Merge dev into main: v3.0.0 stable release

Replaced by parallel version for faster API responses

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -0,0 +1,123 @@
+name: Bug Report
+description: Report a bug or unexpected behavior
+title: "[Bug]: "
+labels: ["bug"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for taking the time to report a bug! Please fill out the form below.
+
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      description: Please confirm the following before submitting
+      options:
+        - label: I have searched existing issues and this bug hasn't been reported yet
+          required: true
+        - label: I am using the latest version of SpotiFLAC (Stable Version)
+          required: true
+
+  - type: textarea
+    id: description
+    attributes:
+      label: Bug Description
+      description: A clear and concise description of what the bug is
+      placeholder: Describe the bug...
+    validations:
+      required: true
+
+  - type: textarea
+    id: steps
+    attributes:
+      label: Steps to Reproduce
+      description: Steps to reproduce the behavior
+      placeholder: |
+        1. Go to '...'
+        2. Click on '...'
+        3. See error
+    validations:
+      required: true
+
+  - type: textarea
+    id: expected
+    attributes:
+      label: Expected Behavior
+      description: What did you expect to happen?
+      placeholder: Describe what you expected...
+    validations:
+      required: true
+
+  - type: textarea
+    id: actual
+    attributes:
+      label: Actual Behavior
+      description: What actually happened?
+      placeholder: Describe what actually happened...
+    validations:
+      required: true
+
+  - type: input
+    id: version
+    attributes:
+      label: App Version
+      description: Which version of SpotiFLAC are you using? (Check in Settings > About)
+      placeholder: "e.g., v2.2.0"
+    validations:
+      required: true
+
+  - type: dropdown
+    id: platform
+    attributes:
+      label: Platform
+      description: Which platform are you using?
+      options:
+        - Android
+        - iOS
+    validations:
+      required: true
+
+  - type: input
+    id: device
+    attributes:
+      label: Device & OS Version
+      description: What device and OS version are you using?
+      placeholder: "e.g., Samsung Galaxy S24, Android 14"
+    validations:
+      required: true
+
+  - type: dropdown
+    id: download-service
+    attributes:
+      label: Download Service
+      description: Which download service were you using when the bug occurred?
+      options:
+        - Tidal
+        - Qobuz
+        - Amazon Music
+        - Deezer (search only)
+        - Not applicable
+    validations:
+      required: true
+
+  - type: textarea
+    id: logs
+    attributes:
+      label: Logs / Screenshots
+      description: |
+        If applicable, add logs or screenshots to help explain your problem.
+        
+        **To get logs:**
+        1. Go to Settings > Options > Detailed Logging (turn ON)
+        2. Reproduce the bug
+        3. Go to Settings > Logs
+        4. Tap Share button to export logs
+      placeholder: Paste logs or drag & drop screenshots here...
+
+  - type: textarea
+    id: additional
+    attributes:
+      label: Additional Context
+      description: Any other context about the problem
+      placeholder: Add any other context...

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - name: README
+    url: https://github.com/zarzet/SpotiFLAC-Mobile#readme
+    about: Check the README for setup instructions and FAQ
+  - name: Extension Development Guide
+    url: https://zarz.moe/docs
+    about: Documentation for building SpotiFLAC extensions

.github/ISSUE_TEMPLATE/download_issue.yml

@@ -0,0 +1,111 @@
+name: Download Issue
+description: Report issues with downloading specific tracks or albums
+title: "[Download]: "
+labels: ["download-issue"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Having trouble downloading a specific track or album? Please provide details below.
+
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      description: Please confirm the following before submitting
+      options:
+        - label: I have tried downloading with a different service (Tidal/Qobuz/Amazon)
+          required: true
+        - label: I am using the latest version of SpotiFLAC (Stable Version)
+          required: true
+
+  - type: dropdown
+    id: issue-type
+    attributes:
+      label: Issue Type
+      description: What kind of download issue are you experiencing?
+      options:
+        - Track not found on service
+        - Wrong track downloaded
+        - Download fails/errors
+        - Metadata incorrect
+        - Audio quality issue
+        - Other
+    validations:
+      required: true
+
+  - type: input
+    id: spotify-url
+    attributes:
+      label: Spotify URL
+      description: The Spotify URL of the track/album you're trying to download
+      placeholder: "https://open.spotify.com/track/..."
+    validations:
+      required: true
+
+  - type: input
+    id: track-info
+    attributes:
+      label: Track Info
+      description: Artist name and track title
+      placeholder: "Artist - Track Title"
+    validations:
+      required: true
+
+  - type: dropdown
+    id: download-service
+    attributes:
+      label: Download Service
+      description: Which service did you try to download from?
+      options:
+        - Tidal
+        - Qobuz
+        - Amazon Music
+        - All services
+    validations:
+      required: true
+
+  - type: dropdown
+    id: search-service
+    attributes:
+      label: Search Service
+      description: Which search service are you using?
+      options:
+        - Spotify
+        - Deezer
+    validations:
+      required: true
+
+  - type: textarea
+    id: description
+    attributes:
+      label: Description
+      description: Describe the issue in detail
+      placeholder: |
+        What happened? What did you expect?
+        If wrong track was downloaded, what track was downloaded instead?
+    validations:
+      required: true
+
+  - type: input
+    id: version
+    attributes:
+      label: App Version
+      description: Which version of SpotiFLAC are you using?
+      placeholder: "e.g., v2.2.0"
+    validations:
+      required: true
+
+  - type: textarea
+    id: screenshots
+    attributes:
+      label: Screenshots / Logs
+      description: |
+        If applicable, add screenshots or logs.
+        
+        **To get logs:**
+        1. Go to Settings > Options > Detailed Logging (turn ON)
+        2. Try downloading the track again
+        3. Go to Settings > Logs
+        4. Tap Share button to export logs
+      placeholder: Drag & drop screenshots or paste logs here...

.github/ISSUE_TEMPLATE/extension_feature_request.yml

@@ -0,0 +1,117 @@
+name: Extension API Feature Request
+description: Request new API features or capabilities for extension development
+title: "[Extension API]: "
+labels: ["enhancement", "extension-api"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for helping improve the SpotiFLAC Extension API! 
+        This form is for extension developers who need new features or capabilities that don't exist yet.
+
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      description: Please confirm the following before submitting
+      options:
+        - label: I have read the [Extension Development Guide](https://github.com/zarzet/SpotiFLAC-Mobile/blob/main/docs/EXTENSION_DEVELOPMENT.md)
+          required: true
+        - label: I have searched existing issues and this API feature hasn't been requested yet
+          required: true
+
+  - type: textarea
+    id: extension_goal
+    attributes:
+      label: What are you trying to build?
+      description: Describe the extension or feature you're developing
+      placeholder: "I'm building an extension that downloads from [service name] / provides metadata from [source]..."
+    validations:
+      required: true
+
+  - type: textarea
+    id: current_limitation
+    attributes:
+      label: Current API Limitation
+      description: What's missing or limiting in the current extension API?
+      placeholder: |
+        The current API doesn't support:
+        - [missing feature 1]
+        - [missing feature 2]
+        
+        This prevents me from...
+    validations:
+      required: true
+
+  - type: textarea
+    id: proposed_api
+    attributes:
+      label: Proposed API / Feature
+      description: Describe the API or feature you'd like to see added
+      placeholder: |
+        I would like to have:
+        - A new function `api.newFeature()` that does X
+        - A new manifest field `newOption` that enables Y
+        - Access to Z capability...
+    validations:
+      required: true
+
+  - type: textarea
+    id: use_case
+    attributes:
+      label: Use Case Example
+      description: Provide a code example of how you would use this feature
+      placeholder: |
+        ```javascript
+        // Example usage in extension code
+        function download(request, progressCallback) {
+          const result = api.proposedFeature(params);
+          // ...
+        }
+        ```
+    validations:
+      required: false
+
+  - type: dropdown
+    id: api_category
+    attributes:
+      label: API Category
+      description: What category does this feature fall under?
+      options:
+        - HTTP/Network API
+        - File System API
+        - Storage API
+        - FFmpeg/Audio Processing
+        - Manifest Options
+        - Runtime Functions
+        - UI Integration
+        - Authentication
+        - Other
+    validations:
+      required: true
+
+  - type: dropdown
+    id: priority
+    attributes:
+      label: How critical is this for your extension?
+      options:
+        - Blocker - Cannot build my extension without this
+        - High - Major functionality depends on this
+        - Medium - Would significantly improve my extension
+        - Low - Nice to have
+    validations:
+      required: true
+
+  - type: textarea
+    id: workaround
+    attributes:
+      label: Current Workaround
+      description: Are you using any workaround currently? If so, describe it.
+      placeholder: "Currently I'm working around this by..."
+
+  - type: textarea
+    id: additional
+    attributes:
+      label: Additional Context
+      description: Add any other context, links to similar APIs, or examples from other platforms
+      placeholder: "Similar feature in other platforms: ..."

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -0,0 +1,66 @@
+name: Feature Request
+description: Suggest a new feature or improvement
+title: "[Feature]: "
+labels: ["enhancement"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for suggesting a feature! Please fill out the form below.
+
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      description: Please confirm the following before submitting
+      options:
+        - label: I have searched existing issues and this feature hasn't been requested yet
+          required: true
+
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem / Motivation
+      description: Is your feature request related to a problem? Please describe.
+      placeholder: "A clear description of what the problem is. Ex: I'm always frustrated when..."
+    validations:
+      required: true
+
+  - type: textarea
+    id: solution
+    attributes:
+      label: Proposed Solution
+      description: Describe the solution you'd like
+      placeholder: A clear description of what you want to happen...
+    validations:
+      required: true
+
+  - type: textarea
+    id: alternatives
+    attributes:
+      label: Alternatives Considered
+      description: Describe any alternative solutions or features you've considered
+      placeholder: Other approaches you've thought about...
+
+  - type: dropdown
+    id: category
+    attributes:
+      label: Category
+      description: What category does this feature fall under?
+      options:
+        - UI/UX Improvement
+        - Download Feature
+        - New Service Integration
+        - Metadata/Tagging
+        - Performance
+        - Settings/Configuration
+        - Other
+    validations:
+      required: true
+
+  - type: textarea
+    id: additional
+    attributes:
+      label: Additional Context
+      description: Add any other context, mockups, or screenshots about the feature request
+      placeholder: Add any other context or screenshots...

.github/workflows/release.yml

@@ -3,13 +3,13 @@ name: Release
 on:
   push:
     tags:
-      - 'v*'
+      - "v*"
   workflow_dispatch:
     inputs:
       version:
-        description: 'Version tag (e.g., v1.0.0)'
+        description: "Version tag (e.g., v1.0.0)"
         required: true
-        default: 'v1.0.0'
+        default: "v1.0.0"
 
 jobs:
   # Get version first (quick job)
@@ -28,7 +28,7 @@ jobs:
             VERSION="${GITHUB_REF#refs/tags/}"
           fi
           echo "version=$VERSION" >> $GITHUB_OUTPUT
-          
+
           # Check if version contains -preview, -beta, -rc, or -alpha (NOT -hotfix)
           VERSION_LOWER=$(echo "$VERSION" | tr '[:upper:]' '[:lower:]')
           if [[ "$VERSION_LOWER" == *"-preview"* ]] || [[ "$VERSION_LOWER" == *"-beta"* ]] || [[ "$VERSION_LOWER" == *"-rc"* ]] || [[ "$VERSION_LOWER" == *"-alpha"* ]]; then
@@ -43,7 +43,7 @@ jobs:
   build-android:
     runs-on: ubuntu-latest
     needs: get-version
-    
+
     steps:
       - name: Free disk space
         run: |
@@ -65,13 +65,13 @@ jobs:
       - name: Setup Java
         uses: actions/setup-java@v4
         with:
-          distribution: 'temurin'
+          distribution: "temurin"
-          java-version: '17'
+          java-version: "17"
 
       - name: Setup Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.21'
+          go-version: "1.21"
           cache-dependency-path: go_backend/go.sum
 
       # Cache Gradle for faster builds
@@ -85,7 +85,20 @@ jobs:
           restore-keys: gradle-${{ runner.os }}-
 
       - name: Install Android SDK & NDK
-        uses: android-actions/setup-android@v3
+        run: |
+          # Use pre-installed Android SDK on GitHub runners
+          echo "ANDROID_HOME=$ANDROID_HOME"
+          echo "ANDROID_SDK_ROOT=$ANDROID_SDK_ROOT"
+
+          # Accept licenses
+          yes | $ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager --licenses || true
+
+          # Install NDK r27d LTS (required for 16KB page size support on Android 15+)
+          # Platform android-36 and build-tools 36.0.0 for targetSdk 36 (Android 16)
+          $ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager "ndk;27.3.13750724" "platforms;android-36" "build-tools;36.0.0"
+
+          # Set NDK path
+          echo "ANDROID_NDK_HOME=$ANDROID_HOME/ndk/27.3.13750724" >> $GITHUB_ENV
 
       - name: Install gomobile
         run: |
@@ -103,7 +116,7 @@ jobs:
       - name: Setup Flutter
         uses: subosito/flutter-action@v2
         with:
-          channel: 'stable'
+          channel: "stable"
           cache: true
 
       - name: Get Flutter dependencies
@@ -113,7 +126,14 @@ jobs:
         run: dart run flutter_launcher_icons
 
       - name: Build APK (Release - unsigned)
-        run: flutter build apk --release --split-per-abi
+        run: |
+          flutter build apk --release --split-per-abi || true
+          # Verify APKs were created
+          ls -la build/app/outputs/flutter-apk/
+          if [ ! -f "build/app/outputs/flutter-apk/app-arm64-v8a-release.apk" ]; then
+            echo "ERROR: APK not found!"
+            exit 1
+          fi
 
       - name: Sign APKs
         uses: r0adkll/sign-android-release@v1
@@ -125,7 +145,7 @@ jobs:
           keyStorePassword: ${{ secrets.KEYSTORE_PASSWORD }}
           keyPassword: ${{ secrets.KEY_PASSWORD }}
         env:
-          BUILD_TOOLS_VERSION: "34.0.0"
+          BUILD_TOOLS_VERSION: "36.0.0"
 
       - name: Rename APKs
         run: |
@@ -145,8 +165,8 @@ jobs:
 
   build-ios:
     runs-on: macos-latest
-    needs: get-version  # Only depends on version, NOT android build!
+    needs: get-version # Only depends on version, NOT android build!
-    
+
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
@@ -154,7 +174,7 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.21'
+          go-version: "1.21"
           cache-dependency-path: go_backend/go.sum
 
       # Cache CocoaPods
@@ -182,51 +202,51 @@ jobs:
         run: |
           ls -la ios/Frameworks/
           ls -la ios/Frameworks/Gobackend.xcframework/ || (echo "ERROR: XCFramework not found!" && exit 1)
-          
+
       - name: Add XCFramework to Xcode project
         run: |
           # Install xcodeproj gem for modifying Xcode project
           sudo gem install xcodeproj
-          
+
           # Create Ruby script to add framework
           cat > add_framework.rb << 'EOF'
           require 'xcodeproj'
-          
+
           project_path = 'ios/Runner.xcodeproj'
           project = Xcodeproj::Project.open(project_path)
-          
+
           # Get the main target
           target = project.targets.find { |t| t.name == 'Runner' }
-          
+
           # Get or create Frameworks group
           frameworks_group = project.main_group.find_subpath('Frameworks', true)
           frameworks_group ||= project.main_group.new_group('Frameworks')
-          
+
           # Add XCFramework reference
           framework_path = 'Frameworks/Gobackend.xcframework'
           framework_ref = frameworks_group.new_file(framework_path, :project)
-          
+
           # Add to frameworks build phase
           frameworks_build_phase = target.frameworks_build_phase
           frameworks_build_phase.add_file_reference(framework_ref)
-          
+
           # Add to embed frameworks build phase
           embed_phase = target.build_phases.find { |p| p.is_a?(Xcodeproj::Project::Object::PBXCopyFilesBuildPhase) && p.name == 'Embed Frameworks' }
           if embed_phase
             build_file = embed_phase.add_file_reference(framework_ref)
             build_file.settings = { 'ATTRIBUTES' => ['CodeSignOnCopy', 'RemoveHeadersOnCopy'] }
           end
-          
+
           project.save
           puts "Successfully added Gobackend.xcframework to Xcode project"
           EOF
-          
+
           ruby add_framework.rb
 
       - name: Setup Flutter
         uses: subosito/flutter-action@v2
         with:
-          channel: 'stable'
+          channel: "stable"
           cache: true
 
       # Swap pubspec for iOS build (includes ffmpeg_kit_flutter)
@@ -253,18 +273,44 @@ jobs:
         run: dart run flutter_launcher_icons
 
       - name: Build iOS (unsigned)
-        run: flutter build ios --release --no-codesign
+        run: |
+          # Build Flutter iOS without codesigning
+          flutter build ios --release --no-codesign --config-only
+
+          # Use xcodebuild with code signing disabled
+          cd ios
+          xcodebuild -workspace Runner.xcworkspace \
+            -scheme Runner \
+            -configuration Release \
+            -sdk iphoneos \
+            -destination 'generic/platform=iOS' \
+            -archivePath build/Runner.xcarchive \
+            archive \
+            CODE_SIGNING_ALLOWED=NO \
+            CODE_SIGNING_REQUIRED=NO \
+            CODE_SIGN_IDENTITY="" \
+            DEVELOPMENT_TEAM=""
 
       - name: Create IPA
         run: |
           VERSION=${{ needs.get-version.outputs.version }}
           mkdir -p build/ios/ipa
-          cd build/ios/iphoneos
+          cd ios/build/Runner.xcarchive/Products/Applications
           mkdir Payload
           cp -r Runner.app Payload/
-          zip -r ../ipa/SpotiFLAC-${VERSION}-ios-unsigned.ipa Payload
+          # Use absolute path to avoid relative path issues
+          zip -r $GITHUB_WORKSPACE/build/ios/ipa/SpotiFLAC-${VERSION}-ios-unsigned.ipa Payload
           rm -rf Payload
 
+      - name: Verify IPA created
+        run: |
+          ls -la build/ios/ipa/
+          VERSION=${{ needs.get-version.outputs.version }}
+          if [ ! -f "build/ios/ipa/SpotiFLAC-${VERSION}-ios-unsigned.ipa" ]; then
+            echo "ERROR: IPA not created!"
+            exit 1
+          fi
+
       - name: Upload IPA artifact
         uses: actions/upload-artifact@v4
         with:
@@ -276,7 +322,7 @@ jobs:
     needs: [get-version, build-android, build-ios]
     permissions:
       contents: write
-    
+
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
@@ -286,21 +332,23 @@ jobs:
         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 "$CHANGELOG" > /tmp/changelog.txt
           echo "Extracted changelog:"
@@ -322,32 +370,34 @@ jobs:
         run: |
           VERSION=${{ needs.get-version.outputs.version }}
           cat > /tmp/release_body.txt << 'HEADER'
-          ## SpotiFLAC $VERSION
-          
-          Download Spotify tracks in FLAC quality from Tidal, Qobuz & Amazon Music.
-          
           ### What's New
           HEADER
-          
+
-          # Replace $VERSION in header
-          sed -i "s/\$VERSION/$VERSION/g" /tmp/release_body.txt
-          
           cat /tmp/changelog.txt >> /tmp/release_body.txt
+
+          REPO_OWNER="${{ github.repository_owner }}"
+          REPO_NAME="${{ github.event.repository.name }}"
           
           cat >> /tmp/release_body.txt << FOOTER
-          
+
           ---
-          
+
           ### Downloads
-          - **Android (arm64)**: \`SpotiFLAC-${VERSION}-arm64.apk\` (recommended)
+
-          - **Android (arm32)**: \`SpotiFLAC-${VERSION}-arm32.apk\` (older devices)
+          #### Android
+          - **arm64**: \`SpotiFLAC-${VERSION}-arm64.apk\` (recommended for modern devices)
+          - **arm32**: \`SpotiFLAC-${VERSION}-arm32.apk\` (older devices)
+
+          #### iOS
           - **iOS**: \`SpotiFLAC-${VERSION}-ios-unsigned.ipa\` (sideload required)
-          
+
           ### Installation
           **Android**: Enable "Install from unknown sources" and install the APK
           **iOS**: Use AltStore, Sideloadly, or similar tools to sideload the IPA
+
+          ![arm64](https://img.shields.io/github/downloads/${REPO_OWNER}/${REPO_NAME}/${VERSION}/SpotiFLAC-${VERSION}-arm64.apk?style=flat-square&logo=android&label=arm64&color=3DDC84) ![arm32](https://img.shields.io/github/downloads/${REPO_OWNER}/${REPO_NAME}/${VERSION}/SpotiFLAC-${VERSION}-arm32.apk?style=flat-square&logo=android&label=arm32&color=3DDC84) ![iOS](https://img.shields.io/github/downloads/${REPO_OWNER}/${REPO_NAME}/${VERSION}/SpotiFLAC-${VERSION}-ios-unsigned.ipa?style=flat-square&logo=apple&label=iOS&color=0078D6)
           FOOTER
-          
+
           echo "Release body:"
           cat /tmp/release_body.txt
 

.gitignore

@@ -13,8 +13,8 @@ Thumbs.db
 # Reference folder (development only)
 referensi/
 
-# Development notes
+# Documentation (development only, published separately)
-COMPARISON_PC_vs_ANDROID.md
+docs/
 
 # Old spotiflac_android folder (moved to root)
 spotiflac_android/
@@ -38,7 +38,7 @@ go_backend/*.xcframework/
 
 # Android
 android/.gradle/
-android/app/libs/
+android/app/libs/gobackend.aar
 android/local.properties
 android/*.iml
 android/key.properties
@@ -52,3 +52,10 @@ ios/Pods/
 ios/.symlinks/
 ios/Flutter/Flutter.framework/
 ios/Flutter/Flutter.podspec
+android/app/libs/gobackend-sources.jar
+
+# Extension folder
+extension/
+
+# Agent instructions
+AGENTS.md

README.md

@@ -1,4 +1,5 @@
 [![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/09c6260e9ebaf2ff0d15f30deda939642f41887f11aad602ac697cb37fa0308c/)
 
 <div align="center">
 
@@ -22,14 +23,45 @@ Get Spotify tracks in true FLAC from Tidal, Qobuz & Amazon Music — no account
   <img src="assets/images/4.jpg?v=2" width="200" />
 </p>
 
+## Metadata Source
+
+SpotiFLAC supports two metadata sources for searching tracks:
+
+| Source | Pros | Cons |
+|--------|------|------|
+| **Deezer** (Default) | No developer account needed, rate limit per user IP | Slightly less comprehensive catalog |
+| **Spotify** | More comprehensive catalog, better search results | Requires developer API credentials to avoid rate limiting |
+
+### Using Spotify
+To use Spotify as your search source without hitting rate limits:
+1. Create a Spotify Developer account at [developer.spotify.com](https://developer.spotify.com)
+2. Create an app to get your Client ID and Client Secret
+3. Go to **Settings > Options > Spotify API > Change from Deezer to Spotify > Input Custom Credentials**
+4. Enter your Client ID and Secret
+5. Change **Search Source** to Spotify
+
+## Extensions
+
+Extensions allow the community to add new music sources and features without waiting for app updates. When a streaming service API changes or a new source becomes available, extensions can be updated independently.
+
+### 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**
+
+### Developing Extensions
+Want to create your own extension? Check out the [Extension Development Guide](https://zarz.moe/docs) for complete documentation.
+
 ## Other project
 
 ### [SpotiFLAC (Desktop)](https://github.com/afkarxyz/SpotiFLAC)
 Get Spotify tracks in true FLAC from Tidal, Qobuz & Amazon Music for Windows, macOS & Linux
 
-## Disclaimer
+[![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)
 
-> **iOS Support**: This app is primarily tested on Android. iOS support is experimental and may have bugs — the developer is too poor to afford an iPhone for proper testing. If you encounter issues on iOS, please report them!
+## Disclaimer
 
 This project is for **educational and private use only**. The developer does not condone or encourage copyright infringement.
 

android/app/build.gradle.kts

@@ -1,3 +1,6 @@
+import java.util.Properties
+import java.io.FileInputStream
+
 plugins {
     id("com.android.application")
     id("kotlin-android")
@@ -7,9 +10,9 @@ plugins {
 
 // Load keystore properties for local builds
 val keystorePropertiesFile = rootProject.file("key.properties")
-val keystoreProperties = java.util.Properties()
+val keystoreProperties = Properties()
 if (keystorePropertiesFile.exists()) {
-    keystoreProperties.load(java.io.FileInputStream(keystorePropertiesFile))
+    keystoreProperties.load(FileInputStream(keystorePropertiesFile))
 }
 
 android {
@@ -32,10 +35,10 @@ android {
     signingConfigs {
         if (keystorePropertiesFile.exists()) {
             create("release") {
-                keyAlias = keystoreProperties["keyAlias"] as String
+                keyAlias = keystoreProperties.getProperty("keyAlias")
-                keyPassword = keystoreProperties["keyPassword"] as String
+                keyPassword = keystoreProperties.getProperty("keyPassword")
-                storeFile = file(keystoreProperties["storeFile"] as String)
+                storeFile = file(keystoreProperties.getProperty("storeFile"))
-                storePassword = keystoreProperties["storePassword"] as String
+                storePassword = keystoreProperties.getProperty("storePassword")
             }
         }
     }
@@ -43,7 +46,7 @@ android {
     defaultConfig {
         applicationId = "com.zarz.spotiflac"
         minSdk = flutter.minSdkVersion
-        targetSdk = 34
+        targetSdk = 36
         versionCode = flutter.versionCode
         versionName = flutter.versionName
         multiDexEnabled = true
@@ -94,8 +97,10 @@ repositories {
 
 dependencies {
     coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.1.4")
-    implementation(files("libs/gobackend.aar"))
+    
-    implementation(files("libs/ffmpeg-kit-with-lame.aar"))
+    // 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")
 }

android/app/proguard-rules.pro

@@ -6,6 +6,14 @@
 -keep class io.flutter.** { *; }
 -keep class io.flutter.plugins.** { *; }
 
+# Ignore missing Play Core classes (not used, but referenced by Flutter)
+-dontwarn com.google.android.play.core.splitcompat.**
+-dontwarn com.google.android.play.core.splitinstall.**
+-dontwarn com.google.android.play.core.tasks.**
+
+# Ignore missing javax.xml.stream (not used on Android)
+-dontwarn javax.xml.stream.**
+
 # Go backend (gobackend.aar)
 -keep class gobackend.** { *; }
 -keep class go.** { *; }
@@ -14,6 +22,9 @@
 -keep class com.arthenica.ffmpegkit.** { *; }
 -keep class com.arthenica.smartexception.** { *; }
 
+# Apache Tika (if used by FFmpeg)
+-dontwarn org.apache.tika.**
+
 # Keep native methods
 -keepclasseswithmembernames class * {
     native <methods>;

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

@@ -15,6 +15,9 @@ import androidx.core.app.NotificationCompat
 /**
  * Foreground service to keep downloads running when app is in background.
  * This prevents Android from killing the download process or throttling network.
+ * 
+ * Note: Android 15+ (API 35+) has a 6-hour timeout for dataSync foreground services.
+ * The service will be stopped automatically after 6 hours of cumulative runtime in 24 hours.
  */
 class DownloadService : Service() {
     
@@ -106,6 +109,19 @@ class DownloadService : Service() {
     
     override fun onBind(intent: Intent?): IBinder? = null
     
+    /**
+     * Called when the foreground service timeout is reached (Android 15+, API 35+).
+     * dataSync services have a 6-hour limit in a 24-hour period.
+     * 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()
+    }
+    
     private fun createNotificationChannel() {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
             val channel = NotificationChannel(

