{artist} - {track} - {track_raw} - d{disc} - d{disc_raw} - {title}",
+		metadata,
+	)
+
+	expected := "Artist Name - 01 - 1 - d2 - d2 - Song Name"
+	if formatted != expected {
+		t.Fatalf("expected %q, got %q", expected, formatted)
+	}
+}
+
+func TestBuildFilenameFromTemplate_RawPlaceholdersEmptyWhenZero(t *testing.T) {
+	metadata := map[string]interface{}{
+		"title":  "Song Name",
+		"artist": "Artist Name",
+		"track":  0,
+		"disc":   0,
+	}
+
+	formatted := buildFilenameFromTemplate("{track_raw}-{disc_raw}-{title}", metadata)
+	expected := "--Song Name"
+	if formatted != expected {
+		t.Fatalf("expected %q, got %q", expected, formatted)
+	}
+}
+
+func TestBuildFilenameFromTemplate_InlineNumberFormatting(t *testing.T) {
+	metadata := map[string]interface{}{
+		"track": 3,
+		"disc":  2,
+	}
+
+	formatted := buildFilenameFromTemplate("{track:1}-{track:02}-{disc:03}", metadata)
+	expected := "3-03-002"
+	if formatted != expected {
+		t.Fatalf("expected %q, got %q", expected, formatted)
+	}
+}
+
+func TestBuildFilenameFromTemplate_DateStrftimeFormatting(t *testing.T) {
+	metadata := map[string]interface{}{
+		"artist":       "Artist Name",
+		"title":        "Song Name",
+		"release_date": "2024-03-09",
+		"track_number": 7,
+		"disc_number":  1,
+	}
+
+	formatted := buildFilenameFromTemplate(
+		"{artist} - {track:02} - {title} - {date:%Y-%m-%d} - {year}",
+		metadata,
+	)
+	expected := "Artist Name - 07 - Song Name - 2024-03-09 - 2024"
+	if formatted != expected {
+		t.Fatalf("expected %q, got %q", expected, formatted)
+	}
+}
+
+func TestBuildFilenameFromTemplate_DateStrftimeFormattingWithYearOnly(t *testing.T) {
+	metadata := map[string]interface{}{
+		"artist": "Artist Name",
+		"title":  "Song Name",
+		"date":   "2019",
+	}
+
+	formatted := buildFilenameFromTemplate("{date:%Y}-{date:%m}-{date:%d}", metadata)
+	expected := "2019-01-01"
+	if formatted != expected {
+		t.Fatalf("expected %q, got %q", expected, formatted)
+	}
+}

go_backend/go.mod

@@ -1,23 +1,29 @@
 module github.com/zarz/spotiflac_android/go_backend
 
-go 1.24.0
+go 1.25.0
 
-toolchain go1.24.5
+toolchain go1.25.7
 
 require (
-	github.com/dop251/goja v0.0.0-20260106131823-651366fbe6e3
-	github.com/go-flac/flacpicture v0.3.0
-	github.com/go-flac/flacvorbis v0.2.0
-	github.com/go-flac/go-flac v1.0.0
+	github.com/dop251/goja v0.0.0-20260216154549-8b74ce4618c5
+	github.com/go-flac/flacpicture/v2 v2.0.2
+	github.com/go-flac/flacvorbis/v2 v2.0.2
+	github.com/go-flac/go-flac/v2 v2.0.4
+	github.com/refraction-networking/utls v1.8.2
+	golang.org/x/mobile v0.0.0-20260211191516-dcd2a3258864
+	golang.org/x/net v0.50.0
 )
 
 require (
+	github.com/andybalholm/brotli v1.0.6 // indirect
 	github.com/dlclark/regexp2 v1.11.4 // indirect
 	github.com/go-sourcemap/sourcemap v2.1.3+incompatible // indirect
 	github.com/google/pprof v0.0.0-20230207041349-798e818bf904 // indirect
-	golang.org/x/mobile v0.0.0-20251209145715-2553ed8ce294 // indirect
-	golang.org/x/mod v0.31.0 // indirect
+	github.com/klauspost/compress v1.17.4 // indirect
+	golang.org/x/crypto v0.48.0 // indirect
+	golang.org/x/mod v0.33.0 // indirect
 	golang.org/x/sync v0.19.0 // indirect
-	golang.org/x/text v0.3.8 // indirect
-	golang.org/x/tools v0.40.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
+	golang.org/x/text v0.34.0 // indirect
+	golang.org/x/tools v0.42.0 // indirect
 )

go_backend/go.sum

@@ -1,28 +1,68 @@
 github.com/Masterminds/semver/v3 v3.2.1 h1:RN9w6+7QoMeJVGyfmbcgs28Br8cvmnucEXnY0rYXWg0=
 github.com/Masterminds/semver/v3 v3.2.1/go.mod h1:qvl/7zhW3nngYb5+80sSMF+FG2BjYrf8m9wsX0PNOMQ=
+github.com/andybalholm/brotli v1.0.6 h1:Yf9fFpf49Zrxb9NlQaluyE92/+X7UVHlhMNJN2sxfOI=
+github.com/andybalholm/brotli v1.0.6/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dlclark/regexp2 v1.11.4 h1:rPYF9/LECdNymJufQKmri9gV604RvvABwgOA8un7yAo=
 github.com/dlclark/regexp2 v1.11.4/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
 github.com/dop251/goja v0.0.0-20260106131823-651366fbe6e3 h1:bVp3yUzvSAJzu9GqID+Z96P+eu5TKnIMJSV4QaZMauM=
 github.com/dop251/goja v0.0.0-20260106131823-651366fbe6e3/go.mod h1:MxLav0peU43GgvwVgNbLAj1s/bSGboKkhuULvq/7hx4=
-github.com/go-flac/flacpicture v0.3.0 h1:LkmTxzFLIynwfhHiZsX0s8xcr3/u33MzvV89u+zOT8I=
-github.com/go-flac/flacpicture v0.3.0/go.mod h1:DPbrzVYQ3fJcvSgLFp9HXIrEQEdfdk/+m0nQCzwodZI=
-github.com/go-flac/flacvorbis v0.2.0 h1:KH0xjpkNTXFER4cszH4zeJxYcrHbUobz/RticWGOESs=
-github.com/go-flac/flacvorbis v0.2.0/go.mod h1:uIysHOtuU7OLGoCRG92bvnkg7QEqHx19qKRV6K1pBrI=
-github.com/go-flac/go-flac v1.0.0 h1:6qI9XOVLcO50xpzm3nXvO31BgDgHhnr/p/rER/K/doY=
-github.com/go-flac/go-flac v1.0.0/go.mod h1:WnZhcpmq4u1UdZMNn9LYSoASpWOCMOoxXxcWEHSzkW8=
+github.com/dop251/goja v0.0.0-20260216154549-8b74ce4618c5 h1:QckvTXtu55YMopmVeDrPQ/r+T6xjw8KMCmE3UgUldkw=
+github.com/dop251/goja v0.0.0-20260216154549-8b74ce4618c5/go.mod h1:MxLav0peU43GgvwVgNbLAj1s/bSGboKkhuULvq/7hx4=
+github.com/go-flac/flacpicture/v2 v2.0.2 h1:HCaJIVZpxnpdWs6G3ECEVRelzqS5xOi1Ba1AGmtXbzE=
+github.com/go-flac/flacpicture/v2 v2.0.2/go.mod h1:DMZBPWPAmdLqNhqFSy5ZBs9wyBzOekXutGfP7/TFCuo=
+github.com/go-flac/flacvorbis/v2 v2.0.2 h1:xCL3OhxrxWkHrbWUBvGNe+6FQ03yLmBbz0v5z4V2PoQ=
+github.com/go-flac/flacvorbis/v2 v2.0.2/go.mod h1:SwTB5gs13VaM/N7rstwPoUsPibiMKklgwybYP9dYo2g=
+github.com/go-flac/go-flac/v2 v2.0.4 h1:atf/kFa8U9idtkA//NO22XGr+MzQLeXZecnmP9sYBf0=
+github.com/go-flac/go-flac/v2 v2.0.4/go.mod h1:sYOlTKxutMW0RDYF+KlD6Zn+VOCZlIFQG/r/usPveCs=
 github.com/go-sourcemap/sourcemap v2.1.3+incompatible h1:W1iEw64niKVGogNgBN3ePyLFfuisuzeidWPMPWmECqU=
 github.com/go-sourcemap/sourcemap v2.1.3+incompatible/go.mod h1:F8jJfvm2KbVjc5NqelyYJmf/v5J0dwNLS2mL4sNA1Jg=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/pprof v0.0.0-20230207041349-798e818bf904 h1:4/hN5RUoecvl+RmJRE2YxKWtnnQls6rQjjW5oV7qg2U=
 github.com/google/pprof v0.0.0-20230207041349-798e818bf904/go.mod h1:uglQLonpP8qtYCYyzA+8c/9qtqgA3qsXGYqCPKARAFg=
-golang.org/x/mobile v0.0.0-20251209145715-2553ed8ce294 h1:Cr6kbEvA6nqvdHynE4CtVKlqpZB9dS1Jva/6IsHA19g=
-golang.org/x/mobile v0.0.0-20251209145715-2553ed8ce294/go.mod h1:RdZ+3sb4CVgpCFnzv+I4haEpwqFfsfzlLHs3L7ok+e0=
-golang.org/x/mod v0.31.0 h1:HaW9xtz0+kOcWKwli0ZXy79Ix+UW/vOfmWI5QVd2tgI=
-golang.org/x/mod v0.31.0/go.mod h1:43JraMp9cGx1Rx3AqioxrbrhNsLl2l/iNAvuBkrezpg=
+github.com/klauspost/compress v1.17.4 h1:Ej5ixsIri7BrIjBkRZLTo6ghwrEtHFk7ijlczPW4fZ4=
+github.com/klauspost/compress v1.17.4/go.mod h1:/dCuZOvVtNoHsyb+cuJD3itjs3NbnF6KH9zAO4BDxPM=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/refraction-networking/utls v1.8.2 h1:j4Q1gJj0xngdeH+Ox/qND11aEfhpgoEvV+S9iJ2IdQo=
+github.com/refraction-networking/utls v1.8.2/go.mod h1:jkSOEkLqn+S/jtpEHPOsVv/4V4EVnelwbMQl4vCWXAM=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/crypto v0.47.0 h1:V6e3FRj+n4dbpw86FJ8Fv7XVOql7TEwpHapKoMJ/GO8=
+golang.org/x/crypto v0.47.0/go.mod h1:ff3Y9VzzKbwSSEzWqJsJVBnWmRwRSHt/6Op5n9bQc4A=
+golang.org/x/crypto v0.48.0 h1:/VRzVqiRSggnhY7gNRxPauEQ5Drw9haKdM0jqfcCFts=
+golang.org/x/crypto v0.48.0/go.mod h1:r0kV5h3qnFPlQnBSrULhlsRfryS2pmewsg+XfMgkVos=
+golang.org/x/mobile v0.0.0-20260204172633-1dceadbbeea3 h1:NiJtT7g4ncNFVjVZMAYNBrPSNhIjFYPj8UKA8MEw2A4=
+golang.org/x/mobile v0.0.0-20260204172633-1dceadbbeea3/go.mod h1:wReH3Q1agKmmLapipWFnd4NSs8KPz3fK6mSEZjXLkrg=
+golang.org/x/mobile v0.0.0-20260209203831-923679eb55af h1:VqXrZNyqFISxo0rNDFZQlRDRIp7RXSJDeh/LbrK+W1k=
+golang.org/x/mobile v0.0.0-20260209203831-923679eb55af/go.mod h1:tbwefIr7RlQD1OpZ0KEZ9nux/uiihAOGdafgZfJkmII=
+golang.org/x/mobile v0.0.0-20260211191516-dcd2a3258864 h1:cTVynMSsMYgbUrtia2HB1jrhdUwQNtQti91vUCyjMp4=
+golang.org/x/mobile v0.0.0-20260211191516-dcd2a3258864/go.mod h1:4OGHIUSBiIqyFAQDaX1tpY0BVnO20DvNDeATBu8aeFQ=
+golang.org/x/mod v0.32.0 h1:9F4d3PHLljb6x//jOyokMv3eX+YDeepZSEo3mFJy93c=
+golang.org/x/mod v0.32.0/go.mod h1:SgipZ/3h2Ci89DlEtEXWUk/HteuRin+HHhN+WbNhguU=
+golang.org/x/mod v0.33.0 h1:tHFzIWbBifEmbwtGz65eaWyGiGZatSrT9prnU8DbVL8=
+golang.org/x/mod v0.33.0/go.mod h1:swjeQEj+6r7fODbD2cqrnje9PnziFuw4bmLbBZFrQ5w=
+golang.org/x/net v0.49.0 h1:eeHFmOGUTtaaPSGNmjBKpbng9MulQsJURQUAfUwY++o=
+golang.org/x/net v0.49.0/go.mod h1:/ysNB2EvaqvesRkuLAyjI1ycPZlQHM3q01F02UY/MV8=
+golang.org/x/net v0.50.0 h1:ucWh9eiCGyDR3vtzso0WMQinm2Dnt8cFMuQa9K33J60=
+golang.org/x/net v0.50.0/go.mod h1:UgoSli3F/pBgdJBHCTc+tp3gmrU4XswgGRgtnwWTfyM=
 golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
 golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
-golang.org/x/text v0.3.8 h1:nAL+RVCQ9uMn3vJZbV+MRnydTJFPf8qqY42YiA6MrqY=
-golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
-golang.org/x/tools v0.40.0 h1:yLkxfA+Qnul4cs9QA3KnlFu0lVmd8JJfoq+E41uSutA=
-golang.org/x/tools v0.40.0/go.mod h1:Ik/tzLRlbscWpqqMRjyWYDisX8bG13FrdXp3o4Sr9lc=
+golang.org/x/sys v0.40.0 h1:DBZZqJ2Rkml6QMQsZywtnjnnGvHza6BTfYFWY9kjEWQ=
+golang.org/x/sys v0.40.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
+golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.33.0 h1:B3njUFyqtHDUI5jMn1YIr5B0IE2U0qck04r6d4KPAxE=
+golang.org/x/text v0.33.0/go.mod h1:LuMebE6+rBincTi9+xWTY8TztLzKHc/9C1uBCG27+q8=
+golang.org/x/text v0.34.0 h1:oL/Qq0Kdaqxa1KbNeMKwQq0reLCCaFtqu2eNuSeNHbk=
+golang.org/x/text v0.34.0/go.mod h1:homfLqTYRFyVYemLBFl5GgL/DWEiH5wcsQ5gSh1yziA=
+golang.org/x/tools v0.41.0 h1:a9b8iMweWG+S0OBnlU36rzLp20z1Rp10w+IY2czHTQc=
+golang.org/x/tools v0.41.0/go.mod h1:XSY6eDqxVNiYgezAVqqCeihT4j1U2CCsqvH3WhQpnlg=
+golang.org/x/tools v0.42.0 h1:uNgphsn75Tdz5Ji2q36v/nsFSfR/9BRFvqhGBaJGd5k=
+golang.org/x/tools v0.42.0/go.mod h1:Ma6lCIwGZvHK6XtgbswSoWroEkhugApmsXyrUmBhfr0=
 gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

go_backend/httputil.go

@@ -11,74 +11,43 @@ import (
 	"net/url"
 	"strconv"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 )
 
-// HTTP utility functions for consistent request handling across all downloaders
-
-// getRandomUserAgent generates a random Windows Chrome User-Agent string
-// Uses same format as PC version (referensi/backend/spotify_metadata.go) for better API compatibility
 func getRandomUserAgent() string {
-	winMajor := rand.Intn(2) + 10
-
-	chromeVersion := rand.Intn(25) + 100
-	chromeBuild := rand.Intn(1500) + 3000
-	chromePatch := rand.Intn(65) + 60
+	chromeVersion := rand.Intn(26) + 120
+	chromeBuild := rand.Intn(1500) + 6000
+	chromePatch := rand.Intn(200) + 100
 
 	return fmt.Sprintf(
-		"Mozilla/5.0 (Windows NT %d.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/537.36",
-		winMajor,
+		"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/537.36",
 		chromeVersion,
 		chromeBuild,
 		chromePatch,
 	)
 }
 
-// getRandomMacUserAgent generates a random Mac Chrome User-Agent string
-// Alternative format matching referensi/backend/spotify_metadata.go exactly
-// func getRandomMacUserAgent() string {
-// 	macMajor := rand.Intn(4) + 11 // macOS 11-14
-// 	macMinor := rand.Intn(5) + 4  // Minor 4-8
-// 	webkitMajor := rand.Intn(7) + 530
-// 	webkitMinor := rand.Intn(7) + 30
-// 	chromeMajor := rand.Intn(25) + 80
-// 	chromeBuild := rand.Intn(1500) + 3000
-// 	chromePatch := rand.Intn(65) + 60
-// 	safariMajor := rand.Intn(7) + 530
-// 	safariMinor := rand.Intn(6) + 30
-//
-// 	return fmt.Sprintf(
-// 		"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_%d_%d) AppleWebKit/%d.%d (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/%d.%d",
-// 		macMajor,
-// 		macMinor,
-// 		webkitMajor,
-// 		webkitMinor,
-// 		chromeMajor,
-// 		chromeBuild,
-// 		chromePatch,
-// 		safariMajor,
-// 		safariMinor,
-// 	)
-// }
-
-// getRandomDesktopUserAgent randomly picks between Windows and Mac User-Agent
-// func getRandomDesktopUserAgent() string {
-// 	if rand.Intn(2) == 0 {
-// 		return getRandomUserAgent() // Windows
-// 	}
-// 	return getRandomMacUserAgent() // Mac
-// }
-
 const (
 	DefaultTimeout    = 60 * time.Second
-	DownloadTimeout   = 120 * time.Second
+	DownloadTimeout   = 24 * time.Hour
 	SongLinkTimeout   = 30 * time.Second
 	DefaultMaxRetries = 3
 	DefaultRetryDelay = 1 * time.Second
+	Second            = time.Second
+)
+
+type NetworkCompatibilityOptions struct {
+	AllowHTTP   bool
+	InsecureTLS bool
+}
+
+var (
+	networkCompatibilityMu      sync.RWMutex
+	networkCompatibilityOptions NetworkCompatibilityOptions
 )
 
-// Shared transport with connection pooling to prevent TCP exhaustion
 var sharedTransport = &http.Transport{
 	DialContext: (&net.Dialer{
 		Timeout:   30 * time.Second,
@@ -97,20 +66,49 @@ var sharedTransport = &http.Transport{
 	DisableCompression:    true,
 }
 
+// metadataTransport is a separate transport for metadata API calls (Deezer, Spotify, SongLink).
+// Isolated from download traffic so that download failures cannot poison
+// the connection pool used by metadata enrichment.
+var metadataTransport = &http.Transport{
+	DialContext: (&net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 30 * time.Second,
+	}).DialContext,
+	MaxIdleConns:          30,
+	MaxIdleConnsPerHost:   5,
+	MaxConnsPerHost:       10,
+	IdleConnTimeout:       90 * time.Second,
+	TLSHandshakeTimeout:   10 * time.Second,
+	ExpectContinueTimeout: 1 * time.Second,
+	DisableKeepAlives:     false,
+	ForceAttemptHTTP2:     true,
+	WriteBufferSize:       32 * 1024,
+	ReadBufferSize:        32 * 1024,
+	DisableCompression:    true,
+}
+
 var sharedClient = &http.Client{
-	Transport: sharedTransport,
+	Transport: newCompatibilityTransport(sharedTransport),
 	Timeout:   DefaultTimeout,
 }
 
 var downloadClient = &http.Client{
-	Transport: sharedTransport,
+	Transport: newCompatibilityTransport(sharedTransport),
 	Timeout:   DownloadTimeout,
 }
 
-// NewHTTPClientWithTimeout creates an HTTP client with specified timeout
 func NewHTTPClientWithTimeout(timeout time.Duration) *http.Client {
 	return &http.Client{
-		Transport: sharedTransport,
+		Transport: newCompatibilityTransport(sharedTransport),
+		Timeout:   timeout,
+	}
+}
+
+// NewMetadataHTTPClient creates an HTTP client using the isolated metadata transport.
+// Use this for API calls that should not be affected by download traffic.
+func NewMetadataHTTPClient(timeout time.Duration) *http.Client {
+	return &http.Client{
+		Transport: newCompatibilityTransport(metadataTransport),
 		Timeout:   timeout,
 	}
 }
@@ -123,12 +121,114 @@ func GetDownloadClient() *http.Client {
 	return downloadClient
 }
 
-// CloseIdleConnections closes idle connections in the shared transport
 func CloseIdleConnections() {
 	sharedTransport.CloseIdleConnections()
+	metadataTransport.CloseIdleConnections()
+}
+
+func SetNetworkCompatibilityOptions(allowHTTP, insecureTLS bool) {
+	networkCompatibilityMu.Lock()
+	networkCompatibilityOptions = NetworkCompatibilityOptions{
+		AllowHTTP:   allowHTTP,
+		InsecureTLS: insecureTLS,
+	}
+	networkCompatibilityMu.Unlock()
+
+	applyTLSCompatibility(sharedTransport, insecureTLS)
+	applyTLSCompatibility(metadataTransport, insecureTLS)
+	CloseIdleConnections()
+
+	GoLog("[HTTP] Network compatibility options updated: allow_http=%v insecure_tls=%v\n", allowHTTP, insecureTLS)
+}
+
+func GetNetworkCompatibilityOptions() NetworkCompatibilityOptions {
+	networkCompatibilityMu.RLock()
+	defer networkCompatibilityMu.RUnlock()
+	return networkCompatibilityOptions
+}
+
+func applyTLSCompatibility(transport *http.Transport, insecureTLS bool) {
+	if insecureTLS {
+		cfg := &tls.Config{InsecureSkipVerify: true}
+		if transport.TLSClientConfig != nil {
+			cfg = transport.TLSClientConfig.Clone()
+			cfg.InsecureSkipVerify = true
+		}
+		transport.TLSClientConfig = cfg
+		return
+	}
+
+	transport.TLSClientConfig = nil
+}
+
+type compatibilityTransport struct {
+	base http.RoundTripper
+}
+
+func newCompatibilityTransport(base http.RoundTripper) http.RoundTripper {
+	return &compatibilityTransport{base: base}
+}
+
+func (t *compatibilityTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	if req == nil || req.URL == nil {
+		return t.base.RoundTrip(req)
+	}
+
+	opts := GetNetworkCompatibilityOptions()
+	if !opts.AllowHTTP || req.URL.Scheme != "https" {
+		return t.base.RoundTrip(req)
+	}
+
+	// Compatibility mode should prefer HTTPS and only fallback to HTTP on
+	// transport-level failures. Forcing HTTP unconditionally can trigger
+	// redirect loops (http -> https) on providers that enforce HTTPS.
+	resp, err := t.base.RoundTrip(req)
+	if err == nil {
+		return resp, nil
+	}
+
+	if !canFallbackToHTTP(req) {
+		return nil, err
+	}
+
+	fallbackReq, cloneErr := cloneRequestWithHTTPScheme(req, "http")
+	if cloneErr != nil {
+		return nil, err
+	}
+
+	GoLog("[HTTP] HTTPS request failed for %s, retrying over HTTP: %v\n", req.URL.Host, err)
+	return t.base.RoundTrip(fallbackReq)
+}
+
+func canFallbackToHTTP(req *http.Request) bool {
+	if req == nil {
+		return false
+	}
+
+	switch strings.ToUpper(req.Method) {
+	case http.MethodGet, http.MethodHead, http.MethodOptions, http.MethodDelete:
+		return true
+	default:
+		return req.GetBody != nil
+	}
+}
+
+func cloneRequestWithHTTPScheme(req *http.Request, scheme string) (*http.Request, error) {
+	reqCopy := req.Clone(req.Context())
+	if req.Body != nil && req.GetBody != nil {
+		bodyCopy, err := req.GetBody()
+		if err != nil {
+			return nil, err
+		}
+		reqCopy.Body = bodyCopy
+	}
+
+	urlCopy := *req.URL
+	urlCopy.Scheme = scheme
+	reqCopy.URL = &urlCopy
+	return reqCopy, nil
 }
 
-// DoRequestWithUserAgent executes an HTTP request with a random User-Agent header
 // Also checks for ISP blocking on errors
 func DoRequestWithUserAgent(client *http.Client, req *http.Request) (*http.Response, error) {
 	req.Header.Set("User-Agent", getRandomUserAgent())
@@ -147,7 +247,6 @@ type RetryConfig struct {
 	BackoffFactor float64
 }
 