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

@@ -180,6 +180,13 @@ class MainActivity: FlutterActivity() {
                             }
                             result.success(null)
                         }
+                        "readFileMetadata" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.readFileMetadata(filePath)
+                            }
+                            result.success(response)
+                        }
                         "startDownloadService" -> {
                             val trackName = call.argument<String>("track_name") ?: ""
                             val artistName = call.argument<String>("artist_name") ?: ""
@@ -211,6 +218,418 @@ class MainActivity: FlutterActivity() {
                             }
                             result.success(null)
                         }
+                        "hasSpotifyCredentials" -> {
+                            val hasCredentials = withContext(Dispatchers.IO) {
+                                Gobackend.checkSpotifyCredentials()
+                            }
+                            result.success(hasCredentials)
+                        }
+                        "preWarmTrackCache" -> {
+                            val tracksJson = call.argument<String>("tracks") ?: "[]"
+                            withContext(Dispatchers.IO) {
+                                Gobackend.preWarmTrackCacheJSON(tracksJson)
+                            }
+                            result.success(null)
+                        }
+                        "getTrackCacheSize" -> {
+                            val size = withContext(Dispatchers.IO) {
+                                Gobackend.getTrackCacheSize()
+                            }
+                            result.success(size.toInt())
+                        }
+                        "clearTrackCache" -> {
+                            withContext(Dispatchers.IO) {
+                                Gobackend.clearTrackIDCache()
+                            }
+                            result.success(null)
+                        }
+                        // Deezer API methods
+                        "searchDeezerAll" -> {
+                            val query = call.argument<String>("query") ?: ""
+                            val trackLimit = call.argument<Int>("track_limit") ?: 15
+                            val artistLimit = call.argument<Int>("artist_limit") ?: 3
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.searchDeezerAll(query, trackLimit.toLong(), artistLimit.toLong())
+                            }
+                            result.success(response)
+                        }
+                        "getDeezerMetadata" -> {
+                            val resourceType = call.argument<String>("resource_type") ?: ""
+                            val resourceId = call.argument<String>("resource_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getDeezerMetadata(resourceType, resourceId)
+                            }
+                            result.success(response)
+                        }
+                        "parseDeezerUrl" -> {
+                            val url = call.argument<String>("url") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.parseDeezerURLExport(url)
+                            }
+                            result.success(response)
+                        }
+                        "searchDeezerByISRC" -> {
+                            val isrc = call.argument<String>("isrc") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.searchDeezerByISRC(isrc)
+                            }
+                            result.success(response)
+                        }
+                        "convertSpotifyToDeezer" -> {
+                            val resourceType = call.argument<String>("resource_type") ?: ""
+                            val spotifyId = call.argument<String>("spotify_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.convertSpotifyToDeezer(resourceType, spotifyId)
+                            }
+                            result.success(response)
+                        }
+                        "getSpotifyMetadataWithFallback" -> {
+                            val url = call.argument<String>("url") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getSpotifyMetadataWithDeezerFallback(url)
+                            }
+                            result.success(response)
+                        }
+                        // Log methods
+                        "getLogs" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getLogs()
+                            }
+                            result.success(response)
+                        }
+                        "getLogsSince" -> {
+                            val index = call.argument<Int>("index") ?: 0
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getLogsSince(index.toLong())
+                            }
+                            result.success(response)
+                        }
+                        "clearLogs" -> {
+                            withContext(Dispatchers.IO) {
+                                Gobackend.clearLogs()
+                            }
+                            result.success(null)
+                        }
+                        "getLogCount" -> {
+                            val count = withContext(Dispatchers.IO) {
+                                Gobackend.getLogCount()
+                            }
+                            result.success(count.toInt())
+                        }
+                        "setLoggingEnabled" -> {
+                            val enabled = call.argument<Boolean>("enabled") ?: false
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setLoggingEnabled(enabled)
+                            }
+                            result.success(null)
+                        }
+                        // Extension System methods
+                        "initExtensionSystem" -> {
+                            val extensionsDir = call.argument<String>("extensions_dir") ?: ""
+                            val dataDir = call.argument<String>("data_dir") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.initExtensionSystem(extensionsDir, dataDir)
+                            }
+                            result.success(null)
+                        }
+                        "loadExtensionsFromDir" -> {
+                            val dirPath = call.argument<String>("dir_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.loadExtensionsFromDir(dirPath)
+                            }
+                            result.success(response)
+                        }
+                        "loadExtensionFromPath" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.loadExtensionFromPath(filePath)
+                            }
+                            result.success(response)
+                        }
+                        "unloadExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.unloadExtensionByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "removeExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.removeExtensionByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "upgradeExtension" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.upgradeExtensionFromPath(filePath)
+                            }
+                            result.success(response)
+                        }
+                        "checkExtensionUpgrade" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.checkExtensionUpgradeFromPath(filePath)
+                            }
+                            result.success(response)
+                        }
+                        "getInstalledExtensions" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getInstalledExtensions()
+                            }
+                            result.success(response)
+                        }
+                        "setExtensionEnabled" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val enabled = call.argument<Boolean>("enabled") ?: false
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionEnabledByID(extensionId, enabled)
+                            }
+                            result.success(null)
+                        }
+                        "setProviderPriority" -> {
+                            val priorityJson = call.argument<String>("priority") ?: "[]"
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setProviderPriorityJSON(priorityJson)
+                            }
+                            result.success(null)
+                        }
+                        "getProviderPriority" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getProviderPriorityJSON()
+                            }
+                            result.success(response)
+                        }
+                        "setMetadataProviderPriority" -> {
+                            val priorityJson = call.argument<String>("priority") ?: "[]"
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setMetadataProviderPriorityJSON(priorityJson)
+                            }
+                            result.success(null)
+                        }
+                        "getMetadataProviderPriority" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getMetadataProviderPriorityJSON()
+                            }
+                            result.success(response)
+                        }
+                        "getExtensionSettings" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getExtensionSettingsJSON(extensionId)
+                            }
+                            result.success(response)
+                        }
+                        "setExtensionSettings" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val settingsJson = call.argument<String>("settings") ?: "{}"
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionSettingsJSON(extensionId, settingsJson)
+                            }
+                            result.success(null)
+                        }
+                        "searchTracksWithExtensions" -> {
+                            val query = call.argument<String>("query") ?: ""
+                            val limit = call.argument<Int>("limit") ?: 20
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.searchTracksWithExtensionsJSON(query, limit.toLong())
+                            }
+                            result.success(response)
+                        }
+                        "downloadWithExtensions" -> {
+                            val requestJson = call.arguments as String
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.downloadWithExtensionsJSON(requestJson)
+                            }
+                            result.success(response)
+                        }
+                        "removeExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.removeExtensionByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "cleanupExtensions" -> {
+                            withContext(Dispatchers.IO) {
+                                Gobackend.cleanupExtensions()
+                            }
+                            result.success(null)
+                        }
+                        // Extension Auth API methods
+                        "getExtensionPendingAuth" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getExtensionPendingAuthJSON(extensionId)
+                            }
+                            if (response.isNullOrEmpty()) {
+                                result.success(null)
+                            } else {
+                                result.success(response)
+                            }
+                        }
+                        "setExtensionAuthCode" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val authCode = call.argument<String>("auth_code") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionAuthCodeByID(extensionId, authCode)
+                            }
+                            result.success(null)
+                        }
+                        "setExtensionTokens" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val accessToken = call.argument<String>("access_token") ?: ""
+                            val refreshToken = call.argument<String>("refresh_token") ?: ""
+                            val expiresIn = call.argument<Int>("expires_in") ?: 0
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionTokensByID(extensionId, accessToken, refreshToken, expiresIn.toLong())
+                            }
+                            result.success(null)
+                        }
+                        "clearExtensionPendingAuth" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.clearExtensionPendingAuthByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "isExtensionAuthenticated" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val isAuth = withContext(Dispatchers.IO) {
+                                Gobackend.isExtensionAuthenticatedByID(extensionId)
+                            }
+                            result.success(isAuth)
+                        }
+                        "getAllPendingAuthRequests" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getAllPendingAuthRequestsJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension FFmpeg API
+                        "getPendingFFmpegCommand" -> {
+                            val commandId = call.argument<String>("command_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getPendingFFmpegCommandJSON(commandId)
+                            }
+                            if (response.isNullOrEmpty()) {
+                                result.success(null)
+                            } else {
+                                result.success(response)
+                            }
+                        }
+                        "setFFmpegCommandResult" -> {
+                            val commandId = call.argument<String>("command_id") ?: ""
+                            val success = call.argument<Boolean>("success") ?: false
+                            val output = call.argument<String>("output") ?: ""
+                            val error = call.argument<String>("error") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setFFmpegCommandResultByID(commandId, success, output, error)
+                            }
+                            result.success(null)
+                        }
+                        "getAllPendingFFmpegCommands" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getAllPendingFFmpegCommandsJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension Custom Search API
+                        "customSearchWithExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val query = call.argument<String>("query") ?: ""
+                            val optionsJson = call.argument<String>("options") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.customSearchWithExtensionJSON(extensionId, query, optionsJson)
+                            }
+                            result.success(response)
+                        }
+                        "getSearchProviders" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getSearchProvidersJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension URL Handler API
+                        "handleURLWithExtension" -> {
+                            val url = call.argument<String>("url") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.handleURLWithExtensionJSON(url)
+                            }
+                            result.success(response)
+                        }
+                        "findURLHandler" -> {
+                            val url = call.argument<String>("url") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.findURLHandlerJSON(url)
+                            }
+                            result.success(response)
+                        }
+                        "getURLHandlers" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getURLHandlersJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension Post-Processing API
+                        "runPostProcessing" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val metadataJson = call.argument<String>("metadata") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.runPostProcessingJSON(filePath, metadataJson)
+                            }
+                            result.success(response)
+                        }
+                        "getPostProcessingProviders" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getPostProcessingProvidersJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension Store
+                        "initExtensionStore" -> {
+                            val cacheDir = call.argument<String>("cache_dir") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.initExtensionStoreJSON(cacheDir)
+                            }
+                            result.success(null)
+                        }
+                        "getStoreExtensions" -> {
+                            val forceRefresh = call.argument<Boolean>("force_refresh") ?: false
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getStoreExtensionsJSON(forceRefresh)
+                            }
+                            result.success(response)
+                        }
+                        "searchStoreExtensions" -> {
+                            val query = call.argument<String>("query") ?: ""
+                            val category = call.argument<String>("category") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.searchStoreExtensionsJSON(query, category)
+                            }
+                            result.success(response)
+                        }
+                        "getStoreCategories" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getStoreCategoriesJSON()
+                            }
+                            result.success(response)
+                        }
+                        "downloadStoreExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val destDir = call.argument<String>("dest_dir") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.downloadStoreExtensionJSON(extensionId, destDir)
+                            }
+                            result.success(response)
+                        }
+                        "clearStoreCache" -> {
+                            withContext(Dispatchers.IO) {
+                                Gobackend.clearStoreCacheJSON()
+                            }
+                            result.success(null)
+                        }
                         else -> result.notImplemented()
                     }
                 } catch (e: Exception) {

build_assets/ffmpeg_service_ios.dart

@@ -105,6 +105,78 @@ class FFmpegServiceIOS {
     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;
+  }
+
   /// Check if FFmpeg is available
   static Future<bool> isAvailable() async {
     try {

go_backend/amazon.go

@@ -1,6 +1,7 @@
 package gobackend
 
 import (
+	"bufio"
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
@@ -10,15 +11,26 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"time"
 )
 
 // AmazonDownloader handles Amazon Music downloads using DoubleDouble service (same as PC)
 type AmazonDownloader struct {
-	client  *http.Client
+	client           *http.Client
-	regions []string // us, eu regions for DoubleDouble service
+	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 (
+	// Global Amazon downloader instance for connection reuse
+	globalAmazonDownloader *AmazonDownloader
+	amazonDownloaderOnce   sync.Once
+	amazonRateLimitMu      sync.Mutex // Mutex for rate limiting
+)
+
 // DoubleDoubleSubmitResponse is the response from DoubleDouble submit endpoint
 type DoubleDoubleSubmitResponse struct {
 	Success bool   `json:"success"`
@@ -40,46 +52,46 @@ type DoubleDoubleStatusResponse struct {
 func amazonArtistsMatch(expectedArtist, foundArtist string) bool {
 	normExpected := strings.ToLower(strings.TrimSpace(expectedArtist))
 	normFound := strings.ToLower(strings.TrimSpace(foundArtist))
-	
+
 	// Exact match
 	if normExpected == normFound {
 		return true
 	}
-	
+
 	// Check if one contains the other
 	if strings.Contains(normExpected, normFound) || strings.Contains(normFound, normExpected) {
 		return true
 	}
-	
+
 	// Check first artist (before comma or feat)
 	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
 	}
-	
+
 	// Check if first artist is contained in the other
 	if strings.Contains(expectedFirst, foundFirst) || strings.Contains(foundFirst, expectedFirst) {
 		return true
 	}
-	
+
 	// If scripts are different (one is ASCII, one is non-ASCII like Japanese/Chinese/Korean),
 	// assume they're the same artist with different transliteration
 	expectedASCII := amazonIsASCIIString(expectedArtist)
 	foundASCII := amazonIsASCIIString(foundArtist)
 	if expectedASCII != foundASCII {
-		fmt.Printf("[Amazon] Artist names in different scripts, assuming match: '%s' vs '%s'\n", expectedArtist, foundArtist)
+		GoLog("[Amazon] Artist names in different scripts, assuming match: '%s' vs '%s'\n", expectedArtist, foundArtist)
 		return true
 	}
-	
+
 	return false
 }
 
@@ -93,12 +105,57 @@ func amazonIsASCIIString(s string) bool {
 	return true
 }
 
-// NewAmazonDownloader creates a new Amazon downloader using DoubleDouble service
+// NewAmazonDownloader creates a new Amazon downloader (returns singleton for connection reuse)
 func NewAmazonDownloader() *AmazonDownloader {
-	return &AmazonDownloader{
+	amazonDownloaderOnce.Do(func() {
-		client:  NewHTTPClientWithTimeout(120 * time.Second), // 120s timeout like PC
+		globalAmazonDownloader = &AmazonDownloader{
-		regions: []string{"us", "eu"},                        // Same regions as PC
+			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()
+
+	// Reset counter every minute
+	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)
+		}
+	}
+
+	// Update tracking
+	a.lastAPICallTime = time.Now()
+	a.apiCallCount++
 }
 
 // GetAvailableAPIs returns list of available DoubleDouble regions
@@ -113,26 +170,28 @@ func (a *AmazonDownloader) GetAvailableAPIs() []string {
 	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, outputDir string) (string, string, string, error) {
+func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, _ string) (string, string, string, error) {
 	var lastError error
 
 	for _, region := range a.regions {
-		fmt.Printf("[Amazon] Trying region: %s...\n", region)
+		GoLog("[Amazon] Trying region: %s...\n", region)
 
 		// Build base URL for DoubleDouble service
 		// Decode base64 service URL (same as PC)
-		serviceBase, _ := base64.StdEncoding.DecodeString("aHR0cHM6Ly8=")         // https://
+		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
+		// 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)
@@ -142,15 +201,43 @@ func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, outputDir
 		req.Header.Set("User-Agent", getRandomUserAgent())
 
 		fmt.Println("[Amazon] Submitting download request...")
-		resp, err := a.client.Do(req)
+
-		if err != nil {
+		// Retry logic for 429 errors (like PC version: 3 retries with 15s wait)
-			lastError = fmt.Errorf("failed to submit request: %w", err)
+		var resp *http.Response
-			continue
+		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 resp.StatusCode != 200 {
+		if err != nil || lastError != nil {
-			resp.Body.Close()
+			if resp != nil {
-			lastError = fmt.Errorf("submit failed with status %d", resp.StatusCode)
+				resp.Body.Close()
+			}
 			continue
 		}
 
@@ -168,7 +255,7 @@ func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, outputDir
 		}
 
 		downloadID := submitResp.ID
-		fmt.Printf("[Amazon] Download ID: %s\n", downloadID)
+		GoLog("[Amazon] Download ID: %s\n", downloadID)
 
 		// Step 2: Poll for completion
 		statusURL := fmt.Sprintf("%s/dl/%s", baseURL, downloadID)
@@ -223,7 +310,7 @@ func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, outputDir
 				trackName := status.Current.Name
 				artist := status.Current.Artist
 
-				fmt.Printf("[Amazon] Downloading: %s - %s\n", artist, trackName)
+				GoLog("[Amazon] Downloading: %s - %s\n", artist, trackName)
 				return fileURL, trackName, artist, nil
 
 			} else if status.Status == "error" {
@@ -257,7 +344,6 @@ func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, outputDir
 	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 {
 	// Initialize item progress (required for all downloads)
@@ -283,39 +369,70 @@ func (a *AmazonDownloader) DownloadFile(downloadURL, outputPath, itemID string)
 		return fmt.Errorf("download failed: HTTP %d", resp.StatusCode)
 	}
 
+	expectedSize := resp.ContentLength
 	// Set total bytes if available
-	if resp.ContentLength > 0 && itemID != "" {
+	if expectedSize > 0 && itemID != "" {
-		SetItemBytesTotal(itemID, resp.ContentLength)
+		SetItemBytesTotal(itemID, expectedSize)
 	}
 
 	out, err := os.Create(outputPath)
 	if err != nil {
 		return err
 	}
-	defer out.Close()
 
-	// Use item progress writer
+	// Use buffered writer for better performance (256KB buffer)
-	var bytesWritten int64
+	bufWriter := bufio.NewWriterSize(out, 256*1024)
+
+	// Use item progress writer with buffered output
+	var written int64
 	if itemID != "" {
-		pw := NewItemProgressWriter(out, itemID)
+		pw := NewItemProgressWriter(bufWriter, itemID)
-		bytesWritten, err = io.Copy(pw, resp.Body)
+		written, err = io.Copy(pw, resp.Body)
 	} else {
 		// Fallback: direct copy without progress tracking
-		bytesWritten, err = io.Copy(out, resp.Body)
+		written, err = io.Copy(bufWriter, resp.Body)
-	}
-	if err != nil {
-		return fmt.Errorf("failed to write file: %w", err)
 	}
 
-	fmt.Printf("\r[Amazon] Downloaded: %.2f MB (Complete)\n", float64(bytesWritten)/(1024*1024))
+	// Flush buffer before checking for errors
+	flushErr := bufWriter.Flush()
+	closeErr := out.Close()
+
+	// Check for any errors
+	if err != nil {
+		os.Remove(outputPath)
+		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
+	FilePath    string
-	BitDepth   int
+	BitDepth    int
-	SampleRate 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
@@ -330,7 +447,22 @@ func downloadFromAmazon(req DownloadRequest) (AmazonDownloadResult, error) {
 
 	// Get Amazon URL from SongLink
 	songlink := NewSongLinkClient()
-	availability, err := songlink.CheckTrackAvailability(req.SpotifyID, req.ISRC)
+	var availability *TrackAvailability
+	var err error
+
+	// Check if SpotifyID is actually a Deezer ID (format: "deezer:xxxxx")
+	if strings.HasPrefix(req.SpotifyID, "deezer:") {
+		// Extract Deezer ID and use Deezer-based lookup
+		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 != "" {
+		// Use Spotify ID
+		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)
 	}
@@ -354,12 +486,12 @@ func downloadFromAmazon(req DownloadRequest) (AmazonDownloadResult, error) {
 
 	// Verify artist matches
 	if artistName != "" && !amazonArtistsMatch(req.ArtistName, artistName) {
-		fmt.Printf("[Amazon] Artist mismatch: expected '%s', got '%s'. Rejecting.\n", 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)
 	}
 
 	// Log match found
-	fmt.Printf("[Amazon] Match found: '%s' by '%s'\n", trackName, artistName)
+	GoLog("[Amazon] Match found: '%s' by '%s'\n", trackName, artistName)
 
 	// Build filename using Spotify metadata (more accurate)
 	filename := buildFilenameFromTemplate(req.FilenameFormat, map[string]interface{}{
@@ -378,11 +510,29 @@ func downloadFromAmazon(req DownloadRequest) (AmazonDownloadResult, error) {
 		return AmazonDownloadResult{FilePath: "EXISTS:" + outputPath}, nil
 	}
 
-	// Download file with item ID for progress tracking
+	// 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,
+		)
+	}()
+
+	// Download audio file with item ID for progress tracking
 	if err := downloader.DownloadFile(downloadURL, outputPath, req.ItemID); err != nil {
 		return AmazonDownloadResult{}, fmt.Errorf("download failed: %w", err)
 	}
 
+	// Wait for parallel operations to complete
+	<-parallelDone
+
 	// Set progress to 100% and status to finalizing (before embedding)
 	// This makes the UI show "Finalizing..." while embedding happens
 	if req.ItemID != "" {
@@ -392,78 +542,109 @@ func downloadFromAmazon(req DownloadRequest) (AmazonDownloadResult, error) {
 
 	// Log track info from DoubleDouble (for debugging)
 	if trackName != "" && artistName != "" {
-		fmt.Printf("[Amazon] DoubleDouble returned: %s - %s\n", artistName, trackName)
+		GoLog("[Amazon] DoubleDouble returned: %s - %s\n", artistName, trackName)
+	}
+
+	// Read existing metadata from downloaded file BEFORE embedding
+	// Amazon/DoubleDouble files often have correct track/disc numbers that we should preserve
+	existingMeta, metaErr := ReadMetadata(outputPath)
+	actualTrackNum := req.TrackNumber
+	actualDiscNum := req.DiscNumber
+
+	if metaErr == nil && existingMeta != nil {
+		// Use file metadata if it has valid track/disc numbers and request doesn't have them
+		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: req.TrackNumber,
+		TrackNumber: actualTrackNum,
 		TotalTracks: req.TotalTracks,
-		DiscNumber:  req.DiscNumber,
+		DiscNumber:  actualDiscNum,
 		ISRC:        req.ISRC,
 	}
 
-	// Download cover to memory (avoids file permission issues on Android)
+	// Use cover data from parallel fetch
 	var coverData []byte
-	if req.CoverURL != "" {
+	if parallelResult != nil && parallelResult.CoverData != nil {
-		fmt.Println("[Amazon] Downloading cover to memory...")
+		coverData = parallelResult.CoverData
-		data, err := downloadCoverToMemory(req.CoverURL, req.EmbedMaxQualityCover)
+		GoLog("[Amazon] Using parallel-fetched cover (%d bytes)\n", len(coverData))
-		if err == nil {
-			coverData = data
-			fmt.Printf("[Amazon] Cover downloaded successfully (%d bytes)\n", len(coverData))
-		} else {
-			fmt.Printf("[Amazon] Warning: failed to download cover: %v\n", err)
-		}
 	}
 
 	if err := EmbedMetadataWithCoverData(outputPath, metadata, coverData); err != nil {
 		fmt.Printf("Warning: failed to embed metadata: %v\n", err)
 	}
 
-	// Embed lyrics if enabled
+	// Embed lyrics from parallel fetch
-	if req.EmbedLyrics {
+	if req.EmbedLyrics && parallelResult != nil && parallelResult.LyricsLRC != "" {
-		fmt.Println("[Amazon] Fetching lyrics...")
+		GoLog("[Amazon] Embedding parallel-fetched lyrics (%d lines)...\n", len(parallelResult.LyricsData.Lines))
-		lyricsClient := NewLyricsClient()
+		if embedErr := EmbedLyrics(outputPath, parallelResult.LyricsLRC); embedErr != nil {
-		lyrics, lyricsErr := lyricsClient.FetchLyricsAllSources(req.SpotifyID, req.TrackName, req.ArtistName)
+			GoLog("[Amazon] Warning: failed to embed lyrics: %v\n", embedErr)
-		if lyricsErr != nil {
-			fmt.Printf("[Amazon] Warning: lyrics fetch error: %v\n", lyricsErr)
-		} else if lyrics == nil || len(lyrics.Lines) == 0 {
-			fmt.Println("[Amazon] No lyrics found for this track")
 		} else {
-			fmt.Printf("[Amazon] Lyrics found (%d lines), embedding...\n", len(lyrics.Lines))
+			fmt.Println("[Amazon] Lyrics embedded successfully")
-			lrcContent := convertToLRC(lyrics)
-			if embedErr := EmbedLyrics(outputPath, lrcContent); embedErr != nil {
-				fmt.Printf("[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")
-	
+
 	// Read actual quality from the downloaded FLAC file
 	// Amazon API doesn't provide quality info, but we can read it from the file itself
 	quality, err := GetAudioQuality(outputPath)
 	if err != nil {
-		fmt.Printf("[Amazon] Warning: couldn't read quality from file: %v\n", err)
+		GoLog("[Amazon] Warning: couldn't read quality from file: %v\n", err)
-		// Return 0 to indicate unknown quality
+	} else {
-		return AmazonDownloadResult{
+		GoLog("[Amazon] Actual quality: %d-bit/%dHz\n", quality.BitDepth, quality.SampleRate)
-			FilePath:   outputPath,
-			BitDepth:   0,
-			SampleRate: 0,
-		}, nil
 	}
-	
+
-	fmt.Printf("[Amazon] Actual quality: %d-bit/%dHz\n", quality.BitDepth, quality.SampleRate)
+	// Read metadata from file AFTER embedding to get accurate values
+	// This ensures we return what's actually in the file
+	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 != "" {
+			// Use date from file if available
+			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,
+		FilePath:    outputPath,
-		BitDepth:   quality.BitDepth,
+		BitDepth:    bitDepth,
-		SampleRate: quality.SampleRate,
+		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

@@ -9,10 +9,20 @@ import (
 
 // Spotify image size codes (same as PC version)
 const (
-	spotifySize640 = "ab67616d0000b273" // 640x640
+	spotifySize300 = "ab67616d00001e02" // 300x300 (small)
+	spotifySize640 = "ab67616d0000b273" // 640x640 (medium)
 	spotifySizeMax = "ab67616d000082c1" // Max resolution (~2000x2000)
 )
 
+// 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)
+	}
+	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) {
@@ -20,17 +30,27 @@ func downloadCoverToMemory(coverURL string, maxQuality bool) ([]byte, error) {
 		return nil, fmt.Errorf("no cover URL provided")
 	}
 
-	fmt.Printf("[Cover] Downloading cover from: %s\n", coverURL)
+	GoLog("[Cover] Original URL: %s", coverURL)
 
-	// Upgrade to max quality if requested
+	// First upgrade small (300) to medium (640) - always do this
-	downloadURL := coverURL
+	downloadURL := convertSmallToMedium(coverURL)
+	if downloadURL != coverURL {
+		GoLog("[Cover] Upgraded 300x300 → 640x640")
+	}
+
+	// Then upgrade to max quality if requested
 	if maxQuality {
-		downloadURL = upgradeToMaxQuality(coverURL)
+		maxURL := upgradeToMaxQuality(downloadURL)
-		if downloadURL != coverURL {
+		if maxURL != downloadURL {
-			fmt.Printf("[Cover] Upgraded to max quality URL: %s\n", downloadURL)
+			downloadURL = maxURL
+			GoLog("[Cover] Upgraded to max resolution (~2000x2000)")
+		} else {
+			GoLog("[Cover] Max resolution not available, using 640x640")
 		}
 	}
 
+	GoLog("[Cover] Final URL: %s", downloadURL)
+
 	client := NewHTTPClientWithTimeout(DefaultTimeout)
 
 	// Create request with User-Agent (required by Spotify CDN)
@@ -54,12 +74,25 @@ func downloadCoverToMemory(coverURL string, maxQuality bool) ([]byte, error) {
 		return nil, fmt.Errorf("failed to read cover data: %w", err)
 	}
 
-	fmt.Printf("[Cover] Downloaded %d bytes\n", len(data))
+	// Calculate approximate resolution from file size
+	// JPEG ~2000x2000 is typically 300-600KB, 640x640 is ~50-100KB
+	sizeKB := len(data) / 1024
+	var resolution string
+	if sizeKB > 200 {
+		resolution = "~2000x2000 (hi-res)"
+	} else if sizeKB > 50 {
+		resolution = "~640x640"
+	} else {
+		resolution = "~300x300"
+	}
+	GoLog("[Cover] Downloaded %d KB (%s)", sizeKB, resolution)
+
 	return data, nil
 }
 
 // upgradeToMaxQuality upgrades Spotify cover URL to maximum quality
-// Uses same logic as PC version - replaces 640x640 size code with max resolution
+// Same logic as PC version - directly replaces 640x640 size code with max resolution
+// No HEAD verification needed - Spotify CDN always serves max resolution if available
 func upgradeToMaxQuality(coverURL string) string {
 	// Spotify image URLs can be upgraded by changing the size parameter
 	// Format: https://i.scdn.co/image/ab67616d0000b273...
@@ -67,21 +100,7 @@ func upgradeToMaxQuality(coverURL string) string {
 	// ab67616d000082c1 = Max resolution (~2000x2000)
 
 	if strings.Contains(coverURL, spotifySize640) {
-		// Try max resolution first
+		return strings.Replace(coverURL, spotifySize640, spotifySizeMax, 1)
-		maxURL := strings.Replace(coverURL, spotifySize640, spotifySizeMax, 1)
-
-		// Verify max resolution URL is available
-		client := NewHTTPClientWithTimeout(DefaultTimeout)
-		req, err := http.NewRequest("HEAD", maxURL, nil)
-		if err == nil {
-			resp, err := DoRequestWithUserAgent(client, req)
-			if err == nil {
-				resp.Body.Close()
-				if resp.StatusCode == http.StatusOK {
-					return maxURL
-				}
-			}
-		}
 	}
 
 	return coverURL
@@ -93,9 +112,12 @@ func GetCoverFromSpotify(imageURL string, maxQuality bool) string {
 		return ""
 	}
 
+	// Always upgrade small to medium first
+	result := convertSmallToMedium(imageURL)
+
 	if maxQuality {
-		return upgradeToMaxQuality(imageURL)
+		result = upgradeToMaxQuality(result)
 	}
 
-	return imageURL
+	return result
 }

go_backend/deezer.go

@@ -0,0 +1,750 @@
+package gobackend
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	deezerBaseURL     = "https://api.deezer.com/2.0"
+	deezerSearchURL   = deezerBaseURL + "/search"
+	deezerTrackURL    = deezerBaseURL + "/track/%s"
+	deezerAlbumURL    = deezerBaseURL + "/album/%s"
+	deezerArtistURL   = deezerBaseURL + "/artist/%s"
+	deezerPlaylistURL = deezerBaseURL + "/playlist/%s"
+
+	deezerCacheTTL = 10 * time.Minute
+
+	// Parallel ISRC fetching settings
+	deezerMaxParallelISRC = 10 // Max concurrent ISRC fetches
+)
+
+// DeezerClient handles Deezer API interactions (no auth required)
+type DeezerClient struct {
+	httpClient  *http.Client
+	searchCache map[string]*cacheEntry
+	albumCache  map[string]*cacheEntry
+	artistCache map[string]*cacheEntry
+	isrcCache   map[string]string // trackID -> ISRC cache
+	cacheMu     sync.RWMutex
+}
+
+// Singleton instance
+var (
+	deezerClient     *DeezerClient
+	deezerClientOnce sync.Once
+)
+
+// GetDeezerClient returns singleton Deezer client
+func GetDeezerClient() *DeezerClient {
+	deezerClientOnce.Do(func() {
+		deezerClient = &DeezerClient{
+			httpClient:  NewHTTPClientWithTimeout(15 * time.Second),
+			searchCache: make(map[string]*cacheEntry),
+			albumCache:  make(map[string]*cacheEntry),
+			artistCache: make(map[string]*cacheEntry),
+			isrcCache:   make(map[string]string),
+		}
+	})
+	return deezerClient
+}
+
+// Deezer API response types
+type deezerTrack struct {
+	ID            int64             `json:"id"`
+	Title         string            `json:"title"`
+	Duration      int               `json:"duration"` // in seconds
+	TrackPosition int               `json:"track_position"`
+	DiskNumber    int               `json:"disk_number"`
+	ISRC          string            `json:"isrc"`
+	Link          string            `json:"link"`
+	ReleaseDate   string            `json:"release_date"` // Sometimes at track level
+	Artist        deezerArtist      `json:"artist"`
+	Album         deezerAlbumSimple `json:"album"`
+	Contributors  []deezerArtist    `json:"contributors"`
+}
+
+type deezerArtist struct {
+	ID            int64  `json:"id"`
+	Name          string `json:"name"`
+	Picture       string `json:"picture"`
+	PictureMedium string `json:"picture_medium"`
+	PictureBig    string `json:"picture_big"`
+	PictureXL     string `json:"picture_xl"`
+	NbFan         int    `json:"nb_fan"`
+}
+
+type deezerAlbumSimple struct {
+	ID          int64  `json:"id"`
+	Title       string `json:"title"`
+	Cover       string `json:"cover"`
+	CoverMedium string `json:"cover_medium"`
+	CoverBig    string `json:"cover_big"`
+	CoverXL     string `json:"cover_xl"`
+	ReleaseDate string `json:"release_date"` // Sometimes at album level
+}
+
+// ... (skip other structs as they are fine/unchanged) ...
+
+// ... (in convertTrack) ...
+func (c *DeezerClient) convertTrack(track deezerTrack) TrackMetadata {
+	artistName := track.Artist.Name
+	if len(track.Contributors) > 0 {
+		names := make([]string, len(track.Contributors))
+		for i, a := range track.Contributors {
+			names[i] = a.Name
+		}
+		artistName = strings.Join(names, ", ")
+	}
+
+	albumImage := track.Album.CoverXL
+	if albumImage == "" {
+		albumImage = track.Album.CoverBig
+	}
+	if albumImage == "" {
+		albumImage = track.Album.CoverMedium
+	}
+	if albumImage == "" {
+		albumImage = track.Album.Cover
+	}
+
+	// Try to find release date
+	releaseDate := track.ReleaseDate
+	if releaseDate == "" {
+		releaseDate = track.Album.ReleaseDate
+	}
+
+	return TrackMetadata{
+		SpotifyID:   fmt.Sprintf("deezer:%d", track.ID),
+		Artists:     artistName,
+		Name:        track.Title,
+		AlbumName:   track.Album.Title,
+		AlbumArtist: track.Artist.Name,
+		DurationMS:  track.Duration * 1000,
+		Images:      albumImage,
+		ReleaseDate: releaseDate, // Added this
+		TrackNumber: track.TrackPosition,
+		DiscNumber:  track.DiskNumber,
+		ExternalURL: track.Link,
+		ISRC:        track.ISRC,
+	}
+}
+
+type deezerAlbumFull struct {
+	ID           int64          `json:"id"`
+	Title        string         `json:"title"`
+	Cover        string         `json:"cover"`
+	CoverMedium  string         `json:"cover_medium"`
+	CoverBig     string         `json:"cover_big"`
+	CoverXL      string         `json:"cover_xl"`
+	ReleaseDate  string         `json:"release_date"`
+	NbTracks     int            `json:"nb_tracks"`
+	RecordType   string         `json:"record_type"` // album, single, ep, compile
+	Artist       deezerArtist   `json:"artist"`
+	Contributors []deezerArtist `json:"contributors"`
+	Tracks       struct {
+		Data []deezerTrack `json:"data"`
+	} `json:"tracks"`
+}
+
+type deezerArtistFull struct {
+	ID            int64  `json:"id"`
+	Name          string `json:"name"`
+	Picture       string `json:"picture"`
+	PictureMedium string `json:"picture_medium"`
+	PictureBig    string `json:"picture_big"`
+	PictureXL     string `json:"picture_xl"`
+	NbFan         int    `json:"nb_fan"`
+	NbAlbum       int    `json:"nb_album"`
+}
+
+type deezerPlaylistFull struct {
+	ID            int64  `json:"id"`
+	Title         string `json:"title"`
+	Picture       string `json:"picture"`
+	PictureMedium string `json:"picture_medium"`
+	PictureBig    string `json:"picture_big"`
+	PictureXL     string `json:"picture_xl"`
+	NbTracks      int    `json:"nb_tracks"`
+	Creator       struct {
+		Name string `json:"name"`
+	} `json:"creator"`
+	Tracks struct {
+		Data []deezerTrack `json:"data"`
+	} `json:"tracks"`
+}
+
+// SearchAll searches for tracks and artists on Deezer
+// NOTE: ISRC is NOT fetched during search for performance - use GetTrackISRC when needed for download
+func (c *DeezerClient) SearchAll(ctx context.Context, query string, trackLimit, artistLimit int) (*SearchAllResult, error) {
+	GoLog("[Deezer] SearchAll: query=%q, trackLimit=%d, artistLimit=%d\n", query, trackLimit, artistLimit)
+
+	cacheKey := fmt.Sprintf("deezer:all:%s:%d:%d", query, trackLimit, artistLimit)
+
+	c.cacheMu.RLock()
+	if entry, ok := c.searchCache[cacheKey]; ok && !entry.isExpired() {
+		c.cacheMu.RUnlock()
+		GoLog("[Deezer] SearchAll: returning cached result\n")
+		return entry.data.(*SearchAllResult), nil
+	}
+	c.cacheMu.RUnlock()
+
+	result := &SearchAllResult{
+		Tracks:  make([]TrackMetadata, 0),
+		Artists: make([]SearchArtistResult, 0),
+	}
+
+	// Search tracks - NO ISRC fetch for performance
+	trackURL := fmt.Sprintf("%s/track?q=%s&limit=%d", deezerSearchURL, url.QueryEscape(query), trackLimit)
+	GoLog("[Deezer] Fetching tracks from: %s\n", trackURL)
+
+	var trackResp struct {
+		Data  []deezerTrack `json:"data"`
+		Error *struct {
+			Type    string `json:"type"`
+			Message string `json:"message"`
+			Code    int    `json:"code"`
+		} `json:"error"`
+	}
+	if err := c.getJSON(ctx, trackURL, &trackResp); err != nil {
+		GoLog("[Deezer] Track search failed: %v\n", err)
+		return nil, fmt.Errorf("deezer track search failed: %w", err)
+	}
+
+	if trackResp.Error != nil {
+		GoLog("[Deezer] API error: type=%s, code=%d, message=%s\n", trackResp.Error.Type, trackResp.Error.Code, trackResp.Error.Message)
+		return nil, fmt.Errorf("deezer API error: %s (code %d)", trackResp.Error.Message, trackResp.Error.Code)
+	}
+
+	GoLog("[Deezer] Got %d tracks from API\n", len(trackResp.Data))
+
+	for _, track := range trackResp.Data {
+		// Convert directly without fetching ISRC - much faster
+		result.Tracks = append(result.Tracks, c.convertTrack(track))
+	}
+
+	// Search artists
+	artistURL := fmt.Sprintf("%s/artist?q=%s&limit=%d", deezerSearchURL, url.QueryEscape(query), artistLimit)
+	GoLog("[Deezer] Fetching artists from: %s\n", artistURL)
+
+	var artistResp struct {
+		Data  []deezerArtist `json:"data"`
+		Error *struct {
+			Type    string `json:"type"`
+			Message string `json:"message"`
+			Code    int    `json:"code"`
+		} `json:"error"`
+	}
+	if err := c.getJSON(ctx, artistURL, &artistResp); err == nil {
+		if artistResp.Error != nil {
+			GoLog("[Deezer] Artist API error: type=%s, code=%d, message=%s\n", artistResp.Error.Type, artistResp.Error.Code, artistResp.Error.Message)
+		} else {
+			GoLog("[Deezer] Got %d artists from API\n", len(artistResp.Data))
+			for _, artist := range artistResp.Data {
+				result.Artists = append(result.Artists, SearchArtistResult{
+					ID:         fmt.Sprintf("deezer:%d", artist.ID),
+					Name:       artist.Name,
+					Images:     c.getBestArtistImage(artist),
+					Followers:  artist.NbFan,
+					Popularity: 0,
+				})
+			}
+		}
+	} else {
+		GoLog("[Deezer] Artist search failed: %v\n", err)
+	}
+
+	GoLog("[Deezer] SearchAll complete: %d tracks, %d artists\n", len(result.Tracks), len(result.Artists))
+
+	// Cache result
+	c.cacheMu.Lock()
+	c.searchCache[cacheKey] = &cacheEntry{
+		data:      result,
+		expiresAt: time.Now().Add(deezerCacheTTL),
+	}
+	c.cacheMu.Unlock()
+
+	return result, nil
+}
+
+// GetTrack fetches a single track by Deezer ID
+func (c *DeezerClient) GetTrack(ctx context.Context, trackID string) (*TrackResponse, error) {
+	trackURL := fmt.Sprintf(deezerTrackURL, trackID)
+
+	var track deezerTrack
+	if err := c.getJSON(ctx, trackURL, &track); err != nil {
+		return nil, err
+	}
+
+	return &TrackResponse{
+		Track: c.convertTrack(track),
+	}, nil
+}
+
+// GetAlbum fetches album with tracks
+// ISRC is fetched in parallel for better performance
+func (c *DeezerClient) GetAlbum(ctx context.Context, albumID string) (*AlbumResponsePayload, error) {
+	c.cacheMu.RLock()
+	if entry, ok := c.albumCache[albumID]; ok && !entry.isExpired() {
+		c.cacheMu.RUnlock()
+		return entry.data.(*AlbumResponsePayload), nil
+	}
+	c.cacheMu.RUnlock()
+
+	albumURL := fmt.Sprintf(deezerAlbumURL, albumID)
+
+	var album deezerAlbumFull
+	if err := c.getJSON(ctx, albumURL, &album); err != nil {
+		return nil, err
+	}
+
+	albumImage := c.getBestAlbumImage(album)
+	artistName := album.Artist.Name
+	if len(album.Contributors) > 0 {
+		names := make([]string, len(album.Contributors))
+		for i, a := range album.Contributors {
+			names[i] = a.Name
+		}
+		artistName = strings.Join(names, ", ")
+	}
+
+	info := AlbumInfoMetadata{
+		TotalTracks: album.NbTracks,
+		Name:        album.Title,
+		ReleaseDate: album.ReleaseDate,
+		Artists:     artistName,
+		Images:      albumImage,
+	}
+
+	// Fetch ISRCs in parallel
+	isrcMap := c.fetchISRCsParallel(ctx, album.Tracks.Data)
+
+	tracks := make([]AlbumTrackMetadata, 0, len(album.Tracks.Data))
+	// Normalize record_type (Deezer uses "compile" instead of "compilation")
+	albumType := album.RecordType
+	if albumType == "compile" {
+		albumType = "compilation"
+	}
+
+	for _, track := range album.Tracks.Data {
+		trackIDStr := fmt.Sprintf("%d", track.ID)
+		isrc := isrcMap[trackIDStr]
+
+		tracks = append(tracks, AlbumTrackMetadata{
+			SpotifyID:   fmt.Sprintf("deezer:%d", track.ID),
+			Artists:     track.Artist.Name,
+			Name:        track.Title,
+			AlbumName:   album.Title,
+			AlbumArtist: artistName,
+			DurationMS:  track.Duration * 1000,
+			Images:      albumImage,
+			ReleaseDate: album.ReleaseDate,
+			TrackNumber: track.TrackPosition,
+			TotalTracks: album.NbTracks,
+			DiscNumber:  track.DiskNumber,
+			ExternalURL: track.Link,
+			ISRC:        isrc,
+			AlbumID:     fmt.Sprintf("deezer:%d", album.ID),
+			AlbumType:   albumType,
+		})
+	}
+
+	result := &AlbumResponsePayload{
+		AlbumInfo: info,
+		TrackList: tracks,
+	}
+
+	c.cacheMu.Lock()
+	c.albumCache[albumID] = &cacheEntry{
+		data:      result,
+		expiresAt: time.Now().Add(deezerCacheTTL),
+	}
+	c.cacheMu.Unlock()
+
+	return result, nil
+}
+
+// GetArtist fetches artist with albums
+func (c *DeezerClient) GetArtist(ctx context.Context, artistID string) (*ArtistResponsePayload, error) {
+	c.cacheMu.RLock()
+	if entry, ok := c.artistCache[artistID]; ok && !entry.isExpired() {
+		c.cacheMu.RUnlock()
+		return entry.data.(*ArtistResponsePayload), nil
+	}
+	c.cacheMu.RUnlock()
+
+	// Fetch artist info
+	artistURL := fmt.Sprintf(deezerArtistURL, artistID)
+	var artist deezerArtistFull
+	if err := c.getJSON(ctx, artistURL, &artist); err != nil {
+		return nil, err
+	}
+
+	artistInfo := ArtistInfoMetadata{
+		ID:         fmt.Sprintf("deezer:%d", artist.ID),
+		Name:       artist.Name,
+		Images:     c.getBestArtistImageFull(artist),
+		Followers:  artist.NbFan,
+		Popularity: 0,
+	}
+
+	// Fetch artist albums
+	albumsURL := fmt.Sprintf("%s/albums?limit=100", fmt.Sprintf(deezerArtistURL, artistID))
+	var albumsResp struct {
+		Data []struct {
+			ID          int64  `json:"id"`
+			Title       string `json:"title"`
+			ReleaseDate string `json:"release_date"`
+			NbTracks    int    `json:"nb_tracks"`
+			Cover       string `json:"cover"`
+			CoverMedium string `json:"cover_medium"`
+			CoverBig    string `json:"cover_big"`
+			CoverXL     string `json:"cover_xl"`
+			RecordType  string `json:"record_type"` // album, single, ep, compile
+		} `json:"data"`
+	}
+
+	albums := make([]ArtistAlbumMetadata, 0)
+	if err := c.getJSON(ctx, albumsURL, &albumsResp); err == nil {
+		for _, album := range albumsResp.Data {
+			albumType := album.RecordType
+			if albumType == "compile" {
+				albumType = "compilation"
+			}
+
+			coverURL := album.CoverXL
+			if coverURL == "" {
+				coverURL = album.CoverBig
+			}
+			if coverURL == "" {
+				coverURL = album.CoverMedium
+			}
+			if coverURL == "" {
+				coverURL = album.Cover
+			}
+
+			albums = append(albums, ArtistAlbumMetadata{
+				ID:          fmt.Sprintf("deezer:%d", album.ID),
+				Name:        album.Title,
+				ReleaseDate: album.ReleaseDate,
+				TotalTracks: album.NbTracks,
+				Images:      coverURL,
+				AlbumType:   albumType,
+				Artists:     artist.Name,
+			})
+		}
+	}
+
+	result := &ArtistResponsePayload{
+		ArtistInfo: artistInfo,
+		Albums:     albums,
+	}
+
+	c.cacheMu.Lock()
+	c.artistCache[artistID] = &cacheEntry{
+		data:      result,
+		expiresAt: time.Now().Add(deezerCacheTTL),
+	}
+	c.cacheMu.Unlock()
+
+	return result, nil
+}
+
+// GetPlaylist fetches playlist with tracks
+// ISRC is fetched in parallel for better performance
+func (c *DeezerClient) GetPlaylist(ctx context.Context, playlistID string) (*PlaylistResponsePayload, error) {
+	playlistURL := fmt.Sprintf(deezerPlaylistURL, playlistID)
+
+	var playlist deezerPlaylistFull
+	if err := c.getJSON(ctx, playlistURL, &playlist); err != nil {
+		return nil, err
+	}
+
+	playlistImage := playlist.PictureXL
+	if playlistImage == "" {
+		playlistImage = playlist.PictureBig
+	}
+	if playlistImage == "" {
+		playlistImage = playlist.PictureMedium
+	}
+
+	var info PlaylistInfoMetadata
+	info.Tracks.Total = playlist.NbTracks
+	info.Owner.DisplayName = playlist.Creator.Name
+	info.Owner.Name = playlist.Title
+	info.Owner.Images = playlistImage
+
+	// Fetch ISRCs in parallel
+	isrcMap := c.fetchISRCsParallel(ctx, playlist.Tracks.Data)
+
+	tracks := make([]AlbumTrackMetadata, 0, len(playlist.Tracks.Data))
+	for _, track := range playlist.Tracks.Data {
+		albumImage := track.Album.CoverXL
+		if albumImage == "" {
+			albumImage = track.Album.CoverBig
+		}
+		if albumImage == "" {
+			albumImage = track.Album.CoverMedium
+		}
+
+		trackIDStr := fmt.Sprintf("%d", track.ID)
+		isrc := isrcMap[trackIDStr]
+
+		tracks = append(tracks, AlbumTrackMetadata{
+			SpotifyID:   fmt.Sprintf("deezer:%d", track.ID),
+			Artists:     track.Artist.Name,
+			Name:        track.Title,
+			AlbumName:   track.Album.Title,
+			AlbumArtist: track.Artist.Name,
+			DurationMS:  track.Duration * 1000,
+			Images:      albumImage,
+			ReleaseDate: "",
+			TrackNumber: track.TrackPosition,
+			DiscNumber:  track.DiskNumber,
+			ExternalURL: track.Link,
+			ISRC:        isrc,
+			AlbumID:     fmt.Sprintf("deezer:%d", track.Album.ID),
+		})
+	}
+
+	return &PlaylistResponsePayload{
+		PlaylistInfo: info,
+		TrackList:    tracks,
+	}, nil
+}
+
+// SearchByISRC searches for a track by ISRC using direct endpoint
+func (c *DeezerClient) SearchByISRC(ctx context.Context, isrc string) (*TrackMetadata, error) {
+	// Use direct ISRC endpoint (API 2.0)
+	// https://api.deezer.com/2.0/track/isrc:{ISRC}
+	directURL := fmt.Sprintf("%s/track/isrc:%s", deezerBaseURL, isrc)
+
+	var track deezerTrack
+	if err := c.getJSON(ctx, directURL, &track); err != nil {
+		// Fallback to search if direct endpoint fails
+		searchURL := fmt.Sprintf("%s/track?q=isrc:%s&limit=1", deezerSearchURL, isrc)
+		var resp struct {
+			Data []deezerTrack `json:"data"`
+		}
+		if err := c.getJSON(ctx, searchURL, &resp); err != nil {
+			return nil, err
+		}
+		if len(resp.Data) == 0 {
+			return nil, fmt.Errorf("no track found for ISRC: %s", isrc)
+		}
+		result := c.convertTrack(resp.Data[0])
+		return &result, nil
+	}
+
+	// Check if we got a valid response (ID > 0)
+	if track.ID == 0 {
+		return nil, fmt.Errorf("no track found for ISRC: %s", isrc)
+	}
+
+	result := c.convertTrack(track)
+	return &result, nil
+}
+
+func (c *DeezerClient) fetchFullTrack(ctx context.Context, trackID string) (*deezerTrack, error) {
+	trackURL := fmt.Sprintf(deezerTrackURL, trackID)
+	var track deezerTrack
+	if err := c.getJSON(ctx, trackURL, &track); err != nil {
+		return nil, err
+	}
+	return &track, nil
+}
+
+// fetchISRCsParallel fetches ISRCs for multiple tracks in parallel with caching
+func (c *DeezerClient) fetchISRCsParallel(ctx context.Context, tracks []deezerTrack) map[string]string {
+	result := make(map[string]string)
+	var resultMu sync.Mutex
+
+	// First, check cache for existing ISRCs
+	var tracksToFetch []deezerTrack
+	c.cacheMu.RLock()
+	for _, track := range tracks {
+		trackIDStr := fmt.Sprintf("%d", track.ID)
+		if isrc, ok := c.isrcCache[trackIDStr]; ok {
+			result[trackIDStr] = isrc
+		} else {
+			tracksToFetch = append(tracksToFetch, track)
+		}
+	}
+	c.cacheMu.RUnlock()
+
+	if len(tracksToFetch) == 0 {
+		return result
+	}
+
+	// Use semaphore to limit concurrent requests
+	sem := make(chan struct{}, deezerMaxParallelISRC)
+	var wg sync.WaitGroup
+
+	for _, track := range tracksToFetch {
+		wg.Add(1)
+		go func(t deezerTrack) {
+			defer wg.Done()
+
+			// Acquire semaphore
+			select {
+			case sem <- struct{}{}:
+				defer func() { <-sem }()
+			case <-ctx.Done():
+				return
+			}
+
+			trackIDStr := fmt.Sprintf("%d", t.ID)
+			fullTrack, err := c.fetchFullTrack(ctx, trackIDStr)
+			if err != nil || fullTrack == nil {
+				return
+			}
+
+			// Store in result and cache
+			resultMu.Lock()
+			result[trackIDStr] = fullTrack.ISRC
+			resultMu.Unlock()
+
+			c.cacheMu.Lock()
+			c.isrcCache[trackIDStr] = fullTrack.ISRC
+			c.cacheMu.Unlock()
+		}(track)
+	}
+
+	wg.Wait()
+	return result
+}
+
+// GetTrackISRC fetches ISRC for a single track (with caching)
+// Use this when you need ISRC for download
+func (c *DeezerClient) GetTrackISRC(ctx context.Context, trackID string) (string, error) {
+	// Check cache first
+	c.cacheMu.RLock()
+	if isrc, ok := c.isrcCache[trackID]; ok {
+		c.cacheMu.RUnlock()
+		return isrc, nil
+	}
+	c.cacheMu.RUnlock()
+
+	// Fetch from API
+	fullTrack, err := c.fetchFullTrack(ctx, trackID)
+	if err != nil {
+		return "", err
+	}
+
+	// Cache the result
+	c.cacheMu.Lock()
+	c.isrcCache[trackID] = fullTrack.ISRC
+	c.cacheMu.Unlock()
+
+	return fullTrack.ISRC, nil
+}
+
+func (c *DeezerClient) getBestArtistImage(artist deezerArtist) string {
+	if artist.PictureXL != "" {
+		return artist.PictureXL
+	}
+	if artist.PictureBig != "" {
+		return artist.PictureBig
+	}
+	if artist.PictureMedium != "" {
+		return artist.PictureMedium
+	}
+	return artist.Picture
+}
+
+func (c *DeezerClient) getBestArtistImageFull(artist deezerArtistFull) string {
+	if artist.PictureXL != "" {
+		return artist.PictureXL
+	}
+	if artist.PictureBig != "" {
+		return artist.PictureBig
+	}
+	if artist.PictureMedium != "" {
+		return artist.PictureMedium
+	}
+	return artist.Picture
+}
+
+func (c *DeezerClient) getBestAlbumImage(album deezerAlbumFull) string {
+	if album.CoverXL != "" {
+		return album.CoverXL
+	}
+	if album.CoverBig != "" {
+		return album.CoverBig
+	}
+	if album.CoverMedium != "" {
+		return album.CoverMedium
+	}
+	return album.Cover
+}
+
+func (c *DeezerClient) getJSON(ctx context.Context, endpoint string, dst interface{}) error {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("Accept", "application/json")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("deezer API returned status %d: %s", resp.StatusCode, string(body))
+	}
+
+	return json.Unmarshal(body, dst)
+}
+
+// parseDeezerURL is internal function, returns type and ID
+func parseDeezerURL(input string) (string, string, error) {
+	trimmed := strings.TrimSpace(input)
+	if trimmed == "" {
+		return "", "", fmt.Errorf("empty URL")
+	}
+
+	parsed, err := url.Parse(trimmed)
+	if err != nil {
+		return "", "", err
+	}
+
+	if parsed.Host != "www.deezer.com" && parsed.Host != "deezer.com" && parsed.Host != "deezer.page.link" {
+		return "", "", fmt.Errorf("not a Deezer URL")
+	}
+
+	parts := strings.Split(strings.Trim(parsed.Path, "/"), "/")
+
+	// Skip language prefix if present (e.g., /en/, /fr/)
+	if len(parts) > 0 && len(parts[0]) == 2 {
+		parts = parts[1:]
+	}
+
+	if len(parts) < 2 {
+		return "", "", fmt.Errorf("invalid Deezer URL format")
+	}
+
+	resourceType := parts[0]
+	resourceID := parts[1]
+
+	switch resourceType {
+	case "track", "album", "artist", "playlist":
+		return resourceType, resourceID, nil
+	default:
+		return "", "", fmt.Errorf("unsupported Deezer resource type: %s", resourceType)
+	}
+}

go_backend/duplicate.go

@@ -1,49 +1,144 @@
 package gobackend
 
 import (
+	"encoding/json"
+	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
+	"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
+	buildTime time.Time
+	mu        sync.RWMutex
+}
+
+// Global ISRC index cache (per output directory)
+var (
+	isrcIndexCache   = make(map[string]*ISRCIndex)
+	isrcIndexCacheMu sync.RWMutex
+	isrcIndexTTL     = 5 * time.Minute // Cache TTL - rebuild after 5 minutes
+)
+
+// GetISRCIndex returns or builds an ISRC index for the given directory
+func GetISRCIndex(outputDir string) *ISRCIndex {
+	isrcIndexCacheMu.RLock()
+	idx, exists := isrcIndexCache[outputDir]
+	isrcIndexCacheMu.RUnlock()
+
+	// Return cached index if still valid
+	if exists && time.Since(idx.buildTime) < isrcIndexTTL {
+		return idx
+	}
+
+	// Build new index
+	return buildISRCIndex(outputDir)
+}
+
+// buildISRCIndex scans a directory and builds a map of ISRC -> file path
+// Same implementation as PC version for consistency
+func buildISRCIndex(outputDir string) *ISRCIndex {
+	idx := &ISRCIndex{
+		index:     make(map[string]string),
+		outputDir: outputDir,
+		buildTime: time.Now(),
+	}
+
+	if outputDir == "" {
+		return idx
+	}
+
+	startTime := time.Now()
+	fileCount := 0
+
+	// Walk directory - only check .flac files
+	filepath.Walk(outputDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil || info.IsDir() {
+			return nil
+		}
+
+		ext := strings.ToLower(filepath.Ext(path))
+		if ext != ".flac" {
+			return nil
+		}
+
+		// Read ISRC from file
+		metadata, err := ReadMetadata(path)
+		if err != nil || metadata.ISRC == "" {
+			return nil
+		}
+
+		// Store in index (uppercase for case-insensitive matching)
+		idx.index[strings.ToUpper(metadata.ISRC)] = path
+		fileCount++
+		return nil
+	})
+
+	fmt.Printf("[ISRCIndex] Built index for %s: %d files in %v\n", 
+		outputDir, fileCount, time.Since(startTime).Round(time.Millisecond))
+
+	// Cache the index
+	isrcIndexCacheMu.Lock()
+	isrcIndexCache[outputDir] = idx
+	isrcIndexCacheMu.Unlock()
+
+	return idx
+}
+
+// lookup checks if an ISRC exists in the index (internal, returns bool)
+func (idx *ISRCIndex) lookup(isrc string) (string, bool) {
+	if isrc == "" {
+		return "", false
+	}
+
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+
+	path, exists := idx.index[strings.ToUpper(isrc)]
+	return path, exists
+}
+
+// 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
+	}
+
+	idx.mu.Lock()
+	defer idx.mu.Unlock()
+
+	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
 	}
 
-	// Walk through directory looking for FLAC files
+	// Use index for fast lookup
-	var foundFile string
+	idx := GetISRCIndex(outputDir)
-	filepath.Walk(outputDir, func(path string, info os.FileInfo, err error) error {
+	return idx.lookup(isrc)
-		if err != nil {
-			return nil
-		}
-
-		// Only check FLAC files
-		if info.IsDir() || !strings.HasSuffix(strings.ToLower(path), ".flac") {
-			return nil
-		}
-
-		// Read metadata from file
-		metadata, err := ReadMetadata(path)
-		if err != nil {
-			return nil
-		}
-
-		// Check if ISRC matches
-		if metadata.ISRC == isrc {
-			foundFile = path
-			return filepath.SkipAll // Stop walking
-		}
-
-		return nil
-	})
-
-	if foundFile != "" {
-		return foundFile, true
-	}
-
-	return "", false
 }
 
 // CheckISRCExists is the exported version for gomobile (returns string, error)
@@ -61,3 +156,98 @@ 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"`
+	FilePath   string `json:"file_path,omitempty"`
+	TrackName  string `json:"track_name,omitempty"`
+	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) {
+	// Parse input JSON
+	var tracks []struct {
+		ISRC       string `json:"isrc"`
+		TrackName  string `json:"track_name"`
+		ArtistName string `json:"artist_name"`
+	}
+	if err := json.Unmarshal([]byte(tracksJSON), &tracks); err != nil {
+		return "", fmt.Errorf("failed to parse tracks JSON: %w", err)
+	}
+
+	results := make([]FileExistenceResult, len(tracks))
+
+	// Build ISRC index from output directory (scan once)
+	isrcIdx := GetISRCIndex(outputDir)
+
+	// Check each track against the index (parallel)
+	var wg sync.WaitGroup
+	for i, track := range tracks {
+		wg.Add(1)
+		go func(resultIdx int, t struct {
+			ISRC       string `json:"isrc"`
+			TrackName  string `json:"track_name"`
+			ArtistName string `json:"artist_name"`
+		}) {
+			defer wg.Done()
+
+			result := FileExistenceResult{
+				ISRC:       t.ISRC,
+				TrackName:  t.TrackName,
+				ArtistName: t.ArtistName,
+				Exists:     false,
+			}
+
+			if t.ISRC != "" {
+				if filePath, exists := isrcIdx.lookup(t.ISRC); exists {
+					result.Exists = true
+					result.FilePath = filePath
+				}
+			}
+
+			results[resultIdx] = result
+		}(i, track)
+	}
+
+	wg.Wait()
+
+	// Return results as JSON
+	resultJSON, err := json.Marshal(results)
+	if err != nil {
+		return "", fmt.Errorf("failed to marshal results: %w", err)
+	}
+
+	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")
+	}
+
+	buildISRCIndex(outputDir)
+	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
+	}
+
+	isrcIndexCacheMu.RLock()
+	idx, exists := isrcIndexCache[outputDir]
+	isrcIndexCacheMu.RUnlock()
+
+	if exists {
+		idx.Add(isrc, filePath)
+	}
+}

go_backend/extension_manifest.go

@@ -0,0 +1,315 @@
+// Package gobackend provides extension manifest parsing and validation
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// ExtensionType represents the type of extension
+type ExtensionType string
+
+const (
+	ExtensionTypeMetadataProvider ExtensionType = "metadata_provider"
+	ExtensionTypeDownloadProvider ExtensionType = "download_provider"
+)
+
+// SettingType represents the type of a setting field
+type SettingType string
+
+const (
+	SettingTypeString SettingType = "string"
+	SettingTypeNumber SettingType = "number"
+	SettingTypeBool   SettingType = "boolean"
+	SettingTypeSelect SettingType = "select"
+)
+
+// 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
+}
+
+// ExtensionSetting defines a configurable setting for an extension
+type ExtensionSetting struct {
+	Key         string      `json:"key"`
+	Type        SettingType `json:"type"`
+	Label       string      `json:"label"`
+	Description string      `json:"description,omitempty"`
+	Required    bool        `json:"required,omitempty"`
+	Secret      bool        `json:"secret,omitempty"`
+	Default     interface{} `json:"default,omitempty"`
+	Options     []string    `json:"options,omitempty"` // For select type
+}
+
+// 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
+}
+
+// QualitySpecificSetting represents a setting that's specific to a quality option
+type QualitySpecificSetting struct {
+	Key         string      `json:"key"`
+	Type        SettingType `json:"type"`
+	Label       string      `json:"label"`
+	Description string      `json:"description,omitempty"`
+	Required    bool        `json:"required,omitempty"`
+	Secret      bool        `json:"secret,omitempty"`
+	Default     interface{} `json:"default,omitempty"`
+	Options     []string    `json:"options,omitempty"` // For select type
+}
+
+// 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
+}
+
+// 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")
+}
+
+// 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
+}
+
+// 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"])
+}
+
+// PostProcessingConfig defines post-processing capabilities
+type PostProcessingConfig struct {
+	Enabled bool                 `json:"enabled"`         // Whether extension provides post-processing
+	Hooks   []PostProcessingHook `json:"hooks,omitempty"` // Available hooks
+}
+
+// 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
+}
+
+// ManifestValidationError represents a validation error in the manifest
+type ManifestValidationError struct {
+	Field   string
+	Message string
+}
+
+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 {
+		return nil, fmt.Errorf("failed to parse manifest JSON: %w", err)
+	}
+
+	if err := manifest.Validate(); err != nil {
+		return nil, err
+	}
+
+	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"}
+	}
+
+	if strings.TrimSpace(m.Version) == "" {
+		return &ManifestValidationError{Field: "version", Message: "version is required"}
+	}
+
+	if strings.TrimSpace(m.Author) == "" {
+		return &ManifestValidationError{Field: "author", Message: "author is required"}
+	}
+
+	if strings.TrimSpace(m.Description) == "" {
+		return &ManifestValidationError{Field: "description", Message: "description is required"}
+	}
+
+	if len(m.Types) == 0 {
+		return &ManifestValidationError{Field: "type", Message: "at least one type is required"}
+	}
+
+	// Validate extension types
+	for _, t := range m.Types {
+		if t != ExtensionTypeMetadataProvider && t != ExtensionTypeDownloadProvider {
+			return &ManifestValidationError{
+				Field:   "type",
+				Message: fmt.Sprintf("invalid extension type: %s (must be 'metadata_provider' or 'download_provider')", t),
+			}
+		}
+	}
+
+	// Validate settings if present
+	for i, setting := range m.Settings {
+		if strings.TrimSpace(setting.Key) == "" {
+			return &ManifestValidationError{
+				Field:   fmt.Sprintf("settings[%d].key", i),
+				Message: "setting key is required",
+			}
+		}
+
+		if setting.Type == "" {
+			return &ManifestValidationError{
+				Field:   fmt.Sprintf("settings[%d].type", i),
+				Message: "setting type is required",
+			}
+		}
+
+		// Validate setting type
+		validTypes := map[SettingType]bool{
+			SettingTypeString: true,
+			SettingTypeNumber: true,
+			SettingTypeBool:   true,
+			SettingTypeSelect: 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{
+				Field:   fmt.Sprintf("settings[%d].options", i),
+				Message: "select type requires options",
+			}
+		}
+	}
+
+	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 {
+			return true
+		}
+	}
+	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) IsDomainAllowed(domain string) bool {
+	domain = strings.ToLower(strings.TrimSpace(domain))
+	for _, allowed := range m.Permissions.Network {
+		allowed = strings.ToLower(strings.TrimSpace(allowed))
+		if allowed == domain {
+			return true
+		}
+		// Support wildcard subdomains (e.g., *.example.com)
+		if strings.HasPrefix(allowed, "*.") {
+			suffix := allowed[1:] // Remove the *
+			if strings.HasSuffix(domain, suffix) {
+				return true
+			}
+		}
+	}
+	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
+		}
+	}
+	return false
+}
+
+// GetPostProcessingHooks returns all post-processing hooks
+func (m *ExtensionManifest) GetPostProcessingHooks() []PostProcessingHook {
+	if m.PostProcessing == nil {
+		return nil
+	}
+	return m.PostProcessing.Hooks
+}
+
+// ToJSON serializes the manifest to JSON
+func (m *ExtensionManifest) ToJSON() ([]byte, error) {
+	return json.Marshal(m)
+}