-// DefaultRetryConfig returns default retry configuration
 func DefaultRetryConfig() RetryConfig {
 	return RetryConfig{
 		MaxRetries:    DefaultMaxRetries,
@@ -157,16 +256,11 @@ func DefaultRetryConfig() RetryConfig {
 	}
 }
 
-// DoRequestWithRetry executes an HTTP request with retry logic and exponential backoff
-// Handles 429 (Too Many Requests) responses with Retry-After header
-// Also detects and logs ISP blocking
 func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConfig) (*http.Response, error) {
 	var lastErr error
 	delay := config.InitialDelay
-	requestURL := req.URL.String()
 
 	for attempt := 0; attempt <= config.MaxRetries; attempt++ {
-		// Clone request for retry (body needs to be re-readable)
 		reqCopy := req.Clone(req.Context())
 		reqCopy.Header.Set("User-Agent", getRandomUserAgent())
 
@@ -174,10 +268,8 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 		if err != nil {
 			lastErr = err
 
-			// Check for ISP blocking on network errors
-			if CheckAndLogISPBlocking(err, requestURL, "HTTP") {
-				// Don't retry if ISP blocking is detected - it won't help
-				return nil, WrapErrorWithISPCheck(err, requestURL, "HTTP")
+			if CheckAndLogISPBlocking(err, reqCopy.URL.String(), "HTTP") {
+				return nil, WrapErrorWithISPCheck(err, reqCopy.URL.String(), "HTTP")
 			}
 
 			if attempt < config.MaxRetries {
@@ -189,12 +281,10 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 			continue
 		}
 
-		// Success
 		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
 			return resp, nil
 		}
 
-		// Handle rate limiting (429)
 		if resp.StatusCode == 429 {
 			resp.Body.Close()
 			retryAfter := getRetryAfterDuration(resp)
@@ -234,7 +324,6 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 			}
 		}
 
-		// Server errors (5xx) - retry
 		if resp.StatusCode >= 500 {
 			resp.Body.Close()
 			lastErr = fmt.Errorf("server error: HTTP %d", resp.StatusCode)
@@ -246,33 +335,29 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 			continue
 		}
 
-		// Client errors (4xx except 429) - don't retry
 		return resp, nil
 	}
 
 	return nil, fmt.Errorf("request failed after %d retries: %w", config.MaxRetries+1, lastErr)
 }
 
-// calculateNextDelay calculates the next delay with exponential backoff
 func calculateNextDelay(currentDelay time.Duration, config RetryConfig) time.Duration {
 	nextDelay := time.Duration(float64(currentDelay) * config.BackoffFactor)
 	return min(nextDelay, config.MaxDelay)
 }
 
-// getRetryAfterDuration parses Retry-After header and returns duration
-// Returns 60 seconds as default if header is missing or invalid
+// Returns 0 if the header is missing or invalid so callers can keep their
+// normal exponential backoff instead of stalling for an arbitrary minute.
 func getRetryAfterDuration(resp *http.Response) time.Duration {
 	retryAfter := resp.Header.Get("Retry-After")
 	if retryAfter == "" {
-		return 60 * time.Second // Default wait time
+		return 0
 	}
 
-	// Try parsing as seconds
 	if seconds, err := strconv.Atoi(retryAfter); err == nil {
 		return time.Duration(seconds) * time.Second
 	}
 
-	// Try parsing as HTTP date
 	if t, err := http.ParseTime(retryAfter); err == nil {
 		duration := time.Until(t)
 		if duration > 0 {
@@ -280,11 +365,9 @@ func getRetryAfterDuration(resp *http.Response) time.Duration {
 		}
 	}
 
-	return 60 * time.Second // Default
+	return 0
 }
 
-// ReadResponseBody reads and returns the response body
-// Returns error if body is empty
 func ReadResponseBody(resp *http.Response) ([]byte, error) {
 	if resp == nil {
 		return nil, fmt.Errorf("response is nil")
@@ -302,7 +385,6 @@ func ReadResponseBody(resp *http.Response) ([]byte, error) {
 	return body, nil
 }
 
-// ValidateResponse checks if response is valid (non-nil, status 2xx)
 func ValidateResponse(resp *http.Response) error {
 	if resp == nil {
 		return fmt.Errorf("response is nil")
@@ -315,14 +397,12 @@ func ValidateResponse(resp *http.Response) error {
 	return nil
 }
 
-// BuildErrorMessage creates a detailed error message for API failures
 func BuildErrorMessage(apiURL string, statusCode int, responsePreview string) string {
 	msg := fmt.Sprintf("API %s failed", apiURL)
 	if statusCode > 0 {
 		msg += fmt.Sprintf(" (HTTP %d)", statusCode)
 	}
 	if responsePreview != "" {
-		// Truncate preview if too long
 		if len(responsePreview) > 100 {
 			responsePreview = responsePreview[:100] + "..."
 		}
@@ -331,7 +411,6 @@ func BuildErrorMessage(apiURL string, statusCode int, responsePreview string) st
 	return msg
 }
 
-// ISPBlockingError represents an error caused by ISP blocking
 type ISPBlockingError struct {
 	Domain      string
 	Reason      string
@@ -342,18 +421,14 @@ func (e *ISPBlockingError) Error() string {
 	return fmt.Sprintf("ISP blocking detected for %s: %s", e.Domain, e.Reason)
 }
 
-// IsISPBlocking checks if an error is likely caused by ISP blocking
-// Returns the ISPBlockingError if detected, nil otherwise
 func IsISPBlocking(err error, requestURL string) *ISPBlockingError {
 	if err == nil {
 		return nil
 	}
 
-	// Extract domain from URL
 	domain := extractDomain(requestURL)
 	errStr := strings.ToLower(err.Error())
 
-	// Check for DNS resolution failure (common ISP blocking method)
 	var dnsErr *net.DNSError
 	if errors.As(err, &dnsErr) {
 		if dnsErr.IsNotFound || dnsErr.IsTemporary {
@@ -365,11 +440,9 @@ func IsISPBlocking(err error, requestURL string) *ISPBlockingError {
 		}
 	}
 
-	// Check for connection refused (ISP firewall blocking)
 	var opErr *net.OpError
 	if errors.As(err, &opErr) {
 		if opErr.Op == "dial" {
-			// Check for specific syscall errors
 			var syscallErr syscall.Errno
 			if errors.As(opErr.Err, &syscallErr) {
 				switch syscallErr {
@@ -408,7 +481,6 @@ func IsISPBlocking(err error, requestURL string) *ISPBlockingError {
 		}
 	}
 
-	// Check for TLS handshake failure (ISP MITM or blocking HTTPS)
 	var tlsErr *tls.RecordHeaderError
 	if errors.As(err, &tlsErr) {
 		return &ISPBlockingError{
@@ -418,7 +490,6 @@ func IsISPBlocking(err error, requestURL string) *ISPBlockingError {
 		}
 	}
 
-	// Check error message patterns for common ISP blocking indicators
 	blockingPatterns := []struct {
 		pattern string
 		reason  string
@@ -447,7 +518,6 @@ func IsISPBlocking(err error, requestURL string) *ISPBlockingError {
 	return nil
 }
 
-// CheckAndLogISPBlocking checks for ISP blocking and logs if detected
 // Returns true if ISP blocking was detected
 func CheckAndLogISPBlocking(err error, requestURL string, tag string) bool {
 	ispErr := IsISPBlocking(err, requestURL)
@@ -462,7 +532,6 @@ func CheckAndLogISPBlocking(err error, requestURL string, tag string) bool {
 	return false
 }
 
-// extractDomain extracts the domain from a URL string
 func extractDomain(rawURL string) string {
 	if rawURL == "" {
 		return "unknown"
@@ -470,7 +539,6 @@ func extractDomain(rawURL string) string {
 
 	parsed, err := url.Parse(rawURL)
 	if err != nil {
-		// Try to extract domain manually
 		rawURL = strings.TrimPrefix(rawURL, "https://")
 		rawURL = strings.TrimPrefix(rawURL, "http://")
 		if idx := strings.Index(rawURL, "/"); idx > 0 {
@@ -485,7 +553,6 @@ func extractDomain(rawURL string) string {
 	return "unknown"
 }
 
-// WrapErrorWithISPCheck wraps an error with ISP blocking detection
 // If ISP blocking is detected, returns a more descriptive error
 func WrapErrorWithISPCheck(err error, requestURL string, tag string) error {
 	if err == nil {

go_backend/httputil_ios.go

@@ -0,0 +1,27 @@
+//go:build ios
+
+package gobackend
+
+import (
+	"net/http"
+)
+
+// iOS version: uTLS is not supported on iOS due to cgo DNS resolver issues
+// Fall back to standard HTTP client
+
+// GetCloudflareBypassClient returns the standard HTTP client on iOS
+// uTLS is not available on iOS due to cgo DNS resolver compatibility issues
+func GetCloudflareBypassClient() *http.Client {
+	return sharedClient
+}
+
+// DoRequestWithCloudflareBypass on iOS just uses the standard client
+// uTLS Chrome fingerprint bypass is not available on iOS
+func DoRequestWithCloudflareBypass(req *http.Request) (*http.Response, error) {
+	req.Header.Set("User-Agent", getRandomUserAgent())
+	resp, err := sharedClient.Do(req)
+	if err != nil {
+		CheckAndLogISPBlocking(err, req.URL.String(), "HTTP")
+	}
+	return resp, err
+}

go_backend/httputil_utls.go

@@ -0,0 +1,175 @@
+//go:build !ios
+
+package gobackend
+
+import (
+	"context"
+	"crypto/tls"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+
+	utls "github.com/refraction-networking/utls"
+	"golang.org/x/net/http2"
+)
+
+// uTLS transport that mimics Chrome's TLS fingerprint to bypass Cloudflare
+// Uses HTTP/2 for optimal performance as uTLS works best with HTTP/2
+type utlsTransport struct {
+	dialer       *net.Dialer
+	mu           sync.Mutex
+	h2Transports map[string]*http2.Transport
+}
+
+func newUTLSTransport() *utlsTransport {
+	return &utlsTransport{
+		dialer: &net.Dialer{
+			Timeout:   30 * Second,
+			KeepAlive: 30 * Second,
+		},
+		h2Transports: make(map[string]*http2.Transport),
+	}
+}
+
+func (t *utlsTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	if req.URL.Scheme != "https" {
+		return sharedTransport.RoundTrip(req)
+	}
+
+	host := req.URL.Hostname()
+	port := t.getPort(req.URL)
+	addr := net.JoinHostPort(host, port)
+
+	conn, err := t.dialer.DialContext(req.Context(), "tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+
+	tlsConn := utls.UClient(conn, &utls.Config{
+		ServerName: host,
+		NextProtos: []string{"h2", "http/1.1"},
+	}, utls.HelloChrome_Auto)
+
+	if err := tlsConn.Handshake(); err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	negotiatedProto := tlsConn.ConnectionState().NegotiatedProtocol
+
+	if negotiatedProto == "h2" {
+		h2Transport := &http2.Transport{
+			DialTLSContext: func(ctx context.Context, network, addr string, cfg *tls.Config) (net.Conn, error) {
+				return tlsConn, nil
+			},
+			AllowHTTP:          false,
+			DisableCompression: false,
+		}
+		return h2Transport.RoundTrip(req)
+	}
+
+	transport := &http.Transport{
+		DialTLSContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			return tlsConn, nil
+		},
+		DisableKeepAlives: true,
+	}
+
+	return transport.RoundTrip(req)
+}
+
+func (t *utlsTransport) getPort(u *url.URL) string {
+	if u.Port() != "" {
+		return u.Port()
+	}
+	if u.Scheme == "https" {
+		return "443"
+	}
+	return "80"
+}
+
+var cloudflareBypassTransport = newUTLSTransport()
+
+var cloudflareBypassClient = &http.Client{
+	Transport: cloudflareBypassTransport,
+	Timeout:   DefaultTimeout,
+}
+
+// GetCloudflareBypassClient returns an HTTP client that mimics Chrome's TLS fingerprint
+// Use this when requests are blocked by Cloudflare (common when using VPN)
+func GetCloudflareBypassClient() *http.Client {
+	return cloudflareBypassClient
+}
+
+// DoRequestWithCloudflareBypass attempts request with standard client first,
+// then retries with uTLS Chrome fingerprint if Cloudflare blocks it.
+// This is useful when using VPN as Cloudflare detects Go's default TLS fingerprint.
+func DoRequestWithCloudflareBypass(req *http.Request) (*http.Response, error) {
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := sharedClient.Do(req)
+	if err == nil {
+		// Check for Cloudflare challenge page (403 with specific markers)
+		if resp.StatusCode == 403 || resp.StatusCode == 503 {
+			body, readErr := io.ReadAll(resp.Body)
+			resp.Body.Close()
+
+			if readErr == nil {
+				bodyStr := strings.ToLower(string(body))
+				cloudflareMarkers := []string{
+					"cloudflare", "cf-ray", "checking your browser",
+					"please wait", "ddos protection", "ray id",
+					"enable javascript", "challenge-platform",
+				}
+
+				isCloudflare := false
+				for _, marker := range cloudflareMarkers {
+					if strings.Contains(bodyStr, marker) {
+						isCloudflare = true
+						break
+					}
+				}
+
+				if isCloudflare {
+					LogDebug("HTTP", "Cloudflare detected, retrying with Chrome TLS fingerprint...")
+
+					reqCopy := req.Clone(req.Context())
+					reqCopy.Header.Set("User-Agent", getRandomUserAgent())
+
+					return cloudflareBypassClient.Do(reqCopy)
+				}
+			}
+
+			// Not Cloudflare, return original response (recreate body)
+			return &http.Response{
+				Status:     resp.Status,
+				StatusCode: resp.StatusCode,
+				Header:     resp.Header,
+				Body:       io.NopCloser(strings.NewReader(string(body))),
+			}, nil
+		}
+		return resp, nil
+	}
+
+	// Check if error might be TLS-related (Cloudflare blocking)
+	errStr := strings.ToLower(err.Error())
+	tlsRelated := strings.Contains(errStr, "tls") ||
+		strings.Contains(errStr, "handshake") ||
+		strings.Contains(errStr, "certificate") ||
+		strings.Contains(errStr, "connection reset")
+
+	if tlsRelated {
+		LogDebug("HTTP", "TLS error detected, retrying with Chrome TLS fingerprint: %v", err)
+
+		reqCopy := req.Clone(req.Context())
+		reqCopy.Header.Set("User-Agent", getRandomUserAgent())
+
+		return cloudflareBypassClient.Do(reqCopy)
+	}
+
+	CheckAndLogISPBlocking(err, req.URL.String(), "HTTP")
+	return nil, err
+}

go_backend/idhs.go

@@ -0,0 +1,182 @@
+package gobackend
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+// IDHSClient is a client for I Don't Have Spotify API
+// Used as fallback when SongLink fails or is rate limited
+type IDHSClient struct {
+	client *http.Client
+}
+
+var (
+	globalIDHSClient *IDHSClient
+	idhsClientOnce   sync.Once
+	idhsRateLimiter  = NewRateLimiter(8, time.Minute) // 8 req/min (below 10 limit)
+)
+
+type IDHSSearchRequest struct {
+	Link     string   `json:"link"`
+	Adapters []string `json:"adapters,omitempty"`
+}
+
+type IDHSSearchResponse struct {
+	ID            string     `json:"id"`
+	Type          string     `json:"type"` // song, album, artist, podcast, show
+	Title         string     `json:"title"`
+	Description   string     `json:"description"`
+	Image         string     `json:"image,omitempty"`
+	Audio         string     `json:"audio,omitempty"`
+	Source        string     `json:"source"`
+	UniversalLink string     `json:"universalLink"`
+	Links         []IDHSLink `json:"links"`
+}
+
+type IDHSLink struct {
+	Type         string `json:"type"` // spotify, youTube, appleMusic, deezer, soundCloud, tidal
+	URL          string `json:"url"`
+	IsVerified   bool   `json:"isVerified,omitempty"`
+	NotAvailable bool   `json:"notAvailable,omitempty"`
+}
+
+func NewIDHSClient() *IDHSClient {
+	idhsClientOnce.Do(func() {
+		globalIDHSClient = &IDHSClient{
+			client: NewHTTPClientWithTimeout(15 * time.Second),
+		}
+	})
+	return globalIDHSClient
+}
+
+// Search converts a music link to links on other platforms
+func (c *IDHSClient) Search(link string, adapters []string) (*IDHSSearchResponse, error) {
+	idhsRateLimiter.WaitForSlot()
+
+	reqBody := IDHSSearchRequest{
+		Link:     link,
+		Adapters: adapters,
+	}
+
+	jsonBody, err := json.Marshal(reqBody)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal request: %w", err)
+	}
+
+	req, err := http.NewRequest("POST", "https://idonthavespotify.sjdonado.com/api/search?v=1", bytes.NewBuffer(jsonBody))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == 400 {
+		return nil, fmt.Errorf("invalid link or missing parameters")
+	}
+	if resp.StatusCode == 429 {
+		return nil, fmt.Errorf("IDHS rate limit exceeded")
+	}
+	if resp.StatusCode == 500 {
+		return nil, fmt.Errorf("IDHS processing failed")
+	}
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("IDHS API returned status %d", resp.StatusCode)
+	}
+
+	body, err := ReadResponseBody(resp)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	var result IDHSSearchResponse
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, fmt.Errorf("failed to decode response: %w", err)
+	}
+
+	return &result, nil
+}
+
+// GetAvailabilityFromSpotify checks track availability using IDHS as fallback
+func (c *IDHSClient) GetAvailabilityFromSpotify(spotifyTrackID string) (*TrackAvailability, error) {
+	spotifyURL := fmt.Sprintf("https://open.spotify.com/track/%s", spotifyTrackID)
+
+	adapters := []string{"tidal", "deezer"}
+
+	result, err := c.Search(spotifyURL, adapters)
+	if err != nil {
+		return nil, err
+	}
+
+	availability := &TrackAvailability{
+		SpotifyID: spotifyTrackID,
+	}
+
+	for _, link := range result.Links {
+		if link.NotAvailable {
+			continue
+		}
+
+		switch strings.ToLower(link.Type) {
+		case "tidal":
+			availability.Tidal = true
+			availability.TidalURL = link.URL
+		case "deezer":
+			availability.Deezer = true
+			availability.DeezerURL = link.URL
+			availability.DeezerID = extractDeezerIDFromURL(link.URL)
+		}
+	}
+
+	LogDebug("IDHS", "Availability from Spotify %s: Tidal=%v, Deezer=%v",
+		spotifyTrackID, availability.Tidal, availability.Deezer)
+
+	return availability, nil
+}
+
+func (c *IDHSClient) GetAvailabilityFromDeezer(deezerTrackID string) (*TrackAvailability, error) {
+	deezerURL := fmt.Sprintf("https://www.deezer.com/track/%s", deezerTrackID)
+
+	adapters := []string{"spotify", "tidal"}
+
+	result, err := c.Search(deezerURL, adapters)
+	if err != nil {
+		return nil, err
+	}
+
+	availability := &TrackAvailability{
+		Deezer:   true,
+		DeezerID: deezerTrackID,
+	}
+
+	for _, link := range result.Links {
+		if link.NotAvailable {
+			continue
+		}
+
+		switch strings.ToLower(link.Type) {
+		case "spotify":
+			availability.SpotifyID = extractSpotifyIDFromURL(link.URL)
+		case "tidal":
+			availability.Tidal = true
+			availability.TidalURL = link.URL
+		}
+	}
+
+	LogDebug("IDHS", "Availability from Deezer %s: Spotify=%s, Tidal=%v",
+		deezerTrackID, availability.SpotifyID, availability.Tidal)
+
+	return availability, nil
+}

go_backend/library_scan.go

@@ -0,0 +1,818 @@
+package gobackend
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+type LibraryScanResult struct {
+	ID          string `json:"id"`
+	TrackName   string `json:"trackName"`
+	ArtistName  string `json:"artistName"`
+	AlbumName   string `json:"albumName"`
+	AlbumArtist string `json:"albumArtist,omitempty"`
+	FilePath    string `json:"filePath"`
+	CoverPath   string `json:"coverPath,omitempty"`
+	ScannedAt   string `json:"scannedAt"`
+	FileModTime int64  `json:"fileModTime,omitempty"` // Unix timestamp in milliseconds
+	ISRC        string `json:"isrc,omitempty"`
+	TrackNumber int    `json:"trackNumber,omitempty"`
+	DiscNumber  int    `json:"discNumber,omitempty"`
+	Duration    int    `json:"duration,omitempty"`
+	ReleaseDate string `json:"releaseDate,omitempty"`
+	BitDepth    int    `json:"bitDepth,omitempty"`
+	SampleRate  int    `json:"sampleRate,omitempty"`
+	Bitrate     int    `json:"bitrate,omitempty"` // kbps, for lossy formats (MP3, Opus, Vorbis)
+	Genre       string `json:"genre,omitempty"`
+	Format      string `json:"format,omitempty"`
+}
+
+type LibraryScanProgress struct {
+	TotalFiles   int     `json:"total_files"`
+	ScannedFiles int     `json:"scanned_files"`
+	CurrentFile  string  `json:"current_file"`
+	ErrorCount   int     `json:"error_count"`
+	ProgressPct  float64 `json:"progress_pct"`
+	IsComplete   bool    `json:"is_complete"`
+}
+
+type IncrementalScanResult struct {
+	Scanned      []LibraryScanResult `json:"scanned"`      // New or updated files
+	DeletedPaths []string            `json:"deletedPaths"` // Files that no longer exist
+	SkippedCount int                 `json:"skippedCount"` // Files that were unchanged
+	TotalFiles   int                 `json:"totalFiles"`   // Total files in folder
+}
+
+var (
+	libraryScanProgress   LibraryScanProgress
+	libraryScanProgressMu sync.RWMutex
+	libraryScanCancel     chan struct{}
+	libraryScanCancelMu   sync.Mutex
+	libraryCoverCacheDir  string
+	libraryCoverCacheMu   sync.RWMutex
+)
+
+var supportedAudioFormats = map[string]bool{
+	".flac": true,
+	".m4a":  true,
+	".mp3":  true,
+	".opus": true,
+	".ogg":  true,
+	".cue":  true,
+}
+
+type libraryAudioFileInfo struct {
+	path    string
+	modTime int64
+}
+
+type scannedCueFileInfo struct {
+	sheet     *CueSheet
+	audioPath string
+}
+
+func collectLibraryAudioFiles(folderPath string, cancelCh <-chan struct{}) ([]libraryAudioFileInfo, error) {
+	var files []libraryAudioFileInfo
+
+	err := filepath.Walk(folderPath, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return nil
+		}
+
+		select {
+		case <-cancelCh:
+			return fmt.Errorf("scan cancelled")
+		default:
+		}
+
+		if info.IsDir() {
+			return nil
+		}
+
+		ext := strings.ToLower(filepath.Ext(path))
+		if !supportedAudioFormats[ext] {
+			return nil
+		}
+
+		files = append(files, libraryAudioFileInfo{
+			path:    path,
+			modTime: info.ModTime().UnixMilli(),
+		})
+		return nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return files, nil
+}
+
+func SetLibraryCoverCacheDir(cacheDir string) {
+	libraryCoverCacheMu.Lock()
+	libraryCoverCacheDir = cacheDir
+	libraryCoverCacheMu.Unlock()
+}
+
+func ScanLibraryFolder(folderPath string) (string, error) {
+	if folderPath == "" {
+		return "[]", fmt.Errorf("folder path is empty")
+	}
+
+	info, err := os.Stat(folderPath)
+	if err != nil {
+		return "[]", fmt.Errorf("folder not found: %w", err)
+	}
+	if !info.IsDir() {
+		return "[]", fmt.Errorf("path is not a folder: %s", folderPath)
+	}
+
+	libraryScanProgressMu.Lock()
+	libraryScanProgress = LibraryScanProgress{}
+	libraryScanProgressMu.Unlock()
+
+	libraryScanCancelMu.Lock()
+	if libraryScanCancel != nil {
+		close(libraryScanCancel)
+	}
+	libraryScanCancel = make(chan struct{})
+	cancelCh := libraryScanCancel
+	libraryScanCancelMu.Unlock()
+
+	audioFileInfos, err := collectLibraryAudioFiles(folderPath, cancelCh)
+	if err != nil {
+		return "[]", err
+	}
+
+	totalFiles := len(audioFileInfos)
+	libraryScanProgressMu.Lock()
+	libraryScanProgress.TotalFiles = totalFiles
+	libraryScanProgressMu.Unlock()
+
+	if totalFiles == 0 {
+		libraryScanProgressMu.Lock()
+		libraryScanProgress.IsComplete = true
+		libraryScanProgressMu.Unlock()
+		return "[]", nil
+	}
+
+	GoLog("[LibraryScan] Found %d audio files to scan\n", totalFiles)
+
+	results := make([]LibraryScanResult, 0, totalFiles)
+	scanTime := time.Now().UTC().Format(time.RFC3339)
+	errorCount := 0
+
+	// Track audio files referenced by .cue sheets to avoid duplicates
+	cueReferencedAudioFiles := make(map[string]bool)
+	parsedCueFiles := make(map[string]scannedCueFileInfo)
+
+	// First pass: scan .cue files to collect referenced audio paths
+	for _, fileInfo := range audioFileInfos {
+		filePath := fileInfo.path
+		ext := strings.ToLower(filepath.Ext(filePath))
+		if ext == ".cue" {
+			sheet, err := ParseCueFile(filePath)
+			if err == nil && sheet.FileName != "" {
+				audioPath := ResolveCueAudioPath(filePath, sheet.FileName)
+				if audioPath != "" {
+					parsedCueFiles[filePath] = scannedCueFileInfo{
+						sheet:     sheet,
+						audioPath: audioPath,
+					}
+					cueReferencedAudioFiles[audioPath] = true
+				}
+			}
+		}
+	}
+
+	for i, fileInfo := range audioFileInfos {
+		filePath := fileInfo.path
+		select {
+		case <-cancelCh:
+			return "[]", fmt.Errorf("scan cancelled")
+		default:
+		}
+
+		libraryScanProgressMu.Lock()
+		libraryScanProgress.ScannedFiles = i + 1
+		libraryScanProgress.CurrentFile = filepath.Base(filePath)
+		libraryScanProgress.ProgressPct = float64(i+1) / float64(totalFiles) * 100
+		libraryScanProgressMu.Unlock()
+
+		ext := strings.ToLower(filepath.Ext(filePath))
+
+		// Handle .cue files: produce multiple track results
+		if ext == ".cue" {
+			var cueResults []LibraryScanResult
+			cueInfo, ok := parsedCueFiles[filePath]
+			if ok {
+				cueResults, err = scanCueSheetForLibrary(
+					filePath,
+					cueInfo.sheet,
+					cueInfo.audioPath,
+					"",
+					fileInfo.modTime,
+					scanTime,
+				)
+			} else {
+				cueResults, err = ScanCueFileForLibrary(filePath, scanTime)
+			}
+			if err != nil {
+				errorCount++
+				GoLog("[LibraryScan] Error scanning cue %s: %v\n", filePath, err)
+				continue
+			}
+			results = append(results, cueResults...)
+			GoLog("[LibraryScan] CUE sheet %s: %d tracks\n", filepath.Base(filePath), len(cueResults))
+			continue
+		}
+
+		// Skip audio files that are referenced by a .cue sheet
+		// (they will be represented by the cue sheet's track entries instead)
+		if cueReferencedAudioFiles[filePath] {
+			GoLog("[LibraryScan] Skipping %s (referenced by .cue sheet)\n", filepath.Base(filePath))
+			continue
+		}
+
+		result, err := scanAudioFileWithKnownModTime(filePath, scanTime, fileInfo.modTime)
+		if err != nil {
+			errorCount++
+			GoLog("[LibraryScan] Error scanning %s: %v\n", filePath, err)
+			continue
+		}
+
+		results = append(results, *result)
+	}
+
+	libraryScanProgressMu.Lock()
+	libraryScanProgress.ErrorCount = errorCount
+	libraryScanProgress.IsComplete = true
+	libraryScanProgressMu.Unlock()
+
+	GoLog("[LibraryScan] Scan complete: %d tracks found, %d errors\n", len(results), errorCount)
+
+	jsonBytes, err := json.Marshal(results)
+	if err != nil {
+		return "[]", fmt.Errorf("failed to marshal results: %w", err)
+	}
+
+	return string(jsonBytes), nil
+}
+
+func scanAudioFile(filePath, scanTime string) (*LibraryScanResult, error) {
+	return scanAudioFileWithKnownModTimeAndDisplayName(filePath, "", scanTime, 0)
+}
+
+func scanAudioFileWithKnownModTime(filePath, scanTime string, knownModTime int64) (*LibraryScanResult, error) {
+	return scanAudioFileWithKnownModTimeAndDisplayName(filePath, "", scanTime, knownModTime)
+}
+
+func scanAudioFileWithKnownModTimeAndDisplayName(filePath, displayNameHint, scanTime string, knownModTime int64) (*LibraryScanResult, error) {
+	ext := resolveLibraryAudioExt(filePath, displayNameHint)
+
+	result := &LibraryScanResult{
+		ID:        generateLibraryID(filePath),
+		FilePath:  filePath,
+		ScannedAt: scanTime,
+		Format:    strings.TrimPrefix(ext, "."),
+	}
+
+	if knownModTime > 0 {
+		result.FileModTime = knownModTime
+	} else if info, err := os.Stat(filePath); err == nil {
+		result.FileModTime = info.ModTime().UnixMilli()
+	}
+
+	libraryCoverCacheMu.RLock()
+	coverCacheDir := libraryCoverCacheDir
+	libraryCoverCacheMu.RUnlock()
+	if coverCacheDir != "" && ext != ".m4a" {
+		coverPath, err := SaveCoverToCacheWithHint(filePath, displayNameHint, coverCacheDir)
+		if err == nil && coverPath != "" {
+			result.CoverPath = coverPath
+		}
+	}
+
+	switch ext {
+	case ".flac":
+		return scanFLACFile(filePath, result)
+	case ".m4a":
+		return scanM4AFile(filePath, result)
+	case ".mp3":
+		return scanMP3File(filePath, result)
+	case ".opus", ".ogg":
+		return scanOggFile(filePath, result, displayNameHint)
+	default:
+		return scanFromFilename(filePath, displayNameHint, result)
+	}
+}
+
+func resolveLibraryAudioExt(filePath, displayNameHint string) string {
+	ext := strings.ToLower(filepath.Ext(filePath))
+	if ext != "" {
+		return ext
+	}
+	return strings.ToLower(filepath.Ext(displayNameHint))
+}
+
+func libraryDisplayNameOrPath(filePath, displayNameHint string) string {
+	if displayNameHint != "" {
+		return displayNameHint
+	}
+	return filePath
+}
+
+func applyDefaultLibraryMetadata(filePath, displayNameHint string, result *LibraryScanResult) {
+	nameSource := libraryDisplayNameOrPath(filePath, displayNameHint)
+	if result.TrackName == "" {
+		result.TrackName = strings.TrimSuffix(filepath.Base(nameSource), filepath.Ext(nameSource))
+	}
+	if result.ArtistName == "" {
+		result.ArtistName = "Unknown Artist"
+	}
+	if result.AlbumName == "" {
+		result.AlbumName = "Unknown Album"
+	}
+}
+
+func scanFLACFile(filePath string, result *LibraryScanResult) (*LibraryScanResult, error) {
+	metadata, err := ReadMetadata(filePath)
+	if err != nil {
+		return scanFromFilename(filePath, "", result)
+	}
+
+	result.TrackName = metadata.Title
+	result.ArtistName = metadata.Artist
+	result.AlbumName = metadata.Album
+	result.AlbumArtist = metadata.AlbumArtist
+	result.ISRC = metadata.ISRC
+	result.TrackNumber = metadata.TrackNumber
+	result.DiscNumber = metadata.DiscNumber
+	result.ReleaseDate = metadata.Date
+	result.Genre = metadata.Genre
+
+	quality, err := GetAudioQuality(filePath)
+	if err == nil {
+		result.BitDepth = quality.BitDepth
+		result.SampleRate = quality.SampleRate
+		if quality.SampleRate > 0 && quality.TotalSamples > 0 {
+			result.Duration = int(quality.TotalSamples / int64(quality.SampleRate))
+		}
+	}
+
+	applyDefaultLibraryMetadata(filePath, "", result)
+
+	return result, nil
+}
+
+func scanM4AFile(filePath string, result *LibraryScanResult) (*LibraryScanResult, error) {
+	quality, err := GetM4AQuality(filePath)
+	if err == nil {
+		result.BitDepth = quality.BitDepth
+		result.SampleRate = quality.SampleRate
+	}
+
+	return scanFromFilename(filePath, "", result)
+}
+
+func scanMP3File(filePath string, result *LibraryScanResult) (*LibraryScanResult, error) {
+	metadata, err := ReadID3Tags(filePath)
+	if err != nil {
+		GoLog("[LibraryScan] ID3 read error for %s: %v\n", filePath, err)
+		return scanFromFilename(filePath, "", result)
+	}
+
+	result.TrackName = metadata.Title
+	result.ArtistName = metadata.Artist
+	result.AlbumName = metadata.Album
+	result.AlbumArtist = metadata.AlbumArtist
+	result.TrackNumber = metadata.TrackNumber
+	result.DiscNumber = metadata.DiscNumber
+	result.Genre = metadata.Genre
+	if metadata.Date != "" {
+		result.ReleaseDate = metadata.Date
+	} else {
+		result.ReleaseDate = metadata.Year
+	}
+	result.ISRC = metadata.ISRC
+
+	quality, err := GetMP3Quality(filePath)
+	if err == nil {
+		result.SampleRate = quality.SampleRate
+		result.BitDepth = quality.BitDepth // 0 for lossy
+		result.Duration = quality.Duration
+		if quality.Bitrate > 0 {
+			result.Bitrate = quality.Bitrate / 1000 // convert bps to kbps
+		}
+	}
+
+	applyDefaultLibraryMetadata(filePath, "", result)
+
+	return result, nil
+}
+
+func scanOggFile(filePath string, result *LibraryScanResult, displayNameHint string) (*LibraryScanResult, error) {
+	metadata, err := ReadOggVorbisComments(filePath)
+	if err != nil {
+		GoLog("[LibraryScan] Ogg/Opus read error for %s: %v\n", filePath, err)
+		return scanFromFilename(filePath, displayNameHint, result)
+	}
+
+	result.TrackName = metadata.Title
+	result.ArtistName = metadata.Artist
+	result.AlbumName = metadata.Album
+	result.AlbumArtist = metadata.AlbumArtist
+	result.ISRC = metadata.ISRC
+	result.TrackNumber = metadata.TrackNumber
+	result.DiscNumber = metadata.DiscNumber
+	result.Genre = metadata.Genre
+	result.ReleaseDate = metadata.Date
+
+	quality, err := GetOggQuality(filePath)
+	if err == nil {
+		result.SampleRate = quality.SampleRate
+		result.BitDepth = quality.BitDepth // 0 for lossy
+		result.Duration = quality.Duration
+		if quality.Bitrate > 0 {
+			result.Bitrate = quality.Bitrate / 1000 // convert bps to kbps
+		}
+	}
+
+	applyDefaultLibraryMetadata(filePath, displayNameHint, result)
+
+	return result, nil
+}
+
+func scanFromFilename(filePath, displayNameHint string, result *LibraryScanResult) (*LibraryScanResult, error) {
+	nameSource := libraryDisplayNameOrPath(filePath, displayNameHint)
+	filename := strings.TrimSuffix(filepath.Base(nameSource), filepath.Ext(nameSource))
+
+	parts := strings.SplitN(filename, " - ", 2)
+	if len(parts) == 2 {
+		if len(parts[0]) <= 3 && isNumeric(parts[0]) {
+			result.TrackName = parts[1]
+			result.ArtistName = "Unknown Artist"
+		} else {
+			result.ArtistName = parts[0]
+			result.TrackName = parts[1]
+		}
+	} else {
+		if len(filename) > 3 && isNumeric(filename[:2]) {
+			title := strings.TrimLeft(filename[2:], " .-")
+			result.TrackName = title
+		} else {
+			result.TrackName = filename
+		}
+		result.ArtistName = "Unknown Artist"
+	}
+
+	dir := filepath.Dir(filePath)
+	result.AlbumName = filepath.Base(dir)
+	if result.AlbumName == "." || result.AlbumName == "" || result.AlbumName == "fd" || result.AlbumName == "self" {
+		result.AlbumName = "Unknown Album"
+	}
+
+	return result, nil
+}
+
+func isNumeric(s string) bool {
+	for _, c := range s {
+		if c < '0' || c > '9' {
+			return false
+		}
+	}
+	return len(s) > 0
+}
+
+func generateLibraryID(filePath string) string {
+	return fmt.Sprintf("lib_%x", hashString(filePath))
+}
+
+func hashString(s string) uint32 {
+	var hash uint32 = 5381
+	for _, c := range s {
+		hash = ((hash << 5) + hash) + uint32(c)
+	}
+	return hash
+}
+
+func GetLibraryScanProgress() string {
+	libraryScanProgressMu.RLock()
+	defer libraryScanProgressMu.RUnlock()
+
+	jsonBytes, _ := json.Marshal(libraryScanProgress)
+	return string(jsonBytes)
+}
+
+func CancelLibraryScan() {
+	libraryScanCancelMu.Lock()
+	defer libraryScanCancelMu.Unlock()
+
+	if libraryScanCancel != nil {
+		close(libraryScanCancel)
+		libraryScanCancel = nil
+	}
+}
+
+func ReadAudioMetadata(filePath string) (string, error) {
+	return ReadAudioMetadataWithDisplayName(filePath, "")
+}
+
+func ReadAudioMetadataWithDisplayName(filePath, displayNameHint string) (string, error) {
+	scanTime := time.Now().UTC().Format(time.RFC3339)
+	result, err := scanAudioFileWithKnownModTimeAndDisplayName(filePath, displayNameHint, scanTime, 0)
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", fmt.Errorf("failed to marshal result: %w", err)
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ScanLibraryFolderIncremental performs an incremental scan of the library folder
+// existingFilesJSON is a JSON object mapping filePath -> modTime (unix millis)
+// Only files that are new or have changed modification time will be scanned
+func loadExistingFilesSnapshot(snapshotPath string) (map[string]int64, error) {
+	existingFiles := make(map[string]int64)
+	if snapshotPath == "" {
+		return existingFiles, nil
+	}
+
+	file, err := os.Open(snapshotPath)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "" {
+			continue
+		}
+		parts := strings.SplitN(line, "\t", 2)
+		if len(parts) != 2 {
+			continue
+		}
+		modTime, err := strconv.ParseInt(parts[0], 10, 64)
+		if err != nil {
+			continue
+		}
+		existingFiles[parts[1]] = modTime
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return existingFiles, nil
+}
+
+func scanLibraryFolderIncrementalWithExistingFiles(folderPath string, existingFiles map[string]int64) (string, error) {
+	if folderPath == "" {
+		return "{}", fmt.Errorf("folder path is empty")
+	}
+
+	info, err := os.Stat(folderPath)
+	if err != nil {
+		return "{}", fmt.Errorf("folder not found: %w", err)
+	}
+	if !info.IsDir() {
+		return "{}", fmt.Errorf("path is not a folder: %s", folderPath)
+	}
+
+	GoLog("[LibraryScan] Incremental scan starting, %d existing files in database\n", len(existingFiles))
+
+	libraryScanProgressMu.Lock()
+	libraryScanProgress = LibraryScanProgress{}
+	libraryScanProgressMu.Unlock()
+
+	libraryScanCancelMu.Lock()
+	if libraryScanCancel != nil {
+		close(libraryScanCancel)
+	}
+	libraryScanCancel = make(chan struct{})
+	cancelCh := libraryScanCancel
+	libraryScanCancelMu.Unlock()
+
+	currentFiles, err := collectLibraryAudioFiles(folderPath, cancelCh)
+	if err != nil {
+		return "{}", err
+	}
+	currentPathSet := make(map[string]bool, len(currentFiles))
+	for _, fileInfo := range currentFiles {
+		currentPathSet[fileInfo.path] = true
+	}
+
+	totalFiles := len(currentFiles)
+	libraryScanProgressMu.Lock()
+	libraryScanProgress.TotalFiles = totalFiles
+	libraryScanProgressMu.Unlock()
+
+	// Find files to scan (new or modified)
+	var filesToScan []libraryAudioFileInfo
+	skippedCount := 0
+	existingCueTrackModTimes := make(map[string]int64)
+	for existingPath, modTime := range existingFiles {
+		if idx := strings.LastIndex(existingPath, "#track"); idx > 0 {
+			baseCuePath := existingPath[:idx]
+			if _, exists := existingCueTrackModTimes[baseCuePath]; !exists {
+				existingCueTrackModTimes[baseCuePath] = modTime
+			}
+		}
+	}
+
+	for _, f := range currentFiles {
+		existingModTime, exists := existingFiles[f.path]
+		if !exists {
+			// For .cue files, also check if any virtual path entries exist
+			if strings.ToLower(filepath.Ext(f.path)) == ".cue" {
+				if cueTrackModTime, hasCueTracks := existingCueTrackModTimes[f.path]; hasCueTracks {
+					// CUE file exists in DB via virtual paths; check if modTime changed
+					if f.modTime == cueTrackModTime {
+						skippedCount++
+					} else {
+						filesToScan = append(filesToScan, f)
+					}
+					continue
+				}
+			}
+			filesToScan = append(filesToScan, f)
+		} else if f.modTime != existingModTime {
+			filesToScan = append(filesToScan, f)
+		} else {
+			skippedCount++
+		}
+	}
+
+	var deletedPaths []string
+	for existingPath := range existingFiles {
+		// For CUE virtual paths (e.g. "/path/album.cue#track01"),
+		// check if the base .cue file still exists on disk
+		if idx := strings.LastIndex(existingPath, "#track"); idx > 0 {
+			baseCuePath := existingPath[:idx]
+			if currentPathSet[baseCuePath] {
+				continue // Base .cue file still exists, not deleted
+			}
+			// Base CUE file is gone, mark virtual path as deleted
+			deletedPaths = append(deletedPaths, existingPath)
+		} else if !currentPathSet[existingPath] {
+			deletedPaths = append(deletedPaths, existingPath)
+		}
+	}
+
+	GoLog("[LibraryScan] Incremental: %d to scan, %d skipped, %d deleted\n",
+		len(filesToScan), skippedCount, len(deletedPaths))
+
+	if len(filesToScan) == 0 {
+		libraryScanProgressMu.Lock()
+		libraryScanProgress.ScannedFiles = totalFiles
+		libraryScanProgress.IsComplete = true
+		libraryScanProgress.ProgressPct = 100
+		libraryScanProgressMu.Unlock()
+
+		result := IncrementalScanResult{
+			Scanned:      []LibraryScanResult{},
+			DeletedPaths: deletedPaths,
+			SkippedCount: skippedCount,
+			TotalFiles:   totalFiles,
+		}
+		jsonBytes, _ := json.Marshal(result)
+		return string(jsonBytes), nil
+	}
+
+	results := make([]LibraryScanResult, 0, len(filesToScan))
+	scanTime := time.Now().UTC().Format(time.RFC3339)
+	errorCount := 0
+
+	// Track audio files referenced by .cue sheets to avoid duplicates (incremental)
+	cueReferencedAudioFilesInc := make(map[string]bool)
+	parsedCueFiles := make(map[string]scannedCueFileInfo)
+	for _, f := range filesToScan {
+		ext := strings.ToLower(filepath.Ext(f.path))
+		if ext == ".cue" {
+			sheet, err := ParseCueFile(f.path)
+			if err == nil && sheet.FileName != "" {
+				audioPath := ResolveCueAudioPath(f.path, sheet.FileName)
+				if audioPath != "" {
+					parsedCueFiles[f.path] = scannedCueFileInfo{
+						sheet:     sheet,
+						audioPath: audioPath,
+					}
+					cueReferencedAudioFilesInc[audioPath] = true
+				}
+			}
+		}
+	}
+
+	for i, f := range filesToScan {
+		select {
+		case <-cancelCh:
+			return "{}", fmt.Errorf("scan cancelled")
+		default:
+		}
+
+		libraryScanProgressMu.Lock()
+		libraryScanProgress.ScannedFiles = skippedCount + i + 1
+		libraryScanProgress.CurrentFile = filepath.Base(f.path)
+		libraryScanProgress.ProgressPct = float64(skippedCount+i+1) / float64(totalFiles) * 100
+		libraryScanProgressMu.Unlock()
+
+		ext := strings.ToLower(filepath.Ext(f.path))
+
+		// Handle .cue files: produce multiple track results
+		if ext == ".cue" {
+			var cueResults []LibraryScanResult
+			cueInfo, ok := parsedCueFiles[f.path]
+			if ok {
+				cueResults, err = scanCueSheetForLibrary(
+					f.path,
+					cueInfo.sheet,
+					cueInfo.audioPath,
+					"",
+					f.modTime,
+					scanTime,
+				)
+			} else {
+				cueResults, err = ScanCueFileForLibrary(f.path, scanTime)
+			}
+			if err != nil {
+				errorCount++
+				GoLog("[LibraryScan] Error scanning cue %s: %v\n", f.path, err)
+				continue
+			}
+			results = append(results, cueResults...)
+			continue
+		}
+
+		// Skip audio files referenced by .cue sheets
+		if cueReferencedAudioFilesInc[f.path] {
+			continue
+		}
+
+		result, err := scanAudioFileWithKnownModTime(f.path, scanTime, f.modTime)
+		if err != nil {
+			errorCount++
+			GoLog("[LibraryScan] Error scanning %s: %v\n", f.path, err)
+			continue
+		}
+
+		results = append(results, *result)
+	}
+
+	libraryScanProgressMu.Lock()
+	libraryScanProgress.ErrorCount = errorCount
+	libraryScanProgress.IsComplete = true
+	libraryScanProgress.ScannedFiles = totalFiles
+	libraryScanProgress.ProgressPct = 100
+	libraryScanProgressMu.Unlock()
+
+	GoLog("[LibraryScan] Incremental scan complete: %d scanned, %d skipped, %d deleted, %d errors\n",
+		len(results), skippedCount, len(deletedPaths), errorCount)
+
+	scanResult := IncrementalScanResult{
+		Scanned:      results,
+		DeletedPaths: deletedPaths,
+		SkippedCount: skippedCount,
+		TotalFiles:   totalFiles,
+	}
+
+	jsonBytes, err := json.Marshal(scanResult)
+	if err != nil {
+		return "{}", fmt.Errorf("failed to marshal results: %w", err)
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ScanLibraryFolderIncremental performs an incremental scan of the library folder
+// existingFilesJSON is a JSON object mapping filePath -> modTime (unix millis)
+// Only files that are new or have changed modification time will be scanned
+func ScanLibraryFolderIncremental(folderPath, existingFilesJSON string) (string, error) {
+	existingFiles := make(map[string]int64)
+	if existingFilesJSON != "" && existingFilesJSON != "{}" {
+		if err := json.Unmarshal([]byte(existingFilesJSON), &existingFiles); err != nil {
+			GoLog("[LibraryScan] Warning: failed to parse existing files JSON: %v\n", err)
+		}
+	}
+	return scanLibraryFolderIncrementalWithExistingFiles(folderPath, existingFiles)
+}
+
+func ScanLibraryFolderIncrementalFromSnapshot(folderPath, snapshotPath string) (string, error) {
+	existingFiles, err := loadExistingFilesSnapshot(snapshotPath)
+	if err != nil {
+		return "{}", fmt.Errorf("failed to load incremental snapshot: %w", err)
+	}
+	return scanLibraryFolderIncrementalWithExistingFiles(folderPath, existingFiles)
+}

go_backend/logbuffer.go

@@ -3,12 +3,12 @@ package gobackend
 import (
 	"encoding/json"
 	"fmt"
+	"regexp"
 	"strings"
 	"sync"
 	"time"
 )
 
-// LogEntry represents a single log entry
 type LogEntry struct {
 	Timestamp string `json:"timestamp"`
 	Level     string `json:"level"`
@@ -16,7 +16,6 @@ type LogEntry struct {
 	Message   string `json:"message"`
 }
 
-// LogBuffer stores logs in a circular buffer for retrieval by Flutter
 type LogBuffer struct {
 	entries        []LogEntry
 	maxSize        int
@@ -24,38 +23,61 @@ type LogBuffer struct {
 	loggingEnabled bool
 }
 