go_backend/extension_runtime.go

@@ -0,0 +1,340 @@
+// Package gobackend provides extension runtime with sandboxed execution
+package gobackend
+
+import (
+	"net/http"
+	"net/url"
+	"sync"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// Default timeout for JS execution (30 seconds)
+const DefaultJSTimeout = 30 * time.Second
+
+// Global auth state for extensions (stores pending auth codes)
+var (
+	extensionAuthState   = make(map[string]*ExtensionAuthState)
+	extensionAuthStateMu sync.RWMutex
+)
+
+// ExtensionAuthState holds auth state for an extension
+type ExtensionAuthState struct {
+	PendingAuthURL  string
+	AuthCode        string
+	AccessToken     string
+	RefreshToken    string
+	ExpiresAt       time.Time
+	IsAuthenticated bool
+	// PKCE support
+	PKCEVerifier  string
+	PKCEChallenge string
+}
+
+// PendingAuthRequest holds a pending OAuth request that needs Flutter to open URL
+type PendingAuthRequest struct {
+	ExtensionID string
+	AuthURL     string
+	CallbackURL string
+}
+
+// Global pending auth requests (Flutter polls this)
+var (
+	pendingAuthRequests   = make(map[string]*PendingAuthRequest)
+	pendingAuthRequestsMu sync.RWMutex
+)
+
+// GetPendingAuthRequest returns pending auth request for an extension (called from Flutter)
+func GetPendingAuthRequest(extensionID string) *PendingAuthRequest {
+	pendingAuthRequestsMu.RLock()
+	defer pendingAuthRequestsMu.RUnlock()
+	return pendingAuthRequests[extensionID]
+}
+
+// ClearPendingAuthRequest clears pending auth request (called from Flutter after opening URL)
+func ClearPendingAuthRequest(extensionID string) {
+	pendingAuthRequestsMu.Lock()
+	defer pendingAuthRequestsMu.Unlock()
+	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()
+
+	state, exists := extensionAuthState[extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[extensionID] = state
+	}
+	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()
+
+	state, exists := extensionAuthState[extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[extensionID] = state
+	}
+	state.AccessToken = accessToken
+	state.RefreshToken = refreshToken
+	state.ExpiresAt = expiresAt
+	state.IsAuthenticated = accessToken != ""
+}
+
+// ExtensionRuntime provides sandboxed APIs for extensions
+type ExtensionRuntime struct {
+	extensionID string
+	manifest    *ExtensionManifest
+	settings    map[string]interface{}
+	httpClient  *http.Client
+	cookieJar   http.CookieJar
+	dataDir     string
+	vm          *goja.Runtime
+}
+
+// NewExtensionRuntime creates a new runtime for an extension
+func NewExtensionRuntime(ext *LoadedExtension) *ExtensionRuntime {
+	// Create a cookie jar for this extension
+	jar, _ := newSimpleCookieJar()
+
+	runtime := &ExtensionRuntime{
+		extensionID: ext.ID,
+		manifest:    ext.Manifest,
+		settings:    make(map[string]interface{}),
+		cookieJar:   jar,
+		dataDir:     ext.DataDir,
+		vm:          ext.VM,
+	}
+
+	// Create HTTP client with redirect validation to prevent SSRF via open redirect
+	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
+		},
+	}
+	runtime.httpClient = client
+
+	return runtime
+}
+
+// RedirectBlockedError is returned when a redirect is blocked due to domain validation
+type RedirectBlockedError struct {
+	Domain    string
+	IsPrivate bool
+}
+
+func (e *RedirectBlockedError) Error() string {
+	if e.IsPrivate {
+		return "redirect blocked: private/local network access denied"
+	}
+	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 := 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" {
+		return true
+	}
+
+	return false
+}
+
+// simpleCookieJar is a simple in-memory cookie jar
+type simpleCookieJar struct {
+	cookies map[string][]*http.Cookie
+	mu      sync.RWMutex
+}
+
+func newSimpleCookieJar() (*simpleCookieJar, error) {
+	return &simpleCookieJar{
+		cookies: make(map[string][]*http.Cookie),
+	}, nil
+}
+
+func (j *simpleCookieJar) SetCookies(u *url.URL, cookies []*http.Cookie) {
+	j.mu.Lock()
+	defer j.mu.Unlock()
+	key := u.Host
+	j.cookies[key] = append(j.cookies[key], cookies...)
+}
+
+func (j *simpleCookieJar) Cookies(u *url.URL) []*http.Cookie {
+	j.mu.RLock()
+	defer j.mu.RUnlock()
+	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("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)
+	credentialsObj.Set("remove", r.credentialsRemove)
+	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)
+	authObj.Set("setAuthCode", r.authSetCode)
+	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)
+	fileObj.Set("delete", r.fileDelete)
+	fileObj.Set("read", r.fileRead)
+	fileObj.Set("write", r.fileWrite)
+	fileObj.Set("copy", r.fileCopy)
+	fileObj.Set("move", r.fileMove)
+	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)
+	utilsObj.Set("md5", r.md5Hash)
+	utilsObj.Set("sha256", r.sha256Hash)
+	utilsObj.Set("hmacSHA256", r.hmacSHA256)
+	utilsObj.Set("hmacSHA256Base64", r.hmacSHA256Base64)
+	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)
+	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)
+	logObj.Set("warn", r.logWarn)
+	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

@@ -0,0 +1,547 @@
+// Package gobackend provides Auth API and PKCE support for extension runtime
+package gobackend
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Auth API (OAuth Support) ====================
+
+// 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{}{
+			"success": false,
+			"error":   "auth URL is required",
+		})
+	}
+
+	authURL := call.Arguments[0].String()
+	callbackURL := ""
+	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) {
+		callbackURL = call.Arguments[1].String()
+	}
+
+	// Store pending auth request for Flutter to pick up
+	pendingAuthRequestsMu.Lock()
+	pendingAuthRequests[r.extensionID] = &PendingAuthRequest{
+		ExtensionID: r.extensionID,
+		AuthURL:     authURL,
+		CallbackURL: callbackURL,
+	}
+	pendingAuthRequestsMu.Unlock()
+
+	// Update auth state
+	extensionAuthStateMu.Lock()
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.PendingAuthURL = authURL
+	state.AuthCode = "" // Clear any previous auth code
+	extensionAuthStateMu.Unlock()
+
+	GoLog("[Extension:%s] Auth URL requested: %s\n", r.extensionID, authURL)
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"message": "Auth URL will be opened by the app",
+	})
+}
+
+// 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()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists || state.AuthCode == "" {
+		return goja.Undefined()
+	}
+
+	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()
+	defer extensionAuthStateMu.Unlock()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+
+	switch v := arg.(type) {
+	case string:
+		state.AuthCode = v
+	case map[string]interface{}:
+		if code, ok := v["code"].(string); ok {
+			state.AuthCode = code
+		}
+		if accessToken, ok := v["access_token"].(string); ok {
+			state.AccessToken = accessToken
+			state.IsAuthenticated = true
+		}
+		if refreshToken, ok := v["refresh_token"].(string); ok {
+			state.RefreshToken = refreshToken
+		}
+		if expiresIn, ok := v["expires_in"].(float64); ok {
+			state.ExpiresAt = time.Now().Add(time.Duration(expiresIn) * time.Second)
+		}
+	}
+
+	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)
+	extensionAuthStateMu.Unlock()
+
+	pendingAuthRequestsMu.Lock()
+	delete(pendingAuthRequests, r.extensionID)
+	pendingAuthRequestsMu.Unlock()
+
+	GoLog("[Extension:%s] Auth state cleared\n", r.extensionID)
+	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()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		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)
+	}
+
+	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()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		return r.vm.ToValue(map[string]interface{}{})
+	}
+
+	result := map[string]interface{}{
+		"access_token":     state.AccessToken,
+		"refresh_token":    state.RefreshToken,
+		"is_authenticated": state.IsAuthenticated,
+	}
+
+	if !state.ExpiresAt.IsZero() {
+		result["expires_at"] = state.ExpiresAt.Unix()
+		result["is_expired"] = time.Now().After(state.ExpiresAt)
+	}
+
+	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 {
+		length = 43
+	}
+	if length > 128 {
+		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]
+	}
+
+	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 {
+			length = int(l)
+		}
+	}
+
+	verifier, err := generatePKCEVerifier(length)
+	if err != nil {
+		GoLog("[Extension:%s] PKCE generation error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	challenge := generatePKCEChallenge(verifier)
+
+	// Store in auth state for later use
+	extensionAuthStateMu.Lock()
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.PKCEVerifier = verifier
+	state.PKCEChallenge = challenge
+	extensionAuthStateMu.Unlock()
+
+	GoLog("[Extension:%s] PKCE generated (verifier length: %d)\n", r.extensionID, len(verifier))
+
+	return r.vm.ToValue(map[string]interface{}{
+		"verifier":  verifier,
+		"challenge": challenge,
+		"method":    "S256",
+	})
+}
+
+// authGetPKCE returns the current PKCE verifier and challenge (if generated)
+func (r *ExtensionRuntime) authGetPKCE(call goja.FunctionCall) goja.Value {
+	extensionAuthStateMu.RLock()
+	defer extensionAuthStateMu.RUnlock()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists || state.PKCEVerifier == "" {
+		return r.vm.ToValue(map[string]interface{}{})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"verifier":  state.PKCEVerifier,
+		"challenge": state.PKCEChallenge,
+		"method":    "S256",
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "config object is required",
+		})
+	}
+
+	configObj := call.Arguments[0].Export()
+	config, ok := configObj.(map[string]interface{})
+	if !ok {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "config must be an object",
+		})
+	}
+
+	// Required fields
+	authURL, _ := config["authUrl"].(string)
+	clientID, _ := config["clientId"].(string)
+	redirectURI, _ := config["redirectUri"].(string)
+
+	if authURL == "" || clientID == "" || redirectURI == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "authUrl, clientId, and redirectUri are required",
+		})
+	}
+
+	// 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{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to generate PKCE: %v", err),
+		})
+	}
+	challenge := generatePKCEChallenge(verifier)
+
+	// Store PKCE in auth state
+	extensionAuthStateMu.Lock()
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.PKCEVerifier = verifier
+	state.PKCEChallenge = challenge
+	state.AuthCode = "" // Clear any previous auth code
+	extensionAuthStateMu.Unlock()
+
+	// Build OAuth URL with PKCE parameters
+	parsedURL, err := url.Parse(authURL)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("invalid authUrl: %v", err),
+		})
+	}
+
+	query := parsedURL.Query()
+	query.Set("client_id", clientID)
+	query.Set("redirect_uri", redirectURI)
+	query.Set("response_type", "code")
+	query.Set("code_challenge", challenge)
+	query.Set("code_challenge_method", "S256")
+
+	if scope != "" {
+		query.Set("scope", scope)
+	}
+
+	// Add extra params
+	for k, v := range extraParams {
+		query.Set(k, fmt.Sprintf("%v", v))
+	}
+
+	parsedURL.RawQuery = query.Encode()
+	fullAuthURL := parsedURL.String()
+
+	// Store pending auth request for Flutter
+	pendingAuthRequestsMu.Lock()
+	pendingAuthRequests[r.extensionID] = &PendingAuthRequest{
+		ExtensionID: r.extensionID,
+		AuthURL:     fullAuthURL,
+		CallbackURL: redirectURI,
+	}
+	pendingAuthRequestsMu.Unlock()
+
+	GoLog("[Extension:%s] PKCE OAuth started: %s\n", r.extensionID, fullAuthURL)
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"authUrl": fullAuthURL,
+		"pkce": map[string]interface{}{
+			"verifier":  verifier,
+			"challenge": challenge,
+			"method":    "S256",
+		},
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "config object is required",
+		})
+	}
+
+	configObj := call.Arguments[0].Export()
+	config, ok := configObj.(map[string]interface{})
+	if !ok {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "config must be an object",
+		})
+	}
+
+	// Required fields
+	tokenURL, _ := config["tokenUrl"].(string)
+	clientID, _ := config["clientId"].(string)
+	redirectURI, _ := config["redirectUri"].(string)
+	code, _ := config["code"].(string)
+
+	if tokenURL == "" || clientID == "" || code == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "tokenUrl, clientId, and code are required",
+		})
+	}
+
+	// Get stored PKCE verifier
+	extensionAuthStateMu.RLock()
+	state, exists := extensionAuthState[r.extensionID]
+	var verifier string
+	if exists {
+		verifier = state.PKCEVerifier
+	}
+	extensionAuthStateMu.RUnlock()
+
+	if verifier == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "no PKCE verifier found - call generatePKCE or startOAuthWithPKCE first",
+		})
+	}
+
+	// Validate domain
+	if err := r.validateDomain(tokenURL); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Build token request body
+	formData := url.Values{}
+	formData.Set("grant_type", "authorization_code")
+	formData.Set("client_id", clientID)
+	formData.Set("code", code)
+	formData.Set("code_verifier", verifier)
+	if redirectURI != "" {
+		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{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("User-Agent", "SpotiFLAC-Extension/1.0")
+
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// 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),
+		})
+	}
+
+	// Check for error in response
+	if errMsg, ok := tokenResp["error"].(string); ok {
+		errDesc, _ := tokenResp["error_description"].(string)
+		return r.vm.ToValue(map[string]interface{}{
+			"success":           false,
+			"error":             errMsg,
+			"error_description": errDesc,
+		})
+	}
+
+	// Extract tokens
+	accessToken, _ := tokenResp["access_token"].(string)
+	refreshToken, _ := tokenResp["refresh_token"].(string)
+	expiresIn, _ := tokenResp["expires_in"].(float64)
+
+	if accessToken == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "no access_token in response",
+			"body":    string(body),
+		})
+	}
+
+	// Store tokens in auth state
+	extensionAuthStateMu.Lock()
+	state, exists = extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.AccessToken = accessToken
+	state.RefreshToken = refreshToken
+	state.IsAuthenticated = true
+	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,
+		"refresh_token": refreshToken,
+		"token_type":    tokenResp["token_type"],
+	}
+	if expiresIn > 0 {
+		result["expires_in"] = expiresIn
+	}
+	// Include any additional fields from response
+	if scope, ok := tokenResp["scope"].(string); ok {
+		result["scope"] = scope
+	}
+
+	return r.vm.ToValue(result)
+}

go_backend/extension_runtime_ffmpeg.go

@@ -0,0 +1,204 @@
+// Package gobackend provides FFmpeg API for extension runtime
+package gobackend
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== FFmpeg API (Post-Processing) ====================
+
+// FFmpegCommand holds a pending FFmpeg command for Flutter to execute
+type FFmpegCommand struct {
+	ExtensionID string
+	Command     string
+	InputPath   string
+	OutputPath  string
+	Completed   bool
+	Success     bool
+	Error       string
+	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()
+	if cmd, exists := ffmpegCommands[commandID]; exists {
+		cmd.Completed = true
+		cmd.Success = success
+		cmd.Output = output
+		cmd.Error = errorMsg
+	}
+}
+
+// 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{}{
+			"success": false,
+			"error":   "command is required",
+		})
+	}
+
+	command := call.Arguments[0].String()
+
+	// Generate unique command ID
+	ffmpegCommandsMu.Lock()
+	ffmpegCommandID++
+	cmdID := fmt.Sprintf("%s_%d", r.extensionID, ffmpegCommandID)
+	ffmpegCommands[cmdID] = &FFmpegCommand{
+		ExtensionID: r.extensionID,
+		Command:     command,
+		Completed:   false,
+	}
+	ffmpegCommandsMu.Unlock()
+
+	GoLog("[Extension:%s] FFmpeg command queued: %s\n", r.extensionID, cmdID)
+
+	// Wait for completion (with timeout)
+	timeout := 5 * time.Minute
+	start := time.Now()
+	for {
+		ffmpegCommandsMu.RLock()
+		cmd := ffmpegCommands[cmdID]
+		completed := cmd != nil && cmd.Completed
+		ffmpegCommandsMu.RUnlock()
+
+		if completed {
+			ffmpegCommandsMu.RLock()
+			result := map[string]interface{}{
+				"success": cmd.Success,
+				"output":  cmd.Output,
+			}
+			if cmd.Error != "" {
+				result["error"] = cmd.Error
+			}
+			ffmpegCommandsMu.RUnlock()
+
+			// Cleanup
+			ClearFFmpegCommand(cmdID)
+			return r.vm.ToValue(result)
+		}
+
+		if time.Since(start) > timeout {
+			ClearFFmpegCommand(cmdID)
+			return r.vm.ToValue(map[string]interface{}{
+				"success": false,
+				"error":   "FFmpeg command timed out",
+			})
+		}
+
+		time.Sleep(100 * time.Millisecond)
+	}
+}
+
+// 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{}{
+			"success": false,
+			"error":   "file path is required",
+		})
+	}
+
+	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{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success":       true,
+		"bit_depth":     quality.BitDepth,
+		"sample_rate":   quality.SampleRate,
+		"total_samples": quality.TotalSamples,
+		"duration":      float64(quality.TotalSamples) / float64(quality.SampleRate),
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "input and output paths are required",
+		})
+	}
+
+	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 {
+			options = opts
+		}
+	}
+
+	// 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)},
+	}
+	return r.ffmpegExecute(execCall)
+}

go_backend/extension_runtime_file.go

@@ -0,0 +1,523 @@
+// Package gobackend provides File API for extension runtime
+package gobackend
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"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()
+	allowedDownloadDirs = dirs
+	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()
+	absDir, err := filepath.Abs(dir)
+	if err == nil {
+		allowedDownloadDirs = append(allowedDownloadDirs, absDir)
+	}
+}
+
+// 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) {
+			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 (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) {
+		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{}{
+			"success": false,
+			"error":   "URL and output path are required",
+		})
+	}
+
+	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,
+			"error":   err.Error(),
+		})
+	}
+
+	// Validate output path (allows absolute paths for download queue)
+	fullPath, err := r.validatePath(outputPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// 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
+				}
+			}
+		}
+	}
+
+	// Create directory if needed
+	dir := filepath.Dir(fullPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	// Create HTTP request
+	req, err := http.NewRequest("GET", urlStr, nil)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Set headers
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	if req.Header.Get("User-Agent") == "" {
+		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{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("HTTP error: %d", resp.StatusCode),
+		})
+	}
+
+	// Create output file
+	out, err := os.Create(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create file: %v", err),
+		})
+	}
+	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
+	for {
+		nr, er := resp.Body.Read(buf)
+		if nr > 0 {
+			nw, ew := out.Write(buf[0:nr])
+			if nw < 0 || nr < nw {
+				nw = 0
+				if ew == nil {
+					ew = fmt.Errorf("invalid write result")
+				}
+			}
+			written += int64(nw)
+			if ew != nil {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   fmt.Sprintf("failed to write file: %v", ew),
+				})
+			}
+			if nr != nw {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   "short write",
+				})
+			}
+
+			// Report progress
+			if onProgress != nil && contentLength > 0 {
+				_, _ = onProgress(goja.Undefined(), r.vm.ToValue(written), r.vm.ToValue(contentLength))
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   fmt.Sprintf("failed to read response: %v", er),
+				})
+			}
+			break
+		}
+	}
+
+	GoLog("[Extension:%s] Downloaded %d bytes to %s\n", r.extensionID, written, fullPath)
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullPath,
+		"size":    written,
+	})
+}
+
+// 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)
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(false)
+	}
+
+	_, err = os.Stat(fullPath)
+	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{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	if err := os.Remove(fullPath); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	data, err := os.ReadFile(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"data":    string(data),
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "path and data are required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	data := call.Arguments[1].String()
+
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Create directory if needed
+	dir := filepath.Dir(fullPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	if err := os.WriteFile(fullPath, []byte(data), 0644); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullPath,
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "source and destination paths are required",
+		})
+	}
+
+	srcPath := call.Arguments[0].String()
+	dstPath := call.Arguments[1].String()
+
+	fullSrc, err := r.validatePath(srcPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	fullDst, err := r.validatePath(dstPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Read source file
+	data, err := os.ReadFile(fullSrc)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to read source: %v", err),
+		})
+	}
+
+	// Create destination directory if needed
+	dir := filepath.Dir(fullDst)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	// Write to destination
+	if err := os.WriteFile(fullDst, data, 0644); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to write destination: %v", err),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullDst,
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "source and destination paths are required",
+		})
+	}
+
+	srcPath := call.Arguments[0].String()
+	dstPath := call.Arguments[1].String()
+
+	fullSrc, err := r.validatePath(srcPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	fullDst, err := r.validatePath(dstPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Create destination directory if needed
+	dir := filepath.Dir(fullDst)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	if err := os.Rename(fullSrc, fullDst); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to move file: %v", err),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullDst,
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	info, err := os.Stat(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"size":    info.Size(),
+	})
+}

go_backend/extension_runtime_http.go

@@ -0,0 +1,505 @@
+// Package gobackend provides HTTP API for extension runtime
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"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()
+
+	// Block private/local network access (SSRF protection)
+	if isPrivateIP(domain) {
+		return fmt.Errorf("network access denied: private/local network '%s' not allowed", domain)
+	}
+
+	if !r.manifest.IsDomainAllowed(domain) {
+		return fmt.Errorf("network access denied: domain '%s' not in allowed list", domain)
+	}
+
+	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{}{
+			"error": "URL is required",
+		})
+	}
+
+	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{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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()
+		if h, ok := headersObj.(map[string]interface{}); ok {
+			for k, v := range h {
+				headers[k] = fmt.Sprintf("%v", v)
+			}
+		}
+	}
+
+	// Create request
+	req, err := http.NewRequest("GET", urlStr, nil)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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
+		}
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode, // Alias for convenience
+		"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{}{
+			"error": "URL is required",
+		})
+	}
+
+	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{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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()
+		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{}{
+					"error": fmt.Sprintf("failed to stringify body: %v", err),
+				})
+			}
+			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()
+		if h, ok := headersObj.(map[string]interface{}); ok {
+			for k, v := range h {
+				headers[k] = fmt.Sprintf("%v", v)
+			}
+		}
+	}
+
+	// Create request
+	req, err := http.NewRequest("POST", urlStr, strings.NewReader(bodyStr))
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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")
+	}
+	if req.Header.Get("Content-Type") == "" {
+		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{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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
+		}
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode, // Alias for convenience
+		"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{}{
+			"error": "URL is required",
+		})
+	}
+
+	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{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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{}{
+							"error": fmt.Sprintf("failed to stringify body: %v", err),
+						})
+					}
+					bodyStr = string(jsonBytes)
+				default:
+					bodyStr = fmt.Sprintf("%v", v)
+				}
+			}
+
+			// Get headers
+			if h, ok := opts["headers"].(map[string]interface{}); ok {
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+		}
+	}
+
+	// Create request
+	var reqBody io.Reader
+	if bodyStr != "" {
+		reqBody = strings.NewReader(bodyStr)
+	}
+
+	req, err := http.NewRequest(method, urlStr, reqBody)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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")
+	}
+	if bodyStr != "" && req.Header.Get("Content-Type") == "" {
+		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{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// 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
+		}
+	}
+
+	// Return response with helper properties
+	return r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode, // Alias for convenience
+		"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{}{
+			"error": "URL is required",
+		})
+	}
+
+	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{}{
+			"error": err.Error(),
+		})
+	}
+
+	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 {
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+		}
+	} 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) {
+			case string:
+				bodyStr = v
+			case map[string]interface{}, []interface{}:
+				jsonBytes, err := json.Marshal(v)
+				if err != nil {
+					return r.vm.ToValue(map[string]interface{}{
+						"error": fmt.Sprintf("failed to stringify body: %v", err),
+					})
+				}
+				bodyStr = string(jsonBytes)
+			default:
+				bodyStr = call.Arguments[1].String()
+			}
+		}
+
+		if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
+			headersObj := call.Arguments[2].Export()
+			if h, ok := headersObj.(map[string]interface{}); ok {
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+		}
+	}
+
+	// Create request
+	var reqBody io.Reader
+	if bodyStr != "" {
+		reqBody = strings.NewReader(bodyStr)
+	}
+
+	req, err := http.NewRequest(method, urlStr, reqBody)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Set headers - user headers first
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
+	}
+	if bodyStr != "" && req.Header.Get("Content-Type") == "" {
+		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{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Extract response 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 r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode,
+		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
+		"body":       string(body),
+		"headers":    respHeaders,
+	})
+}
+
+// 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()
+		jar.cookies = make(map[string][]*http.Cookie)
+		jar.mu.Unlock()
+		GoLog("[Extension:%s] Cookies cleared\n", r.extensionID)
+		return r.vm.ToValue(true)
+	}
+	return r.vm.ToValue(false)
+}

go_backend/extension_runtime_matching.go

@@ -0,0 +1,151 @@
+// Package gobackend provides Track Matching API for extension runtime
+package gobackend
+
+import (
+	"strings"
+
+	"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)
+	}
+
+	str1 := strings.ToLower(strings.TrimSpace(call.Arguments[0].String()))
+	str2 := strings.ToLower(strings.TrimSpace(call.Arguments[1].String()))
+
+	if str1 == str2 {
+		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)
+	}
+
+	dur1 := int(call.Arguments[0].ToInteger())
+	dur2 := int(call.Arguments[1].ToInteger())
+
+	// Default tolerance: 3 seconds
+	tolerance := 3000 // milliseconds
+	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) {
+		tolerance = int(call.Arguments[2].ToInteger())
+	}
+
+	diff := dur1 - dur2
+	if diff < 0 {
+		diff = -diff
+	}
+
+	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("")
+	}
+
+	str := call.Arguments[0].String()
+	normalized := normalizeStringForMatching(str)
+	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
+	}
+	if len(s1) == 0 || len(s2) == 0 {
+		return 0.0
+	}
+
+	// Use Levenshtein distance
+	distance := levenshteinDistance(s1, s2)
+	maxLen := len(s1)
+	if len(s2) > maxLen {
+		maxLen = len(s2)
+	}
+
+	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)
+	}
+	if len(s2) == 0 {
+		return len(s1)
+	}
+
+	// Create matrix
+	matrix := make([][]int, len(s1)+1)
+	for i := range matrix {
+		matrix[i] = make([]int, len(s2)+1)
+		matrix[i][0] = i
+	}
+	for j := range matrix[0] {
+		matrix[0][j] = j
+	}
+
+	// Fill matrix
+	for i := 1; i <= len(s1); i++ {
+		for j := 1; j <= len(s2); j++ {
+			cost := 1
+			if s1[i-1] == s2[j-1] {
+				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
+			)
+		}
+	}
+
+	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",
+		" (explicit)", " (clean)", " [explicit]", " [clean]",
+		" (album version)", " (single version)", " (radio edit)",
+		" (feat.", " (ft.", " feat.", " ft.",
+	}
+	for _, suffix := range suffixes {
+		if idx := strings.Index(s, suffix); idx != -1 {
+			s = s[:idx]
+		}
+	}
+
+	// Remove special characters
+	var result strings.Builder
+	for _, r := range s {
+		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == ' ' {
+			result.WriteRune(r)
+		}
+	}
+
+	// Collapse multiple spaces
+	s = strings.Join(strings.Fields(result.String()), " ")
+
+	return strings.TrimSpace(s)
+}