+const (
+	defaultLogBufferSize = 500
+	maxLogMessageLength  = 500
+)
+
 var (
 	globalLogBuffer *LogBuffer
 	logBufferOnce   sync.Once
+
+	authorizationBearerPattern = regexp.MustCompile(`(?i)\bAuthorization\b\s*[:=]\s*Bearer\s+[A-Za-z0-9._~+/\-]+=*`)
+	genericKeyValuePattern     = regexp.MustCompile(`(?i)\b(access[_\s-]?token|refresh[_\s-]?token|id[_\s-]?token|client[_\s-]?secret|authorization|password|api[_\s-]?key)\b(\s*[:=]\s*)([^\s,;]+)`)
+	queryTokenPattern          = regexp.MustCompile(`(?i)([?&](?:access_token|refresh_token|id_token|token|client_secret|api_key|apikey|password)=)[^&\s]+`)
+	bearerTokenPattern         = regexp.MustCompile(`(?i)\bBearer\s+[A-Za-z0-9._~+/\-]+=*`)
 )
 
-// GetLogBuffer returns the singleton log buffer instance
+func sanitizeSensitiveLogText(message string) string {
+	redacted := message
+	redacted = authorizationBearerPattern.ReplaceAllString(redacted, "Authorization: Bearer [REDACTED]")
+	redacted = genericKeyValuePattern.ReplaceAllString(redacted, `${1}${2}[REDACTED]`)
+	redacted = queryTokenPattern.ReplaceAllString(redacted, `${1}[REDACTED]`)
+	redacted = bearerTokenPattern.ReplaceAllString(redacted, "Bearer [REDACTED]")
+	return redacted
+}
+
 func GetLogBuffer() *LogBuffer {
 	logBufferOnce.Do(func() {
 		globalLogBuffer = &LogBuffer{
-			entries:        make([]LogEntry, 0, 1000),
-			maxSize:        1000,
+			entries:        make([]LogEntry, 0, defaultLogBufferSize),
+			maxSize:        defaultLogBufferSize,
 			loggingEnabled: false, // Default: disabled for performance (user can enable in settings)
 		}
 	})
 	return globalLogBuffer
 }
 
-// SetLoggingEnabled enables or disables logging
+func truncateLogMessage(message string) string {
+	runes := []rune(message)
+	if len(runes) <= maxLogMessageLength {
+		return message
+	}
+	return string(runes[:maxLogMessageLength]) + "...[truncated]"
+}
+
 func (lb *LogBuffer) SetLoggingEnabled(enabled bool) {
 	lb.mu.Lock()
 	defer lb.mu.Unlock()
 	lb.loggingEnabled = enabled
 }
 
-// IsLoggingEnabled returns whether logging is enabled
 func (lb *LogBuffer) IsLoggingEnabled() bool {
 	lb.mu.RLock()
 	defer lb.mu.RUnlock()
 	return lb.loggingEnabled
 }
 
-// Add adds a log entry to the buffer
 func (lb *LogBuffer) Add(level, tag, message string) {
 	lb.mu.Lock()
 	defer lb.mu.Unlock()
@@ -64,6 +86,9 @@ func (lb *LogBuffer) Add(level, tag, message string) {
 		return
 	}
 
+	message = sanitizeSensitiveLogText(message)
+	message = truncateLogMessage(message)
+
 	entry := LogEntry{
 		Timestamp: time.Now().Format("15:04:05.000"),
 		Level:     level,
@@ -79,7 +104,6 @@ func (lb *LogBuffer) Add(level, tag, message string) {
 	fmt.Printf("[%s] %s\n", tag, message)
 }
 
-// GetAll returns all log entries as JSON
 func (lb *LogBuffer) GetAll() string {
 	lb.mu.RLock()
 	defer lb.mu.RUnlock()
@@ -103,21 +127,18 @@ func (lb *LogBuffer) getSince(index int) ([]LogEntry, int) {
 	return entries, len(lb.entries)
 }
 
-// Clear clears all log entries
 func (lb *LogBuffer) Clear() {
 	lb.mu.Lock()
 	defer lb.mu.Unlock()
 	lb.entries = lb.entries[:0]
 }
 
-// Count returns the number of log entries
 func (lb *LogBuffer) Count() int {
 	lb.mu.RLock()
 	defer lb.mu.RUnlock()
 	return len(lb.entries)
 }
 
-// Helper functions for logging with different levels
 func LogDebug(tag, format string, args ...interface{}) {
 	GetLogBuffer().Add("DEBUG", tag, fmt.Sprintf(format, args...))
 }
@@ -154,11 +175,11 @@ func GoLog(format string, args ...interface{}) {
 
 	// Determine level from message content
 	msgLower := strings.ToLower(message)
-	if strings.Contains(msgLower, "error") || strings.Contains(msgLower, "failed") || strings.HasPrefix(message, "✗") {
+	if strings.Contains(msgLower, "error") || strings.Contains(msgLower, "failed") {
 		level = "ERROR"
 	} else if strings.Contains(msgLower, "warning") || strings.Contains(msgLower, "warn") {
 		level = "WARN"
-	} else if strings.HasPrefix(message, "✓") || strings.Contains(msgLower, "success") || strings.Contains(msgLower, "match found") {
+	} else if strings.Contains(msgLower, "success") || strings.Contains(msgLower, "match found") {
 		level = "INFO"
 	} else if strings.Contains(msgLower, "searching") || strings.Contains(msgLower, "trying") || strings.Contains(msgLower, "found") {
 		level = "DEBUG"
@@ -167,15 +188,10 @@ func GoLog(format string, args ...interface{}) {
 	GetLogBuffer().Add(level, tag, message)
 }
 
-// Exported functions for Flutter
-
-// GetLogs returns all logs as JSON array
 func GetLogs() string {
 	return GetLogBuffer().GetAll()
 }
 
-// GetLogsSince returns logs since the given index
-// Returns JSON: {"logs": [...], "next_index": N}
 func GetLogsSince(index int) string {
 	entries, nextIndex := GetLogBuffer().getSince(index)
 	logsJson, _ := json.Marshal(entries)
@@ -183,17 +199,14 @@ func GetLogsSince(index int) string {
 	return result
 }
 
-// ClearLogs clears all logs
 func ClearLogs() {
 	GetLogBuffer().Clear()
 }
 
-// GetLogCount returns the number of log entries
 func GetLogCount() int {
 	return GetLogBuffer().Count()
 }
 
-// SetLoggingEnabled enables or disables logging from Flutter
 func SetLoggingEnabled(enabled bool) {
 	GetLogBuffer().SetLoggingEnabled(enabled)
 }

go_backend/lyrics.go

@@ -6,6 +6,8 @@ import (
 	"math"
 	"net/http"
 	"net/url"
+	"os"
+	"path/filepath"
 	"regexp"
 	"strconv"
 	"strings"
@@ -13,15 +15,153 @@ import (
 	"time"
 )
 
-// ========================================
-// Lyrics Cache with TTL
-// ========================================
-
 const (
-	lyricsCacheTTL       = 24 * time.Hour // Cache lyrics for 24 hours
-	durationToleranceSec = 10.0           // Duration matching tolerance in seconds
+	lyricsCacheTTL       = 24 * time.Hour
+	durationToleranceSec = 10.0
 )
 
+// Lyrics provider names (used in settings and cascade ordering)
+const (
+	LyricsProviderSpotifyAPI = "spotify_api"
+	LyricsProviderLRCLIB     = "lrclib"
+	LyricsProviderNetease    = "netease"
+	LyricsProviderMusixmatch = "musixmatch"
+	LyricsProviderAppleMusic = "apple_music"
+	LyricsProviderQQMusic    = "qqmusic"
+)
+
+// DefaultLyricsProviders is the default cascade order for lyrics fetching.
+// LRCLIB first (no proxy dependency), then the others.
+var DefaultLyricsProviders = []string{
+	LyricsProviderLRCLIB,
+	LyricsProviderSpotifyAPI,
+	LyricsProviderMusixmatch,
+	LyricsProviderNetease,
+	LyricsProviderAppleMusic,
+	LyricsProviderQQMusic,
+}
+
+var (
+	lyricsProvidersMu sync.RWMutex
+	lyricsProviders   []string // ordered list of enabled providers
+)
+
+var (
+	spotifyLyricsRateLimitMu    sync.RWMutex
+	spotifyLyricsRateLimitedTil time.Time
+)
+
+// LyricsFetchOptions controls optional provider-specific enhancements.
+type LyricsFetchOptions struct {
+	IncludeTranslationNetease  bool   `json:"include_translation_netease"`
+	IncludeRomanizationNetease bool   `json:"include_romanization_netease"`
+	MultiPersonWordByWord      bool   `json:"multi_person_word_by_word"`
+	MusixmatchLanguage         string `json:"musixmatch_language,omitempty"`
+}
+
+var defaultLyricsFetchOptions = LyricsFetchOptions{
+	IncludeTranslationNetease:  false,
+	IncludeRomanizationNetease: false,
+	MultiPersonWordByWord:      true,
+	MusixmatchLanguage:         "",
+}
+
+var (
+	lyricsFetchOptionsMu sync.RWMutex
+	lyricsFetchOptions   = defaultLyricsFetchOptions
+)
+
+// SetLyricsProviderOrder sets the ordered list of lyrics providers to try.
+// Providers not in the list are disabled. An empty list resets to defaults.
+func SetLyricsProviderOrder(providers []string) {
+	lyricsProvidersMu.Lock()
+	defer lyricsProvidersMu.Unlock()
+
+	if len(providers) == 0 {
+		lyricsProviders = nil
+		return
+	}
+
+	// Validate provider names
+	validNames := map[string]bool{
+		LyricsProviderSpotifyAPI: true,
+		LyricsProviderLRCLIB:     true,
+		LyricsProviderNetease:    true,
+		LyricsProviderMusixmatch: true,
+		LyricsProviderAppleMusic: true,
+		LyricsProviderQQMusic:    true,
+	}
+
+	var valid []string
+	for _, p := range providers {
+		normalized := strings.ToLower(strings.TrimSpace(p))
+		if validNames[normalized] {
+			valid = append(valid, normalized)
+		}
+	}
+
+	lyricsProviders = valid
+	GoLog("[Lyrics] Provider order set to: %v\n", valid)
+}
+
+// GetLyricsProviderOrder returns the current lyrics provider order.
+func GetLyricsProviderOrder() []string {
+	lyricsProvidersMu.RLock()
+	defer lyricsProvidersMu.RUnlock()
+
+	if len(lyricsProviders) == 0 {
+		return DefaultLyricsProviders
+	}
+
+	result := make([]string, len(lyricsProviders))
+	copy(result, lyricsProviders)
+	return result
+}
+
+// GetAvailableLyricsProviders returns metadata about all available providers.
+func GetAvailableLyricsProviders() []map[string]interface{} {
+	return []map[string]interface{}{
+		{"id": LyricsProviderSpotifyAPI, "name": "Spotify Lyrics API", "has_proxy_dependency": true, "description": "Spotify-sourced synced lyrics via community API"},
+		{"id": LyricsProviderLRCLIB, "name": "LRCLIB", "has_proxy_dependency": false, "description": "Open-source synced lyrics database"},
+		{"id": LyricsProviderNetease, "name": "Netease", "has_proxy_dependency": false, "description": "NetEase Cloud Music (good for Asian songs)"},
+		{"id": LyricsProviderMusixmatch, "name": "Musixmatch", "has_proxy_dependency": true, "description": "Largest lyrics database (multi-language)"},
+		{"id": LyricsProviderAppleMusic, "name": "Apple Music", "has_proxy_dependency": true, "description": "Word-by-word synced lyrics"},
+		{"id": LyricsProviderQQMusic, "name": "QQ Music", "has_proxy_dependency": true, "description": "QQ Music lyrics (good for Chinese songs)"},
+	}
+}
+
+func normalizeLyricsFetchOptions(opts LyricsFetchOptions) LyricsFetchOptions {
+	opts.MusixmatchLanguage = strings.ToLower(strings.TrimSpace(opts.MusixmatchLanguage))
+	opts.MusixmatchLanguage = regexp.MustCompile(`[^a-z0-9\-_]`).ReplaceAllString(opts.MusixmatchLanguage, "")
+	if len(opts.MusixmatchLanguage) > 16 {
+		opts.MusixmatchLanguage = opts.MusixmatchLanguage[:16]
+	}
+	return opts
+}
+
+// SetLyricsFetchOptions sets provider-specific lyric fetch behavior.
+func SetLyricsFetchOptions(opts LyricsFetchOptions) {
+	normalized := normalizeLyricsFetchOptions(opts)
+
+	lyricsFetchOptionsMu.Lock()
+	defer lyricsFetchOptionsMu.Unlock()
+	lyricsFetchOptions = normalized
+
+	GoLog("[Lyrics] Fetch options set: translation=%v romanization=%v multi_person=%v musixmatch_lang=%q\n",
+		normalized.IncludeTranslationNetease,
+		normalized.IncludeRomanizationNetease,
+		normalized.MultiPersonWordByWord,
+		normalized.MusixmatchLanguage,
+	)
+}
+
+// GetLyricsFetchOptions returns current provider-specific lyric fetch behavior.
+func GetLyricsFetchOptions() LyricsFetchOptions {
+	lyricsFetchOptionsMu.RLock()
+	defer lyricsFetchOptionsMu.RUnlock()
+	return lyricsFetchOptions
+}
+
 type lyricsCacheEntry struct {
 	response  *LyricsResponse
 	expiresAt time.Time
@@ -37,10 +177,8 @@ var globalLyricsCache = &lyricsCache{
 }
 
 func (c *lyricsCache) generateKey(artist, track string, durationSec float64) string {
-	// Normalize key: lowercase, trim spaces
 	normalizedArtist := strings.ToLower(strings.TrimSpace(artist))
 	normalizedTrack := strings.ToLower(strings.TrimSpace(track))
-	// Round duration to nearest 10 seconds for cache key
 	roundedDuration := math.Round(durationSec/10) * 10
 	return fmt.Sprintf("%s|%s|%.0f", normalizedArtist, normalizedTrack, roundedDuration)
 }
@@ -55,7 +193,6 @@ func (c *lyricsCache) Get(artist, track string, durationSec float64) (*LyricsRes
 		return nil, false
 	}
 
-	// Check if expired
 	if time.Now().After(entry.expiresAt) {
 		return nil, false
 	}
@@ -74,7 +211,6 @@ func (c *lyricsCache) Set(artist, track string, durationSec float64, response *L
 	}
 }
 
-// CleanExpired removes expired entries from cache
 func (c *lyricsCache) CleanExpired() int {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -90,13 +226,21 @@ func (c *lyricsCache) CleanExpired() int {
 	return cleaned
 }
 
-// Size returns current cache size
 func (c *lyricsCache) Size() int {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 	return len(c.cache)
 }
 
+func (c *lyricsCache) ClearAll() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	cleared := len(c.cache)
+	c.cache = make(map[string]*lyricsCacheEntry)
+	return cleared
+}
+
 type LRCLibResponse struct {
 	ID           int     `json:"id"`
 	Name         string  `json:"name"`
@@ -109,6 +253,18 @@ type LRCLibResponse struct {
 	SyncedLyrics string  `json:"syncedLyrics"`
 }
 
+type SpotifyLyricsLine struct {
+	TimeTag string `json:"timeTag"`
+	Words   string `json:"words"`
+}
+
+type SpotifyLyricsAPIResponse struct {
+	Error    bool                `json:"error"`
+	Message  string              `json:"message"`
+	SyncType string              `json:"syncType"`
+	Lines    []SpotifyLyricsLine `json:"lines"`
+}
+
 type LyricsLine struct {
 	StartTimeMs int64  `json:"startTimeMs"`
 	Words       string `json:"words"`
@@ -130,9 +286,7 @@ type LyricsClient struct {
 
 func NewLyricsClient() *LyricsClient {
 	return &LyricsClient{
-		httpClient: &http.Client{
-			Timeout: 15 * time.Second,
-		},
+		httpClient: NewHTTPClientWithTimeout(15 * time.Second),
 	}
 }
 
@@ -148,7 +302,7 @@ func (c *LyricsClient) FetchLyricsWithMetadata(artist, track string) (*LyricsRes
 	if err != nil {
 		return nil, fmt.Errorf("failed to create request: %w", err)
 	}
-	req.Header.Set("User-Agent", "SpotiFLAC-Android/1.0")
+	req.Header.Set("User-Agent", getRandomUserAgent())
 
 	resp, err := c.httpClient.Do(req)
 	if err != nil {
@@ -172,8 +326,6 @@ func (c *LyricsClient) FetchLyricsWithMetadata(artist, track string) (*LyricsRes
 	return c.parseLRCLibResponse(&lrcResp), nil
 }
 
-// FetchLyricsFromLRCLibSearch searches lyrics with optional duration matching
-// durationSec: track duration in seconds, use 0 to skip duration matching
 func (c *LyricsClient) FetchLyricsFromLRCLibSearch(query string, durationSec float64) (*LyricsResponse, error) {
 	baseURL := "https://lrclib.net/api/search"
 	params := url.Values{}
@@ -185,7 +337,7 @@ func (c *LyricsClient) FetchLyricsFromLRCLibSearch(query string, durationSec flo
 	if err != nil {
 		return nil, fmt.Errorf("failed to create request: %w", err)
 	}
-	req.Header.Set("User-Agent", "SpotiFLAC-Android/1.0")
+	req.Header.Set("User-Agent", getRandomUserAgent())
 
 	resp, err := c.httpClient.Do(req)
 	if err != nil {
@@ -206,13 +358,11 @@ func (c *LyricsClient) FetchLyricsFromLRCLibSearch(query string, durationSec flo
 		return nil, fmt.Errorf("no lyrics found")
 	}
 
-	// Filter and score results based on duration matching and synced lyrics
 	bestMatch := c.findBestMatch(results, durationSec)
 	if bestMatch != nil {
 		return c.parseLRCLibResponse(bestMatch), nil
 	}
 
-	// Fallback: return first result with synced lyrics
 	for _, result := range results {
 		if result.SyncedLyrics != "" {
 			return c.parseLRCLibResponse(&result), nil
@@ -222,7 +372,172 @@ func (c *LyricsClient) FetchLyricsFromLRCLibSearch(query string, durationSec flo
 	return c.parseLRCLibResponse(&results[0]), nil
 }
 
-// findBestMatch finds the best matching lyrics based on duration and sync status
+func parseSpotifyLyricsTimeTagToMs(tag string) int64 {
+	raw := strings.TrimSpace(tag)
+	raw = strings.TrimPrefix(raw, "[")
+	raw = strings.TrimSuffix(raw, "]")
+	if raw == "" {
+		return 0
+	}
+
+	if ms, err := strconv.ParseInt(raw, 10, 64); err == nil {
+		return ms
+	}
+
+	re := regexp.MustCompile(`^(\d{1,2}):(\d{2})\.(\d{1,3})$`)
+	matches := re.FindStringSubmatch(raw)
+	if len(matches) != 4 {
+		return 0
+	}
+
+	minutes, _ := strconv.ParseInt(matches[1], 10, 64)
+	seconds, _ := strconv.ParseInt(matches[2], 10, 64)
+	fraction := matches[3]
+	fractionInt, _ := strconv.ParseInt(fraction, 10, 64)
+	if len(fraction) == 2 {
+		fractionInt *= 10
+	} else if len(fraction) == 1 {
+		fractionInt *= 100
+	}
+	return minutes*60*1000 + seconds*1000 + fractionInt
+}
+
+func getSpotifyLyricsRateLimitUntil() time.Time {
+	spotifyLyricsRateLimitMu.RLock()
+	defer spotifyLyricsRateLimitMu.RUnlock()
+	return spotifyLyricsRateLimitedTil
+}
+
+func setSpotifyLyricsRateLimitUntil(until time.Time) {
+	spotifyLyricsRateLimitMu.Lock()
+	spotifyLyricsRateLimitedTil = until
+	spotifyLyricsRateLimitMu.Unlock()
+}
+
+func parseSpotifyRetryAfter(retryAfter string, now time.Time) time.Time {
+	raw := strings.TrimSpace(retryAfter)
+	if raw == "" {
+		return now.Add(10 * time.Minute)
+	}
+
+	if sec, err := strconv.Atoi(raw); err == nil && sec > 0 {
+		return now.Add(time.Duration(sec) * time.Second)
+	}
+
+	if when, err := http.ParseTime(raw); err == nil && when.After(now) {
+		return when
+	}
+
+	return now.Add(10 * time.Minute)
+}
+
+func (c *LyricsClient) FetchLyricsFromSpotifyAPI(spotifyID string) (*LyricsResponse, error) {
+	now := time.Now()
+	if limitedUntil := getSpotifyLyricsRateLimitUntil(); limitedUntil.After(now) {
+		waitFor := int(math.Ceil(limitedUntil.Sub(now).Seconds()))
+		return nil, fmt.Errorf(
+			"Spotify Lyrics API cooldown active (%ds remaining after previous 429)",
+			waitFor,
+		)
+	}
+
+	spotifyID = strings.TrimSpace(spotifyID)
+	if spotifyID == "" {
+		return nil, fmt.Errorf("spotify ID is empty")
+	}
+	if parsed, err := parseSpotifyURI(spotifyID); err == nil && parsed.Type == "track" && parsed.ID != "" {
+		spotifyID = parsed.ID
+	}
+
+	apiURL := fmt.Sprintf("https://spotify-lyrics-api-pi.vercel.app/?trackid=%s&format=lrc", url.QueryEscape(spotifyID))
+	req, err := http.NewRequest("GET", apiURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch from Spotify Lyrics API: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		if resp.StatusCode == http.StatusTooManyRequests {
+			retryUntil := parseSpotifyRetryAfter(resp.Header.Get("Retry-After"), now)
+			setSpotifyLyricsRateLimitUntil(retryUntil)
+		}
+		var payload map[string]interface{}
+		if err := json.NewDecoder(resp.Body).Decode(&payload); err == nil {
+			if msg, ok := payload["message"].(string); ok && strings.TrimSpace(msg) != "" {
+				return nil, fmt.Errorf("Spotify Lyrics API returned status %d: %s", resp.StatusCode, strings.TrimSpace(msg))
+			}
+			if msg, ok := payload["error"].(string); ok && strings.TrimSpace(msg) != "" {
+				return nil, fmt.Errorf("Spotify Lyrics API returned status %d: %s", resp.StatusCode, strings.TrimSpace(msg))
+			}
+		}
+		return nil, fmt.Errorf("Spotify Lyrics API returned status %d", resp.StatusCode)
+	}
+
+	var apiResp SpotifyLyricsAPIResponse
+	if err := json.NewDecoder(resp.Body).Decode(&apiResp); err != nil {
+		return nil, fmt.Errorf("failed to parse Spotify Lyrics API response: %w", err)
+	}
+
+	if apiResp.Error {
+		msg := strings.TrimSpace(apiResp.Message)
+		if msg == "" {
+			msg = "Spotify Lyrics API returned error"
+		}
+		return nil, fmt.Errorf("%s", msg)
+	}
+
+	result := &LyricsResponse{
+		Lines:        make([]LyricsLine, 0, len(apiResp.Lines)),
+		SyncType:     apiResp.SyncType,
+		Instrumental: false,
+		PlainLyrics:  "",
+		Provider:     "Spotify Lyrics API",
+		Source:       "Spotify Lyrics API",
+	}
+
+	for _, line := range apiResp.Lines {
+		words := strings.TrimSpace(line.Words)
+		if words == "" {
+			continue
+		}
+		startMs := parseSpotifyLyricsTimeTagToMs(line.TimeTag)
+		result.Lines = append(result.Lines, LyricsLine{
+			StartTimeMs: startMs,
+			Words:       words,
+			EndTimeMs:   0,
+		})
+	}
+
+	if len(result.Lines) > 1 {
+		for i := 0; i < len(result.Lines)-1; i++ {
+			nextStart := result.Lines[i+1].StartTimeMs
+			if nextStart > result.Lines[i].StartTimeMs {
+				result.Lines[i].EndTimeMs = nextStart
+			}
+		}
+		last := len(result.Lines) - 1
+		if result.Lines[last].EndTimeMs == 0 {
+			result.Lines[last].EndTimeMs = result.Lines[last].StartTimeMs + 5000
+		}
+	}
+
+	if len(result.Lines) == 0 {
+		return nil, fmt.Errorf("Spotify Lyrics API returned empty lines")
+	}
+
+	if result.SyncType == "" {
+		result.SyncType = "LINE_SYNCED"
+	}
+
+	return result, nil
+}
+
 func (c *LyricsClient) findBestMatch(results []LRCLibResponse, targetDurationSec float64) *LRCLibResponse {
 	var bestSynced *LRCLibResponse
 	var bestPlain *LRCLibResponse
@@ -230,11 +545,9 @@ func (c *LyricsClient) findBestMatch(results []LRCLibResponse, targetDurationSec
 	for i := range results {
 		result := &results[i]
 