go_backend/extension_runtime_polyfills.go

@@ -0,0 +1,488 @@
+// Package gobackend provides Browser-like Polyfills for extension runtime
+package gobackend
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Browser-like Polyfills ====================
+// These polyfills make porting browser/Node.js libraries easier
+// without compromising sandbox security
+
+// fetchPolyfill implements browser-compatible fetch() API
+// 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)
+
+	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)
+			}
+
+			// Body - support string, object (auto-stringify), or nil
+			if bodyArg, ok := opts["body"]; ok && bodyArg != nil {
+				switch v := bodyArg.(type) {
+				case string:
+					bodyStr = v
+				case map[string]interface{}, []interface{}:
+					jsonBytes, err := json.Marshal(v)
+					if err != nil {
+						return r.createFetchError(fmt.Sprintf("failed to stringify body: %v", err))
+					}
+					bodyStr = string(jsonBytes)
+				default:
+					bodyStr = fmt.Sprintf("%v", v)
+				}
+			}
+
+			// Headers
+			if h, ok := opts["headers"]; ok && h != nil {
+				switch hv := h.(type) {
+				case map[string]interface{}:
+					for k, v := range hv {
+						headers[k] = fmt.Sprintf("%v", v)
+					}
+				}
+			}
+		}
+	}
+
+	// Create HTTP request
+	var reqBody io.Reader
+	if bodyStr != "" {
+		reqBody = strings.NewReader(bodyStr)
+	}
+
+	req, err := http.NewRequest(method, urlStr, reqBody)
+	if err != nil {
+		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")
+	}
+	if bodyStr != "" && req.Header.Get("Content-Type") == "" {
+		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 {
+			respHeaders[k] = v[0]
+		} else {
+			respHeaders[k] = v
+		}
+	}
+
+	// Create Response object (browser-compatible)
+	responseObj := r.vm.NewObject()
+	responseObj.Set("ok", resp.StatusCode >= 200 && resp.StatusCode < 300)
+	responseObj.Set("status", resp.StatusCode)
+	responseObj.Set("statusText", http.StatusText(resp.StatusCode))
+	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 {
+			GoLog("[Extension:%s] fetch json() parse error: %v\n", r.extensionID, err)
+			return goja.Undefined()
+		}
+		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)
+		}
+		return r.vm.ToValue(byteArray)
+	})
+
+	return responseObj
+}
+
+// createFetchError creates a fetch error response
+func (r *ExtensionRuntime) createFetchError(message string) goja.Value {
+	errorObj := r.vm.NewObject()
+	errorObj.Set("ok", false)
+	errorObj.Set("status", 0)
+	errorObj.Set("statusText", "Network Error")
+	errorObj.Set("error", message)
+	errorObj.Set("text", func(call goja.FunctionCall) goja.Value {
+		return r.vm.ToValue("")
+	})
+	errorObj.Set("json", func(call goja.FunctionCall) goja.Value {
+		return goja.Undefined()
+	})
+	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("")
+	}
+	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)
+			return r.vm.ToValue("")
+		}
+	}
+	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("")
+	}
+	input := call.Arguments[0].String()
+	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{})
+			}
+			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)
+			}
+			return vm.ToValue(result)
+		})
+
+		// encodeInto() method
+		encoder.Set("encodeInto", func(call goja.FunctionCall) goja.Value {
+			// Simplified implementation
+			if len(call.Arguments) < 2 {
+				return vm.ToValue(map[string]interface{}{"read": 0, "written": 0})
+			}
+			input := call.Arguments[0].String()
+			return vm.ToValue(map[string]interface{}{
+				"read":    len(input),
+				"written": len([]byte(input)),
+			})
+		})
+
+		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()
+		}
+		decoder.Set("encoding", encoding)
+		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
+
+			switch v := input.(type) {
+			case []byte:
+				bytes = v
+			case []interface{}:
+				bytes = make([]byte, len(v))
+				for i, val := range v {
+					switch n := val.(type) {
+					case int64:
+						bytes[i] = byte(n)
+					case float64:
+						bytes[i] = byte(n)
+					case int:
+						bytes[i] = byte(n)
+					}
+				}
+			case string:
+				// Already a string, just return it
+				return vm.ToValue(v)
+			default:
+				return vm.ToValue("")
+			}
+
+			return vm.ToValue(string(bytes))
+		})
+
+		return nil
+	})
+}
+
+// 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
+
+		if len(call.Arguments) < 1 {
+			urlObj.Set("href", "")
+			return nil
+		}
+
+		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)
+			if err == nil {
+				relURL, err := url.Parse(urlStr)
+				if err == nil {
+					urlStr = baseURL.ResolveReference(relURL).String()
+				}
+			}
+		}
+
+		parsed, err := url.Parse(urlStr)
+		if err != nil {
+			urlObj.Set("href", urlStr)
+			return nil
+		}
+
+		// Set URL properties
+		urlObj.Set("href", parsed.String())
+		urlObj.Set("protocol", parsed.Scheme+":")
+		urlObj.Set("host", parsed.Host)
+		urlObj.Set("hostname", parsed.Hostname())
+		urlObj.Set("port", parsed.Port())
+		urlObj.Set("pathname", parsed.Path)
+		urlObj.Set("search", "")
+		if parsed.RawQuery != "" {
+			urlObj.Set("search", "?"+parsed.RawQuery)
+		}
+		urlObj.Set("hash", "")
+		if parsed.Fragment != "" {
+			urlObj.Set("hash", "#"+parsed.Fragment)
+		}
+		urlObj.Set("origin", parsed.Scheme+"://"+parsed.Host)
+		urlObj.Set("username", parsed.User.Username())
+		password, _ := parsed.User.Password()
+		urlObj.Set("password", password)
+
+		// searchParams object
+		searchParams := vm.NewObject()
+		queryValues := parsed.Query()
+
+		searchParams.Set("get", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return goja.Null()
+			}
+			key := call.Arguments[0].String()
+			if val := queryValues.Get(key); val != "" {
+				return vm.ToValue(val)
+			}
+			return goja.Null()
+		})
+
+		searchParams.Set("getAll", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue([]string{})
+			}
+			key := call.Arguments[0].String()
+			return vm.ToValue(queryValues[key])
+		})
+
+		searchParams.Set("has", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue(false)
+			}
+			key := call.Arguments[0].String()
+			return vm.ToValue(queryValues.Has(key))
+		})
+
+		searchParams.Set("toString", func(call goja.FunctionCall) goja.Value {
+			return vm.ToValue(queryValues.Encode())
+		})
+
+		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())
+		})
+
+		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{}:
+				for k, val := range v {
+					values.Set(k, fmt.Sprintf("%v", val))
+				}
+			}
+		}
+
+		paramsObj.Set("append", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) >= 2 {
+				values.Add(call.Arguments[0].String(), call.Arguments[1].String())
+			}
+			return goja.Undefined()
+		})
+
+		paramsObj.Set("delete", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) >= 1 {
+				values.Del(call.Arguments[0].String())
+			}
+			return goja.Undefined()
+		})
+
+		paramsObj.Set("get", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return goja.Null()
+			}
+			if val := values.Get(call.Arguments[0].String()); val != "" {
+				return vm.ToValue(val)
+			}
+			return goja.Null()
+		})
+
+		paramsObj.Set("getAll", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue([]string{})
+			}
+			return vm.ToValue(values[call.Arguments[0].String()])
+		})
+
+		paramsObj.Set("has", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue(false)
+			}
+			return vm.ToValue(values.Has(call.Arguments[0].String()))
+		})
+
+		paramsObj.Set("set", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) >= 2 {
+				values.Set(call.Arguments[0].String(), call.Arguments[1].String())
+			}
+			return goja.Undefined()
+		})
+
+		paramsObj.Set("toString", func(call goja.FunctionCall) goja.Value {
+			return vm.ToValue(values.Encode())
+		})
+
+		return nil
+	})
+}
+
+// registerJSONGlobal ensures JSON global is properly set up
+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 = {
+				parse: function(text) {
+					return utils.parseJSON(text);
+				},
+				stringify: function(value, replacer, space) {
+					return utils.stringifyJSON(value);
+				}
+			};
+		}
+	`
+	_, _ = vm.RunString(jsonScript)
+}

go_backend/extension_runtime_storage.go

@@ -0,0 +1,381 @@
+// Package gobackend provides Storage and Credentials API for extension runtime
+package gobackend
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Storage API ====================
+
+// 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) {
+	storagePath := r.getStoragePath()
+	data, err := os.ReadFile(storagePath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return make(map[string]interface{}), nil
+		}
+		return nil, err
+	}
+
+	var storage map[string]interface{}
+	if err := json.Unmarshal(data, &storage); err != nil {
+		return nil, err
+	}
+
+	return storage, 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, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return os.WriteFile(storagePath, data, 0644)
+}
+
+// storageGet retrieves a value from storage
+func (r *ExtensionRuntime) storageGet(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return goja.Undefined()
+	}
+
+	key := call.Arguments[0].String()
+
+	storage, err := r.loadStorage()
+	if err != nil {
+		GoLog("[Extension:%s] Storage load error: %v\n", r.extensionID, err)
+		return goja.Undefined()
+	}
+
+	value, exists := storage[key]
+	if !exists {
+		// Return default value if provided
+		if len(call.Arguments) > 1 {
+			return call.Arguments[1]
+		}
+		return goja.Undefined()
+	}
+
+	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)
+	}
+
+	key := call.Arguments[0].String()
+	value := call.Arguments[1].Export()
+
+	storage, err := r.loadStorage()
+	if 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)
+		return r.vm.ToValue(false)
+	}
+
+	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)
+	}
+
+	key := call.Arguments[0].String()
+
+	storage, err := r.loadStorage()
+	if 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)
+		return r.vm.ToValue(false)
+	}
+
+	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)
+	}
+
+	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) {
+	credPath := r.getCredentialsPath()
+	data, err := os.ReadFile(credPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return make(map[string]interface{}), nil
+		}
+		return nil, err
+	}
+
+	// Decrypt the data
+	key, err := r.getEncryptionKey()
+	if err != nil {
+		return nil, 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)
+	}
+
+	var creds map[string]interface{}
+	if err := json.Unmarshal(decrypted, &creds); err != nil {
+		return nil, err
+	}
+
+	return creds, 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)
+	}
+	encrypted, err := encryptAES(data, key)
+	if err != nil {
+		return fmt.Errorf("failed to encrypt credentials: %w", err)
+	}
+
+	credPath := r.getCredentialsPath()
+	return os.WriteFile(credPath, encrypted, 0600) // Restrictive permissions
+}
+
+// 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{}{
+			"success": false,
+			"error":   "key and value are required",
+		})
+	}
+
+	key := call.Arguments[0].String()
+	value := call.Arguments[1].Export()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	creds[key] = value
+
+	if err := r.saveCredentials(creds); err != nil {
+		GoLog("[Extension:%s] Credentials save error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+	})
+}
+
+// credentialsGet retrieves a decrypted credential
+func (r *ExtensionRuntime) credentialsGet(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return goja.Undefined()
+	}
+
+	key := call.Arguments[0].String()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
+		return goja.Undefined()
+	}
+
+	value, exists := creds[key]
+	if !exists {
+		// Return default value if provided
+		if len(call.Arguments) > 1 {
+			return call.Arguments[1]
+		}
+		return goja.Undefined()
+	}
+
+	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)
+	}
+
+	key := call.Arguments[0].String()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	delete(creds, key)
+
+	if err := r.saveCredentials(creds); err != nil {
+		GoLog("[Extension:%s] Credentials save error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	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)
+	}
+
+	key := call.Arguments[0].String()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		return r.vm.ToValue(false)
+	}
+
+	_, exists := creds[key]
+	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 {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, err
+	}
+
+	ciphertext := gcm.Seal(nonce, nonce, plaintext, nil)
+	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 {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonceSize := gcm.NonceSize()
+	if len(ciphertext) < nonceSize {
+		return nil, fmt.Errorf("ciphertext too short")
+	}
+
+	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
+	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return plaintext, nil
+}

go_backend/extension_runtime_utils.go

@@ -0,0 +1,372 @@
+// Package gobackend provides Utility functions for extension runtime
+package gobackend
+
+import (
+	"crypto/hmac"
+	"crypto/md5"
+	"crypto/rand"
+	"crypto/sha1"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"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("")
+	}
+	input := call.Arguments[0].String()
+	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("")
+	}
+	input := call.Arguments[0].String()
+	decoded, err := base64.StdEncoding.DecodeString(input)
+	if err != nil {
+		return r.vm.ToValue("")
+	}
+	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("")
+	}
+	input := call.Arguments[0].String()
+	hash := md5.Sum([]byte(input))
+	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("")
+	}
+	input := call.Arguments[0].String()
+	hash := sha256.Sum256([]byte(input))
+	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("")
+	}
+	message := call.Arguments[0].String()
+	key := call.Arguments[1].String()
+
+	mac := hmac.New(sha256.New, []byte(key))
+	mac.Write([]byte(message))
+	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("")
+	}
+	message := call.Arguments[0].String()
+	key := call.Arguments[1].String()
+
+	mac := hmac.New(sha256.New, []byte(key))
+	mac.Write([]byte(message))
+	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) {
+	case string:
+		keyBytes = []byte(k)
+	case []interface{}:
+		keyBytes = make([]byte, len(k))
+		for i, v := range k {
+			if num, ok := v.(int64); ok {
+				keyBytes[i] = byte(num)
+			} else if num, ok := v.(float64); ok {
+				keyBytes[i] = byte(int(num))
+			}
+		}
+	default:
+		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) {
+	case string:
+		msgBytes = []byte(m)
+	case []interface{}:
+		msgBytes = make([]byte, len(m))
+		for i, v := range m {
+			if num, ok := v.(int64); ok {
+				msgBytes[i] = byte(num)
+			} else if num, ok := v.(float64); ok {
+				msgBytes[i] = byte(int(num))
+			}
+		}
+	default:
+		return r.vm.ToValue([]byte{})
+	}
+
+	mac := hmac.New(sha1.New, keyBytes)
+	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)
+	}
+	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()
+	}
+	input := call.Arguments[0].String()
+
+	var result interface{}
+	if err := json.Unmarshal([]byte(input), &result); err != nil {
+		GoLog("[Extension:%s] JSON parse error: %v\n", r.extensionID, err)
+		return goja.Undefined()
+	}
+
+	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("")
+	}
+	input := call.Arguments[0].Export()
+
+	data, err := json.Marshal(input)
+	if err != nil {
+		GoLog("[Extension:%s] JSON stringify error: %v\n", r.extensionID, err)
+		return r.vm.ToValue("")
+	}
+
+	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{}{
+			"success": false,
+			"error":   "plaintext and key are required",
+		})
+	}
+
+	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[:])
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"data":    base64.StdEncoding.EncodeToString(encrypted),
+	})
+}
+
+// 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{}{
+			"success": false,
+			"error":   "ciphertext and key are required",
+		})
+	}
+
+	ciphertextB64 := call.Arguments[0].String()
+	keyStr := call.Arguments[1].String()
+
+	ciphertext, err := base64.StdEncoding.DecodeString(ciphertextB64)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "invalid base64 ciphertext",
+		})
+	}
+
+	// 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(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"data":    string(decrypted),
+	})
+}
+
+// cryptoGenerateKey generates a random encryption key
+func (r *ExtensionRuntime) cryptoGenerateKey(call goja.FunctionCall) goja.Value {
+	length := 32 // Default 256-bit key
+	if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
+		if l, ok := call.Arguments[0].Export().(float64); ok {
+			length = int(l)
+		}
+	}
+
+	key := make([]byte, length)
+	if _, err := rand.Read(key); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"key":     base64.StdEncoding.EncodeToString(key),
+		"hex":     hex.EncodeToString(key),
+	})
+}
+
+// ==================== Logging Functions ====================
+
+func (r *ExtensionRuntime) logDebug(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:DEBUG] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) logInfo(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:INFO] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) logWarn(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:WARN] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) logError(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:ERROR] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) formatLogArgs(args []goja.Value) string {
+	parts := make([]string, len(args))
+	for i, arg := range args {
+		parts[i] = fmt.Sprintf("%v", arg.Export())
+	}
+	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("")
+	}
+	input := call.Arguments[0].String()
+	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) {
+		gobackendObj = vm.NewObject()
+		vm.Set("gobackend", gobackendObj)
+	}
+
+	obj := gobackendObj.(*goja.Object)
+
+	// Expose sanitizeFilename
+	obj.Set("sanitizeFilename", func(call goja.FunctionCall) goja.Value {
+		if len(call.Arguments) < 1 {
+			return vm.ToValue("")
+		}
+		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{}{
+				"error": "file path is required",
+			})
+		}
+
+		filePath := call.Arguments[0].String()
+		quality, err := GetAudioQuality(filePath)
+		if err != nil {
+			return vm.ToValue(map[string]interface{}{
+				"error": err.Error(),
+			})
+		}
+
+		return vm.ToValue(map[string]interface{}{
+			"bitDepth":     quality.BitDepth,
+			"sampleRate":   quality.SampleRate,
+			"totalSamples": quality.TotalSamples,
+		})
+	})
+
+	// Expose buildFilename
+	obj.Set("buildFilename", func(call goja.FunctionCall) goja.Value {
+		if len(call.Arguments) < 2 {
+			return vm.ToValue("")
+		}
+
+		template := call.Arguments[0].String()
+		metadataObj := call.Arguments[1].Export()
+
+		metadata, ok := metadataObj.(map[string]interface{})
+		if !ok {
+			return vm.ToValue("")
+		}
+
+		return vm.ToValue(buildFilenameFromTemplate(template, metadata))
+	})
+}

go_backend/extension_settings.go

@@ -0,0 +1,221 @@
+// Package gobackend provides extension settings storage
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"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{
+			settings: make(map[string]map[string]interface{}),
+		}
+	})
+	return globalSettingsStore
+}
+
+// SetDataDir sets the data directory for settings storage
+func (s *ExtensionSettingsStore) SetDataDir(dataDir string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.dataDir = dataDir
+	if err := os.MkdirAll(dataDir, 0755); err != nil {
+		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 {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			extensionID := entry.Name()
+			settings, err := s.loadSettings(extensionID)
+			if err != nil {
+				GoLog("[ExtensionSettings] Failed to load settings for %s: %v\n", extensionID, err)
+				continue
+			}
+			s.settings[extensionID] = settings
+		}
+	}
+
+	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)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return make(map[string]interface{}), nil
+		}
+		return nil, err
+	}
+
+	var settings map[string]interface{}
+	if err := json.Unmarshal(data, &settings); err != nil {
+		return nil, err
+	}
+
+	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
+	}
+
+	data, err := json.MarshalIndent(settings, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	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()
+
+	extSettings, exists := s.settings[extensionID]
+	if !exists {
+		return nil, fmt.Errorf("extension '%s' settings not found", extensionID)
+	}
+
+	value, exists := extSettings[key]
+	if !exists {
+		return nil, fmt.Errorf("setting '%s' not found for extension '%s'", key, extensionID)
+	}
+	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()
+
+	extSettings, exists := s.settings[extensionID]
+	if !exists {
+		return make(map[string]interface{})
+	}
+
+	// Return a copy
+	result := make(map[string]interface{})
+	for k, v := range extSettings {
+		result[k] = v
+	}
+	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()
+
+	if _, exists := s.settings[extensionID]; !exists {
+		s.settings[extensionID] = make(map[string]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()
+
+	extSettings, exists := s.settings[extensionID]
+	if !exists {
+		return nil
+	}
+
+	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
+	}
+
+	return nil
+}
+
+// GetAllExtensionSettings returns settings for all extensions as JSON
+func (s *ExtensionSettingsStore) GetAllExtensionSettingsJSON() (string, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	data, err := json.Marshal(s.settings)
+	if err != nil {
+		return "", err
+	}
+
+	return string(data), nil
+}

go_backend/extension_store.go

@@ -0,0 +1,453 @@
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+)
+
+// Extension categories
+const (
+	CategoryMetadata    = "metadata"
+	CategoryDownload    = "download"
+	CategoryUtility     = "utility"
+	CategoryLyrics      = "lyrics"
+	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"`
+}
+
+// getDisplayName returns display name, falling back to name (private to avoid gomobile conflict)
+func (e *StoreExtension) getDisplayName() string {
+	if e.DisplayName != "" {
+		return e.DisplayName
+	}
+	if e.DisplayNameAlt != "" {
+		return e.DisplayNameAlt
+	}
+	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
+	}
+	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
+	}
+	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
+	}
+	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"`
+	DisplayName      string   `json:"display_name"`
+	Version          string   `json:"version"`
+	Author           string   `json:"author"`
+	Description      string   `json:"description"`
+	DownloadURL      string   `json:"download_url"`
+	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"`
+	IsInstalled      bool     `json:"is_installed"`
+	InstalledVersion string   `json:"installed_version,omitempty"`
+	HasUpdate        bool     `json:"has_update"`
+}
+
+// ToResponse converts StoreExtension to normalized response
+func (e *StoreExtension) ToResponse() StoreExtensionResponse {
+	return StoreExtensionResponse{
+		ID:            e.ID,
+		Name:          e.Name,
+		DisplayName:   e.getDisplayName(),
+		Version:       e.Version,
+		Author:        e.Author,
+		Description:   e.Description,
+		DownloadURL:   e.getDownloadURL(),
+		IconURL:       e.getIconURL(),
+		Category:      e.Category,
+		Tags:          e.Tags,
+		Downloads:     e.Downloads,
+		UpdatedAt:     e.UpdatedAt,
+		MinAppVersion: e.getMinAppVersion(),
+	}
+}
+
+// ExtensionStore manages the extension store
+type ExtensionStore struct {
+	registryURL string
+	cacheDir    string
+	cache       *StoreRegistry
+	cacheMu     sync.RWMutex
+	cacheTime   time.Time
+	cacheTTL    time.Duration
+}
+
+var (
+	extensionStore   *ExtensionStore
+	extensionStoreMu sync.Mutex
+)
+
+const (
+	defaultRegistryURL = "https://raw.githubusercontent.com/zarzet/SpotiFLAC-Extension/main/registry.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,
+			cacheDir:    cacheDir,
+			cacheTTL:    cacheTTL,
+		}
+		// Try to load from disk cache
+		extensionStore.loadDiskCache()
+	}
+	return extensionStore
+}
+
+// GetExtensionStore returns the singleton store instance
+func GetExtensionStore() *ExtensionStore {
+	extensionStoreMu.Lock()
+	defer extensionStoreMu.Unlock()
+	return extensionStore
+}
+
+// loadDiskCache loads cached registry from disk
+func (s *ExtensionStore) loadDiskCache() {
+	if s.cacheDir == "" {
+		return
+	}
+
+	cachePath := filepath.Join(s.cacheDir, cacheFileName)
+	data, err := os.ReadFile(cachePath)
+	if err != nil {
+		return
+	}
+
+	var cacheData struct {
+		Registry  StoreRegistry `json:"registry"`
+		CacheTime int64         `json:"cache_time"`
+	}
+
+	if err := json.Unmarshal(data, &cacheData); err != nil {
+		return
+	}
+
+	s.cache = &cacheData.Registry
+	s.cacheTime = time.Unix(cacheData.CacheTime, 0)
+	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
+	}
+
+	cacheData := struct {
+		Registry  StoreRegistry `json:"registry"`
+		CacheTime int64         `json:"cache_time"`
+	}{
+		Registry:  *s.cache,
+		CacheTime: s.cacheTime.Unix(),
+	}
+
+	data, err := json.Marshal(cacheData)
+	if err != nil {
+		return
+	}
+
+	cachePath := filepath.Join(s.cacheDir, cacheFileName)
+	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
+	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
+	}
+
+	LogInfo("ExtensionStore", "Fetching registry from %s", s.registryURL)
+
+	client := &http.Client{Timeout: 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
+		}
+		return nil, fmt.Errorf("failed to fetch registry: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		if s.cache != nil {
+			LogWarn("ExtensionStore", "HTTP %d, using cached registry", resp.StatusCode)
+			return s.cache, nil
+		}
+		return nil, fmt.Errorf("registry returned HTTP %d", resp.StatusCode)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read registry: %w", err)
+	}
+
+	var registry StoreRegistry
+	if err := json.Unmarshal(body, &registry); err != nil {
+		return nil, fmt.Errorf("failed to parse registry: %w", err)
+	}
+
+	s.cache = &registry
+	s.cacheTime = time.Now()
+	s.saveDiskCache()
+
+	LogInfo("ExtensionStore", "Fetched %d extensions from registry", len(registry.Extensions))
+	return &registry, nil
+}
+
+// GetExtensionsWithStatus returns extensions with installation status
+func (s *ExtensionStore) GetExtensionsWithStatus() ([]StoreExtensionResponse, error) {
+	registry, err := s.FetchRegistry(false)
+	if err != nil {
+		return nil, err
+	}
+
+	manager := GetExtensionManager()
+	installed := make(map[string]string) // id -> version
+
+	if manager != nil {
+		for _, ext := range manager.GetAllExtensions() {
+			installed[ext.ID] = ext.Manifest.Version
+		}
+	}
+
+	result := make([]StoreExtensionResponse, len(registry.Extensions))
+	for i, ext := range registry.Extensions {
+		resp := ext.ToResponse()
+
+		if installedVersion, ok := installed[ext.ID]; ok {
+			resp.IsInstalled = true
+			resp.InstalledVersion = installedVersion
+			resp.HasUpdate = compareVersions(ext.Version, installedVersion) > 0
+		}
+
+		result[i] = resp
+	}
+
+	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 {
+		return err
+	}
+
+	var ext *StoreExtension
+	for _, e := range registry.Extensions {
+		if e.ID == extensionID {
+			ext = &e
+			break
+		}
+	}
+
+	if ext == nil {
+		return fmt.Errorf("extension %s not found in store", extensionID)
+	}
+
+	LogInfo("ExtensionStore", "Downloading %s from %s", ext.getDisplayName(), ext.getDownloadURL())
+
+	client := &http.Client{Timeout: 5 * time.Minute}
+	resp, err := client.Get(ext.getDownloadURL())
+	if err != nil {
+		return fmt.Errorf("failed to download: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		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)
+	}
+	defer out.Close()
+
+	_, err = io.Copy(out, resp.Body)
+	if err != nil {
+		os.Remove(destPath)
+		return fmt.Errorf("failed to write file: %w", err)
+	}
+
+	LogInfo("ExtensionStore", "Downloaded %s to %s", ext.getDisplayName(), destPath)
+	return nil
+}
+
+// GetCategories returns all available categories
+func (s *ExtensionStore) GetCategories() []string {
+	return []string{
+		CategoryMetadata,
+		CategoryDownload,
+		CategoryUtility,
+		CategoryLyrics,
+		CategoryIntegration,
+	}
+}
+
+// SearchExtensions searches extensions by query
+func (s *ExtensionStore) SearchExtensions(query string, category string) ([]StoreExtensionResponse, error) {
+	extensions, err := s.GetExtensionsWithStatus()
+	if err != nil {
+		return nil, err
+	}
+
+	if query == "" && category == "" {
+		return extensions, nil
+	}
+
+	var result []StoreExtensionResponse
+	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) &&
+				!containsIgnoreCase(ext.Description, queryLower) &&
+				!containsIgnoreCase(ext.Author, queryLower) {
+				// Check tags
+				found := false
+				for _, tag := range ext.Tags {
+					if containsIgnoreCase(tag, queryLower) {
+						found = true
+						break
+					}
+				}
+				if !found {
+					continue
+				}
+			}
+		}
+
+		result = append(result, ext)
+	}
+
+	return result, nil
+}
+
+// ClearCache clears the in-memory and disk cache
+func (s *ExtensionStore) ClearCache() {
+	s.cacheMu.Lock()
+	defer s.cacheMu.Unlock()
+
+	s.cache = nil
+	s.cacheTime = time.Time{}
+
+	if s.cacheDir != "" {
+		cachePath := filepath.Join(s.cacheDir, cacheFileName)
+		os.Remove(cachePath)
+	}
+
+	LogInfo("ExtensionStore", "Cache cleared")
+}
+
+// Helper: case-insensitive contains
+func containsIgnoreCase(s, substr string) bool {
+	return containsStr(toLower(s), substr)
+}
+
+func toLower(s string) string {
+	result := make([]byte, len(s))
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if c >= 'A' && c <= 'Z' {
+			c += 'a' - 'A'
+		}
+		result[i] = c
+	}
+	return string(result)
+}
+
+func containsStr(s, substr string) bool {
+	return len(substr) == 0 || (len(s) >= len(substr) && findSubstring(s, substr) >= 0)
+}
+
+func findSubstring(s, substr string) int {
+	for i := 0; i <= len(s)-len(substr); i++ {
+		if s[i:i+len(substr)] == substr {
+			return i
+		}
+	}
+	return -1
+}

go_backend/extension_test.go

@@ -0,0 +1,329 @@
+package gobackend
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/dop251/goja"
+)
+
+func TestParseManifest_Valid(t *testing.T) {
+	validManifest := `{
+		"name": "test-provider",
+		"displayName": "Test Provider",
+		"version": "1.0.0",
+		"author": "Test Author",
+		"description": "A test extension",
+		"type": ["metadata_provider"],
+		"permissions": {
+			"network": ["api.test.com"],
+			"storage": true
+		}
+	}`
+
+	manifest, err := ParseManifest([]byte(validManifest))
+	if err != nil {
+		t.Fatalf("Expected valid manifest to parse, got error: %v", err)
+	}
+
+	if manifest.Name != "test-provider" {
+		t.Errorf("Expected name 'test-provider', got '%s'", manifest.Name)
+	}
+
+	if manifest.Version != "1.0.0" {
+		t.Errorf("Expected version '1.0.0', got '%s'", manifest.Version)
+	}
+
+	if !manifest.IsMetadataProvider() {
+		t.Error("Expected IsMetadataProvider() to return true")
+	}
+
+	if manifest.IsDownloadProvider() {
+		t.Error("Expected IsDownloadProvider() to return false")
+	}
+}
+
+func TestParseManifest_MissingName(t *testing.T) {
+	invalidManifest := `{
+		"version": "1.0.0",
+		"author": "Test Author",
+		"description": "A test extension",
+		"type": ["metadata_provider"]
+	}`
+
+	_, err := ParseManifest([]byte(invalidManifest))
+	if err == nil {
+		t.Fatal("Expected error for missing name")
+	}
+}
+
+func TestParseManifest_MissingType(t *testing.T) {
+	invalidManifest := `{
+		"name": "test-provider",
+		"version": "1.0.0",
+		"author": "Test Author",
+		"description": "A test extension"
+	}`
+
+	_, err := ParseManifest([]byte(invalidManifest))
+	if err == nil {
+		t.Fatal("Expected error for missing type")
+	}
+}
+
+func TestIsDomainAllowed(t *testing.T) {
+	manifest := &ExtensionManifest{
+		Permissions: ExtensionPermissions{
+			Network: []string{"api.test.com", "*.example.com"},
+		},
+	}
+
+	tests := []struct {
+		domain   string
+		expected bool
+	}{
+		{"api.test.com", true},
+		{"api.example.com", true},
+		{"sub.example.com", true},
+		{"notallowed.com", false},
+		{"test.com", false},
+	}
+
+	for _, tt := range tests {
+		result := manifest.IsDomainAllowed(tt.domain)
+		if result != tt.expected {
+			t.Errorf("IsDomainAllowed(%s) = %v, expected %v", tt.domain, result, tt.expected)
+		}
+	}
+}
+
+func TestExtensionRuntime_NetworkSandbox(t *testing.T) {
+	// Create a mock extension with limited network permissions
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+			Permissions: ExtensionPermissions{
+				Network: []string{"api.allowed.com", "*.wildcard.com"},
+			},
+		},
+		DataDir: t.TempDir(),
+	}
+
+	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)
+	}
+
+	if err := runtime.validateDomain("https://sub.wildcard.com/path"); err != nil {
+		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")
+	}
+
+	if err := runtime.validateDomain("https://notallowed.com/path"); err == nil {
+		t.Error("Expected notallowed.com to be denied")
+	}
+}
+
+func TestExtensionRuntime_FileSandbox(t *testing.T) {
+	tempDir := t.TempDir()
+
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+			Permissions: ExtensionPermissions{
+				File: true, // Enable file permission for test
+			},
+		},
+		DataDir: tempDir,
+	}
+
+	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)
+	}
+	if validPath == "" {
+		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)
+	}
+	if nestedPath == "" {
+		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
+	} else {
+		absPath = "/etc/passwd" // Unix
+	}
+	_, 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
+			},
+		},
+		DataDir: tempDir,
+	}
+	runtimeNoFile := NewExtensionRuntime(extNoFile)
+	_, err = runtimeNoFile.validatePath("test.txt")
+	if err == nil {
+		t.Error("Expected file access to be denied without file permission")
+	}
+}
+
+func TestExtensionRuntime_UtilityFunctions(t *testing.T) {
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+		},
+		DataDir: t.TempDir(),
+	}
+
+	runtime := NewExtensionRuntime(ext)
+	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)
+	}
+	if result.String() != "aGVsbG8=" {
+		t.Errorf("Expected 'aGVsbG8=', got '%s'", result.String())
+	}
+
+	result, err = vm.RunString(`utils.base64Decode("aGVsbG8=")`)
+	if err != nil {
+		t.Fatalf("base64Decode failed: %v", err)
+	}
+	if result.String() != "hello" {
+		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)
+	}
+	if result.String() != "5d41402abc4b2a76b9719d911017c592" {
+		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)
+	}
+	// JSON output may vary in order, just check it's valid
+	if result.String() == "" {
+		t.Error("Expected non-empty JSON string")
+	}
+}
+
+func TestExtensionRuntime_SSRFProtection(t *testing.T) {
+	// Create extension with limited network permissions
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+			Permissions: ExtensionPermissions{
+				Network: []string{"api.example.com"},
+			},
+		},
+		DataDir: t.TempDir(),
+	}
+
+	runtime := NewExtensionRuntime(ext)
+
+	// Test that private IPs are blocked (SSRF protection)
+	privateIPs := []string{
+		"http://localhost/admin",
+		"http://127.0.0.1/admin",
+		"http://192.168.1.1/admin",
+		"http://10.0.0.1/admin",
+		"http://172.16.0.1/admin",
+		"http://169.254.169.254/latest/meta-data/", // AWS metadata
+		"http://router.local/admin",
+	}
+
+	for _, url := range privateIPs {
+		err := runtime.validateDomain(url)
+		if err == nil {
+			t.Errorf("Expected private IP/host '%s' to be blocked", url)
+		}
+	}
+
+	// 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)
+	}
+}
+
+func TestIsPrivateIP(t *testing.T) {
+	tests := []struct {
+		host     string
+		expected bool
+	}{
+		// Private IPs should be blocked
+		{"localhost", true},
+		{"127.0.0.1", true},
+		{"127.0.0.2", true},
+		{"10.0.0.1", true},
+		{"10.255.255.255", true},
+		{"172.16.0.1", true},
+		{"172.31.255.255", true},
+		{"192.168.0.1", true},
+		{"192.168.255.255", true},
+		{"169.254.169.254", true}, // AWS metadata
+		{"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
+	}
+
+	for _, tt := range tests {
+		result := isPrivateIP(tt.host)
+		if result != tt.expected {
+			t.Errorf("isPrivateIP(%s) = %v, expected %v", tt.host, result, tt.expected)
+		}
+	}
+}

go_backend/extension_timeout.go

@@ -0,0 +1,118 @@
+// Package gobackend provides timeout execution for extension JS code
+package gobackend
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// JSExecutionError represents an error during JS execution
+type JSExecutionError struct {
+	Message   string
+	IsTimeout bool
+}
+
+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
+	}
+
+	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()
+
+				if wasInterrupted {
+					resultCh <- result{nil, &JSExecutionError{
+						Message:   "execution timeout exceeded",
+						IsTimeout: true,
+					}}
+				} else {
+					resultCh <- result{nil, fmt.Errorf("panic during execution: %v", r)}
+				}
+			}
+		}()
+
+		val, err := vm.RunString(script)
+		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
+			}
+			return nil, &JSExecutionError{
+				Message:   "execution timeout exceeded",
+				IsTimeout: true,
+			}
+		case <-time.After(1 * time.Second):
+			// Force return timeout error
+			return nil, &JSExecutionError{
+				Message:   "execution timeout exceeded (force)",
+				IsTimeout: true,
+			}
+		}
+	}
+}
+
+// RunWithTimeoutAndRecover runs JS with timeout and clears interrupt state after
+// This should be used when you want to continue using the VM after a timeout
+func RunWithTimeoutAndRecover(vm *goja.Runtime, script string, timeout time.Duration) (goja.Value, error) {
+	result, err := RunWithTimeout(vm, script, timeout)
+
+	// Clear any interrupt state so VM can be reused
+	vm.ClearInterrupt()
+
+	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
+	}
+	return false
+}

go_backend/go.mod

@@ -5,14 +5,19 @@ go 1.24.0
 toolchain go1.24.5
 
 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
 )
 
 require (
+	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
 	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/text v0.3.8 // indirect
 	golang.org/x/tools v0.40.0 // indirect
 )

go_backend/go.sum

@@ -1,14 +1,28 @@
+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/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/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/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=
 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=
+gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
+gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=

go_backend/httputil.go

@@ -1,48 +1,90 @@
 package gobackend
 
 import (
+	"crypto/tls"
+	"errors"
 	"fmt"
 	"io"
 	"math/rand"
 	"net"
 	"net/http"
+	"net/url"
 	"strconv"
+	"strings"
+	"syscall"
 	"time"
 )
 