-		// Check duration match if target duration is provided
 		durationMatches := targetDurationSec == 0 || c.durationMatches(result.Duration, targetDurationSec)
 
 		if durationMatches {
-			// Prefer synced lyrics over plain
 			if result.SyncedLyrics != "" && bestSynced == nil {
 				bestSynced = result
 			} else if result.PlainLyrics != "" && bestPlain == nil {
@@ -243,75 +556,217 @@ func (c *LyricsClient) findBestMatch(results []LRCLibResponse, targetDurationSec
 		}
 	}
 
-	// Return synced first, then plain
 	if bestSynced != nil {
 		return bestSynced
 	}
 	return bestPlain
 }
 
-// durationMatches checks if two durations are within tolerance
 func (c *LyricsClient) durationMatches(lrcDuration, targetDuration float64) bool {
 	diff := math.Abs(lrcDuration - targetDuration)
 	return diff <= durationToleranceSec
 }
 
-// FetchLyricsAllSources fetches lyrics from multiple sources with caching and duration matching
-// durationSec: track duration in seconds for matching, use 0 to skip duration matching
 func (c *LyricsClient) FetchLyricsAllSources(spotifyID, trackName, artistName string, durationSec float64) (*LyricsResponse, error) {
-	// Check cache first
+	primaryArtist := normalizeArtistName(artistName)
+	fetchOptions := GetLyricsFetchOptions()
+
+	extManager := GetExtensionManager()
+	var extensionProviders []*ExtensionProviderWrapper
+	if extManager != nil {
+		extensionProviders = extManager.GetLyricsProviders()
+	}
+
+	var cachedNonExtension *LyricsResponse
 	if cached, found := globalLyricsCache.Get(artistName, trackName, durationSec); found {
-		fmt.Printf("[Lyrics] Cache hit for: %s - %s\n", artistName, trackName)
-		cachedCopy := *cached
-		cachedCopy.Source = cached.Source + " (cached)"
-		return &cachedCopy, nil
+		isExtensionCache := strings.HasPrefix(cached.Source, "Extension:")
+		if len(extensionProviders) == 0 || isExtensionCache {
+			fmt.Printf("[Lyrics] Cache hit for: %s - %s\n", artistName, trackName)
+			cachedCopy := *cached
+			cachedCopy.Source = cached.Source + " (cached)"
+			return &cachedCopy, nil
+		}
+
+		// If extension providers are currently enabled, don't let stale built-in cache
+		// mask newly installed/activated extensions.
+		cachedNonExtension = cached
+		GoLog("[Lyrics] Ignoring cached non-extension lyrics because extension providers are available\n")
 	}
 
-	var lyrics *LyricsResponse
-	var err error
-
-	// Try exact match first
-	lyrics, err = c.FetchLyricsWithMetadata(artistName, trackName)
-	if err == nil && lyrics != nil && len(lyrics.Lines) > 0 {
-		lyrics.Source = "LRCLIB"
-		globalLyricsCache.Set(artistName, trackName, durationSec, lyrics)
-		return lyrics, nil
+	isValidResult := func(l *LyricsResponse) bool {
+		return lyricsHasUsableText(l)
 	}
 
-	// Try with simplified track name
-	simplifiedTrack := simplifyTrackName(trackName)
-	if simplifiedTrack != trackName {
-		lyrics, err = c.FetchLyricsWithMetadata(artistName, simplifiedTrack)
-		if err == nil && lyrics != nil && len(lyrics.Lines) > 0 {
-			lyrics.Source = "LRCLIB (simplified)"
-			globalLyricsCache.Set(artistName, trackName, durationSec, lyrics)
-			return lyrics, nil
+	if len(extensionProviders) > 0 {
+		for _, provider := range extensionProviders {
+			GoLog("[Lyrics] Trying extension lyrics provider: %s\n", provider.extension.ID)
+			lyrics, err := provider.FetchLyrics(trackName, artistName, "", durationSec)
+			if err == nil && isValidResult(lyrics) {
+				GoLog("[Lyrics] Got lyrics from extension: %s\n", provider.extension.ID)
+				globalLyricsCache.Set(artistName, trackName, durationSec, lyrics)
+				return lyrics, nil
+			}
+			if err != nil {
+				GoLog("[Lyrics] Extension %s failed: %v\n", provider.extension.ID, err)
+			}
 		}
 	}
 
-	// Search with duration matching
-	query := artistName + " " + trackName
-	lyrics, err = c.FetchLyricsFromLRCLibSearch(query, durationSec)
-	if err == nil && lyrics != nil && len(lyrics.Lines) > 0 {
-		lyrics.Source = "LRCLIB Search"
-		globalLyricsCache.Set(artistName, trackName, durationSec, lyrics)
-		return lyrics, nil
+	if cachedNonExtension != nil {
+		cachedCopy := *cachedNonExtension
+		cachedCopy.Source = cachedNonExtension.Source + " (cached fallback)"
+		GoLog("[Lyrics] Extension providers unavailable for this track, using cached built-in lyrics\n")
+		return &cachedCopy, nil
 	}
 
-	// Search with simplified name and duration matching
-	if simplifiedTrack != trackName {
-		query = artistName + " " + simplifiedTrack
-		lyrics, err = c.FetchLyricsFromLRCLibSearch(query, durationSec)
-		if err == nil && lyrics != nil && len(lyrics.Lines) > 0 {
-			lyrics.Source = "LRCLIB Search (simplified)"
+	providerOrder := GetLyricsProviderOrder()
+	simplifiedTrack := simplifyTrackName(trackName)
+
+	GoLog("[Lyrics] Searching for: %s - %s (providers: %v)\n", artistName, trackName, providerOrder)
+
+	// Cascade through all configured built-in providers
+	for _, providerName := range providerOrder {
+		GoLog("[Lyrics] Trying provider: %s\n", providerName)
+
+		var lyrics *LyricsResponse
+		var err error
+
+		switch providerName {
+		case LyricsProviderSpotifyAPI:
+			lyrics, err = c.FetchLyricsFromSpotifyAPI(spotifyID)
+
+		case LyricsProviderLRCLIB:
+			lyrics, err = c.tryLRCLIB(primaryArtist, artistName, trackName, simplifiedTrack, durationSec)
+
+		case LyricsProviderNetease:
+			neteaseClient := NewNeteaseClient()
+			lyrics, err = neteaseClient.FetchLyrics(
+				trackName,
+				primaryArtist,
+				durationSec,
+				fetchOptions.IncludeTranslationNetease,
+				fetchOptions.IncludeRomanizationNetease,
+			)
+			if err != nil && primaryArtist != artistName {
+				lyrics, err = neteaseClient.FetchLyrics(
+					trackName,
+					artistName,
+					durationSec,
+					fetchOptions.IncludeTranslationNetease,
+					fetchOptions.IncludeRomanizationNetease,
+				)
+			}
+			if err != nil && simplifiedTrack != trackName {
+				lyrics, err = neteaseClient.FetchLyrics(
+					simplifiedTrack,
+					primaryArtist,
+					durationSec,
+					fetchOptions.IncludeTranslationNetease,
+					fetchOptions.IncludeRomanizationNetease,
+				)
+			}
+
+		case LyricsProviderMusixmatch:
+			musixmatchClient := NewMusixmatchClient()
+			lyrics, err = musixmatchClient.FetchLyrics(
+				trackName,
+				primaryArtist,
+				durationSec,
+				fetchOptions.MusixmatchLanguage,
+			)
+			if err != nil && primaryArtist != artistName {
+				lyrics, err = musixmatchClient.FetchLyrics(
+					trackName,
+					artistName,
+					durationSec,
+					fetchOptions.MusixmatchLanguage,
+				)
+			}
+
+		case LyricsProviderAppleMusic:
+			appleClient := NewAppleMusicClient()
+			lyrics, err = appleClient.FetchLyrics(trackName, primaryArtist, durationSec, fetchOptions.MultiPersonWordByWord)
+			if err != nil && primaryArtist != artistName {
+				lyrics, err = appleClient.FetchLyrics(trackName, artistName, durationSec, fetchOptions.MultiPersonWordByWord)
+			}
+
+		case LyricsProviderQQMusic:
+			qqClient := NewQQMusicClient()
+			lyrics, err = qqClient.FetchLyrics(trackName, primaryArtist, durationSec, fetchOptions.MultiPersonWordByWord)
+			if err != nil && primaryArtist != artistName {
+				lyrics, err = qqClient.FetchLyrics(trackName, artistName, durationSec, fetchOptions.MultiPersonWordByWord)
+			}
+
+		default:
+			GoLog("[Lyrics] Unknown provider: %s, skipping\n", providerName)
+			continue
+		}
+
+		if err == nil && isValidResult(lyrics) {
+			GoLog("[Lyrics] Got lyrics from: %s\n", providerName)
 			globalLyricsCache.Set(artistName, trackName, durationSec, lyrics)
 			return lyrics, nil
 		}
+
+		if err != nil {
+			GoLog("[Lyrics] Provider %s failed: %v\n", providerName, err)
+		}
 	}
 
 	return nil, fmt.Errorf("lyrics not found from any source")
 }
 
+// tryLRCLIB attempts all LRCLIB search strategies (exact match, simplified, search).
+func (c *LyricsClient) tryLRCLIB(primaryArtist, artistName, trackName, simplifiedTrack string, durationSec float64) (*LyricsResponse, error) {
+	var lyrics *LyricsResponse
+	var err error
+
+	// 1. Exact match with primary artist
+	lyrics, err = c.FetchLyricsWithMetadata(primaryArtist, trackName)
+	if err == nil && lyrics != nil && (len(lyrics.Lines) > 0 || lyrics.Instrumental) {
+		lyrics.Source = "LRCLIB"
+		return lyrics, nil
+	}
+
+	// 2. Exact match with full artist name
+	if primaryArtist != artistName {
+		lyrics, err = c.FetchLyricsWithMetadata(artistName, trackName)
+		if err == nil && lyrics != nil && (len(lyrics.Lines) > 0 || lyrics.Instrumental) {
+			lyrics.Source = "LRCLIB"
+			return lyrics, nil
+		}
+	}
+
+	// 3. Simplified track name
+	if simplifiedTrack != trackName {
+		lyrics, err = c.FetchLyricsWithMetadata(primaryArtist, simplifiedTrack)
+		if err == nil && lyrics != nil && (len(lyrics.Lines) > 0 || lyrics.Instrumental) {
+			lyrics.Source = "LRCLIB (simplified)"
+			return lyrics, nil
+		}
+	}
+
+	// 4. Search by query
+	query := primaryArtist + " " + trackName
+	lyrics, err = c.FetchLyricsFromLRCLibSearch(query, durationSec)
+	if err == nil && lyrics != nil && (len(lyrics.Lines) > 0 || lyrics.Instrumental) {
+		lyrics.Source = "LRCLIB Search"
+		return lyrics, nil
+	}
+
+	// 5. Search with simplified track name
+	if simplifiedTrack != trackName {
+		query = primaryArtist + " " + simplifiedTrack
+		lyrics, err = c.FetchLyricsFromLRCLibSearch(query, durationSec)
+		if err == nil && lyrics != nil && (len(lyrics.Lines) > 0 || lyrics.Instrumental) {
+			lyrics.Source = "LRCLIB Search (simplified)"
+			return lyrics, nil
+		}
+	}
+
+	return nil, fmt.Errorf("LRCLIB: no lyrics found")
+}
+
 func (c *LyricsClient) parseLRCLibResponse(resp *LRCLibResponse) *LyricsResponse {
 	result := &LyricsResponse{
 		Instrumental: resp.Instrumental,
@@ -349,10 +804,20 @@ func parseSyncedLyrics(syncedLyrics string) []LyricsLine {
 			continue
 		}
 
+		// Preserve Apple/QQ background vocal tags by attaching them to
+		// the previous timed line. This keeps [bg:...] in final exported LRC.
+		if strings.HasPrefix(line, "[bg:") && len(lines) > 0 {
+			lines[len(lines)-1].Words = strings.TrimSpace(lines[len(lines)-1].Words + "\n" + line)
+			continue
+		}
+
 		matches := lrcPattern.FindStringSubmatch(line)
 		if len(matches) == 5 {
 			startMs := lrcTimestampToMs(matches[1], matches[2], matches[3])
 			words := strings.TrimSpace(matches[4])
+			if words == "" {
+				continue
+			}
 
 			lines = append(lines, LyricsLine{
 				StartTimeMs: startMs,
@@ -373,6 +838,79 @@ func parseSyncedLyrics(syncedLyrics string) []LyricsLine {
 	return lines
 }
 
+func plainTextLyricsLines(rawLyrics string) []LyricsLine {
+	var lines []LyricsLine
+	for _, line := range strings.Split(rawLyrics, "\n") {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == "" {
+			continue
+		}
+		lines = append(lines, LyricsLine{
+			StartTimeMs: 0,
+			Words:       trimmed,
+			EndTimeMs:   0,
+		})
+	}
+	return lines
+}
+
+func lyricsHasUsableText(lyrics *LyricsResponse) bool {
+	if lyrics == nil {
+		return false
+	}
+	if lyrics.Instrumental {
+		return true
+	}
+	if strings.TrimSpace(lyrics.PlainLyrics) != "" {
+		return true
+	}
+	for _, line := range lyrics.Lines {
+		if strings.TrimSpace(line.Words) != "" {
+			return true
+		}
+	}
+	return false
+}
+
+// detectLyricsErrorPayload extracts human-readable error messages from
+// JSON payloads returned by lyrics proxies when no lyric is available.
+func detectLyricsErrorPayload(raw string) (string, bool) {
+	trimmed := strings.TrimSpace(raw)
+	if trimmed == "" || !strings.HasPrefix(trimmed, "{") {
+		return "", false
+	}
+
+	var payload map[string]interface{}
+	if err := json.Unmarshal([]byte(trimmed), &payload); err != nil {
+		return "", false
+	}
+
+	lyricsKeys := []string{"lyrics", "lyric", "lrc", "content", "lines", "syncedLyrics", "unsyncedLyrics"}
+	hasLyricsKey := false
+	for _, key := range lyricsKeys {
+		if _, ok := payload[key]; ok {
+			hasLyricsKey = true
+			break
+		}
+	}
+
+	errorKeys := []string{"message", "error", "detail", "reason"}
+	for _, key := range errorKeys {
+		if msg, ok := payload[key].(string); ok {
+			msg = strings.TrimSpace(msg)
+			if msg != "" && !hasLyricsKey {
+				return msg, true
+			}
+		}
+	}
+
+	if success, ok := payload["success"].(bool); ok && !success && !hasLyricsKey {
+		return "request unsuccessful", true
+	}
+
+	return "", false
+}
+
 func lrcTimestampToMs(minutes, seconds, centiseconds string) int64 {
 	min, _ := strconv.ParseInt(minutes, 10, 64)
 	sec, _ := strconv.ParseInt(seconds, 10, 64)
@@ -386,43 +924,18 @@ func lrcTimestampToMs(minutes, seconds, centiseconds string) int64 {
 }
 
 func msToLRCTimestamp(ms int64) string {
+	return fmt.Sprintf("[%s]", msToLRCTimestampInline(ms))
+}
+
+func msToLRCTimestampInline(ms int64) string {
 	totalSeconds := ms / 1000
 	minutes := totalSeconds / 60
 	seconds := totalSeconds % 60
 	centiseconds := (ms % 1000) / 10
 
-	return fmt.Sprintf("[%02d:%02d.%02d]", minutes, seconds, centiseconds)
+	return fmt.Sprintf("%02d:%02d.%02d", minutes, seconds, centiseconds)
 }
 
-// convertToLRC converts lyrics to LRC format string (without metadata headers)
-// Use convertToLRCWithMetadata for full LRC with headers
-// Kept for potential future use
-// func convertToLRC(lyrics *LyricsResponse) string {
-// 	if lyrics == nil || len(lyrics.Lines) == 0 {
-// 		return ""
-// 	}
-//
-// 	var builder strings.Builder
-//
-// 	if lyrics.SyncType == "LINE_SYNCED" {
-// 		for _, line := range lyrics.Lines {
-// 			timestamp := msToLRCTimestamp(line.StartTimeMs)
-// 			builder.WriteString(timestamp)
-// 			builder.WriteString(line.Words)
-// 			builder.WriteString("\n")
-// 		}
-// 	} else {
-// 		for _, line := range lyrics.Lines {
-// 			builder.WriteString(line.Words)
-// 			builder.WriteString("\n")
-// 		}
-// 	}
-//
-// 	return builder.String()
-// }
-
-// convertToLRCWithMetadata converts lyrics to LRC format with metadata headers
-// Includes [ti:], [ar:], [by:] headers
 func convertToLRCWithMetadata(lyrics *LyricsResponse, trackName, artistName string) string {
 	if lyrics == nil || len(lyrics.Lines) == 0 {
 		return ""
@@ -430,13 +943,11 @@ func convertToLRCWithMetadata(lyrics *LyricsResponse, trackName, artistName stri
 
 	var builder strings.Builder
 
-	// Add metadata headers
 	builder.WriteString(fmt.Sprintf("[ti:%s]\n", trackName))
 	builder.WriteString(fmt.Sprintf("[ar:%s]\n", artistName))
 	builder.WriteString("[by:SpotiFLAC-Mobile]\n")
 	builder.WriteString("\n")
 
-	// Add lyrics lines
 	if lyrics.SyncType == "LINE_SYNCED" {
 		for _, line := range lyrics.Lines {
 			if line.Words == "" {
@@ -482,6 +993,49 @@ func simplifyTrackName(name string) string {
 		re := regexp.MustCompile("(?i)" + pattern)
 		result = re.ReplaceAllString(result, "")
 	}
+	result = strings.TrimSpace(result)
+	if result == "" {
+		return result
+	}
+
+	// Add a loose fallback form for provider queries where punctuation
+	// and separators differ (e.g. "/" vs "_" vs spaces).
+	if loose := normalizeLooseTitle(result); loose != "" {
+		return loose
+	}
+
+	return result
+}
+
+func normalizeArtistName(name string) string {
+	separators := []string{", ", "; ", " & ", " feat. ", " ft. ", " featuring ", " with "}
+
+	result := name
+	for _, sep := range separators {
+		if idx := strings.Index(strings.ToLower(result), strings.ToLower(sep)); idx > 0 {
+			result = result[:idx]
+			break
+		}
+	}
 
 	return strings.TrimSpace(result)
 }
+
+func SaveLRCFile(audioFilePath, lrcContent string) (string, error) {
+	if lrcContent == "" {
+		return "", fmt.Errorf("empty LRC content")
+	}
+
+	dir := filepath.Dir(audioFilePath)
+	ext := filepath.Ext(audioFilePath)
+	baseName := strings.TrimSuffix(filepath.Base(audioFilePath), ext)
+
+	lrcFilePath := filepath.Join(dir, baseName+".lrc")
+
+	if err := os.WriteFile(lrcFilePath, []byte(lrcContent), 0644); err != nil {
+		return "", fmt.Errorf("failed to write LRC file: %w", err)
+	}
+
+	GoLog("[Lyrics] Saved LRC file: %s\n", lrcFilePath)
+	return lrcFilePath, nil
+}

go_backend/lyrics_apple.go

@@ -0,0 +1,366 @@
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strings"
+	"sync"
+	"time"
+)
+
+// AppleMusicClient fetches lyrics from Apple Music.
+// Uses a scraped JWT token for search and a proxy for lyrics.
+type AppleMusicClient struct {
+	httpClient *http.Client
+}
+
+// Apple Music token manager — singleton with mutex for thread safety
+type appleTokenManager struct {
+	mu    sync.Mutex
+	token string
+}
+
+var globalAppleTokenManager = &appleTokenManager{}
+
+func (m *appleTokenManager) getToken(client *http.Client) (string, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.token != "" {
+		return m.token, nil
+	}
+
+	// Step 1: Fetch the Apple Music beta page
+	req, err := http.NewRequest("GET", "https://beta.music.apple.com", nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("failed to fetch Apple Music page: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("failed to read Apple Music page: %w", err)
+	}
+
+	// Step 2: Find the index JS file URL
+	indexJsRegex := regexp.MustCompile(`/assets/index~[^/]+\.js`)
+	match := indexJsRegex.Find(body)
+	if match == nil {
+		return "", fmt.Errorf("could not find index JS script URL on Apple Music page")
+	}
+
+	indexJsURL := "https://beta.music.apple.com" + string(match)
+
+	// Step 3: Fetch the JS file
+	jsReq, err := http.NewRequest("GET", indexJsURL, nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to create JS request: %w", err)
+	}
+	jsReq.Header.Set("User-Agent", getRandomUserAgent())
+
+	jsResp, err := client.Do(jsReq)
+	if err != nil {
+		return "", fmt.Errorf("failed to fetch Apple Music JS: %w", err)
+	}
+	defer jsResp.Body.Close()
+
+	jsBody, err := io.ReadAll(jsResp.Body)
+	if err != nil {
+		return "", fmt.Errorf("failed to read Apple Music JS: %w", err)
+	}
+
+	// Step 4: Extract JWT token (starts with eyJh)
+	tokenRegex := regexp.MustCompile(`eyJh[^"]*`)
+	tokenMatch := tokenRegex.Find(jsBody)
+	if tokenMatch == nil {
+		return "", fmt.Errorf("could not find JWT token in Apple Music JS")
+	}
+
+	m.token = string(tokenMatch)
+	GoLog("[AppleMusic] Token obtained successfully (length: %d)\n", len(m.token))
+	return m.token, nil
+}
+
+func (m *appleTokenManager) clearToken() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.token = ""
+}
+
+type appleMusicSearchResponse struct {
+	Results struct {
+		Songs *struct {
+			Data []struct {
+				ID   string `json:"id"`
+				Type string `json:"type"`
+			} `json:"data"`
+		} `json:"songs"`
+	} `json:"results"`
+	Resources *struct {
+		Songs map[string]struct {
+			Attributes struct {
+				Name       string `json:"name"`
+				ArtistName string `json:"artistName"`
+				AlbumName  string `json:"albumName"`
+				URL        string `json:"url"`
+				Artwork    struct {
+					URL string `json:"url"`
+				} `json:"artwork"`
+			} `json:"attributes"`
+		} `json:"songs"`
+	} `json:"resources"`
+}
+
+// PaxResponse represents the lyrics proxy response for word-by-word / line lyrics
+type paxResponse struct {
+	Type    string      `json:"type"`    // "Syllable" or "Line"
+	Content []paxLyrics `json:"content"` // List of lyric lines
+}
+
+type paxLyrics struct {
+	Text           []paxLyricDetail `json:"text"`
+	Timestamp      int              `json:"timestamp"`
+	OppositeTurn   bool             `json:"oppositeTurn"`
+	Background     bool             `json:"background"`
+	BackgroundText []paxLyricDetail `json:"backgroundText"`
+	EndTime        int              `json:"endtime"`
+}
+
+type paxLyricDetail struct {
+	Text      string `json:"text"`
+	Part      bool   `json:"part"`
+	Timestamp *int   `json:"timestamp"`
+	EndTime   *int   `json:"endtime"`
+}
+
+func NewAppleMusicClient() *AppleMusicClient {
+	return &AppleMusicClient{
+		httpClient: NewMetadataHTTPClient(20 * time.Second),
+	}
+}
+
+// SearchSong searches for a song on Apple Music and returns its ID.
+func (c *AppleMusicClient) SearchSong(trackName, artistName string) (string, error) {
+	query := trackName + " " + artistName
+	if strings.TrimSpace(query) == "" {
+		return "", fmt.Errorf("empty search query")
+	}
+
+	token, err := globalAppleTokenManager.getToken(c.httpClient)
+	if err != nil {
+		return "", fmt.Errorf("apple music token error: %w", err)
+	}
+
+	encodedQuery := url.QueryEscape(query)
+	searchURL := fmt.Sprintf(
+		"https://amp-api.music.apple.com/v1/catalog/us/search?term=%s&types=songs&limit=5&l=en-US&platform=web&format[resources]=map&include[songs]=artists&extend=artistUrl",
+		encodedQuery,
+	)
+
+	req, err := http.NewRequest("GET", searchURL, nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to create request: %w", err)
+	}
+
+	req.Header.Set("Authorization", "Bearer "+token)
+	req.Header.Set("Origin", "https://music.apple.com")
+	req.Header.Set("Referer", "https://music.apple.com/")
+	req.Header.Set("User-Agent", getRandomUserAgent())
+	req.Header.Set("Accept", "application/json")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("apple music search failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == 401 {
+		globalAppleTokenManager.clearToken()
+		return "", fmt.Errorf("apple music token expired")
+	}
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("apple music search returned HTTP %d", resp.StatusCode)
+	}
+
+	var searchResp appleMusicSearchResponse
+	if err := json.NewDecoder(resp.Body).Decode(&searchResp); err != nil {
+		return "", fmt.Errorf("failed to decode apple music response: %w", err)
+	}
+
+	if searchResp.Results.Songs == nil || len(searchResp.Results.Songs.Data) == 0 {
+		return "", fmt.Errorf("no songs found on apple music")
+	}
+
+	return searchResp.Results.Songs.Data[0].ID, nil
+}
+
+// FetchLyricsByID fetches lyrics from the paxsenix proxy using Apple Music song ID.
+func (c *AppleMusicClient) FetchLyricsByID(songID string) (string, error) {
+	lyricsURL := fmt.Sprintf("https://lyrics.paxsenix.org/apple-music/lyrics?id=%s", songID)
+
+	req, err := http.NewRequest("GET", lyricsURL, nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("apple music lyrics fetch failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("apple music lyrics proxy returned HTTP %d", resp.StatusCode)
+	}
+
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("failed to read lyrics response: %w", err)
+	}
+
+	bodyStr := strings.TrimSpace(string(bodyBytes))
+	if bodyStr == "" {
+		return "", fmt.Errorf("empty lyrics response from apple music")
+	}
+
+	return bodyStr, nil
+}
+
+func formatPaxLyricsToLRC(rawJSON string, multiPersonWordByWord bool) (string, error) {
+	var paxResp paxResponse
+	if err := json.Unmarshal([]byte(rawJSON), &paxResp); err == nil && paxResp.Content != nil {
+		return formatPaxContent(paxResp.Type, paxResp.Content, multiPersonWordByWord), nil
+	}
+
+	var directLyrics []paxLyrics
+	if err := json.Unmarshal([]byte(rawJSON), &directLyrics); err == nil && len(directLyrics) > 0 {
+		return formatPaxContent("Syllable", directLyrics, multiPersonWordByWord), nil
+	}
+
+	return "", fmt.Errorf("failed to parse pax lyrics response")
+}
+
+func appendPaxLyricDetail(builder *strings.Builder, details []paxLyricDetail) {
+	lastStart := ""
+
+	for _, syllable := range details {
+		if syllable.Timestamp != nil {
+			start := fmt.Sprintf("<%s>", msToLRCTimestampInline(int64(*syllable.Timestamp)))
+			if start != lastStart {
+				builder.WriteString(start)
+				lastStart = start
+			}
+		}
+
+		builder.WriteString(syllable.Text)
+		if !syllable.Part {
+			builder.WriteString(" ")
+		}
+
+		if syllable.EndTime != nil {
+			builder.WriteString(fmt.Sprintf("<%s>", msToLRCTimestampInline(int64(*syllable.EndTime))))
+		}
+	}
+}
+
+func formatPaxContent(lyricsType string, content []paxLyrics, multiPersonWordByWord bool) string {
+	var sb strings.Builder
+
+	for i, line := range content {
+		if i > 0 {
+			sb.WriteString("\n")
+		}
+
+		timestamp := msToLRCTimestamp(int64(line.Timestamp))
+
+		if strings.EqualFold(lyricsType, "Syllable") {
+			sb.WriteString(timestamp)
+			if multiPersonWordByWord {
+				if line.OppositeTurn {
+					sb.WriteString("v2:")
+				} else {
+					sb.WriteString("v1:")
+				}
+			}
+
+			appendPaxLyricDetail(&sb, line.Text)
+
+			if line.Background && multiPersonWordByWord && len(line.BackgroundText) > 0 {
+				sb.WriteString("\n[bg:")
+				appendPaxLyricDetail(&sb, line.BackgroundText)
+				sb.WriteString("]")
+			}
+		} else {
+			if len(line.Text) > 0 {
+				sb.WriteString(timestamp)
+				sb.WriteString(line.Text[0].Text)
+			}
+		}
+	}
+
+	return strings.TrimSpace(sb.String())
+}
+
+// FetchLyrics searches Apple Music and returns parsed LyricsResponse.
+func (c *AppleMusicClient) FetchLyrics(
+	trackName,
+	artistName string,
+	durationSec float64,
+	multiPersonWordByWord bool,
+) (*LyricsResponse, error) {
+	songID, err := c.SearchSong(trackName, artistName)
+	if err != nil {
+		return nil, err
+	}
+
+	rawLyrics, err := c.FetchLyricsByID(songID)
+	if err != nil {
+		return nil, err
+	}
+	if errMsg, isErrorPayload := detectLyricsErrorPayload(rawLyrics); isErrorPayload {
+		return nil, fmt.Errorf("apple music proxy returned non-lyric payload: %s", errMsg)
+	}
+
+	// Try to parse as pax format (word-by-word or line)
+	lrcText, err := formatPaxLyricsToLRC(rawLyrics, multiPersonWordByWord)
+	if err != nil {
+		// If pax parsing fails, try to parse as direct LRC text
+		lrcText = rawLyrics
+	}
+
+	lines := parseSyncedLyrics(lrcText)
+	if len(lines) > 0 {
+		return &LyricsResponse{
+			Lines:    lines,
+			SyncType: "LINE_SYNCED",
+			Provider: "Apple Music",
+			Source:   "Apple Music",
+		}, nil
+	}
+
+	// Fall back to plain text if no timestamps found
+	resultLines := plainTextLyricsLines(lrcText)
+
+	if len(resultLines) > 0 {
+		return &LyricsResponse{
+			Lines:    resultLines,
+			SyncType: "UNSYNCED",
+			Provider: "Apple Music",
+			Source:   "Apple Music",
+		}, nil
+	}
+
+	return nil, fmt.Errorf("no lyrics found on apple music")
+}

go_backend/lyrics_musixmatch.go

@@ -0,0 +1,189 @@
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// MusixmatchClient fetches lyrics from Musixmatch via a proxy server.
+// The proxy handles Musixmatch authentication internally.
+type MusixmatchClient struct {
+	httpClient *http.Client
+	baseURL    string
+}
+
+type musixmatchSearchResponse struct {
+	ID                 int64                     `json:"id"`
+	SongName           string                    `json:"songName"`
+	ArtistName         string                    `json:"artistName"`
+	AlbumName          string                    `json:"albumName"`
+	Artwork            string                    `json:"artwork"`
+	ReleaseDate        string                    `json:"releaseDate"`
+	Duration           int                       `json:"duration"`
+	URL                string                    `json:"url"`
+	AlbumID            int64                     `json:"albumId"`
+	HasSyncedLyrics    bool                      `json:"hasSyncedLyrics"`
+	HasUnsyncedLyrics  bool                      `json:"hasUnsyncedLyrics"`
+	AvailableLanguages []string                  `json:"availableLanguages"`
+	OriginalLanguage   string                    `json:"originalLanguage"`
+	SyncedLyrics       *musixmatchLyricsResponse `json:"syncedLyrics"`
+	UnsyncedLyrics     *musixmatchLyricsResponse `json:"unsyncedLyrics"`
+}
+
+type musixmatchLyricsResponse struct {
+	ID          int64  `json:"id"`
+	Duration    int    `json:"duration"`
+	Language    string `json:"language"`
+	UpdatedTime string `json:"updatedTime"`
+	Lyrics      string `json:"lyrics"`
+}
+
+func NewMusixmatchClient() *MusixmatchClient {
+	return &MusixmatchClient{
+		httpClient: NewMetadataHTTPClient(15 * time.Second),
+		baseURL:    "http://158.180.60.95",
+	}
+}
+
+// searchAndGetLyrics searches for a song and retrieves its lyrics in one call.
+// The Musixmatch proxy returns both search result and lyrics in a single response.
+func (c *MusixmatchClient) searchAndGetLyrics(trackName, artistName string) (*musixmatchSearchResponse, error) {
+	if strings.TrimSpace(trackName) == "" || strings.TrimSpace(artistName) == "" {
+		return nil, fmt.Errorf("empty track or artist name")
+	}
+
+	encodedArtist := url.QueryEscape(artistName)
+	encodedTrack := url.QueryEscape(trackName)
+
+	fullURL := fmt.Sprintf("%s/v2/full?artist=%s&track=%s", c.baseURL, encodedArtist, encodedTrack)
+
+	req, err := http.NewRequest("GET", fullURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("musixmatch search failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("musixmatch proxy returned HTTP %d", resp.StatusCode)
+	}
+
+	var result musixmatchSearchResponse
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return nil, fmt.Errorf("failed to decode musixmatch response: %w", err)
+	}
+
+	return &result, nil
+}
+
+// FetchLyricsInLanguage retrieves lyrics from Musixmatch for a specific language code.
+func (c *MusixmatchClient) FetchLyricsInLanguage(songID int64, language string) (*LyricsResponse, error) {
+	lang := strings.ToLower(strings.TrimSpace(language))
+	if songID <= 0 || lang == "" {
+		return nil, fmt.Errorf("invalid song id or language")
+	}
+
+	fullURL := fmt.Sprintf("%s/v2/full?id=%d&lang=%s", c.baseURL, songID, url.QueryEscape(lang))
+
+	req, err := http.NewRequest("GET", fullURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("musixmatch language fetch failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("musixmatch language endpoint returned HTTP %d", resp.StatusCode)
+	}
+
+	var result musixmatchSearchResponse
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return nil, fmt.Errorf("failed to decode musixmatch language response: %w", err)
+	}
+
+	if result.SyncedLyrics != nil && strings.TrimSpace(result.SyncedLyrics.Lyrics) != "" {
+		lines := parseSyncedLyrics(result.SyncedLyrics.Lyrics)
+		if len(lines) > 0 {
+			return &LyricsResponse{
+				Lines:    lines,
+				SyncType: "LINE_SYNCED",
+				Provider: "Musixmatch",
+				Source:   fmt.Sprintf("Musixmatch (%s)", lang),
+			}, nil
+		}
+	}
+
+	if result.UnsyncedLyrics != nil && strings.TrimSpace(result.UnsyncedLyrics.Lyrics) != "" {
+		lines := plainTextLyricsLines(result.UnsyncedLyrics.Lyrics)
+
+		if len(lines) > 0 {
+			return &LyricsResponse{
+				Lines:       lines,
+				SyncType:    "UNSYNCED",
+				PlainLyrics: result.UnsyncedLyrics.Lyrics,
+				Provider:    "Musixmatch",
+				Source:      fmt.Sprintf("Musixmatch (%s)", lang),
+			}, nil
+		}
+	}
+
+	return nil, fmt.Errorf("no lyrics found on musixmatch for language %s", lang)
+}
+
+// FetchLyrics searches Musixmatch and returns parsed LyricsResponse.
+func (c *MusixmatchClient) FetchLyrics(trackName, artistName string, durationSec float64, preferredLanguage string) (*LyricsResponse, error) {
+	result, err := c.searchAndGetLyrics(trackName, artistName)
+	if err != nil {
+		return nil, err
+	}
+
+	if preferred := strings.ToLower(strings.TrimSpace(preferredLanguage)); preferred != "" && result.ID > 0 {
+		localized, localizedErr := c.FetchLyricsInLanguage(result.ID, preferred)
+		if localizedErr == nil {
+			return localized, nil
+		}
+		GoLog("[Musixmatch] Language override '%s' failed: %v\n", preferred, localizedErr)
+	}
+
+	if result.SyncedLyrics != nil && strings.TrimSpace(result.SyncedLyrics.Lyrics) != "" {
+		lines := parseSyncedLyrics(result.SyncedLyrics.Lyrics)
+		if len(lines) > 0 {
+			return &LyricsResponse{
+				Lines:    lines,
+				SyncType: "LINE_SYNCED",
+				Provider: "Musixmatch",
+				Source:   "Musixmatch",
+			}, nil
+		}
+	}
+
+	if result.UnsyncedLyrics != nil && strings.TrimSpace(result.UnsyncedLyrics.Lyrics) != "" {
+		lines := plainTextLyricsLines(result.UnsyncedLyrics.Lyrics)
+
+		if len(lines) > 0 {
+			return &LyricsResponse{
+				Lines:       lines,
+				SyncType:    "UNSYNCED",
+				PlainLyrics: result.UnsyncedLyrics.Lyrics,
+				Provider:    "Musixmatch",
+				Source:      "Musixmatch",
+			}, nil
+		}
+	}
+
+	return nil, fmt.Errorf("no lyrics found on musixmatch")
+}

go_backend/lyrics_netease.go

@@ -0,0 +1,207 @@
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// NeteaseClient fetches lyrics from NetEase Cloud Music (music.163.com).
+// This is a direct public API — no proxy dependency.
+type NeteaseClient struct {
+	httpClient *http.Client
+}
+
+type neteaseSearchResponse struct {
+	Result struct {
+		Songs []struct {
+			Name    string `json:"name"`
+			ID      int64  `json:"id"`
+			Artists []struct {
+				Name string `json:"name"`
+			} `json:"artists"`
+		} `json:"songs"`
+		SongCount int `json:"songCount"`
+	} `json:"result"`
+	Code int `json:"code"`
+}
+
+type neteaseLyricsResponse struct {
+	LRC     *neteaseLyricField `json:"lrc"`
+	TLyric  *neteaseLyricField `json:"tlyric"`
+	RomaLRC *neteaseLyricField `json:"romalrc"`
+	Code    int                `json:"code"`
+}
+
+type neteaseLyricField struct {
+	Lyric string `json:"lyric"`
+}
+
+var neteaseHeaders = map[string]string{
+	"Accept":          "application/json",
+	"Accept-Language": "en-US,en;q=0.9",
+	"Cache-Control":   "max-age=0",
+}
+
+func NewNeteaseClient() *NeteaseClient {
+	return &NeteaseClient{
+		httpClient: NewMetadataHTTPClient(15 * time.Second),
+	}
+}
+
+// SearchSong searches for a song on Netease and returns the song ID.
+func (c *NeteaseClient) SearchSong(trackName, artistName string) (int64, error) {
+	query := trackName + " " + artistName
+	if strings.TrimSpace(query) == "" {
+		return 0, fmt.Errorf("empty search query")
+	}
+
+	searchURL := "http://music.163.com/api/search/pc"
+	params := url.Values{}
+	params.Set("s", query)
+	params.Set("type", "1")
+	params.Set("limit", "1")
+	params.Set("offset", "0")
+
+	fullURL := searchURL + "?" + params.Encode()
+
+	req, err := http.NewRequest("GET", fullURL, nil)
+	if err != nil {
+		return 0, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	for k, v := range neteaseHeaders {
+		req.Header.Set(k, v)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return 0, fmt.Errorf("netease search failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return 0, fmt.Errorf("netease search returned HTTP %d", resp.StatusCode)
+	}
+
+	var searchResp neteaseSearchResponse
+	if err := json.NewDecoder(resp.Body).Decode(&searchResp); err != nil {
+		return 0, fmt.Errorf("failed to decode netease search: %w", err)
+	}
+
+	if searchResp.Result.SongCount == 0 || len(searchResp.Result.Songs) == 0 {
+		return 0, fmt.Errorf("no songs found on netease")
+	}
+
+	return searchResp.Result.Songs[0].ID, nil
+}
+
+// FetchLyricsByID fetches synced lyrics for a given Netease song ID.
+func (c *NeteaseClient) FetchLyricsByID(songID int64, includeTranslation, includeRomanization bool) (string, error) {
+	lyricsURL := "http://music.163.com/api/song/lyric"
+	params := url.Values{}
+	params.Set("id", fmt.Sprintf("%d", songID))
+	params.Set("lv", "1")
+	params.Set("tv", "1")
+	params.Set("rv", "1")
+
+	fullURL := lyricsURL + "?" + params.Encode()
+
+	req, err := http.NewRequest("GET", fullURL, nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to create request: %w", err)
+	}
+
+	for k, v := range neteaseHeaders {
+		req.Header.Set(k, v)
+	}
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("netease lyrics fetch failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("netease lyrics returned HTTP %d", resp.StatusCode)
+	}
+
+	var lyricsResp neteaseLyricsResponse
+	if err := json.NewDecoder(resp.Body).Decode(&lyricsResp); err != nil {
+		return "", fmt.Errorf("failed to decode netease lyrics: %w", err)
+	}
+
+	if lyricsResp.LRC == nil || strings.TrimSpace(lyricsResp.LRC.Lyric) == "" {
+		return "", fmt.Errorf("no lyrics available on netease")
+	}
+
+	lyric := lyricsResp.LRC.Lyric
+
+	if includeTranslation && lyricsResp.TLyric != nil && strings.TrimSpace(lyricsResp.TLyric.Lyric) != "" {
+		lyric += "\n\n" + lyricsResp.TLyric.Lyric
+	}
+
+	if includeRomanization && lyricsResp.RomaLRC != nil && strings.TrimSpace(lyricsResp.RomaLRC.Lyric) != "" {
+		lyric += "\n\n" + lyricsResp.RomaLRC.Lyric
+	}
+
+	return lyric, nil
+}
+
+// FetchLyrics searches for a track and returns parsed LyricsResponse.
+func (c *NeteaseClient) FetchLyrics(
+	trackName,
+	artistName string,
+	durationSec float64,
+	includeTranslation,
+	includeRomanization bool,
+) (*LyricsResponse, error) {
+	songID, err := c.SearchSong(trackName, artistName)
+	if err != nil {
+		return nil, err
+	}
+
+	lrcText, err := c.FetchLyricsByID(songID, includeTranslation, includeRomanization)
+	if err != nil {
+		return nil, err
+	}
+
+	lines := parseSyncedLyrics(lrcText)
+	if len(lines) == 0 {
+		// May be plain text lyrics without timestamps
+		plainLines := strings.Split(lrcText, "\n")
+		for _, line := range plainLines {
+			trimmed := strings.TrimSpace(line)
+			if trimmed != "" {
+				lines = append(lines, LyricsLine{
+					StartTimeMs: 0,
+					Words:       trimmed,
+					EndTimeMs:   0,
+				})
+			}
+		}
+
+		if len(lines) == 0 {
+			return nil, fmt.Errorf("netease returned empty lyrics")
+		}
+
+		return &LyricsResponse{
+			Lines:    lines,
+			SyncType: "UNSYNCED",
+			Provider: "Netease",
+			Source:   "Netease",
+		}, nil
+	}
+
+	return &LyricsResponse{
+		Lines:    lines,
+		SyncType: "LINE_SYNCED",
+		Provider: "Netease",
+		Source:   "Netease",
+	}, nil
+}

go_backend/lyrics_qqmusic.go

@@ -0,0 +1,198 @@
+package gobackend
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// QQMusicClient fetches lyrics from QQ Music.
+// Search uses public QQ Music API, lyrics use the paxsenix proxy.
+type QQMusicClient struct {
+	httpClient *http.Client
+}
+
+type qqMusicSearchResponse struct {
+	Data struct {
+		Song struct {
+			List []struct {
+				Title  string `json:"title"`
+				Singer []struct {
+					Name string `json:"name"`
+				} `json:"singer"`
+				Album struct {
+					Name string `json:"name"`
+				} `json:"album"`
+				ID int64 `json:"id"`
+			} `json:"list"`
+		} `json:"song"`
+	} `json:"data"`
+}
+
+// QQ Music lyrics request payload for paxsenix proxy
+type qqLyricsPayload struct {
+	Artist []string `json:"artist"`
+	Album  string   `json:"album"`
+	ID     int64    `json:"id"`
+	Title  string   `json:"title"`
+}
+
+func NewQQMusicClient() *QQMusicClient {
+	return &QQMusicClient{
+		httpClient: NewMetadataHTTPClient(15 * time.Second),
+	}
+}
+
+// searchSong searches QQ Music and returns the song info needed for lyrics fetch.
+func (c *QQMusicClient) searchSong(trackName, artistName string) (*qqLyricsPayload, error) {
+	query := trackName + " " + artistName
+	if strings.TrimSpace(query) == "" {
+		return nil, fmt.Errorf("empty search query")
+	}
+
+	searchURL := "https://c.y.qq.com/soso/fcgi-bin/client_search_cp"
+	params := url.Values{}
+	params.Set("format", "json")
+	params.Set("inCharset", "utf8")
+	params.Set("outCharset", "utf8")
+	params.Set("platform", "yqq.json")
+	params.Set("new_json", "1")
+	params.Set("w", query)
+
+	fullURL := searchURL + "?" + params.Encode()
+
+	req, err := http.NewRequest("GET", fullURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("qqmusic search failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("qqmusic search returned HTTP %d", resp.StatusCode)
+	}
+
+	var searchResp qqMusicSearchResponse
+	if err := json.NewDecoder(resp.Body).Decode(&searchResp); err != nil {
+		return nil, fmt.Errorf("failed to decode qqmusic response: %w", err)
+	}
+
+	if len(searchResp.Data.Song.List) == 0 {
+		return nil, fmt.Errorf("no songs found on qqmusic")
+	}
+
+	song := searchResp.Data.Song.List[0]
+
+	var artists []string
+	for _, singer := range song.Singer {
+		artists = append(artists, singer.Name)
+	}
+
+	return &qqLyricsPayload{
+		Artist: artists,
+		Album:  song.Album.Name,
+		ID:     song.ID,
+		Title:  song.Title,
+	}, nil
+}
+
+// fetchLyricsByPayload fetches lyrics from the paxsenix proxy using QQ Music song info.
+func (c *QQMusicClient) fetchLyricsByPayload(payload *qqLyricsPayload) (string, error) {
+	lyricsURL := "https://paxsenix.alwaysdata.net/getQQLyrics.php"
+
+	payloadBytes, err := json.Marshal(payload)
+	if err != nil {
+		return "", fmt.Errorf("failed to marshal payload: %w", err)
+	}
+
+	req, err := http.NewRequest("POST", lyricsURL, bytes.NewReader(payloadBytes))
+	if err != nil {
+		return "", fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("User-Agent", getRandomUserAgent())
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("qqmusic lyrics fetch failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("qqmusic lyrics proxy returned HTTP %d", resp.StatusCode)
+	}
+
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("failed to read lyrics response: %w", err)
+	}
+
+	bodyStr := strings.TrimSpace(string(bodyBytes))
+	if bodyStr == "" {
+		return "", fmt.Errorf("empty lyrics response from qqmusic")
+	}
+
+	return bodyStr, nil
+}
+
+// FetchLyrics searches QQ Music and returns parsed LyricsResponse.
+func (c *QQMusicClient) FetchLyrics(
+	trackName,
+	artistName string,
+	durationSec float64,
+	multiPersonWordByWord bool,
+) (*LyricsResponse, error) {
+	payload, err := c.searchSong(trackName, artistName)
+	if err != nil {
+		return nil, err
+	}
+
+	rawLyrics, err := c.fetchLyricsByPayload(payload)
+	if err != nil {
+		return nil, err
+	}
+	if errMsg, isErrorPayload := detectLyricsErrorPayload(rawLyrics); isErrorPayload {
+		return nil, fmt.Errorf("qqmusic proxy returned non-lyric payload: %s", errMsg)
+	}
+
+	// Try to parse as pax format (word-by-word or line)
+	lrcText, err := formatPaxLyricsToLRC(rawLyrics, multiPersonWordByWord)
+	if err != nil {
+		// If pax parsing fails, try to use as direct LRC text
+		lrcText = rawLyrics
+	}
+
+	lines := parseSyncedLyrics(lrcText)
+	if len(lines) > 0 {
+		return &LyricsResponse{
+			Lines:    lines,
+			SyncType: "LINE_SYNCED",
+			Provider: "QQ Music",
+			Source:   "QQ Music",
+		}, nil
+	}
+
+	resultLines := plainTextLyricsLines(lrcText)
+
+	if len(resultLines) > 0 {
+		return &LyricsResponse{
+			Lines:    resultLines,
+			SyncType: "UNSYNCED",
+			Provider: "QQ Music",
+			Source:   "QQ Music",
+		}, nil
+	}
+
+	return nil, fmt.Errorf("no lyrics found on qqmusic")
+}

go_backend/mobile_deps.go

@@ -0,0 +1,8 @@
+// This file ensures gomobile dependencies are not removed by go mod tidy.
+// These packages are required by gomobile bind but not directly imported in code.
+
+package gobackend
+
+import (
+	_ "golang.org/x/mobile/bind"
+)