 // HTTP utility functions for consistent request handling across all downloaders
 
-// User-Agent pool for Android Chrome browsers
+// getRandomUserAgent generates a random Windows Chrome User-Agent string
-var userAgentTemplates = []string{
+// Uses same format as PC version (referensi/backend/spotify_metadata.go) for better API compatibility
-	"Mozilla/5.0 (Linux; Android %d; SM-G%d) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Mobile Safari/537.36",
-	"Mozilla/5.0 (Linux; Android %d; Pixel %d) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Mobile Safari/537.36",
-	"Mozilla/5.0 (Linux; Android %d; SM-A%d) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Mobile Safari/537.36",
-	"Mozilla/5.0 (Linux; Android %d; Redmi Note %d) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Mobile Safari/537.36",
-}
-
-// getRandomUserAgent generates a random browser-like User-Agent string (Android Chrome format)
 func getRandomUserAgent() string {
-	template := userAgentTemplates[rand.Intn(len(userAgentTemplates))]
+	// Windows 10/11 Chrome format - same as PC version for maximum compatibility
+	// Some APIs may block mobile User-Agents, so we use desktop format
+	winMajor := rand.Intn(2) + 10 // Windows 10 or 11
 
-	androidVersion := rand.Intn(5) + 10 // Android 10-14
+	chromeVersion := rand.Intn(25) + 100  // Chrome 100-124
-	deviceModel := rand.Intn(900) + 100 // Random model number
+	chromeBuild := rand.Intn(1500) + 3000 // Build 3000-4500
-	chromeVersion := rand.Intn(25) + 100 // Chrome 100-124
+	chromePatch := rand.Intn(65) + 60     // Patch 60-125
-	chromeBuild := rand.Intn(5000) + 5000
-	chromePatch := rand.Intn(200) + 100
 
-	return fmt.Sprintf(template, androidVersion, deviceModel, chromeVersion, chromeBuild, chromePatch)
+	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,
+		chromeVersion,
+		chromeBuild,
+		chromePatch,
+	)
 }
 
+// getRandomMacUserAgent generates a random Mac Chrome User-Agent string
+// Alternative format matching referensi/backend/spotify_metadata.go exactly
+// Kept for potential future use
+// 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
+// Kept for potential future use
+// func getRandomDesktopUserAgent() string {
+// 	if rand.Intn(2) == 0 {
+// 		return getRandomUserAgent() // Windows
+// 	}
+// 	return getRandomMacUserAgent() // Mac
+// }
+
 // Default timeout values
 const (
-	DefaultTimeout     = 60 * time.Second  // Default HTTP timeout
+	DefaultTimeout    = 60 * time.Second  // Default HTTP timeout
-	DownloadTimeout    = 120 * time.Second // Timeout for file downloads
+	DownloadTimeout   = 120 * time.Second // Timeout for file downloads
-	SongLinkTimeout    = 30 * time.Second  // Timeout for SongLink API
+	SongLinkTimeout   = 30 * time.Second  // Timeout for SongLink API
-	DefaultMaxRetries  = 3                 // Default retry count
+	DefaultMaxRetries = 3                 // Default retry count
-	DefaultRetryDelay  = 1 * time.Second   // Initial retry delay
+	DefaultRetryDelay = 1 * time.Second   // Initial retry delay
 )
 
 // Shared transport with connection pooling to prevent TCP exhaustion
+// Optimized for large file downloads (FLAC ~30-50MB)
 var sharedTransport = &http.Transport{
 	DialContext: (&net.Dialer{
 		Timeout:   30 * time.Second,
@@ -56,6 +98,9 @@ var sharedTransport = &http.Transport{
 	ExpectContinueTimeout: 1 * time.Second,
 	DisableKeepAlives:     false, // Enable keep-alives for connection reuse
 	ForceAttemptHTTP2:     true,
+	WriteBufferSize:       64 * 1024, // 64KB write buffer
+	ReadBufferSize:        64 * 1024, // 64KB read buffer
+	DisableCompression:    true,      // FLAC is already compressed
 }
 
 // Shared HTTP client for general requests (reuses connections)
@@ -96,9 +141,15 @@ func CloseIdleConnections() {
 }
 
 // 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())
-	return client.Do(req)
+	resp, err := client.Do(req)
+	if err != nil {
+		// Check for ISP blocking
+		CheckAndLogISPBlocking(err, req.URL.String(), "HTTP")
+	}
+	return resp, err
 }
 
 // RetryConfig holds configuration for retry logic
@@ -121,9 +172,11 @@ 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)
@@ -133,7 +186,16 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 		resp, err := client.Do(reqCopy)
 		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 attempt < config.MaxRetries {
+				GoLog("[HTTP] Request failed (attempt %d/%d): %v, retrying in %v...\n",
+					attempt+1, config.MaxRetries+1, err, delay)
 				time.Sleep(delay)
 				delay = calculateNextDelay(delay, config)
 			}
@@ -154,17 +216,43 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 			}
 			lastErr = fmt.Errorf("rate limited (429)")
 			if attempt < config.MaxRetries {
+				GoLog("[HTTP] Rate limited, waiting %v before retry...\n", delay)
 				time.Sleep(delay)
 				delay = calculateNextDelay(delay, config)
 			}
 			continue
 		}
 
+		// Check for ISP blocking via HTTP status codes
+		// Some ISPs return 403 or 451 when blocking content
+		if resp.StatusCode == 403 || resp.StatusCode == 451 {
+			body, _ := io.ReadAll(resp.Body)
+			resp.Body.Close()
+			bodyStr := strings.ToLower(string(body))
+
+			// Check if response looks like ISP blocking page
+			ispBlockingIndicators := []string{
+				"blocked", "forbidden", "access denied", "not available in your",
+				"restricted", "censored", "unavailable for legal", "blocked by",
+			}
+
+			for _, indicator := range ispBlockingIndicators {
+				if strings.Contains(bodyStr, indicator) {
+					LogError("HTTP", "ISP BLOCKING DETECTED via HTTP %d response", resp.StatusCode)
+					LogError("HTTP", "Domain: %s", req.URL.Host)
+					LogError("HTTP", "Response contains: %s", indicator)
+					LogError("HTTP", "Suggestion: Try using a VPN or changing your DNS to 1.1.1.1 or 8.8.8.8")
+					return nil, fmt.Errorf("ISP blocking detected for %s (HTTP %d) - try using VPN or change DNS", req.URL.Host, resp.StatusCode)
+				}
+			}
+		}
+
 		// Server errors (5xx) - retry
 		if resp.StatusCode >= 500 {
 			resp.Body.Close()
 			lastErr = fmt.Errorf("server error: HTTP %d", resp.StatusCode)
 			if attempt < config.MaxRetries {
+				GoLog("[HTTP] Server error %d, retrying in %v...\n", resp.StatusCode, delay)
 				time.Sleep(delay)
 				delay = calculateNextDelay(delay, config)
 			}
@@ -181,10 +269,7 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 // calculateNextDelay calculates the next delay with exponential backoff
 func calculateNextDelay(currentDelay time.Duration, config RetryConfig) time.Duration {
 	nextDelay := time.Duration(float64(currentDelay) * config.BackoffFactor)
-	if nextDelay > config.MaxDelay {
+	return min(nextDelay, config.MaxDelay)
-		nextDelay = config.MaxDelay
-	}
-	return nextDelay
 }
 
 // getRetryAfterDuration parses Retry-After header and returns duration
@@ -258,3 +343,172 @@ 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
+	OriginalErr error
+}
+
+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 {
+			return &ISPBlockingError{
+				Domain:      domain,
+				Reason:      "DNS resolution failed - domain may be blocked by ISP",
+				OriginalErr: err,
+			}
+		}
+	}
+
+	// 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 {
+				case syscall.ECONNREFUSED:
+					return &ISPBlockingError{
+						Domain:      domain,
+						Reason:      "Connection refused - port may be blocked by ISP/firewall",
+						OriginalErr: err,
+					}
+				case syscall.ECONNRESET:
+					return &ISPBlockingError{
+						Domain:      domain,
+						Reason:      "Connection reset - ISP may be intercepting traffic",
+						OriginalErr: err,
+					}
+				case syscall.ETIMEDOUT:
+					return &ISPBlockingError{
+						Domain:      domain,
+						Reason:      "Connection timed out - ISP may be blocking access",
+						OriginalErr: err,
+					}
+				case syscall.ENETUNREACH:
+					return &ISPBlockingError{
+						Domain:      domain,
+						Reason:      "Network unreachable - ISP may be blocking route",
+						OriginalErr: err,
+					}
+				case syscall.EHOSTUNREACH:
+					return &ISPBlockingError{
+						Domain:      domain,
+						Reason:      "Host unreachable - ISP may be blocking destination",
+						OriginalErr: err,
+					}
+				}
+			}
+		}
+	}
+
+	// Check for TLS handshake failure (ISP MITM or blocking HTTPS)
+	var tlsErr *tls.RecordHeaderError
+	if errors.As(err, &tlsErr) {
+		return &ISPBlockingError{
+			Domain:      domain,
+			Reason:      "TLS handshake failed - ISP may be intercepting HTTPS traffic",
+			OriginalErr: err,
+		}
+	}
+
+	// Check error message patterns for common ISP blocking indicators
+	blockingPatterns := []struct {
+		pattern string
+		reason  string
+	}{
+		{"connection reset by peer", "Connection reset - ISP may be intercepting traffic"},
+		{"connection refused", "Connection refused - port may be blocked"},
+		{"no such host", "DNS lookup failed - domain may be blocked by ISP"},
+		{"i/o timeout", "Connection timed out - ISP may be blocking access"},
+		{"network is unreachable", "Network unreachable - ISP may be blocking route"},
+		{"tls: ", "TLS error - ISP may be intercepting HTTPS traffic"},
+		{"certificate", "Certificate error - ISP may be using MITM proxy"},
+		{"eof", "Connection closed unexpectedly - ISP may be blocking"},
+		{"context deadline exceeded", "Request timed out - ISP may be throttling"},
+	}
+
+	for _, bp := range blockingPatterns {
+		if strings.Contains(errStr, bp.pattern) {
+			return &ISPBlockingError{
+				Domain:      domain,
+				Reason:      bp.reason,
+				OriginalErr: err,
+			}
+		}
+	}
+
+	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)
+	if ispErr != nil {
+		LogError(tag, "ISP BLOCKING DETECTED: %s", ispErr.Error())
+		LogError(tag, "Domain: %s", ispErr.Domain)
+		LogError(tag, "Reason: %s", ispErr.Reason)
+		LogError(tag, "Original error: %v", ispErr.OriginalErr)
+		LogError(tag, "Suggestion: Try using a VPN or changing your DNS to 1.1.1.1 or 8.8.8.8")
+		return true
+	}
+	return false
+}
+
+// extractDomain extracts the domain from a URL string
+func extractDomain(rawURL string) string {
+	if rawURL == "" {
+		return "unknown"
+	}
+
+	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 {
+			return rawURL[:idx]
+		}
+		return rawURL
+	}
+
+	if parsed.Host != "" {
+		return parsed.Host
+	}
+	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 {
+		return nil
+	}
+
+	if CheckAndLogISPBlocking(err, requestURL, tag) {
+		domain := extractDomain(requestURL)
+		return fmt.Errorf("ISP blocking detected for %s - try using VPN or change DNS to 1.1.1.1/8.8.8.8: %w", domain, err)
+	}
+
+	return err
+}

go_backend/logbuffer.go

@@ -0,0 +1,203 @@
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+	"sync"
+	"time"
+)
+
+// LogEntry represents a single log entry
+type LogEntry struct {
+	Timestamp string `json:"timestamp"`
+	Level     string `json:"level"`
+	Tag       string `json:"tag"`
+	Message   string `json:"message"`
+}
+
+// LogBuffer stores logs in a circular buffer for retrieval by Flutter
+type LogBuffer struct {
+	entries        []LogEntry
+	maxSize        int
+	mu             sync.RWMutex
+	loggingEnabled bool // Whether logging is enabled (controlled by Flutter)
+}
+
+var (
+	globalLogBuffer *LogBuffer
+	logBufferOnce   sync.Once
+)
+
+// GetLogBuffer returns the singleton log buffer instance
+func GetLogBuffer() *LogBuffer {
+	logBufferOnce.Do(func() {
+		globalLogBuffer = &LogBuffer{
+			entries:        make([]LogEntry, 0, 1000),
+			maxSize:        1000,
+			loggingEnabled: false, // Default: disabled for performance (user can enable in settings)
+		}
+	})
+	return globalLogBuffer
+}
+
+// SetLoggingEnabled enables or disables logging
+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()
+
+	// Skip if logging is disabled (except for errors which are always logged)
+	if !lb.loggingEnabled && level != "ERROR" && level != "FATAL" {
+		return
+	}
+
+	entry := LogEntry{
+		Timestamp: time.Now().Format("15:04:05.000"),
+		Level:     level,
+		Tag:       tag,
+		Message:   message,
+	}
+
+	if len(lb.entries) >= lb.maxSize {
+		// Remove oldest entry
+		lb.entries = lb.entries[1:]
+	}
+	lb.entries = append(lb.entries, entry)
+
+	// Also print to logcat for debugging
+	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()
+
+	jsonBytes, _ := json.Marshal(lb.entries)
+	return string(jsonBytes)
+}
+
+// getSince returns log entries since the given index (internal use)
+func (lb *LogBuffer) getSince(index int) ([]LogEntry, int) {
+	lb.mu.RLock()
+	defer lb.mu.RUnlock()
+
+	if index < 0 {
+		index = 0
+	}
+	if index >= len(lb.entries) {
+		return []LogEntry{}, len(lb.entries)
+	}
+
+	entries := lb.entries[index:]
+	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...))
+}
+
+func LogInfo(tag, format string, args ...interface{}) {
+	GetLogBuffer().Add("INFO", tag, fmt.Sprintf(format, args...))
+}
+
+func LogWarn(tag, format string, args ...interface{}) {
+	GetLogBuffer().Add("WARN", tag, fmt.Sprintf(format, args...))
+}
+
+func LogError(tag, format string, args ...interface{}) {
+	GetLogBuffer().Add("ERROR", tag, fmt.Sprintf(format, args...))
+}
+
+// GoLog is a drop-in replacement for fmt.Printf that also logs to buffer
+// It parses the tag from the format string if it starts with [Tag]
+func GoLog(format string, args ...interface{}) {
+	message := fmt.Sprintf(format, args...)
+	message = strings.TrimSuffix(message, "\n")
+
+	// Extract tag from message if present (e.g., "[Tidal] message")
+	tag := "Go"
+	level := "INFO"
+
+	if strings.HasPrefix(message, "[") {
+		endBracket := strings.Index(message, "]")
+		if endBracket > 1 {
+			tag = message[1:endBracket]
+			message = strings.TrimSpace(message[endBracket+1:])
+		}
+	}
+
+	// Determine level from message content
+	msgLower := strings.ToLower(message)
+	if strings.Contains(msgLower, "error") || strings.Contains(msgLower, "failed") || strings.HasPrefix(message, "✗") {
+		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") {
+		level = "INFO"
+	} else if strings.Contains(msgLower, "searching") || strings.Contains(msgLower, "trying") || strings.Contains(msgLower, "found") {
+		level = "DEBUG"
+	}
+
+	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)
+	result := fmt.Sprintf(`{"logs":%s,"next_index":%d}`, string(logsJson), nextIndex)
+	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

@@ -248,15 +248,54 @@ func msToLRCTimestamp(ms int64) string {
 	return fmt.Sprintf("[%02d:%02d.%02d]", minutes, seconds, centiseconds)
 }
 
-func convertToLRC(lyrics *LyricsResponse) string {
+// 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 ""
 	}
 
 	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 == "" {
+				continue
+			}
 			timestamp := msToLRCTimestamp(line.StartTimeMs)
 			builder.WriteString(timestamp)
 			builder.WriteString(line.Words)
@@ -264,6 +303,9 @@ func convertToLRC(lyrics *LyricsResponse) string {
 		}
 	} else {
 		for _, line := range lyrics.Lines {
+			if line.Words == "" {
+				continue
+			}
 			builder.WriteString(line.Words)
 			builder.WriteString("\n")
 		}

go_backend/metadata.go

@@ -58,7 +58,7 @@ func EmbedMetadata(filePath string, metadata Metadata, coverPath string) error {
 	setComment(cmt, "ALBUM", metadata.Album)
 	setComment(cmt, "ALBUMARTIST", metadata.AlbumArtist)
 	setComment(cmt, "DATE", metadata.Date)
-	
+
 	if metadata.TrackNumber > 0 {
 		if metadata.TotalTracks > 0 {
 			setComment(cmt, "TRACKNUMBER", fmt.Sprintf("%d/%d", metadata.TrackNumber, metadata.TotalTracks))
@@ -66,15 +66,15 @@ func EmbedMetadata(filePath string, metadata Metadata, coverPath string) error {
 			setComment(cmt, "TRACKNUMBER", strconv.Itoa(metadata.TrackNumber))
 		}
 	}
-	
+
 	if metadata.DiscNumber > 0 {
 		setComment(cmt, "DISCNUMBER", strconv.Itoa(metadata.DiscNumber))
 	}
-	
+
 	if metadata.ISRC != "" {
 		setComment(cmt, "ISRC", metadata.ISRC)
 	}
-	
+
 	if metadata.Description != "" {
 		setComment(cmt, "DESCRIPTION", metadata.Description)
 	}
@@ -105,7 +105,7 @@ func EmbedMetadata(filePath string, metadata Metadata, coverPath string) error {
 						f.Meta = append(f.Meta[:i], f.Meta[i+1:]...)
 					}
 				}
-				
+
 				picture, err := flacpicture.NewFromImageData(
 					flacpicture.PictureTypeFrontCover,
 					"Front Cover",
@@ -162,7 +162,7 @@ func EmbedMetadataWithCoverData(filePath string, metadata Metadata, coverData []
 	setComment(cmt, "ALBUM", metadata.Album)
 	setComment(cmt, "ALBUMARTIST", metadata.AlbumArtist)
 	setComment(cmt, "DATE", metadata.Date)
-	
+
 	if metadata.TrackNumber > 0 {
 		if metadata.TotalTracks > 0 {
 			setComment(cmt, "TRACKNUMBER", fmt.Sprintf("%d/%d", metadata.TrackNumber, metadata.TotalTracks))
@@ -170,15 +170,15 @@ func EmbedMetadataWithCoverData(filePath string, metadata Metadata, coverData []
 			setComment(cmt, "TRACKNUMBER", strconv.Itoa(metadata.TrackNumber))
 		}
 	}
-	
+
 	if metadata.DiscNumber > 0 {
 		setComment(cmt, "DISCNUMBER", strconv.Itoa(metadata.DiscNumber))
 	}
-	
+
 	if metadata.ISRC != "" {
 		setComment(cmt, "ISRC", metadata.ISRC)
 	}
-	
+
 	if metadata.Description != "" {
 		setComment(cmt, "DESCRIPTION", metadata.Description)
 	}
@@ -204,7 +204,7 @@ func EmbedMetadataWithCoverData(filePath string, metadata Metadata, coverData []
 				f.Meta = append(f.Meta[:i], f.Meta[i+1:]...)
 			}
 		}
-		
+
 		picture, err := flacpicture.NewFromImageData(
 			flacpicture.PictureTypeFrontCover,
 			"Front Cover",
@@ -257,11 +257,30 @@ func ReadMetadata(filePath string) (*Metadata, error) {
 			if trackNum != "" {
 				fmt.Sscanf(trackNum, "%d", &metadata.TrackNumber)
 			}
+			// Also try lowercase variant (some encoders use lowercase)
+			if metadata.TrackNumber == 0 {
+				trackNum = getComment(cmt, "TRACK")
+				if trackNum != "" {
+					fmt.Sscanf(trackNum, "%d", &metadata.TrackNumber)
+				}
+			}
 
 			discNum := getComment(cmt, "DISCNUMBER")
 			if discNum != "" {
 				fmt.Sscanf(discNum, "%d", &metadata.DiscNumber)
 			}
+			// Also try DISC variant
+			if metadata.DiscNumber == 0 {
+				discNum = getComment(cmt, "DISC")
+				if discNum != "" {
+					fmt.Sscanf(discNum, "%d", &metadata.DiscNumber)
+				}
+			}
+
+			// Try DATE variants
+			if metadata.Date == "" {
+				metadata.Date = getComment(cmt, "YEAR")
+			}
 
 			break
 		}
@@ -291,9 +310,14 @@ func setComment(cmt *flacvorbis.MetaDataBlockVorbisComment, key, value string) {
 }
 
 func getComment(cmt *flacvorbis.MetaDataBlockVorbisComment, key string) string {
+	keyUpper := strings.ToUpper(key) + "="
 	for _, comment := range cmt.Comments {
-		if len(comment) > len(key)+1 && comment[:len(key)+1] == key+"=" {
+		if len(comment) > len(key) {
-			return comment[len(key)+1:]
+			// Case-insensitive comparison for Vorbis comments
+			commentUpper := strings.ToUpper(comment[:len(key)+1])
+			if commentUpper == keyUpper {
+				return comment[len(key)+1:]
+			}
 		}
 	}
 	return ""
@@ -356,13 +380,13 @@ func ExtractLyrics(filePath string) (string, error) {
 			if err != nil {
 				continue
 			}
-			
+
 			// Try LYRICS tag first
 			lyrics, err := cmt.Get("LYRICS")
 			if err == nil && len(lyrics) > 0 && lyrics[0] != "" {
 				return lyrics[0], nil
 			}
-			
+
 			// Fallback to UNSYNCEDLYRICS
 			lyrics, err = cmt.Get("UNSYNCEDLYRICS")
 			if err == nil && len(lyrics) > 0 && lyrics[0] != "" {
@@ -376,12 +400,14 @@ func ExtractLyrics(filePath string) (string, error) {
 
 // AudioQuality represents audio quality info from a FLAC file
 type AudioQuality struct {
-	BitDepth   int `json:"bit_depth"`
+	BitDepth     int   `json:"bit_depth"`
-	SampleRate int `json:"sample_rate"`
+	SampleRate   int   `json:"sample_rate"`
+	TotalSamples int64 `json:"total_samples"`
 }
 
 // GetAudioQuality reads bit depth and sample rate from a FLAC file's StreamInfo block
 // FLAC StreamInfo is always the first metadata block after the 4-byte "fLaC" marker
+// For M4A files, it delegates to GetM4AQuality
 func GetAudioQuality(filePath string) (AudioQuality, error) {
 	file, err := os.Open(filePath)
 	if err != nil {
@@ -389,45 +415,408 @@ func GetAudioQuality(filePath string) (AudioQuality, error) {
 	}
 	defer file.Close()
 
-	// Read FLAC marker (4 bytes: "fLaC")
+	// Read first 4 bytes to detect file type
 	marker := make([]byte, 4)
 	if _, err := file.Read(marker); err != nil {
 		return AudioQuality{}, fmt.Errorf("failed to read marker: %w", err)
 	}
-	if string(marker) != "fLaC" {
+
-		return AudioQuality{}, fmt.Errorf("not a FLAC file")
+	// Check if it's a FLAC file
+	if string(marker) == "fLaC" {
+		// Continue reading FLAC metadata
+		// Read metadata block header (4 bytes)
+		header := make([]byte, 4)
+		if _, err := file.Read(header); err != nil {
+			return AudioQuality{}, fmt.Errorf("failed to read header: %w", err)
+		}
+
+		blockType := header[0] & 0x7F
+		if blockType != 0 {
+			return AudioQuality{}, fmt.Errorf("first block is not STREAMINFO")
+		}
+
+		// Read STREAMINFO block (34 bytes minimum)
+		streamInfo := make([]byte, 34)
+		if _, err := file.Read(streamInfo); err != nil {
+			return AudioQuality{}, fmt.Errorf("failed to read STREAMINFO: %w", err)
+		}
+
+		// Parse sample rate (20 bits starting at byte 10)
+		sampleRate := (int(streamInfo[10]) << 12) | (int(streamInfo[11]) << 4) | (int(streamInfo[12]) >> 4)
+
+		// Parse bits per sample (5 bits)
+		bitsPerSample := ((int(streamInfo[12]) & 0x01) << 4) | (int(streamInfo[13]) >> 4) + 1
+
+		// Parse total samples (36 bits: 4 bits from byte 13, all of bytes 14-17)
+		totalSamples := int64(streamInfo[13]&0x0F)<<32 |
+			int64(streamInfo[14])<<24 |
+			int64(streamInfo[15])<<16 |
+			int64(streamInfo[16])<<8 |
+			int64(streamInfo[17])
+
+		return AudioQuality{
+			BitDepth:     bitsPerSample,
+			SampleRate:   sampleRate,
+			TotalSamples: totalSamples,
+		}, nil
 	}
 
-	// Read metadata block header (4 bytes)
+	// Check if it's an M4A/MP4 file (starts with size + "ftyp")
-	// Byte 0: bit 7 = last block flag, bits 0-6 = block type (0 = STREAMINFO)
+	// First 4 bytes are size, next 4 should be "ftyp"
-	// Bytes 1-3: block length (24-bit big-endian)
+	file.Seek(0, 0) // Reset to beginning
-	header := make([]byte, 4)
+	header8 := make([]byte, 8)
-	if _, err := file.Read(header); err != nil {
+	if _, err := file.Read(header8); err != nil {
 		return AudioQuality{}, fmt.Errorf("failed to read header: %w", err)
 	}
 
-	blockType := header[0] & 0x7F
+	if string(header8[4:8]) == "ftyp" {
-	if blockType != 0 {
+		// It's an M4A/MP4 file, use M4A quality reader
-		return AudioQuality{}, fmt.Errorf("first block is not STREAMINFO")
+		file.Close() // Close before calling GetM4AQuality which opens the file again
+		return GetM4AQuality(filePath)
 	}
 