go_backend/output_fd.go

@@ -0,0 +1,88 @@
+package gobackend
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+func isFDOutput(outputFD int) bool {
+	return outputFD > 0
+}
+
+func openOutputForWrite(outputPath string, outputFD int) (*os.File, error) {
+	if isFDOutput(outputFD) {
+		// Never hand the original detached FD directly to a provider attempt.
+		// Fallback chains may retry with another provider after a failure.
+		// If the first attempt closes the original FD, its numeric ID can be
+		// reused by unrelated resources and a later close may trigger fdsan abort.
+		dupFD, err := dupOutputFD(outputFD)
+		if err != nil {
+			return nil, fmt.Errorf("failed to duplicate output fd %d: %w", outputFD, err)
+		}
+		if err := prepareDupFDForWrite(dupFD, outputFD); err != nil {
+			_ = closeFD(dupFD)
+			return nil, err
+		}
+		return os.NewFile(uintptr(dupFD), fmt.Sprintf("saf_fd_%d_dup_%d", outputFD, dupFD)), nil
+	}
+
+	path := strings.TrimSpace(outputPath)
+	if strings.HasPrefix(path, "/proc/self/fd/") {
+		// Re-open procfs fd path instead of taking ownership of raw detached fd.
+		// Some SAF providers reject O_TRUNC on these descriptors with EACCES/EPERM.
+		file, err := os.OpenFile(path, os.O_WRONLY|os.O_TRUNC, 0)
+		if err == nil {
+			return file, nil
+		}
+		if strings.Contains(strings.ToLower(err.Error()), "permission denied") {
+			return os.OpenFile(path, os.O_WRONLY, 0)
+		}
+		return nil, err
+	}
+
+	return os.Create(outputPath)
+}
+
+func prepareDupFDForWrite(dupFD, originalFD int) error {
+	// Best-effort reset so retries start writing from byte 0.
+	if err := truncateFD(dupFD); err != nil {
+		if isBestEffortTruncateError(err) {
+			GoLog("[OutputFD] truncate not supported on fd %d (dup of %d): %v\n", dupFD, originalFD, err)
+		} else {
+			return fmt.Errorf("failed to truncate output fd %d (dup of %d): %w", dupFD, originalFD, err)
+		}
+	}
+	if err := seekFDStart(dupFD); err != nil {
+		GoLog("[OutputFD] seek reset failed on fd %d (dup of %d): %v\n", dupFD, originalFD, err)
+	}
+	return nil
+}
+
+func closeOwnedOutputFD(outputFD int) {
+	if !isFDOutput(outputFD) {
+		return
+	}
+
+	if err := closeFD(outputFD); err != nil {
+		if !isBadFD(err) {
+			GoLog("[OutputFD] failed to close detached fd %d: %v\n", outputFD, err)
+		}
+		return
+	}
+
+	GoLog("[OutputFD] closed detached fd %d\n", outputFD)
+}
+
+func cleanupOutputOnError(outputPath string, outputFD int) {
+	if isFDOutput(outputFD) {
+		return
+	}
+
+	path := strings.TrimSpace(outputPath)
+	if path == "" || strings.HasPrefix(path, "/proc/self/fd/") {
+		return
+	}
+
+	_ = os.Remove(path)
+}

go_backend/output_fd_unix.go

@@ -0,0 +1,35 @@
+//go:build !windows
+
+package gobackend
+
+import "syscall"
+
+func dupOutputFD(fd int) (int, error) {
+	return syscall.Dup(fd)
+}
+
+func truncateFD(fd int) error {
+	return syscall.Ftruncate(fd, 0)
+}
+
+func seekFDStart(fd int) error {
+	_, err := syscall.Seek(fd, 0, 0)
+	return err
+}
+
+func closeFD(fd int) error {
+	return syscall.Close(fd)
+}
+
+func isBestEffortTruncateError(err error) bool {
+	switch err {
+	case syscall.EPERM, syscall.EACCES, syscall.EINVAL, syscall.ESPIPE, syscall.ENOSYS:
+		return true
+	default:
+		return false
+	}
+}
+
+func isBadFD(err error) bool {
+	return err == syscall.EBADF
+}

go_backend/output_fd_windows.go

@@ -0,0 +1,29 @@
+//go:build windows
+
+package gobackend
+
+func dupOutputFD(fd int) (int, error) {
+	// Windows build is primarily for local tooling/tests.
+	// Android runtime uses the !windows implementation.
+	return fd, nil
+}
+
+func truncateFD(fd int) error {
+	return nil
+}
+
+func seekFDStart(fd int) error {
+	return nil
+}
+
+func closeFD(fd int) error {
+	return nil
+}
+
+func isBestEffortTruncateError(err error) bool {
+	return true
+}
+
+func isBadFD(err error) bool {
+	return false
+}

go_backend/parallel.go

@@ -1,28 +1,24 @@
 package gobackend
 
 import (
+	"encoding/json"
 	"fmt"
 	"sync"
 	"time"
 )
 
-// ========================================
-// ISRC to Track ID Cache
-// ========================================
-
-// TrackIDCacheEntry holds cached track ID with metadata
 type TrackIDCacheEntry struct {
 	TidalTrackID  int64
 	QobuzTrackID  int64
-	AmazonTrackID string
 	ExpiresAt     time.Time
 }
 
-// TrackIDCache caches ISRC to track ID mappings
 type TrackIDCache struct {
-	cache map[string]*TrackIDCacheEntry
-	mu    sync.RWMutex
-	ttl   time.Duration
+	cache           map[string]*TrackIDCacheEntry
+	mu              sync.RWMutex
+	ttl             time.Duration
+	lastCleanup     time.Time
+	cleanupInterval time.Duration
 }
 
 var (
@@ -30,30 +26,48 @@ var (
 	trackIDCacheOnce   sync.Once
 )
 
-// GetTrackIDCache returns the global track ID cache
 func GetTrackIDCache() *TrackIDCache {
 	trackIDCacheOnce.Do(func() {
 		globalTrackIDCache = &TrackIDCache{
-			cache: make(map[string]*TrackIDCacheEntry),
-			ttl:   30 * time.Minute,
+			cache:           make(map[string]*TrackIDCacheEntry),
+			ttl:             30 * time.Minute,
+			cleanupInterval: 5 * time.Minute,
 		}
 	})
 	return globalTrackIDCache
 }
 
-// Get retrieves a cached entry by ISRC
 func (c *TrackIDCache) Get(isrc string) *TrackIDCacheEntry {
 	c.mu.RLock()
-	defer c.mu.RUnlock()
-
 	entry, exists := c.cache[isrc]
-	if !exists || time.Now().After(entry.ExpiresAt) {
+	if !exists {
+		c.mu.RUnlock()
 		return nil
 	}
-	return entry
+	expired := time.Now().After(entry.ExpiresAt)
+	c.mu.RUnlock()
+
+	if !expired {
+		return entry
+	}
+
+	c.mu.Lock()
+	entry, exists = c.cache[isrc]
+	if exists && time.Now().After(entry.ExpiresAt) {
+		delete(c.cache, isrc)
+	}
+	c.mu.Unlock()
+	return nil
+}
+
+func (c *TrackIDCache) pruneExpiredLocked(now time.Time) {
+	for key, entry := range c.cache {
+		if now.After(entry.ExpiresAt) {
+			delete(c.cache, key)
+		}
+	}
 }
 
-// SetTidal caches Tidal track ID for an ISRC
 func (c *TrackIDCache) SetTidal(isrc string, trackID int64) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -64,10 +78,15 @@ func (c *TrackIDCache) SetTidal(isrc string, trackID int64) {
 		c.cache[isrc] = entry
 	}
 	entry.TidalTrackID = trackID
-	entry.ExpiresAt = time.Now().Add(c.ttl)
+	now := time.Now()
+	entry.ExpiresAt = now.Add(c.ttl)
+
+	if c.cleanupInterval > 0 && (c.lastCleanup.IsZero() || now.Sub(c.lastCleanup) >= c.cleanupInterval) {
+		c.pruneExpiredLocked(now)
+		c.lastCleanup = now
+	}
 }
 
-// SetQobuz caches Qobuz track ID for an ISRC
 func (c *TrackIDCache) SetQobuz(isrc string, trackID int64) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -78,42 +97,27 @@ func (c *TrackIDCache) SetQobuz(isrc string, trackID int64) {
 		c.cache[isrc] = entry
 	}
 	entry.QobuzTrackID = trackID
-	entry.ExpiresAt = time.Now().Add(c.ttl)
-}
+	now := time.Now()
+	entry.ExpiresAt = now.Add(c.ttl)
 
-// SetAmazon caches Amazon track ID for an ISRC
-func (c *TrackIDCache) SetAmazon(isrc string, trackID string) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	entry, exists := c.cache[isrc]
-	if !exists {
-		entry = &TrackIDCacheEntry{}
-		c.cache[isrc] = entry
+	if c.cleanupInterval > 0 && (c.lastCleanup.IsZero() || now.Sub(c.lastCleanup) >= c.cleanupInterval) {
+		c.pruneExpiredLocked(now)
+		c.lastCleanup = now
 	}
-	entry.AmazonTrackID = trackID
-	entry.ExpiresAt = time.Now().Add(c.ttl)
 }
 
-// Clear removes all cached entries
 func (c *TrackIDCache) Clear() {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	c.cache = make(map[string]*TrackIDCacheEntry)
 }
 
-// Size returns the number of cached entries
 func (c *TrackIDCache) Size() int {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 	return len(c.cache)
 }
 
-// ========================================
-// Parallel Download Helper
-// ========================================
-
-// ParallelDownloadResult holds results from parallel operations
 type ParallelDownloadResult struct {
 	CoverData  []byte
 	LyricsData *LyricsResponse
@@ -122,9 +126,6 @@ type ParallelDownloadResult struct {
 	LyricsErr  error
 }
 
-// FetchCoverAndLyricsParallel downloads cover and fetches lyrics in parallel
-// This runs while the main audio download is happening
-// durationMs: track duration in milliseconds for lyrics matching
 func FetchCoverAndLyricsParallel(
 	coverURL string,
 	maxQualityCover bool,
@@ -136,43 +137,40 @@ func FetchCoverAndLyricsParallel(
 ) *ParallelDownloadResult {
 	result := &ParallelDownloadResult{}
 	var wg sync.WaitGroup
+	var resultMu sync.Mutex
 
 	if coverURL != "" {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
-			fmt.Println("[Parallel] Starting cover download...")
 			data, err := downloadCoverToMemory(coverURL, maxQualityCover)
+			resultMu.Lock()
 			if err != nil {
 				result.CoverErr = err
-				fmt.Printf("[Parallel] Cover download failed: %v\n", err)
 			} else {
 				result.CoverData = data
-				fmt.Printf("[Parallel] Cover downloaded: %d bytes\n", len(data))
 			}
+			resultMu.Unlock()
 		}()
 	}
 
-	// Fetch lyrics in parallel
 	if embedLyrics {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
-			fmt.Println("[Parallel] Starting lyrics fetch...")
 			client := NewLyricsClient()
 			durationSec := float64(durationMs) / 1000.0
 			lyrics, err := client.FetchLyricsAllSources(spotifyID, trackName, artistName, durationSec)
+			resultMu.Lock()
 			if err != nil {
 				result.LyricsErr = err
-				fmt.Printf("[Parallel] Lyrics fetch failed: %v\n", err)
 			} else if lyrics != nil && len(lyrics.Lines) > 0 {
 				result.LyricsData = lyrics
 				result.LyricsLRC = convertToLRCWithMetadata(lyrics, trackName, artistName)
-				fmt.Printf("[Parallel] Lyrics fetched: %d lines\n", len(lyrics.Lines))
 			} else {
 				result.LyricsErr = fmt.Errorf("no lyrics found")
-				fmt.Println("[Parallel] No lyrics found")
 			}
+			resultMu.Unlock()
 		}()
 	}
 
@@ -180,33 +178,28 @@ func FetchCoverAndLyricsParallel(
 	return result
 }
 
-// ========================================
-// Pre-warm Cache for Album/Playlist
-// ========================================
-
-// PreWarmCacheRequest represents a track to pre-warm cache for
 type PreWarmCacheRequest struct {
 	ISRC       string
 	TrackName  string
 	ArtistName string
-	SpotifyID  string // Needed for Amazon (SongLink lookup)
-	Service    string // "tidal", "qobuz", "amazon"
+	SpotifyID  string
+	Service    string
 }
 
-// PreWarmTrackCache pre-fetches track IDs for multiple tracks (for album/playlist)
-// This runs in background while user is viewing the track list
 func PreWarmTrackCache(requests []PreWarmCacheRequest) {
 	if len(requests) == 0 {
 		return
 	}
 
-	fmt.Printf("[Cache] Pre-warming cache for %d tracks...\n", len(requests))
 	cache := GetTrackIDCache()
 
 	semaphore := make(chan struct{}, 3)
 	var wg sync.WaitGroup
 
 	for _, req := range requests {
+		if req.ISRC == "" {
+			continue
+		}
 		if cached := cache.Get(req.ISRC); cached != nil {
 			continue
 		}
@@ -214,22 +207,19 @@ func PreWarmTrackCache(requests []PreWarmCacheRequest) {
 		wg.Add(1)
 		go func(r PreWarmCacheRequest) {
 			defer wg.Done()
-			semaphore <- struct{}{}        // Acquire
-			defer func() { <-semaphore }() // Release
+			semaphore <- struct{}{}
+			defer func() { <-semaphore }()
 
 			switch r.Service {
 			case "tidal":
 				preWarmTidalCache(r.ISRC, r.TrackName, r.ArtistName)
 			case "qobuz":
-				preWarmQobuzCache(r.ISRC)
-			case "amazon":
-				preWarmAmazonCache(r.ISRC, r.SpotifyID)
+				preWarmQobuzCache(r.ISRC, r.SpotifyID)
 			}
 		}(req)
 	}
 
 	wg.Wait()
-	fmt.Printf("[Cache] Pre-warm complete. Cache size: %d\n", cache.Size())
 }
 
 func preWarmTidalCache(isrc, _, _ string) {
@@ -237,48 +227,66 @@ func preWarmTidalCache(isrc, _, _ string) {
 	track, err := downloader.SearchTrackByISRC(isrc)
 	if err == nil && track != nil {
 		GetTrackIDCache().SetTidal(isrc, track.ID)
-		fmt.Printf("[Cache] Cached Tidal ID for ISRC %s: %d\n", isrc, track.ID)
 	}
 }
 
-func preWarmQobuzCache(isrc string) {
+// preWarmQobuzCache tries to get Qobuz Track ID in the following order:
+// 1. From SongLink (fast, no Qobuz API call needed)
+// 2. Direct ISRC search on Qobuz API (slower, may fail if ISRC not in Qobuz database)
+func preWarmQobuzCache(isrc, spotifyID string) {
+	if spotifyID != "" {
+		client := NewSongLinkClient()
+		availability, err := client.CheckTrackAvailability(spotifyID, isrc)
+		if err == nil && availability != nil && availability.QobuzID != "" {
+			var trackID int64
+			if _, parseErr := fmt.Sscanf(availability.QobuzID, "%d", &trackID); parseErr == nil && trackID > 0 {
+				GoLog("[Qobuz] Pre-warm cache: Got Qobuz ID %d from SongLink for ISRC %s\n", trackID, isrc)
+				GetTrackIDCache().SetQobuz(isrc, trackID)
+				return
+			}
+		}
+	}
+
 	downloader := NewQobuzDownloader()
 	track, err := downloader.SearchTrackByISRC(isrc)
 	if err == nil && track != nil {
+		GoLog("[Qobuz] Pre-warm cache: Got Qobuz ID %d from direct ISRC search for %s\n", track.ID, isrc)
 		GetTrackIDCache().SetQobuz(isrc, track.ID)
-		fmt.Printf("[Cache] Cached Qobuz ID for ISRC %s: %d\n", isrc, track.ID)
 	}
 }
 
-func preWarmAmazonCache(isrc, spotifyID string) {
-	client := NewSongLinkClient()
-	availability, err := client.CheckTrackAvailability(spotifyID, isrc)
-	if err == nil && availability != nil && availability.Amazon {
-		GetTrackIDCache().SetAmazon(isrc, availability.AmazonURL)
-		fmt.Printf("[Cache] Cached Amazon URL for ISRC %s\n", isrc)
-	}
-}
-
-// ========================================
-// Exported Functions for Flutter
-// ========================================
-
-// PreWarmCache is called from Flutter to pre-warm cache for album/playlist tracks
-// tracksJSON is a JSON array of {isrc, track_name, artist_name, service}
 func PreWarmCache(tracksJSON string) error {
-	var requests []PreWarmCacheRequest
+	var tracks []struct {
+		ISRC       string `json:"isrc"`
+		TrackName  string `json:"track_name"`
+		ArtistName string `json:"artist_name"`
+		SpotifyID  string `json:"spotify_id"`
+		Service    string `json:"service"`
+	}
+
+	if err := json.Unmarshal([]byte(tracksJSON), &tracks); err != nil {
+		return fmt.Errorf("failed to parse tracks JSON: %w", err)
+	}
+
+	requests := make([]PreWarmCacheRequest, len(tracks))
+	for i, t := range tracks {
+		requests[i] = PreWarmCacheRequest{
+			ISRC:       t.ISRC,
+			TrackName:  t.TrackName,
+			ArtistName: t.ArtistName,
+			SpotifyID:  t.SpotifyID,
+			Service:    t.Service,
+		}
+	}
 
 	go PreWarmTrackCache(requests)
 	return nil
 }
 
-// ClearTrackCache clears the track ID cache
 func ClearTrackCache() {
 	GetTrackIDCache().Clear()
-	fmt.Println("[Cache] Track ID cache cleared")
 }
 
-// GetCacheSize returns the current cache size
 func GetCacheSize() int {
 	return GetTrackIDCache().Size()
 }

go_backend/progress.go

@@ -6,8 +6,6 @@ import (
 	"time"
 )
 
-// DownloadProgress represents current download progress
-// Now unified - returns data from multi-progress system
 type DownloadProgress struct {
 	CurrentFile   string  `json:"current_file"`
 	Progress      float64 `json:"progress"`
@@ -15,21 +13,19 @@ type DownloadProgress struct {
 	BytesTotal    int64   `json:"bytes_total"`
 	BytesReceived int64   `json:"bytes_received"`
 	IsDownloading bool    `json:"is_downloading"`
-	Status        string  `json:"status"` // "downloading", "finalizing", "completed"
+	Status        string  `json:"status"`
 }
 
-// ItemProgress represents progress for a single download item
 type ItemProgress struct {
 	ItemID        string  `json:"item_id"`
 	BytesTotal    int64   `json:"bytes_total"`
 	BytesReceived int64   `json:"bytes_received"`
-	Progress      float64 `json:"progress"`   // 0.0 to 1.0
-	SpeedMBps     float64 `json:"speed_mbps"` // Download speed in MB/s
+	Progress      float64 `json:"progress"`
+	SpeedMBps     float64 `json:"speed_mbps"`
 	IsDownloading bool    `json:"is_downloading"`
-	Status        string  `json:"status"` // "downloading", "finalizing", "completed"
+	Status        string  `json:"status"`
 }
 
-// MultiProgress holds progress for multiple concurrent downloads
 type MultiProgress struct {
 	Items map[string]*ItemProgress `json:"items"`
 }
@@ -38,12 +34,16 @@ var (
 	downloadDir   string
 	downloadDirMu sync.RWMutex
 
-	// Multi-download progress tracking (unified system)
-	multiProgress = MultiProgress{Items: make(map[string]*ItemProgress)}
-	multiMu       sync.RWMutex
+	multiProgress       = MultiProgress{Items: make(map[string]*ItemProgress)}
+	multiMu             sync.RWMutex
+	multiProgressDirty  = true
+	cachedMultiProgress = "{\"items\":{}}"
 )
 
-// getProgress returns current download progress from multi-progress system
+func markMultiProgressDirtyLocked() {
+	multiProgressDirty = true
+}
+
 func getProgress() DownloadProgress {
 	multiMu.RLock()
 	defer multiMu.RUnlock()
@@ -62,19 +62,29 @@ func getProgress() DownloadProgress {
 	return DownloadProgress{}
 }
 
-// GetMultiProgress returns progress for all active downloads as JSON
 func GetMultiProgress() string {
 	multiMu.RLock()
-	defer multiMu.RUnlock()
+	if !multiProgressDirty {
+		cached := cachedMultiProgress
+		multiMu.RUnlock()
+		return cached
+	}
+	multiMu.RUnlock()
 
+	multiMu.Lock()
+	defer multiMu.Unlock()
+	if !multiProgressDirty {
+		return cachedMultiProgress
+	}
 	jsonBytes, err := json.Marshal(multiProgress)
 	if err != nil {
 		return "{\"items\":{}}"
 	}
-	return string(jsonBytes)
+	cachedMultiProgress = string(jsonBytes)
+	multiProgressDirty = false
+	return cachedMultiProgress
 }
 
-// GetItemProgress returns progress for a specific item as JSON
 func GetItemProgress(itemID string) string {
 	multiMu.RLock()
 	defer multiMu.RUnlock()
@@ -86,7 +96,6 @@ func GetItemProgress(itemID string) string {
 	return "{}"
 }
 
-// StartItemProgress initializes progress tracking for an item
 func StartItemProgress(itemID string) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
@@ -99,19 +108,19 @@ func StartItemProgress(itemID string) {
 		IsDownloading: true,
 		Status:        "downloading",
 	}
+	markMultiProgressDirtyLocked()
 }
 
-// SetItemBytesTotal sets total bytes for an item
 func SetItemBytesTotal(itemID string, total int64) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
 
 	if item, ok := multiProgress.Items[itemID]; ok {
 		item.BytesTotal = total
+		markMultiProgressDirtyLocked()
 	}
 }
 
-// SetItemBytesReceived sets bytes received for an item
 func SetItemBytesReceived(itemID string, received int64) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
@@ -121,10 +130,10 @@ func SetItemBytesReceived(itemID string, received int64) {
 		if item.BytesTotal > 0 {
 			item.Progress = float64(received) / float64(item.BytesTotal)
 		}
+		markMultiProgressDirtyLocked()
 	}
 }
 
-// SetItemBytesReceivedWithSpeed sets bytes received and speed for an item
 func SetItemBytesReceivedWithSpeed(itemID string, received int64, speedMBps float64) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
@@ -135,10 +144,10 @@ func SetItemBytesReceivedWithSpeed(itemID string, received int64, speedMBps floa
 		if item.BytesTotal > 0 {
 			item.Progress = float64(received) / float64(item.BytesTotal)
 		}
+		markMultiProgressDirtyLocked()
 	}
 }
 
-// CompleteItemProgress marks an item as complete
 func CompleteItemProgress(itemID string) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
@@ -147,10 +156,10 @@ func CompleteItemProgress(itemID string) {
 		item.Progress = 1.0
 		item.IsDownloading = false
 		item.Status = "completed"
+		markMultiProgressDirtyLocked()
 	}
 }
 
-// SetItemProgress sets progress for an item directly
 func SetItemProgress(itemID string, progress float64, bytesReceived, bytesTotal int64) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
@@ -163,10 +172,10 @@ func SetItemProgress(itemID string, progress float64, bytesReceived, bytesTotal
 		if bytesTotal > 0 {
 			item.BytesTotal = bytesTotal
 		}
+		markMultiProgressDirtyLocked()
 	}
 }
 
-// SetItemFinalizing marks an item as finalizing (embedding metadata)
 func SetItemFinalizing(itemID string) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
@@ -174,26 +183,26 @@ func SetItemFinalizing(itemID string) {
 	if item, ok := multiProgress.Items[itemID]; ok {
 		item.Progress = 1.0
 		item.Status = "finalizing"
+		markMultiProgressDirtyLocked()
 	}
 }
 
-// RemoveItemProgress removes progress tracking for an item
 func RemoveItemProgress(itemID string) {
 	multiMu.Lock()
 	defer multiMu.Unlock()
 
 	delete(multiProgress.Items, itemID)
+	markMultiProgressDirtyLocked()
 }
 
-// ClearAllItemProgress clears all item progress
 func ClearAllItemProgress() {
 	multiMu.Lock()
 	defer multiMu.Unlock()
 
 	multiProgress.Items = make(map[string]*ItemProgress)
+	markMultiProgressDirtyLocked()
 }
 