-	// Read STREAMINFO block (34 bytes minimum)
+	return AudioQuality{}, fmt.Errorf("unsupported file format (not FLAC or M4A)")
-	// Bytes 10-13 contain sample rate (20 bits), channels (3 bits), bits per sample (5 bits)
+}
-	streamInfo := make([]byte, 34)
+
-	if _, err := file.Read(streamInfo); err != nil {
+// ========================================
-		return AudioQuality{}, fmt.Errorf("failed to read STREAMINFO: %w", err)
+// M4A (MP4/AAC) Metadata Embedding
-	}
+// ========================================
-
+
-	// Parse sample rate (20 bits starting at byte 10)
+// EmbedM4AMetadata embeds metadata into an M4A file using iTunes-style atoms
-	// Bytes 10-12: [SSSS SSSS] [SSSS SSSS] [SSSS CCCC] where S=sample rate, C=channels
+// This is a simplified implementation that writes metadata to the file
-	sampleRate := (int(streamInfo[10]) << 12) | (int(streamInfo[11]) << 4) | (int(streamInfo[12]) >> 4)
+func EmbedM4AMetadata(filePath string, metadata Metadata, coverData []byte) error {
-
+	// Read the entire file
-	// Parse bits per sample (5 bits)
+	data, err := os.ReadFile(filePath)
-	// Byte 12 bits 0-3 and byte 13 bit 7: [.... BBBB] [B...] where B=bits per sample - 1
+	if err != nil {
-	bitsPerSample := ((int(streamInfo[12]) & 0x01) << 4) | (int(streamInfo[13]) >> 4) + 1
+		return fmt.Errorf("failed to read M4A file: %w", err)
-
+	}
-	return AudioQuality{
+
-		BitDepth:   bitsPerSample,
+	// Find moov atom position
-		SampleRate: sampleRate,
+	moovPos := findAtom(data, "moov", 0)
-	}, nil
+	if moovPos < 0 {
+		return fmt.Errorf("moov atom not found in M4A file")
+	}
+
+	// Find udta atom inside moov, or create one
+	moovSize := int(uint32(data[moovPos])<<24 | uint32(data[moovPos+1])<<16 | uint32(data[moovPos+2])<<8 | uint32(data[moovPos+3]))
+	udtaPos := findAtom(data, "udta", moovPos+8)
+
+	// Build new metadata atoms
+	metaAtom := buildMetaAtom(metadata, coverData)
+
+	var newData []byte
+	if udtaPos >= 0 && udtaPos < moovPos+moovSize {
+		// udta exists, find meta inside it or replace
+		udtaSize := int(uint32(data[udtaPos])<<24 | uint32(data[udtaPos+1])<<16 | uint32(data[udtaPos+2])<<8 | uint32(data[udtaPos+3]))
+		metaPos := findAtom(data, "meta", udtaPos+8)
+
+		if metaPos >= 0 && metaPos < udtaPos+udtaSize {
+			// Replace existing meta atom
+			metaSize := int(uint32(data[metaPos])<<24 | uint32(data[metaPos+1])<<16 | uint32(data[metaPos+2])<<8 | uint32(data[metaPos+3]))
+			newData = append(newData, data[:metaPos]...)
+			newData = append(newData, metaAtom...)
+			newData = append(newData, data[metaPos+metaSize:]...)
+		} else {
+			// Add meta atom to udta
+			newUdtaContent := append(data[udtaPos+8:udtaPos+udtaSize], metaAtom...)
+			newUdtaSize := 8 + len(newUdtaContent)
+			newUdta := make([]byte, 4)
+			newUdta[0] = byte(newUdtaSize >> 24)
+			newUdta[1] = byte(newUdtaSize >> 16)
+			newUdta[2] = byte(newUdtaSize >> 8)
+			newUdta[3] = byte(newUdtaSize)
+			newUdta = append(newUdta, []byte("udta")...)
+			newUdta = append(newUdta, newUdtaContent...)
+
+			newData = append(newData, data[:udtaPos]...)
+			newData = append(newData, newUdta...)
+			newData = append(newData, data[udtaPos+udtaSize:]...)
+		}
+	} else {
+		// Create new udta with meta
+		udtaContent := metaAtom
+		udtaSize := 8 + len(udtaContent)
+		newUdta := make([]byte, 4)
+		newUdta[0] = byte(udtaSize >> 24)
+		newUdta[1] = byte(udtaSize >> 16)
+		newUdta[2] = byte(udtaSize >> 8)
+		newUdta[3] = byte(udtaSize)
+		newUdta = append(newUdta, []byte("udta")...)
+		newUdta = append(newUdta, udtaContent...)
+
+		// Insert udta at end of moov
+		insertPos := moovPos + moovSize
+		newData = append(newData, data[:insertPos]...)
+		newData = append(newData, newUdta...)
+		newData = append(newData, data[insertPos:]...)
+	}
+
+	// Update moov size
+	newMoovSize := moovSize + len(newData) - len(data)
+	newData[moovPos] = byte(newMoovSize >> 24)
+	newData[moovPos+1] = byte(newMoovSize >> 16)
+	newData[moovPos+2] = byte(newMoovSize >> 8)
+	newData[moovPos+3] = byte(newMoovSize)
+
+	// Write back to file
+	if err := os.WriteFile(filePath, newData, 0644); err != nil {
+		return fmt.Errorf("failed to write M4A file: %w", err)
+	}
+
+	fmt.Printf("[M4A] Metadata embedded successfully\n")
+	return nil
+}
+
+// findAtom finds an atom by name starting from offset
+func findAtom(data []byte, name string, offset int) int {
+	for i := offset; i < len(data)-8; {
+		size := int(uint32(data[i])<<24 | uint32(data[i+1])<<16 | uint32(data[i+2])<<8 | uint32(data[i+3]))
+		if size < 8 {
+			break
+		}
+		atomName := string(data[i+4 : i+8])
+		if atomName == name {
+			return i
+		}
+		i += size
+	}
+	return -1
+}
+
+// buildMetaAtom builds a complete meta atom with ilst containing metadata
+func buildMetaAtom(metadata Metadata, coverData []byte) []byte {
+	// Build ilst content
+	var ilst []byte
+
+	// ©nam - Title
+	if metadata.Title != "" {
+		ilst = append(ilst, buildTextAtom("©nam", metadata.Title)...)
+	}
+
+	// ©ART - Artist
+	if metadata.Artist != "" {
+		ilst = append(ilst, buildTextAtom("©ART", metadata.Artist)...)
+	}
+
+	// ©alb - Album
+	if metadata.Album != "" {
+		ilst = append(ilst, buildTextAtom("©alb", metadata.Album)...)
+	}
+
+	// aART - Album Artist
+	if metadata.AlbumArtist != "" {
+		ilst = append(ilst, buildTextAtom("aART", metadata.AlbumArtist)...)
+	}
+
+	// ©day - Year/Date
+	if metadata.Date != "" {
+		ilst = append(ilst, buildTextAtom("©day", metadata.Date)...)
+	}
+
+	// trkn - Track Number
+	if metadata.TrackNumber > 0 {
+		ilst = append(ilst, buildTrackNumberAtom(metadata.TrackNumber, metadata.TotalTracks)...)
+	}
+
+	// disk - Disc Number
+	if metadata.DiscNumber > 0 {
+		ilst = append(ilst, buildDiscNumberAtom(metadata.DiscNumber, 0)...)
+	}
+
+	// ©lyr - Lyrics
+	if metadata.Lyrics != "" {
+		ilst = append(ilst, buildTextAtom("©lyr", metadata.Lyrics)...)
+	}
+
+	// covr - Cover Art
+	if len(coverData) > 0 {
+		ilst = append(ilst, buildCoverAtom(coverData)...)
+	}
+
+	// Build ilst atom
+	ilstSize := 8 + len(ilst)
+	ilstAtom := make([]byte, 4)
+	ilstAtom[0] = byte(ilstSize >> 24)
+	ilstAtom[1] = byte(ilstSize >> 16)
+	ilstAtom[2] = byte(ilstSize >> 8)
+	ilstAtom[3] = byte(ilstSize)
+	ilstAtom = append(ilstAtom, []byte("ilst")...)
+	ilstAtom = append(ilstAtom, ilst...)
+
+	// Build hdlr atom (required for meta)
+	hdlr := []byte{
+		0, 0, 0, 33, // size = 33
+		'h', 'd', 'l', 'r',
+		0, 0, 0, 0, // version + flags
+		0, 0, 0, 0, // predefined
+		'm', 'd', 'i', 'r', // handler type
+		'a', 'p', 'p', 'l', // manufacturer
+		0, 0, 0, 0, // component flags
+		0, 0, 0, 0, // component flags mask
+		0, // null terminator
+	}
+
+	// Build meta atom
+	metaContent := append([]byte{0, 0, 0, 0}, hdlr...) // version + flags + hdlr
+	metaContent = append(metaContent, ilstAtom...)
+
+	metaSize := 8 + len(metaContent)
+	metaAtom := make([]byte, 4)
+	metaAtom[0] = byte(metaSize >> 24)
+	metaAtom[1] = byte(metaSize >> 16)
+	metaAtom[2] = byte(metaSize >> 8)
+	metaAtom[3] = byte(metaSize)
+	metaAtom = append(metaAtom, []byte("meta")...)
+	metaAtom = append(metaAtom, metaContent...)
+
+	return metaAtom
+}
+
+// buildTextAtom builds a text metadata atom (©nam, ©ART, etc.)
+func buildTextAtom(name, value string) []byte {
+	valueBytes := []byte(value)
+
+	// data atom
+	dataSize := 16 + len(valueBytes)
+	dataAtom := make([]byte, 4)
+	dataAtom[0] = byte(dataSize >> 24)
+	dataAtom[1] = byte(dataSize >> 16)
+	dataAtom[2] = byte(dataSize >> 8)
+	dataAtom[3] = byte(dataSize)
+	dataAtom = append(dataAtom, []byte("data")...)
+	dataAtom = append(dataAtom, 0, 0, 0, 1) // type = UTF-8
+	dataAtom = append(dataAtom, 0, 0, 0, 0) // locale
+	dataAtom = append(dataAtom, valueBytes...)
+
+	// container atom
+	atomSize := 8 + len(dataAtom)
+	atom := make([]byte, 4)
+	atom[0] = byte(atomSize >> 24)
+	atom[1] = byte(atomSize >> 16)
+	atom[2] = byte(atomSize >> 8)
+	atom[3] = byte(atomSize)
+	atom = append(atom, []byte(name)...)
+	atom = append(atom, dataAtom...)
+
+	return atom
+}
+
+// buildTrackNumberAtom builds trkn atom
+func buildTrackNumberAtom(track, total int) []byte {
+	// data atom with track number
+	dataAtom := []byte{
+		0, 0, 0, 24, // size
+		'd', 'a', 't', 'a',
+		0, 0, 0, 0, // type = implicit
+		0, 0, 0, 0, // locale
+		0, 0, // padding
+		byte(track >> 8), byte(track), // track number
+		byte(total >> 8), byte(total), // total tracks
+		0, 0, // padding
+	}
+
+	// trkn atom
+	atomSize := 8 + len(dataAtom)
+	atom := make([]byte, 4)
+	atom[0] = byte(atomSize >> 24)
+	atom[1] = byte(atomSize >> 16)
+	atom[2] = byte(atomSize >> 8)
+	atom[3] = byte(atomSize)
+	atom = append(atom, []byte("trkn")...)
+	atom = append(atom, dataAtom...)
+
+	return atom
+}
+
+// buildDiscNumberAtom builds disk atom
+func buildDiscNumberAtom(disc, total int) []byte {
+	// data atom with disc number
+	dataAtom := []byte{
+		0, 0, 0, 22, // size
+		'd', 'a', 't', 'a',
+		0, 0, 0, 0, // type = implicit
+		0, 0, 0, 0, // locale
+		0, 0, // padding
+		byte(disc >> 8), byte(disc), // disc number
+		byte(total >> 8), byte(total), // total discs
+	}
+
+	// disk atom
+	atomSize := 8 + len(dataAtom)
+	atom := make([]byte, 4)
+	atom[0] = byte(atomSize >> 24)
+	atom[1] = byte(atomSize >> 16)
+	atom[2] = byte(atomSize >> 8)
+	atom[3] = byte(atomSize)
+	atom = append(atom, []byte("disk")...)
+	atom = append(atom, dataAtom...)
+
+	return atom
+}
+
+// buildCoverAtom builds covr atom with image data
+func buildCoverAtom(coverData []byte) []byte {
+	// Detect image type (JPEG = 13, PNG = 14)
+	imageType := byte(13) // default JPEG
+	if len(coverData) > 8 && coverData[0] == 0x89 && coverData[1] == 'P' && coverData[2] == 'N' && coverData[3] == 'G' {
+		imageType = 14 // PNG
+	}
+
+	// data atom
+	dataSize := 16 + len(coverData)
+	dataAtom := make([]byte, 4)
+	dataAtom[0] = byte(dataSize >> 24)
+	dataAtom[1] = byte(dataSize >> 16)
+	dataAtom[2] = byte(dataSize >> 8)
+	dataAtom[3] = byte(dataSize)
+	dataAtom = append(dataAtom, []byte("data")...)
+	dataAtom = append(dataAtom, 0, 0, 0, imageType) // type = JPEG or PNG
+	dataAtom = append(dataAtom, 0, 0, 0, 0)         // locale
+	dataAtom = append(dataAtom, coverData...)
+
+	// covr atom
+	atomSize := 8 + len(dataAtom)
+	atom := make([]byte, 4)
+	atom[0] = byte(atomSize >> 24)
+	atom[1] = byte(atomSize >> 16)
+	atom[2] = byte(atomSize >> 8)
+	atom[3] = byte(atomSize)
+	atom = append(atom, []byte("covr")...)
+	atom = append(atom, dataAtom...)
+
+	return atom
+}
+
+// GetM4AQuality reads audio quality from M4A file
+func GetM4AQuality(filePath string) (AudioQuality, error) {
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		return AudioQuality{}, fmt.Errorf("failed to read M4A file: %w", err)
+	}
+
+	// Find moov -> trak -> mdia -> minf -> stbl -> stsd
+	moovPos := findAtom(data, "moov", 0)
+	if moovPos < 0 {
+		return AudioQuality{}, fmt.Errorf("moov atom not found")
+	}
+
+	// Search for mp4a or alac atom which contains audio info
+	// This is a simplified search - real implementation would traverse the atom tree
+	for i := moovPos; i < len(data)-20; i++ {
+		if string(data[i:i+4]) == "mp4a" || string(data[i:i+4]) == "alac" {
+			// Sample rate is at offset 22-23 from atom start (16-bit big-endian)
+			if i+24 < len(data) {
+				sampleRate := int(data[i+22])<<8 | int(data[i+23])
+				// For AAC, bit depth is typically 16
+				bitDepth := 16
+				if string(data[i:i+4]) == "alac" {
+					// ALAC can have higher bit depth, check esds or alac specific data
+					bitDepth = 24 // Assume 24-bit for ALAC
+				}
+				return AudioQuality{BitDepth: bitDepth, SampleRate: sampleRate}, nil
+			}
+		}
+	}
+
+	return AudioQuality{}, fmt.Errorf("audio info not found in M4A file")
 }

go_backend/parallel.go

@@ -0,0 +1,289 @@
+package gobackend
+
+import (
+	"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
+}
+
+var (
+	globalTrackIDCache *TrackIDCache
+	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 for 30 minutes
+		}
+	})
+	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) {
+		return nil
+	}
+	return entry
+}
+
+// SetTidal caches Tidal track ID for an ISRC
+func (c *TrackIDCache) SetTidal(isrc string, trackID int64) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	entry, exists := c.cache[isrc]
+	if !exists {
+		entry = &TrackIDCacheEntry{}
+		c.cache[isrc] = entry
+	}
+	entry.TidalTrackID = trackID
+	entry.ExpiresAt = time.Now().Add(c.ttl)
+}
+
+// SetQobuz caches Qobuz track ID for an ISRC
+func (c *TrackIDCache) SetQobuz(isrc string, trackID int64) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	entry, exists := c.cache[isrc]
+	if !exists {
+		entry = &TrackIDCacheEntry{}
+		c.cache[isrc] = entry
+	}
+	entry.QobuzTrackID = trackID
+	entry.ExpiresAt = time.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
+	}
+	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
+	LyricsLRC  string
+	CoverErr   error
+	LyricsErr  error
+}
+
+// FetchCoverAndLyricsParallel downloads cover and fetches lyrics in parallel
+// This runs while the main audio download is happening
+func FetchCoverAndLyricsParallel(
+	coverURL string,
+	maxQualityCover bool,
+	spotifyID string,
+	trackName string,
+	artistName string,
+	embedLyrics bool,
+) *ParallelDownloadResult {
+	result := &ParallelDownloadResult{}
+	var wg sync.WaitGroup
+
+	// Download cover in parallel
+	if coverURL != "" {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			fmt.Println("[Parallel] Starting cover download...")
+			data, err := downloadCoverToMemory(coverURL, maxQualityCover)
+			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))
+			}
+		}()
+	}
+
+	// Fetch lyrics in parallel
+	if embedLyrics {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			fmt.Println("[Parallel] Starting lyrics fetch...")
+			client := NewLyricsClient()
+			lyrics, err := client.FetchLyricsAllSources(spotifyID, trackName, artistName)
+			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
+				// Use LRC with metadata headers (like PC version)
+				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")
+			}
+		}()
+	}
+
+	wg.Wait()
+	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"
+}
+
+// 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()
+
+	// Limit concurrent pre-warm requests
+	semaphore := make(chan struct{}, 3) // Max 3 concurrent
+	var wg sync.WaitGroup
+
+	for _, req := range requests {
+		// Skip if already cached
+		if cached := cache.Get(req.ISRC); cached != nil {
+			continue
+		}
+
+		wg.Add(1)
+		go func(r PreWarmCacheRequest) {
+			defer wg.Done()
+			semaphore <- struct{}{}        // Acquire
+			defer func() { <-semaphore }() // Release
+
+			switch r.Service {
+			case "tidal":
+				preWarmTidalCache(r.ISRC, r.TrackName, r.ArtistName)
+			case "qobuz":
+				preWarmQobuzCache(r.ISRC)
+			case "amazon":
+				preWarmAmazonCache(r.ISRC, r.SpotifyID)
+			}
+		}(req)
+	}
+
+	wg.Wait()
+	fmt.Printf("[Cache] Pre-warm complete. Cache size: %d\n", cache.Size())
+}
+
+func preWarmTidalCache(isrc, _, _ string) {
+	downloader := NewTidalDownloader()
+	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) {
+	downloader := NewQobuzDownloader()
+	track, err := downloader.SearchTrackByISRC(isrc)
+	if err == nil && track != nil {
+		GetTrackIDCache().SetQobuz(isrc, track.ID)
+		fmt.Printf("[Cache] Cached Qobuz ID for ISRC %s: %d\n", isrc, track.ID)
+	}
+}
+
+func preWarmAmazonCache(isrc, spotifyID string) {
+	// Amazon uses SongLink to get URL, so we pre-warm by checking availability
+	client := NewSongLinkClient()
+	availability, err := client.CheckTrackAvailability(spotifyID, isrc)
+	if err == nil && availability != nil && availability.Amazon {
+		// Store Amazon URL in cache (using ISRC as key)
+		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
+	// Parse JSON (simplified - in production use proper JSON parsing)
+	// For now, this is called from exports.go with proper parsing
+
+	go PreWarmTrackCache(requests) // Run in background
+	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

@@ -3,6 +3,7 @@ package gobackend
 import (
 	"encoding/json"
 	"sync"
+	"time"
 )
 
 // DownloadProgress represents current download progress
@@ -22,7 +23,8 @@ 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
+	Progress      float64 `json:"progress"`   // 0.0 to 1.0
+	SpeedMBps     float64 `json:"speed_mbps"` // Download speed in MB/s
 	IsDownloading bool    `json:"is_downloading"`
 	Status        string  `json:"status"` // "downloading", "finalizing", "completed"
 }
@@ -124,6 +126,20 @@ func SetItemBytesReceived(itemID string, received int64) {
 	}
 }
 
+// SetItemBytesReceivedWithSpeed sets bytes received and speed for an item
+func SetItemBytesReceivedWithSpeed(itemID string, received int64, speedMBps float64) {
+	multiMu.Lock()
+	defer multiMu.Unlock()
+
+	if item, ok := multiProgress.Items[itemID]; ok {
+		item.BytesReceived = received
+		item.SpeedMBps = speedMBps
+		if item.BytesTotal > 0 {
+			item.Progress = float64(received) / float64(item.BytesTotal)
+		}
+	}
+}
+
 // CompleteItemProgress marks an item as complete
 func CompleteItemProgress(itemID string) {
 	multiMu.Lock()
@@ -188,35 +204,64 @@ func setDownloadDir(path string) error {
 }
 
 // getDownloadDir returns the default download directory
-func getDownloadDir() string {
+// Kept for potential future use
-	downloadDirMu.RLock()
+// func getDownloadDir() string {
-	defer downloadDirMu.RUnlock()
+// 	downloadDirMu.RLock()
-	return downloadDir
+// 	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) }
+	writer       interface{ Write([]byte) (int, error) }
-	itemID  string
+	itemID       string
-	current int64
+	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
 }
 
+const progressUpdateThreshold = 64 * 1024 // Update progress every 64KB
+
 // 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{
-		writer:  w,
+		writer:       w,
-		itemID:  itemID,
+		itemID:       itemID,
-		current: 0,
+		current:      0,
+		lastReported: 0,
+		startTime:    now,
+		lastTime:     now,
+		lastBytes:    0,
 	}
 }
 
-// Write implements io.Writer
+// Write implements io.Writer with threshold-based progress updates and speed tracking
 func (pw *ItemProgressWriter) Write(p []byte) (int, error) {
 	n, err := pw.writer.Write(p)
 	if err != nil {
 		return n, err
 	}
 	pw.current += int64(n)
-	SetItemBytesReceived(pw.itemID, pw.current)
+
+	// Update progress when we've received at least 64KB since last update
+	// Also update on first write to show download has started
+	if pw.lastReported == 0 || pw.current-pw.lastReported >= progressUpdateThreshold {
+		// Calculate speed (MB/s) based on bytes received since last update
+		now := time.Now()
+		elapsed := now.Sub(pw.lastTime).Seconds()
+		var speedMBps float64
+		if elapsed > 0 {
+			bytesInInterval := pw.current - pw.lastBytes
+			speedMBps = float64(bytesInInterval) / (1024 * 1024) / elapsed
+		}
+
+		SetItemBytesReceivedWithSpeed(pw.itemID, pw.current, speedMBps)
+		pw.lastReported = pw.current
+		pw.lastTime = now
+		pw.lastBytes = pw.current
+	}
 	return n, nil
 }

go_backend/romaji.go

@@ -0,0 +1,222 @@
+package gobackend
+
+import (
+	"strings"
+	"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",
+	'さ': "sa", 'し': "shi", 'す': "su", 'せ': "se", 'そ': "so",
+	'た': "ta", 'ち': "chi", 'つ': "tsu", 'て': "te", 'と': "to",
+	'な': "na", 'に': "ni", 'ぬ': "nu", 'ね': "ne", 'の': "no",
+	'は': "ha", 'ひ': "hi", 'ふ': "fu", 'へ': "he", 'ほ': "ho",
+	'ま': "ma", 'み': "mi", 'む': "mu", 'め': "me", 'も': "mo",
+	'や': "ya", 'ゆ': "yu", 'よ': "yo",
+	'ら': "ra", 'り': "ri", 'る': "ru", 'れ': "re", 'ろ': "ro",
+	'わ': "wa", 'を': "wo", 'ん': "n",
+	// Dakuten (voiced)
+	'が': "ga", 'ぎ': "gi", 'ぐ': "gu", 'げ': "ge", 'ご': "go",
+	'ざ': "za", 'じ': "ji", 'ず': "zu", 'ぜ': "ze", 'ぞ': "zo",
+	'だ': "da", 'ぢ': "ji", 'づ': "zu", 'で': "de", 'ど': "do",
+	'ば': "ba", 'び': "bi", 'ぶ': "bu", 'べ': "be", 'ぼ': "bo",
+	// Handakuten (semi-voiced)
+	'ぱ': "pa", 'ぴ': "pi", 'ぷ': "pu", 'ぺ': "pe", 'ぽ': "po",
+	// Small characters
+	'ゃ': "ya", 'ゅ': "yu", 'ょ': "yo",
+	'っ': "", // Double consonant marker
+	'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",
+	'サ': "sa", 'シ': "shi", 'ス': "su", 'セ': "se", 'ソ': "so",
+	'タ': "ta", 'チ': "chi", 'ツ': "tsu", 'テ': "te", 'ト': "to",
+	'ナ': "na", 'ニ': "ni", 'ヌ': "nu", 'ネ': "ne", 'ノ': "no",
+	'ハ': "ha", 'ヒ': "hi", 'フ': "fu", 'ヘ': "he", 'ホ': "ho",
+	'マ': "ma", 'ミ': "mi", 'ム': "mu", 'メ': "me", 'モ': "mo",
+	'ヤ': "ya", 'ユ': "yu", 'ヨ': "yo",
+	'ラ': "ra", 'リ': "ri", 'ル': "ru", 'レ': "re", 'ロ': "ro",
+	'ワ': "wa", 'ヲ': "wo", 'ン': "n",
+	// Dakuten (voiced)
+	'ガ': "ga", 'ギ': "gi", 'グ': "gu", 'ゲ': "ge", 'ゴ': "go",
+	'ザ': "za", 'ジ': "ji", 'ズ': "zu", 'ゼ': "ze", 'ゾ': "zo",
+	'ダ': "da", 'ヂ': "ji", 'ヅ': "zu", 'デ': "de", 'ド': "do",
+	'バ': "ba", 'ビ': "bi", 'ブ': "bu", 'ベ': "be", 'ボ': "bo",
+	// Handakuten (semi-voiced)
+	'パ': "pa", 'ピ': "pi", 'プ': "pu", 'ペ': "pe", 'ポ': "po",
+	// Small characters
+	'ャ': "ya", 'ュ': "yu", 'ョ': "yo",
+	'ッ': "", // Double consonant marker
+	'ァ': "a", 'ィ': "i", 'ゥ': "u", 'ェ': "e", 'ォ': "o",
+	// Extended katakana
+	'ー': "", // Long vowel mark
+	'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",
+	"ちゃ": "cha", "ちゅ": "chu", "ちょ": "cho",
+	"にゃ": "nya", "にゅ": "nyu", "にょ": "nyo",
+	"ひゃ": "hya", "ひゅ": "hyu", "ひょ": "hyo",
+	"みゃ": "mya", "みゅ": "myu", "みょ": "myo",
+	"りゃ": "rya", "りゅ": "ryu", "りょ": "ryo",
+	"ぎゃ": "gya", "ぎゅ": "gyu", "ぎょ": "gyo",
+	"じゃ": "ja", "じゅ": "ju", "じょ": "jo",
+	"びゃ": "bya", "びゅ": "byu", "びょ": "byo",
+	"ぴゃ": "pya", "ぴゅ": "pyu", "ぴょ": "pyo",
+}
+
+var combinationKatakana = map[string]string{
+	"キャ": "kya", "キュ": "kyu", "キョ": "kyo",
+	"シャ": "sha", "シュ": "shu", "ショ": "sho",
+	"チャ": "cha", "チュ": "chu", "チョ": "cho",
+	"ニャ": "nya", "ニュ": "nyu", "ニョ": "nyo",
+	"ヒャ": "hya", "ヒュ": "hyu", "ヒョ": "hyo",
+	"ミャ": "mya", "ミュ": "myu", "ミョ": "myo",
+	"リャ": "rya", "リュ": "ryu", "リョ": "ryo",
+	"ギャ": "gya", "ギュ": "gyu", "ギョ": "gyo",
+	"ジャ": "ja", "ジュ": "ju", "ジョ": "jo",
+	"ビャ": "bya", "ビュ": "byu", "ビョ": "byo",
+	"ピャ": "pya", "ピュ": "pyu", "ピョ": "pyo",
+	// Extended combinations
+	"ティ": "ti", "ディ": "di", "トゥ": "tu", "ドゥ": "du",
+	"ファ": "fa", "フィ": "fi", "フェ": "fe", "フォ": "fo",
+	"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) {
+			return true
+		}
+	}
+	return false
+}
+
+func isHiragana(r rune) bool {
+	return r >= 0x3040 && r <= 0x309F
+}
+
+func isKatakana(r rune) bool {
+	return r >= 0x30A0 && r <= 0x30FF
+}
+
+func isKanji(r rune) bool {
+	return (r >= 0x4E00 && r <= 0x9FFF) || // CJK Unified Ideographs
+		(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
+	}
+
+	var result strings.Builder
+	runes := []rune(text)
+	i := 0
+
+	for i < len(runes) {
+		// Check for っ/ッ (double consonant)
+		if i < len(runes)-1 && (runes[i] == 'っ' || runes[i] == 'ッ') {
+			nextRomaji := ""
+			if romaji, ok := hiraganaToRomaji[runes[i+1]]; ok {
+				nextRomaji = romaji
+			} else if romaji, ok := katakanaToRomaji[runes[i+1]]; ok {
+				nextRomaji = romaji
+			}
+			if len(nextRomaji) > 0 {
+				result.WriteByte(nextRomaji[0]) // Double the first consonant
+			}
+			i++
+			continue
+		}
+
+		// Check for two-character combinations
+		if i < len(runes)-1 {
+			combo := string(runes[i : i+2])
+			if romaji, ok := combinationHiragana[combo]; ok {
+				result.WriteString(romaji)
+				i += 2
+				continue
+			}
+			if romaji, ok := combinationKatakana[combo]; ok {
+				result.WriteString(romaji)
+				i += 2
+				continue
+			}
+		}
+
+		// Single character conversion
+		r := runes[i]
+		if romaji, ok := hiraganaToRomaji[r]; ok {
+			result.WriteString(romaji)
+		} else if romaji, ok := katakanaToRomaji[r]; ok {
+			result.WriteString(romaji)
+		} else if isKanji(r) {
+			// Keep kanji as-is (would need dictionary for proper conversion)
+			result.WriteRune(r)
+		} else {
+			// Keep other characters (punctuation, spaces, etc.)
+			result.WriteRune(r)
+		}
+		i++
+	}
+
+	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 {
+		if unicode.IsLetter(r) || unicode.IsNumber(r) || unicode.IsSpace(r) {
+			result.WriteRune(r)
+		} else if r == '-' || r == '\'' {
+			result.WriteRune(r)
+		}
+	}
+	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)
+}

go_backend/songlink.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"strings"
+	"sync"
 	"time"
 )
 
@@ -20,20 +22,37 @@ type TrackAvailability struct {
 	Tidal     bool   `json:"tidal"`
 	Amazon    bool   `json:"amazon"`
 	Qobuz     bool   `json:"qobuz"`
+	Deezer    bool   `json:"deezer"`
 	TidalURL  string `json:"tidal_url,omitempty"`
 	AmazonURL string `json:"amazon_url,omitempty"`
 	QobuzURL  string `json:"qobuz_url,omitempty"`
+	DeezerURL string `json:"deezer_url,omitempty"`
+	DeezerID  string `json:"deezer_id,omitempty"`
 }
 
-// NewSongLinkClient creates a new SongLink client
+var (
+	// Global SongLink client instance for connection reuse
+	globalSongLinkClient *SongLinkClient
+	songLinkClientOnce   sync.Once
+)
+
+// NewSongLinkClient creates a new SongLink client (returns singleton for connection reuse)
 func NewSongLinkClient() *SongLinkClient {
-	return &SongLinkClient{
+	songLinkClientOnce.Do(func() {
-		client: NewHTTPClientWithTimeout(SongLinkTimeout), // 30s timeout
+		globalSongLinkClient = &SongLinkClient{
-	}
+			client: NewHTTPClientWithTimeout(SongLinkTimeout), // 30s timeout
+		}
+	})
+	return globalSongLinkClient
 }
 
 // CheckTrackAvailability checks track availability on streaming platforms
 func (s *SongLinkClient) CheckTrackAvailability(spotifyTrackID string, isrc string) (*TrackAvailability, error) {
+	// Validate Spotify ID format (should be 22 characters alphanumeric)
+	if spotifyTrackID == "" {
+		return nil, fmt.Errorf("spotify track ID is empty")
+	}
+	
 	// Use global rate limiter - blocks until request is allowed
 	songLinkRateLimiter.WaitForSlot()
 
@@ -57,8 +76,18 @@ func (s *SongLinkClient) CheckTrackAvailability(spotifyTrackID string, isrc stri
 	}
 	defer resp.Body.Close()
 
+	// Handle specific error codes
+	if resp.StatusCode == 400 {
+		return nil, fmt.Errorf("track not found on SongLink (invalid Spotify ID or track unavailable)")
+	}
+	if resp.StatusCode == 404 {
+		return nil, fmt.Errorf("track not found on any streaming platform")
+	}
+	if resp.StatusCode == 429 {
+		return nil, fmt.Errorf("SongLink rate limit exceeded")
+	}
 	if resp.StatusCode != 200 {
-		return nil, fmt.Errorf("API returned status %d", resp.StatusCode)
+		return nil, fmt.Errorf("SongLink API returned status %d", resp.StatusCode)
 	}
 
 	body, err := ReadResponseBody(resp)
@@ -92,7 +121,15 @@ func (s *SongLinkClient) CheckTrackAvailability(spotifyTrackID string, isrc stri
 		availability.AmazonURL = amazonLink.URL
 	}
 