-// setDownloadDir sets the default download directory
 func setDownloadDir(path string) error {
 	downloadDirMu.Lock()
 	defer downloadDirMu.Unlock()
@@ -201,28 +210,18 @@ func setDownloadDir(path string) error {
 	return nil
 }
 
-// getDownloadDir returns the default download directory
-// Kept for potential future use
-// func getDownloadDir() string {
-// 	downloadDirMu.RLock()
-// 	defer downloadDirMu.RUnlock()
-// 	return downloadDir
-// }
-
-// ItemProgressWriter wraps io.Writer to track download progress for a specific item
 type ItemProgressWriter struct {
 	writer       interface{ Write([]byte) (int, error) }
 	itemID       string
 	current      int64
-	lastReported int64     // Track last reported bytes for threshold-based updates
-	startTime    time.Time // Track start time for speed calculation
-	lastTime     time.Time // Track last update time for speed calculation
-	lastBytes    int64     // Track bytes at last speed calculation
+	lastReported int64
+	startTime    time.Time
+	lastTime     time.Time
+	lastBytes    int64
 }
 
-const progressUpdateThreshold = 64 * 1024 // Update progress every 64KB
+const progressUpdateThreshold = 64 * 1024
 
-// NewItemProgressWriter creates a new progress writer for a specific item
 func NewItemProgressWriter(w interface{ Write([]byte) (int, error) }, itemID string) *ItemProgressWriter {
 	now := time.Now()
 	return &ItemProgressWriter{
@@ -236,7 +235,6 @@ func NewItemProgressWriter(w interface{ Write([]byte) (int, error) }, itemID str
 	}
 }
 
-// Write implements io.Writer with threshold-based progress updates and speed tracking
 func (pw *ItemProgressWriter) Write(p []byte) (int, error) {
 	if pw.itemID != "" && isDownloadCancelled(pw.itemID) {
 		return 0, ErrDownloadCancelled

go_backend/qobuz_test.go

@@ -0,0 +1,413 @@
+package gobackend
+
+import "testing"
+
+func TestParseQobuzURL(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		wantType  string
+		wantID    string
+		expectErr bool
+	}{
+		{
+			name:     "store album url",
+			input:    "https://www.qobuz.com/us-en/album/harry-styles-harry-styles/0886446451985",
+			wantType: "album",
+			wantID:   "0886446451985",
+		},
+		{
+			name:     "store playlist url",
+			input:    "https://www.qobuz.com/us-en/playlists/new-releases/2049430",
+			wantType: "playlist",
+			wantID:   "2049430",
+		},
+		{
+			name:     "store artist url",
+			input:    "https://www.qobuz.com/us-en/interpreter/harry-styles/729886",
+			wantType: "artist",
+			wantID:   "729886",
+		},
+		{
+			name:     "play track url",
+			input:    "https://play.qobuz.com/track/40681594",
+			wantType: "track",
+			wantID:   "40681594",
+		},
+		{
+			name:     "custom scheme playlist url",
+			input:    "qobuzapp://playlist/2049430",
+			wantType: "playlist",
+			wantID:   "2049430",
+		},
+		{
+			name:      "unsupported url",
+			input:     "https://example.com/not-qobuz",
+			expectErr: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			gotType, gotID, err := parseQobuzURL(test.input)
+			if test.expectErr {
+				if err == nil {
+					t.Fatalf("expected error, got none")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+			if gotType != test.wantType || gotID != test.wantID {
+				t.Fatalf("parseQobuzURL(%q) = (%q, %q), want (%q, %q)", test.input, gotType, gotID, test.wantType, test.wantID)
+			}
+		})
+	}
+}
+
+func TestExtractQobuzArtistAlbumIDs(t *testing.T) {
+	body := []byte(`
+<div class="product__item">
+  <button data-itemtype="album" data-itemId="yrpbt0lwm3g0y"></button>
+</div>
+<div class="product__item">
+  <button data-itemtype="album" data-itemId="yrpbt0lwm3g0y"></button>
+</div>
+<div class="product__item">
+  <button data-itemtype="album" data-itemId="0886446451985"></button>
+</div>
+`)
+
+	matches := qobuzArtistAlbumIDRegex.FindAllSubmatch(body, -1)
+	if len(matches) != 3 {
+		t.Fatalf("expected 3 regex matches, got %d", len(matches))
+	}
+	if string(matches[0][1]) != "yrpbt0lwm3g0y" {
+		t.Fatalf("unexpected first album id: %q", matches[0][1])
+	}
+	if string(matches[2][1]) != "0886446451985" {
+		t.Fatalf("unexpected last album id: %q", matches[2][1])
+	}
+}
+
+func TestExtractQobuzDownloadURLFromBody(t *testing.T) {
+	t.Run("reads top-level download_url and quality metadata", func(t *testing.T) {
+		body := []byte(`{"success":true,"download_url":"https://example.test/new.flac","bit_depth":24,"sampling_rate":96}`)
+
+		info, err := extractQobuzDownloadInfoFromBody(body)
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if info.DownloadURL != "https://example.test/new.flac" {
+			t.Fatalf("unexpected URL: %q", info.DownloadURL)
+		}
+		if info.BitDepth != 24 {
+			t.Fatalf("unexpected bit depth: %d", info.BitDepth)
+		}
+		if info.SampleRate != 96000 {
+			t.Fatalf("unexpected sample rate: %d", info.SampleRate)
+		}
+	})
+
+	t.Run("reads nested data.url", func(t *testing.T) {
+		body := []byte(`{"success":true,"data":{"url":"https://example.test/audio.flac"}}`)
+
+		got, err := extractQobuzDownloadURLFromBody(body)
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if got != "https://example.test/audio.flac" {
+			t.Fatalf("unexpected URL: %q", got)
+		}
+	})
+
+	t.Run("reads top-level url", func(t *testing.T) {
+		body := []byte(`{"url":"https://example.test/top.flac"}`)
+
+		got, err := extractQobuzDownloadURLFromBody(body)
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if got != "https://example.test/top.flac" {
+			t.Fatalf("unexpected URL: %q", got)
+		}
+	})
+
+	t.Run("returns API error", func(t *testing.T) {
+		body := []byte(`{"error":"track not found"}`)
+
+		_, err := extractQobuzDownloadURLFromBody(body)
+		if err == nil || err.Error() != "track not found" {
+			t.Fatalf("expected track-not-found error, got %v", err)
+		}
+	})
+
+	t.Run("returns message when success false", func(t *testing.T) {
+		body := []byte(`{"success":false,"message":"blocked"}`)
+
+		_, err := extractQobuzDownloadURLFromBody(body)
+		if err == nil || err.Error() != "blocked" {
+			t.Fatalf("expected blocked error, got %v", err)
+		}
+	})
+
+	t.Run("returns detail error", func(t *testing.T) {
+		body := []byte(`{"detail":"Invalid quality 'lossless'. Choose from: ['mp3', 'cd', 'hi-res', 'hi-res-max']"}`)
+
+		_, err := extractQobuzDownloadURLFromBody(body)
+		if err == nil || err.Error() != "Invalid quality 'lossless'. Choose from: ['mp3', 'cd', 'hi-res', 'hi-res-max']" {
+			t.Fatalf("expected detail error, got %v", err)
+		}
+	})
+}
+
+func TestNormalizeQobuzQualityCode(t *testing.T) {
+	tests := map[string]string{
+		"":           "6",
+		"5":          "6",
+		"6":          "6",
+		"cd":         "6",
+		"lossless":   "6",
+		"7":          "7",
+		"hi-res":     "7",
+		"27":         "27",
+		"hi-res-max": "27",
+		"unexpected": "6",
+	}
+
+	for input, want := range tests {
+		if got := normalizeQobuzQualityCode(input); got != want {
+			t.Fatalf("normalizeQobuzQualityCode(%q) = %q, want %q", input, got, want)
+		}
+	}
+}
+
+func TestGetQobuzDebugKey(t *testing.T) {
+	got := getQobuzDebugKey()
+	if len(got) != len(qobuzDebugKeyObfuscated) {
+		t.Fatalf("unexpected debug key length: %d", len(got))
+	}
+	for i := range got {
+		if got[i]^qobuzDebugKeyXORMask != qobuzDebugKeyObfuscated[i] {
+			t.Fatalf("unexpected debug key reconstruction at index %d", i)
+		}
+	}
+}
+
+func TestExtractQobuzAlbumIDsFromArtistHTML(t *testing.T) {
+	body := []byte(`
+		<button data-itemtype="album" data-itemId="0886446451985"></button>
+		<button data-itemtype="album" data-itemId="0886446451985"></button>
+		<button data-itemtype="album" data-itemId="pvv406bth40ya"></button>
+	`)
+
+	got := extractQobuzAlbumIDsFromArtistHTML(body)
+	if len(got) != 2 {
+		t.Fatalf("expected 2 unique album IDs, got %d (%v)", len(got), got)
+	}
+	if got[0] != "0886446451985" || got[1] != "pvv406bth40ya" {
+		t.Fatalf("unexpected album IDs: %v", got)
+	}
+}
+
+func TestQobuzAvailableProviders(t *testing.T) {
+	providers := NewQobuzDownloader().GetAvailableProviders()
+	if len(providers) != 5 {
+		t.Fatalf("expected 5 Qobuz providers, got %d", len(providers))
+	}
+
+	want := map[string]string{
+		"musicdl":  qobuzAPIKindMusicDL,
+		"dabmusic": qobuzAPIKindStandard,
+		"deeb":     qobuzAPIKindStandard,
+		"qbz":      qobuzAPIKindStandard,
+		"squid":    qobuzAPIKindStandard,
+	}
+
+	for _, provider := range providers {
+		wantKind, ok := want[provider.Name]
+		if !ok {
+			t.Fatalf("unexpected provider %q", provider.Name)
+		}
+		if provider.Kind != wantKind {
+			t.Fatalf("provider %q has kind %q, want %q", provider.Name, provider.Kind, wantKind)
+		}
+		delete(want, provider.Name)
+	}
+
+	if len(want) != 0 {
+		t.Fatalf("missing providers: %v", want)
+	}
+}
+
+func testQobuzTrack(id int64, title, artist string, duration int) *QobuzTrack {
+	track := &QobuzTrack{
+		ID:       id,
+		Title:    title,
+		Duration: duration,
+	}
+	track.Performer.Name = artist
+	return track
+}
+
+func TestResolveQobuzTrackForRequestRejectsSongLinkMismatch(t *testing.T) {
+	origGetTrackByID := qobuzGetTrackByIDFunc
+	origSearchISRC := qobuzSearchTrackByISRCWithDurationFunc
+	origSearchMetadata := qobuzSearchTrackByMetadataWithDurationFunc
+	origSongLinkCheck := songLinkCheckTrackAvailabilityFunc
+	t.Cleanup(func() {
+		qobuzGetTrackByIDFunc = origGetTrackByID
+		qobuzSearchTrackByISRCWithDurationFunc = origSearchISRC
+		qobuzSearchTrackByMetadataWithDurationFunc = origSearchMetadata
+		songLinkCheckTrackAvailabilityFunc = origSongLinkCheck
+		GetTrackIDCache().Clear()
+	})
+	GetTrackIDCache().Clear()
+
+	qobuzGetTrackByIDFunc = func(_ *QobuzDownloader, trackID int64) (*QobuzTrack, error) {
+		if trackID != 111 {
+			t.Fatalf("unexpected track ID lookup: %d", trackID)
+		}
+		return testQobuzTrack(111, "Aperture", "Harry Styles", 180), nil
+	}
+	qobuzSearchTrackByISRCWithDurationFunc = func(_ *QobuzDownloader, isrc string, expectedDurationSec int) (*QobuzTrack, error) {
+		if isrc != "TESTISRC1" {
+			t.Fatalf("unexpected ISRC lookup: %q", isrc)
+		}
+		if expectedDurationSec != 180 {
+			t.Fatalf("unexpected duration: %d", expectedDurationSec)
+		}
+		return testQobuzTrack(222, "Taste Back", "Harry Styles", 180), nil
+	}
+	qobuzSearchTrackByMetadataWithDurationFunc = func(_ *QobuzDownloader, _, _ string, _ int) (*QobuzTrack, error) {
+		t.Fatal("metadata fallback should not run when ISRC fallback succeeds")
+		return nil, nil
+	}
+	songLinkCheckTrackAvailabilityFunc = func(_ *SongLinkClient, spotifyTrackID string, isrc string) (*TrackAvailability, error) {
+		if spotifyTrackID != "spotify-track-id" {
+			t.Fatalf("unexpected spotify ID: %q", spotifyTrackID)
+		}
+		if isrc != "TESTISRC1" {
+			t.Fatalf("unexpected SongLink ISRC: %q", isrc)
+		}
+		return &TrackAvailability{QobuzID: "111"}, nil
+	}
+
+	req := DownloadRequest{
+		ISRC:       "TESTISRC1",
+		SpotifyID:  "spotify-track-id",
+		TrackName:  "Taste Back",
+		ArtistName: "Harry Styles",
+		DurationMS: 180000,
+	}
+
+	track, err := resolveQobuzTrackForRequest(req, &QobuzDownloader{}, "Test")
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if track == nil || track.ID != 222 || track.Title != "Taste Back" {
+		t.Fatalf("unexpected resolved track: %+v", track)
+	}
+
+	cached := GetTrackIDCache().Get(req.ISRC)
+	if cached == nil || cached.QobuzTrackID != 222 {
+		t.Fatalf("expected validated fallback track to be cached, got %+v", cached)
+	}
+}
+
+func TestResolveQobuzTrackForRequestRejectsOdesliMismatch(t *testing.T) {
+	origGetTrackByID := qobuzGetTrackByIDFunc
+	origSearchISRC := qobuzSearchTrackByISRCWithDurationFunc
+	origSearchMetadata := qobuzSearchTrackByMetadataWithDurationFunc
+	origSongLinkCheck := songLinkCheckTrackAvailabilityFunc
+	t.Cleanup(func() {
+		qobuzGetTrackByIDFunc = origGetTrackByID
+		qobuzSearchTrackByISRCWithDurationFunc = origSearchISRC
+		qobuzSearchTrackByMetadataWithDurationFunc = origSearchMetadata
+		songLinkCheckTrackAvailabilityFunc = origSongLinkCheck
+	})
+
+	qobuzGetTrackByIDFunc = func(_ *QobuzDownloader, trackID int64) (*QobuzTrack, error) {
+		if trackID != 333 {
+			t.Fatalf("unexpected track ID lookup: %d", trackID)
+		}
+		return testQobuzTrack(333, "American Girls", "Harry Styles", 181), nil
+	}
+	qobuzSearchTrackByISRCWithDurationFunc = func(_ *QobuzDownloader, _ string, _ int) (*QobuzTrack, error) {
+		t.Fatal("ISRC fallback should not run without an ISRC")
+		return nil, nil
+	}
+	qobuzSearchTrackByMetadataWithDurationFunc = func(_ *QobuzDownloader, trackName, artistName string, expectedDurationSec int) (*QobuzTrack, error) {
+		if trackName != "Taste Back" || artistName != "Harry Styles" || expectedDurationSec != 181 {
+			t.Fatalf("unexpected metadata fallback arguments: %q / %q / %d", trackName, artistName, expectedDurationSec)
+		}
+		return testQobuzTrack(444, "Taste Back", "Harry Styles", 181), nil
+	}
+	songLinkCheckTrackAvailabilityFunc = func(_ *SongLinkClient, _, _ string) (*TrackAvailability, error) {
+		t.Fatal("SongLink should not run when Odesli QobuzID is provided")
+		return nil, nil
+	}
+
+	req := DownloadRequest{
+		QobuzID:    "333",
+		TrackName:  "Taste Back",
+		ArtistName: "Harry Styles",
+		DurationMS: 181000,
+	}
+
+	track, err := resolveQobuzTrackForRequest(req, &QobuzDownloader{}, "Test")
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if track == nil || track.ID != 444 || track.Title != "Taste Back" {
+		t.Fatalf("unexpected resolved track: %+v", track)
+	}
+}
+
+func TestResolveQobuzTrackForRequestUsesPrefixedQobuzIDWithoutSongLink(t *testing.T) {
+	origGetTrackByID := qobuzGetTrackByIDFunc
+	origSearchISRC := qobuzSearchTrackByISRCWithDurationFunc
+	origSearchMetadata := qobuzSearchTrackByMetadataWithDurationFunc
+	origSongLinkCheck := songLinkCheckTrackAvailabilityFunc
+	t.Cleanup(func() {
+		qobuzGetTrackByIDFunc = origGetTrackByID
+		qobuzSearchTrackByISRCWithDurationFunc = origSearchISRC
+		qobuzSearchTrackByMetadataWithDurationFunc = origSearchMetadata
+		songLinkCheckTrackAvailabilityFunc = origSongLinkCheck
+	})
+
+	qobuzGetTrackByIDFunc = func(_ *QobuzDownloader, trackID int64) (*QobuzTrack, error) {
+		if trackID != 40681594 {
+			t.Fatalf("unexpected track ID lookup: %d", trackID)
+		}
+		return testQobuzTrack(40681594, "Sign of the Times", "Harry Styles", 341), nil
+	}
+	qobuzSearchTrackByISRCWithDurationFunc = func(_ *QobuzDownloader, _ string, _ int) (*QobuzTrack, error) {
+		t.Fatal("ISRC fallback should not run when request qobuz id succeeds")
+		return nil, nil
+	}
+	qobuzSearchTrackByMetadataWithDurationFunc = func(_ *QobuzDownloader, _, _ string, _ int) (*QobuzTrack, error) {
+		t.Fatal("metadata fallback should not run when request qobuz id succeeds")
+		return nil, nil
+	}
+	songLinkCheckTrackAvailabilityFunc = func(_ *SongLinkClient, _, _ string) (*TrackAvailability, error) {
+		t.Fatal("SongLink should not run when request qobuz id is provided")
+		return nil, nil
+	}
+
+	req := DownloadRequest{
+		QobuzID:    "qobuz:40681594",
+		TrackName:  "Sign of the Times",
+		ArtistName: "Harry Styles",
+		DurationMS: 341000,
+	}
+
+	track, err := resolveQobuzTrackForRequest(req, &QobuzDownloader{}, "Test")
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if track == nil || track.ID != 40681594 {
+		t.Fatalf("unexpected resolved track: %+v", track)
+	}
+}

go_backend/ratelimit.go

@@ -5,7 +5,6 @@ import (
 	"time"
 )
 
-// RateLimiter implements a sliding window rate limiter
 type RateLimiter struct {
 	mu          sync.Mutex
 	maxRequests int
@@ -13,7 +12,6 @@ type RateLimiter struct {
 	timestamps  []time.Time
 }
 
-// NewRateLimiter creates a new rate limiter with specified max requests per window
 func NewRateLimiter(maxRequests int, window time.Duration) *RateLimiter {
 	return &RateLimiter{
 		maxRequests: maxRequests,
@@ -22,8 +20,6 @@ func NewRateLimiter(maxRequests int, window time.Duration) *RateLimiter {
 	}
 }
 
-// WaitForSlot blocks until a request is allowed under the rate limit
-// Returns immediately if under the limit, otherwise waits until a slot is available
 func (r *RateLimiter) WaitForSlot() {
 	r.mu.Lock()
 	defer r.mu.Unlock()
@@ -52,7 +48,6 @@ func (r *RateLimiter) WaitForSlot() {
 	r.timestamps = append(r.timestamps, time.Now())
 }
 
-// cleanOldTimestamps removes timestamps that are outside the current window
 func (r *RateLimiter) cleanOldTimestamps(now time.Time) {
 	cutoff := now.Add(-r.window)
 	validStart := 0
@@ -70,8 +65,6 @@ func (r *RateLimiter) cleanOldTimestamps(now time.Time) {
 	}
 }
 
-// TryAcquire attempts to acquire a slot without blocking
-// Returns true if successful, false if rate limit would be exceeded
 func (r *RateLimiter) TryAcquire() bool {
 	r.mu.Lock()
 	defer r.mu.Unlock()
@@ -87,7 +80,6 @@ func (r *RateLimiter) TryAcquire() bool {
 	return false
 }
 
-// Available returns the number of requests available in the current window
 func (r *RateLimiter) Available() int {
 	r.mu.Lock()
 	defer r.mu.Unlock()
@@ -99,7 +91,6 @@ func (r *RateLimiter) Available() int {
 // Global SongLink rate limiter - 9 requests per minute (to be safe, limit is 10)
 var songLinkRateLimiter = NewRateLimiter(9, time.Minute)
 
-// GetSongLinkRateLimiter returns the global SongLink rate limiter
 func GetSongLinkRateLimiter() *RateLimiter {
 	return songLinkRateLimiter
 }

go_backend/romaji.go

@@ -5,7 +5,6 @@ import (
 	"unicode"
 )
 
-// Hiragana to Romaji mapping
 var hiraganaToRomaji = map[rune]string{
 	'あ': "a", 'い': "i", 'う': "u", 'え': "e", 'お': "o",
 	'か': "ka", 'き': "ki", 'く': "ku", 'け': "ke", 'こ': "ko",
@@ -30,7 +29,6 @@ var hiraganaToRomaji = map[rune]string{
 	'ぁ': "a", 'ぃ': "i", 'ぅ': "u", 'ぇ': "e", 'ぉ': "o",
 }
 
-// Katakana to Romaji mapping
 var katakanaToRomaji = map[rune]string{
 	'ア': "a", 'イ': "i", 'ウ': "u", 'エ': "e", 'オ': "o",
 	'カ': "ka", 'キ': "ki", 'ク': "ku", 'ケ': "ke", 'コ': "ko",
@@ -58,7 +56,6 @@ var katakanaToRomaji = map[rune]string{
 	'ヴ': "vu",
 }
 
-// Combination mappings for きゃ, しゃ, etc.
 var combinationHiragana = map[string]string{
 	"きゃ": "kya", "きゅ": "kyu", "きょ": "kyo",
 	"しゃ": "sha", "しゅ": "shu", "しょ": "sho",
@@ -91,7 +88,6 @@ var combinationKatakana = map[string]string{
 	"ウィ": "wi", "ウェ": "we", "ウォ": "wo",
 }
 
-// ContainsJapanese checks if a string contains Japanese characters
 func ContainsJapanese(s string) bool {
 	for _, r := range s {
 		if isHiragana(r) || isKatakana(r) || isKanji(r) {
@@ -114,8 +110,6 @@ func isKanji(r rune) bool {
 		(r >= 0x3400 && r <= 0x4DBF) // CJK Unified Ideographs Extension A
 }
 
-// JapaneseToRomaji converts Japanese text (hiragana/katakana) to romaji
-// Note: Kanji cannot be converted without a dictionary, so they are kept as-is
 func JapaneseToRomaji(text string) string {
 	if !ContainsJapanese(text) {
 		return text
@@ -175,21 +169,16 @@ func JapaneseToRomaji(text string) string {
 	return result.String()
 }
 
-// BuildSearchQuery creates a search query from track name and artist
-// Converts Japanese to romaji if present
 func BuildSearchQuery(trackName, artistName string) string {
-	// Convert Japanese to romaji
 	trackRomaji := JapaneseToRomaji(trackName)
 	artistRomaji := JapaneseToRomaji(artistName)
 
-	// Clean up the query - remove special characters that might interfere with search
 	trackClean := cleanSearchQuery(trackRomaji)
 	artistClean := cleanSearchQuery(artistRomaji)
 
 	return strings.TrimSpace(artistClean + " " + trackClean)
 }
 
-// cleanSearchQuery removes special characters that might interfere with search
 func cleanSearchQuery(s string) string {
 	var result strings.Builder
 	for _, r := range s {
@@ -202,21 +191,16 @@ func cleanSearchQuery(s string) string {
 	return strings.TrimSpace(result.String())
 }
 
-// CleanToASCII removes all non-ASCII characters and keeps only letters, numbers, spaces
-// This is useful for creating search queries that work better with Tidal's search
 func CleanToASCII(s string) string {
 	var result strings.Builder
 	for _, r := range s {
-		// Keep only ASCII letters, numbers, spaces, and basic punctuation
 		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') ||
 			(r >= '0' && r <= '9') || r == ' ' || r == '-' || r == '\'' {
 			result.WriteRune(r)
 		} else if r == ',' || r == '.' {
-			// Convert punctuation to space
 			result.WriteRune(' ')
 		}
 	}
-	// Clean up multiple spaces
 	cleaned := strings.Join(strings.Fields(result.String()), " ")
 	return strings.TrimSpace(cleaned)
 }