-	// Check Qobuz using ISRC
+	// Check Deezer
+	if deezerLink, ok := songLinkResp.LinksByPlatform["deezer"]; ok && deezerLink.URL != "" {
+		availability.Deezer = true
+		availability.DeezerURL = deezerLink.URL
+		// Extract Deezer ID from URL (e.g., https://www.deezer.com/track/123456)
+		availability.DeezerID = extractDeezerIDFromURL(deezerLink.URL)
+	}
+
+	// Check Qobuz using ISRC (SongLink doesn't support Qobuz directly)
 	if isrc != "" {
 		availability.Qobuz = checkQobuzAvailability(isrc)
 	}
@@ -151,3 +188,357 @@ func checkQobuzAvailability(isrc string) bool {
 
 	return searchResp.Tracks.Total > 0
 }
+
+// extractDeezerIDFromURL extracts Deezer track/album/artist ID from URL
+func extractDeezerIDFromURL(deezerURL string) string {
+	// URL format: https://www.deezer.com/track/123456 or https://www.deezer.com/en/track/123456
+	parts := strings.Split(deezerURL, "/")
+	if len(parts) > 0 {
+		// Get the last part which should be the ID
+		lastPart := parts[len(parts)-1]
+		// Remove any query parameters
+		if idx := strings.Index(lastPart, "?"); idx > 0 {
+			lastPart = lastPart[:idx]
+		}
+		return lastPart
+	}
+	return ""
+}
+
+// GetDeezerIDFromSpotify converts a Spotify track ID to Deezer track ID using SongLink
+func (s *SongLinkClient) GetDeezerIDFromSpotify(spotifyTrackID string) (string, error) {
+	availability, err := s.CheckTrackAvailability(spotifyTrackID, "")
+	if err != nil {
+		return "", err
+	}
+	
+	if !availability.Deezer || availability.DeezerID == "" {
+		return "", fmt.Errorf("track not found on Deezer")
+	}
+	
+	return availability.DeezerID, nil
+}
+
+// AlbumAvailability represents album availability on different platforms
+type AlbumAvailability struct {
+	SpotifyID string `json:"spotify_id"`
+	Deezer    bool   `json:"deezer"`
+	DeezerURL string `json:"deezer_url,omitempty"`
+	DeezerID  string `json:"deezer_id,omitempty"`
+}
+
+// CheckAlbumAvailability checks album availability on streaming platforms using SongLink
+func (s *SongLinkClient) CheckAlbumAvailability(spotifyAlbumID string) (*AlbumAvailability, error) {
+	// Use global rate limiter
+	songLinkRateLimiter.WaitForSlot()
+
+	// Build API URL for album
+	spotifyBase, _ := base64.StdEncoding.DecodeString("aHR0cHM6Ly9vcGVuLnNwb3RpZnkuY29tL2FsYnVtLw==")
+	spotifyURL := fmt.Sprintf("%s%s", string(spotifyBase), spotifyAlbumID)
+
+	apiBase, _ := base64.StdEncoding.DecodeString("aHR0cHM6Ly9hcGkuc29uZy5saW5rL3YxLWFscGhhLjEvbGlua3M/dXJsPQ==")
+	apiURL := fmt.Sprintf("%s%s", string(apiBase), url.QueryEscape(spotifyURL))
+
+	req, err := http.NewRequest("GET", apiURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	retryConfig := DefaultRetryConfig()
+	resp, err := DoRequestWithRetry(s.client, req, retryConfig)
+	if err != nil {
+		return nil, fmt.Errorf("failed to check album availability: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("API returned status %d", resp.StatusCode)
+	}
+
+	body, err := ReadResponseBody(resp)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	var songLinkResp struct {
+		LinksByPlatform map[string]struct {
+			URL string `json:"url"`
+		} `json:"linksByPlatform"`
+	}
+
+	if err := json.Unmarshal(body, &songLinkResp); err != nil {
+		return nil, fmt.Errorf("failed to decode response: %w", err)
+	}
+
+	availability := &AlbumAvailability{
+		SpotifyID: spotifyAlbumID,
+	}
+
+	// Check Deezer
+	if deezerLink, ok := songLinkResp.LinksByPlatform["deezer"]; ok && deezerLink.URL != "" {
+		availability.Deezer = true
+		availability.DeezerURL = deezerLink.URL
+		availability.DeezerID = extractDeezerIDFromURL(deezerLink.URL)
+	}
+
+	return availability, nil
+}
+
+// GetDeezerAlbumIDFromSpotify converts a Spotify album ID to Deezer album ID using SongLink
+func (s *SongLinkClient) GetDeezerAlbumIDFromSpotify(spotifyAlbumID string) (string, error) {
+	availability, err := s.CheckAlbumAvailability(spotifyAlbumID)
+	if err != nil {
+		return "", err
+	}
+	
+	if !availability.Deezer || availability.DeezerID == "" {
+		return "", fmt.Errorf("album not found on Deezer")
+	}
+	
+	return availability.DeezerID, nil
+}
+
+// ========================================
+// Deezer ID Support - Query SongLink using Deezer as source
+// ========================================
+
+// CheckAvailabilityFromDeezer checks track availability using Deezer track ID as source
+// This is useful when we have Deezer metadata and want to find the track on other platforms
+func (s *SongLinkClient) CheckAvailabilityFromDeezer(deezerTrackID string) (*TrackAvailability, error) {
+	if deezerTrackID == "" {
+		return nil, fmt.Errorf("deezer track ID is empty")
+	}
+	
+	// Use global rate limiter
+	songLinkRateLimiter.WaitForSlot()
+
+	// Build Deezer URL
+	deezerURL := fmt.Sprintf("https://www.deezer.com/track/%s", deezerTrackID)
+
+	// Build API URL using Deezer URL as source
+	apiBase, _ := base64.StdEncoding.DecodeString("aHR0cHM6Ly9hcGkuc29uZy5saW5rL3YxLWFscGhhLjEvbGlua3M/dXJsPQ==")
+	apiURL := fmt.Sprintf("%s%s&userCountry=US", string(apiBase), url.QueryEscape(deezerURL))
+
+	req, err := http.NewRequest("GET", apiURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	retryConfig := DefaultRetryConfig()
+	resp, err := DoRequestWithRetry(s.client, req, retryConfig)
+	if err != nil {
+		return nil, fmt.Errorf("failed to check availability: %w", err)
+	}
+	defer resp.Body.Close()
+
+	// Handle specific error codes
+	if resp.StatusCode == 400 {
+		return nil, fmt.Errorf("track not found on SongLink (invalid Deezer ID)")
+	}
+	if resp.StatusCode == 404 {
+		return nil, fmt.Errorf("track not found on any streaming platform")
+	}
+	if resp.StatusCode == 429 {
+		return nil, fmt.Errorf("SongLink rate limit exceeded")
+	}
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("SongLink API returned status %d", resp.StatusCode)
+	}
+
+	body, err := ReadResponseBody(resp)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	var songLinkResp struct {
+		LinksByPlatform map[string]struct {
+			URL string `json:"url"`
+		} `json:"linksByPlatform"`
+		EntitiesByUniqueId map[string]struct {
+			ID         string `json:"id"`
+			Type       string `json:"type"`
+			Title      string `json:"title"`
+			ArtistName string `json:"artistName"`
+		} `json:"entitiesByUniqueId"`
+	}
+
+	if err := json.Unmarshal(body, &songLinkResp); err != nil {
+		return nil, fmt.Errorf("failed to decode response: %w", err)
+	}
+
+	availability := &TrackAvailability{
+		Deezer:   true,
+		DeezerID: deezerTrackID,
+	}
+
+	// Check Spotify
+	if spotifyLink, ok := songLinkResp.LinksByPlatform["spotify"]; ok && spotifyLink.URL != "" {
+		// Extract Spotify ID from URL
+		availability.SpotifyID = extractSpotifyIDFromURL(spotifyLink.URL)
+	}
+
+	// Check Tidal
+	if tidalLink, ok := songLinkResp.LinksByPlatform["tidal"]; ok && tidalLink.URL != "" {
+		availability.Tidal = true
+		availability.TidalURL = tidalLink.URL
+	}
+
+	// Check Amazon
+	if amazonLink, ok := songLinkResp.LinksByPlatform["amazonMusic"]; ok && amazonLink.URL != "" {
+		availability.Amazon = true
+		availability.AmazonURL = amazonLink.URL
+	}
+
+	// Check Deezer URL
+	if deezerLink, ok := songLinkResp.LinksByPlatform["deezer"]; ok && deezerLink.URL != "" {
+		availability.DeezerURL = deezerLink.URL
+	}
+
+	return availability, nil
+}
+
+// CheckAvailabilityByPlatform checks track availability using any supported platform
+// platform: "spotify", "deezer", "tidal", "amazonMusic", "appleMusic", "youtube", etc.
+// entityType: "song" or "album"
+// entityID: the ID on that platform
+func (s *SongLinkClient) CheckAvailabilityByPlatform(platform, entityType, entityID string) (*TrackAvailability, error) {
+	if entityID == "" {
+		return nil, fmt.Errorf("%s ID is empty", platform)
+	}
+	
+	// Use global rate limiter
+	songLinkRateLimiter.WaitForSlot()
+
+	// Build API URL using platform, type, and id parameters (as per API docs)
+	// https://api.song.link/v1-alpha.1/links?platform=deezer&type=song&id=123456
+	apiURL := fmt.Sprintf("https://api.song.link/v1-alpha.1/links?platform=%s&type=%s&id=%s&userCountry=US",
+		url.QueryEscape(platform),
+		url.QueryEscape(entityType),
+		url.QueryEscape(entityID))
+
+	req, err := http.NewRequest("GET", apiURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	retryConfig := DefaultRetryConfig()
+	resp, err := DoRequestWithRetry(s.client, req, retryConfig)
+	if err != nil {
+		return nil, fmt.Errorf("failed to check availability: %w", err)
+	}
+	defer resp.Body.Close()
+
+	// Handle specific error codes
+	if resp.StatusCode == 400 {
+		return nil, fmt.Errorf("track not found on SongLink (invalid %s ID)", platform)
+	}
+	if resp.StatusCode == 404 {
+		return nil, fmt.Errorf("track not found on any streaming platform")
+	}
+	if resp.StatusCode == 429 {
+		return nil, fmt.Errorf("SongLink rate limit exceeded")
+	}
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("SongLink API returned status %d", resp.StatusCode)
+	}
+
+	body, err := ReadResponseBody(resp)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	var songLinkResp struct {
+		LinksByPlatform map[string]struct {
+			URL string `json:"url"`
+		} `json:"linksByPlatform"`
+	}
+
+	if err := json.Unmarshal(body, &songLinkResp); err != nil {
+		return nil, fmt.Errorf("failed to decode response: %w", err)
+	}
+
+	availability := &TrackAvailability{}
+
+	// Check Spotify
+	if spotifyLink, ok := songLinkResp.LinksByPlatform["spotify"]; ok && spotifyLink.URL != "" {
+		availability.SpotifyID = extractSpotifyIDFromURL(spotifyLink.URL)
+	}
+
+	// Check Tidal
+	if tidalLink, ok := songLinkResp.LinksByPlatform["tidal"]; ok && tidalLink.URL != "" {
+		availability.Tidal = true
+		availability.TidalURL = tidalLink.URL
+	}
+
+	// Check Amazon
+	if amazonLink, ok := songLinkResp.LinksByPlatform["amazonMusic"]; ok && amazonLink.URL != "" {
+		availability.Amazon = true
+		availability.AmazonURL = amazonLink.URL
+	}
+
+	// Check Deezer
+	if deezerLink, ok := songLinkResp.LinksByPlatform["deezer"]; ok && deezerLink.URL != "" {
+		availability.Deezer = true
+		availability.DeezerURL = deezerLink.URL
+		availability.DeezerID = extractDeezerIDFromURL(deezerLink.URL)
+	}
+
+	return availability, nil
+}
+
+// extractSpotifyIDFromURL extracts Spotify track ID from URL
+func extractSpotifyIDFromURL(spotifyURL string) string {
+	// URL format: https://open.spotify.com/track/0Jcij1eWd5bDMU5iPbxe2i
+	parts := strings.Split(spotifyURL, "/track/")
+	if len(parts) > 1 {
+		// Get the ID part and remove any query parameters
+		idPart := parts[1]
+		if idx := strings.Index(idPart, "?"); idx > 0 {
+			idPart = idPart[:idx]
+		}
+		return idPart
+	}
+	return ""
+}
+
+// GetSpotifyIDFromDeezer converts a Deezer track ID to Spotify track ID using SongLink
+func (s *SongLinkClient) GetSpotifyIDFromDeezer(deezerTrackID string) (string, error) {
+	availability, err := s.CheckAvailabilityFromDeezer(deezerTrackID)
+	if err != nil {
+		return "", err
+	}
+	
+	if availability.SpotifyID == "" {
+		return "", fmt.Errorf("track not found on Spotify")
+	}
+	
+	return availability.SpotifyID, nil
+}
+
+// GetTidalURLFromDeezer converts a Deezer track ID to Tidal URL using SongLink
+func (s *SongLinkClient) GetTidalURLFromDeezer(deezerTrackID string) (string, error) {
+	availability, err := s.CheckAvailabilityFromDeezer(deezerTrackID)
+	if err != nil {
+		return "", err
+	}
+	
+	if !availability.Tidal || availability.TidalURL == "" {
+		return "", fmt.Errorf("track not found on Tidal")
+	}
+	
+	return availability.TidalURL, nil
+}
+
+// GetAmazonURLFromDeezer converts a Deezer track ID to Amazon Music URL using SongLink
+func (s *SongLinkClient) GetAmazonURLFromDeezer(deezerTrackID string) (string, error) {
+	availability, err := s.CheckAvailabilityFromDeezer(deezerTrackID)
+	if err != nil {
+		return "", err
+	}
+	
+	if !availability.Amazon || availability.AmazonURL == "" {
+		return "", fmt.Errorf("track not found on Amazon Music")
+	}
+	
+	return availability.AmazonURL, nil
+}

go_backend/spotify.go

@@ -2,7 +2,6 @@ package gobackend
 
 import (
 	"context"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -17,14 +16,14 @@ import (
 )
 
 const (
-	spotifyTokenURL     = "https://accounts.spotify.com/api/token"
+	spotifyTokenURL = "https://accounts.spotify.com/api/token"
-	playlistBaseURL     = "https://api.spotify.com/v1/playlists/%s"
+	playlistBaseURL = "https://api.spotify.com/v1/playlists/%s"
-	albumBaseURL        = "https://api.spotify.com/v1/albums/%s"
+	albumBaseURL    = "https://api.spotify.com/v1/albums/%s"
-	trackBaseURL        = "https://api.spotify.com/v1/tracks/%s"
+	trackBaseURL    = "https://api.spotify.com/v1/tracks/%s"
-	artistBaseURL       = "https://api.spotify.com/v1/artists/%s"
+	artistBaseURL   = "https://api.spotify.com/v1/artists/%s"
-	artistAlbumsURL     = "https://api.spotify.com/v1/artists/%s/albums"
+	artistAlbumsURL = "https://api.spotify.com/v1/artists/%s/albums"
-	searchBaseURL       = "https://api.spotify.com/v1/search"
+	searchBaseURL   = "https://api.spotify.com/v1/search"
-	
+
 	// Cache TTL settings
 	artistCacheTTL = 10 * time.Minute
 	searchCacheTTL = 5 * time.Minute
@@ -54,7 +53,7 @@ type SpotifyMetadataClient struct {
 	rng            *rand.Rand
 	rngMu          sync.Mutex
 	userAgent      string
-	
+
 	// Caches to reduce API calls
 	artistCache map[string]*cacheEntry // key: artistID
 	searchCache map[string]*cacheEntry // key: query+type
@@ -69,8 +68,10 @@ var (
 	credentialsMu      sync.RWMutex
 )
 
+// ErrNoSpotifyCredentials is returned when Spotify credentials are not configured
+var ErrNoSpotifyCredentials = errors.New("Spotify credentials not configured. Please set your own Client ID and Secret in Settings, or use Deezer as metadata source (free, no credentials required)")
+
 // SetSpotifyCredentials sets custom Spotify API credentials
-// Pass empty strings to use default credentials
 func SetSpotifyCredentials(clientID, clientSecret string) {
 	credentialsMu.Lock()
 	defer credentialsMu.Unlock()
@@ -78,39 +79,56 @@ func SetSpotifyCredentials(clientID, clientSecret string) {
 	customClientSecret = clientSecret
 }
 
-// getCredentials returns the current credentials (custom or default)
+// HasSpotifyCredentials checks if Spotify credentials are configured
-func getCredentials() (string, string) {
+func HasSpotifyCredentials() bool {
 	credentialsMu.RLock()
 	defer credentialsMu.RUnlock()
-	
+
+	// Check custom credentials first
 	if customClientID != "" && customClientSecret != "" {
-		return customClientID, customClientSecret
+		return true
-	}
-	
-	// Fall back to default credentials
-	clientID := os.Getenv("SPOTIFY_CLIENT_ID")
-	if clientID == "" {
-		if decoded, err := base64.StdEncoding.DecodeString("NWY1NzNjOTYyMDQ5NGJhZTg3ODkwYzBmMDhhNjAyOTM="); err == nil {
-			clientID = string(decoded)
-		}
 	}
 
-	clientSecret := os.Getenv("SPOTIFY_CLIENT_SECRET")
+	// Check environment variables
-	if clientSecret == "" {
+	if os.Getenv("SPOTIFY_CLIENT_ID") != "" && os.Getenv("SPOTIFY_CLIENT_SECRET") != "" {
-		if decoded, err := base64.StdEncoding.DecodeString("MjEyNDc2ZDliMGYzNDcyZWFhNzYyZDkwYjE5YjBiYTg="); err == nil {
+		return true
-			clientSecret = string(decoded)
-		}
 	}
-	
+
-	return clientID, clientSecret
+	return false
+}
+
+// getCredentials returns the current credentials or error if not configured
+func getCredentials() (string, string, error) {
+	credentialsMu.RLock()
+	defer credentialsMu.RUnlock()
+
+	// Check custom credentials first
+	if customClientID != "" && customClientSecret != "" {
+		return customClientID, customClientSecret, nil
+	}
+
+	// Check environment variables
+	clientID := os.Getenv("SPOTIFY_CLIENT_ID")
+	clientSecret := os.Getenv("SPOTIFY_CLIENT_SECRET")
+
+	if clientID != "" && clientSecret != "" {
+		return clientID, clientSecret, nil
+	}
+
+	// No credentials available
+	return "", "", ErrNoSpotifyCredentials
 }
 
 // NewSpotifyMetadataClient creates a new Spotify client
-func NewSpotifyMetadataClient() *SpotifyMetadataClient {
+// Returns error if credentials are not configured
-	src := rand.NewSource(time.Now().UnixNano())
+func NewSpotifyMetadataClient() (*SpotifyMetadataClient, error) {
+	// Get credentials - will error if not configured
+	clientID, clientSecret, err := getCredentials()
+	if err != nil {
+		return nil, err
+	}
 
-	// Get credentials (custom or default)
+	src := rand.NewSource(time.Now().UnixNano())
-	clientID, clientSecret := getCredentials()
 
 	c := &SpotifyMetadataClient{
 		httpClient:   NewHTTPClientWithTimeout(15 * time.Second), // Use shared transport for connection pooling
@@ -122,7 +140,7 @@ func NewSpotifyMetadataClient() *SpotifyMetadataClient {
 		albumCache:   make(map[string]*cacheEntry),
 	}
 	c.userAgent = c.randomUserAgent()
-	return c
+	return c, nil
 }
 
 // TrackMetadata represents track information
@@ -140,6 +158,7 @@ type TrackMetadata struct {
 	DiscNumber  int    `json:"disc_number,omitempty"`
 	ExternalURL string `json:"external_urls"`
 	ISRC        string `json:"isrc"`
+	AlbumType   string `json:"album_type,omitempty"` // album, single, ep, compilation
 }
 
 // AlbumTrackMetadata holds per-track info for album/playlist
@@ -159,6 +178,7 @@ type AlbumTrackMetadata struct {
 	ISRC        string `json:"isrc"`
 	AlbumID     string `json:"album_id,omitempty"`
 	AlbumURL    string `json:"album_url,omitempty"`
+	AlbumType   string `json:"album_type,omitempty"` // album, single, ep, compilation
 }
 
 // AlbumInfoMetadata holds album information
@@ -283,6 +303,7 @@ type albumSimplified struct {
 	Images      []image     `json:"images"`
 	ExternalURL externalURL `json:"external_urls"`
 	Artists     []artist    `json:"artists"`
+	AlbumType   string      `json:"album_type"` // album, single, compilation
 }
 
 type trackFull struct {
@@ -331,14 +352,14 @@ func (c *SpotifyMetadataClient) SearchTracks(ctx context.Context, query string,
 	}
 
 	searchURL := fmt.Sprintf("%s?q=%s&type=track&limit=%d", searchBaseURL, url.QueryEscape(query), limit)
-	
+
 	var response struct {
 		Tracks struct {
 			Items []trackFull `json:"items"`
 			Total int         `json:"total"`
 		} `json:"tracks"`
 	}
-	
+
 	if err := c.getJSON(ctx, searchURL, token, &response); err != nil {
 		return nil, err
 	}
@@ -363,6 +384,7 @@ func (c *SpotifyMetadataClient) SearchTracks(ctx context.Context, query string,
 			DiscNumber:  track.DiscNumber,
 			ExternalURL: track.ExternalURL.Spotify,
 			ISRC:        track.ExternalID.ISRC,
+			AlbumType:   track.Album.AlbumType,
 		})
 	}
 
@@ -373,7 +395,7 @@ func (c *SpotifyMetadataClient) SearchTracks(ctx context.Context, query string,
 func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, trackLimit, artistLimit int) (*SearchAllResult, error) {
 	// Create cache key
 	cacheKey := fmt.Sprintf("all:%s:%d:%d", query, trackLimit, artistLimit)
-	
+
 	// Check cache first
 	c.cacheMu.RLock()
 	if entry, ok := c.searchCache[cacheKey]; ok && !entry.isExpired() {
@@ -388,24 +410,24 @@ func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, tra
 	}
 
 	searchURL := fmt.Sprintf("%s?q=%s&type=track,artist&limit=%d", searchBaseURL, url.QueryEscape(query), trackLimit)
-	
+
 	var response struct {
 		Tracks struct {
 			Items []trackFull `json:"items"`
 		} `json:"tracks"`
 		Artists struct {
 			Items []struct {
-				ID         string  `json:"id"`
+				ID        string  `json:"id"`
-				Name       string  `json:"name"`
+				Name      string  `json:"name"`
-				Images     []image `json:"images"`
+				Images    []image `json:"images"`
-				Followers  struct {
+				Followers struct {
 					Total int `json:"total"`
 				} `json:"followers"`
 				Popularity int `json:"popularity"`
 			} `json:"items"`
 		} `json:"artists"`
 	}
-	
+
 	if err := c.getJSON(ctx, searchURL, token, &response); err != nil {
 		return nil, err
 	}
@@ -430,6 +452,7 @@ func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, tra
 			DiscNumber:  track.DiscNumber,
 			ExternalURL: track.ExternalURL.Spotify,
 			ISRC:        track.ExternalID.ISRC,
+			AlbumType:   track.Album.AlbumType,
 		})
 	}
 
@@ -438,7 +461,7 @@ func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, tra
 	if artistCount > artistLimit {
 		artistCount = artistLimit
 	}
-	
+
 	for i := 0; i < artistCount; i++ {
 		artist := response.Artists.Items[i]
 		result.Artists = append(result.Artists, SearchArtistResult{
@@ -495,6 +518,17 @@ func (c *SpotifyMetadataClient) fetchAlbum(ctx context.Context, albumID, token s
 	}
 	c.cacheMu.RUnlock()
 
+	// Track item structure for pagination
+	type trackItem struct {
+		ID          string      `json:"id"`
+		Name        string      `json:"name"`
+		DurationMS  int         `json:"duration_ms"`
+		TrackNumber int         `json:"track_number"`
+		DiscNumber  int         `json:"disc_number"`
+		ExternalURL externalURL `json:"external_urls"`
+		Artists     []artist    `json:"artists"`
+	}
+
 	var data struct {
 		Name        string   `json:"name"`
 		ReleaseDate string   `json:"release_date"`
@@ -502,15 +536,8 @@ func (c *SpotifyMetadataClient) fetchAlbum(ctx context.Context, albumID, token s
 		Images      []image  `json:"images"`
 		Artists     []artist `json:"artists"`
 		Tracks      struct {
-			Items []struct {
+			Items []trackItem `json:"items"`
-				ID          string      `json:"id"`
+			Next  string      `json:"next"`
-				Name        string      `json:"name"`
-				DurationMS  int         `json:"duration_ms"`
-				TrackNumber int         `json:"track_number"`
-				DiscNumber  int         `json:"disc_number"`
-				ExternalURL externalURL `json:"external_urls"`
-				Artists     []artist    `json:"artists"`
-			} `json:"items"`
 		} `json:"tracks"`
 	}
 
@@ -527,11 +554,39 @@ func (c *SpotifyMetadataClient) fetchAlbum(ctx context.Context, albumID, token s
 		Images:      albumImage,
 	}
 
-	tracks := make([]AlbumTrackMetadata, 0, len(data.Tracks.Items))
+	// Collect all tracks (including paginated)
-	for _, item := range data.Tracks.Items {
+	allTrackItems := data.Tracks.Items
-		// Fetch ISRC for each track
+	nextURL := data.Tracks.Next
-		isrc := c.fetchTrackISRC(ctx, item.ID, token)
+
-		
+	// Fetch remaining tracks using pagination (no limit)
+	for nextURL != "" {
+		var pageData struct {
+			Items []trackItem `json:"items"`
+			Next  string      `json:"next"`
+		}
+		if err := c.getJSON(ctx, nextURL, token, &pageData); err != nil {
+			fmt.Printf("[Spotify] Warning: failed to fetch album tracks page: %v\n", err)
+			break
+		}
+		allTrackItems = append(allTrackItems, pageData.Items...)
+		nextURL = pageData.Next
+	}
+
+	fmt.Printf("[Spotify] Album has %d tracks (total: %d)\n", len(allTrackItems), data.TotalTracks)
+
+	// Collect track IDs for parallel ISRC fetching
+	trackIDs := make([]string, len(allTrackItems))
+	for i, item := range allTrackItems {
+		trackIDs[i] = item.ID
+	}
+
+	// Fetch ISRCs in parallel for ALL tracks (like Deezer implementation)
+	isrcMap := c.fetchISRCsParallel(ctx, trackIDs, token)
+
+	tracks := make([]AlbumTrackMetadata, 0, len(allTrackItems))
+	for _, item := range allTrackItems {
+		isrc := isrcMap[item.ID]
+
 		tracks = append(tracks, AlbumTrackMetadata{
 			SpotifyID:   item.ID,
 			Artists:     joinArtists(item.Artists),
@@ -566,6 +621,47 @@ func (c *SpotifyMetadataClient) fetchAlbum(ctx context.Context, albumID, token s
 	return result, nil
 }
 
+// fetchISRCsParallel fetches ISRCs for multiple tracks in parallel
+// Similar to Deezer implementation for consistency
+func (c *SpotifyMetadataClient) fetchISRCsParallel(ctx context.Context, trackIDs []string, token string) map[string]string {
+	const maxParallelISRC = 10 // Max concurrent ISRC fetches
+
+	result := make(map[string]string)
+	var resultMu sync.Mutex
+
+	if len(trackIDs) == 0 {
+		return result
+	}
+
+	// Use semaphore to limit concurrent requests
+	sem := make(chan struct{}, maxParallelISRC)
+	var wg sync.WaitGroup
+
+	for _, trackID := range trackIDs {
+		wg.Add(1)
+		go func(id string) {
+			defer wg.Done()
+
+			// Acquire semaphore
+			select {
+			case sem <- struct{}{}:
+				defer func() { <-sem }()
+			case <-ctx.Done():
+				return
+			}
+
+			isrc := c.fetchTrackISRC(ctx, id, token)
+
+			resultMu.Lock()
+			result[id] = isrc
+			resultMu.Unlock()
+		}(trackID)
+	}
+
+	wg.Wait()
+	return result
+}
+
 func (c *SpotifyMetadataClient) fetchPlaylist(ctx context.Context, playlistID, token string) (*PlaylistResponsePayload, error) {
 	// First request to get playlist info and first batch of tracks
 	var data struct {
@@ -595,7 +691,7 @@ func (c *SpotifyMetadataClient) fetchPlaylist(ctx context.Context, playlistID, t
 
 	// Pre-allocate with expected capacity
 	tracks := make([]AlbumTrackMetadata, 0, data.Tracks.Total)
-	
+
 	// Add first batch of tracks
 	for _, item := range data.Tracks.Items {
 		if item.Track == nil {
@@ -620,11 +716,10 @@ func (c *SpotifyMetadataClient) fetchPlaylist(ctx context.Context, playlistID, t
 		})
 	}
 
-	// Fetch remaining tracks using pagination (up to 1000 tracks max)
+	// Fetch remaining tracks using pagination (NO LIMIT - fetch all tracks)
 	nextURL := data.Tracks.Next
-	maxTracks := 1000
+
-	
+	for nextURL != "" {
-	for nextURL != "" && len(tracks) < maxTracks {
 		var pageData struct {
 			Items []struct {
 				Track *trackFull `json:"track"`
@@ -642,9 +737,6 @@ func (c *SpotifyMetadataClient) fetchPlaylist(ctx context.Context, playlistID, t
 			if item.Track == nil {
 				continue
 			}
-			if len(tracks) >= maxTracks {
-				break
-			}
 			tracks = append(tracks, AlbumTrackMetadata{
 				SpotifyID:   item.Track.ID,
 				Artists:     joinArtists(item.Track.Artists),
@@ -686,10 +778,10 @@ func (c *SpotifyMetadataClient) fetchArtist(ctx context.Context, artistID, token
 
 	// Fetch artist info
 	var artistData struct {
-		ID         string  `json:"id"`
+		ID        string  `json:"id"`
-		Name       string  `json:"name"`
+		Name      string  `json:"name"`
-		Images     []image `json:"images"`
+		Images    []image `json:"images"`
-		Followers  struct {
+		Followers struct {
 			Total int `json:"total"`
 		} `json:"followers"`
 		Popularity int `json:"popularity"`
@@ -835,8 +927,16 @@ func (c *SpotifyMetadataClient) getJSON(ctx context.Context, endpoint, token str
 		return err
 	}
 
+	// Set headers (same as PC version baseHeaders)
 	req.Header.Set("User-Agent", c.userAgent)
 	req.Header.Set("Accept", "application/json")
+	req.Header.Set("Accept-Language", "en-US,en;q=0.9")
+	req.Header.Set("sec-ch-ua-platform", "\"Windows\"")
+	req.Header.Set("sec-fetch-dest", "empty")
+	req.Header.Set("sec-fetch-mode", "cors")
+	req.Header.Set("sec-fetch-site", "same-origin")
+	req.Header.Set("Referer", "https://open.spotify.com/")
+	req.Header.Set("Origin", "https://open.spotify.com")
 	if token != "" {
 		req.Header.Set("Authorization", "Bearer "+token)
 	}
@@ -863,13 +963,23 @@ func (c *SpotifyMetadataClient) randomUserAgent() string {
 	c.rngMu.Lock()
 	defer c.rngMu.Unlock()
 
-	chromeMajor := 80 + c.rng.Intn(25)
+	// Use Mac User-Agent format (same as PC version)
-	chromeBuild := 3000 + c.rng.Intn(1500)
+	macMajor := c.rng.Intn(4) + 11         // 11-14
-	chromePatch := 60 + c.rng.Intn(65)
+	macMinor := c.rng.Intn(5) + 4          // 4-8
+	webkitMajor := c.rng.Intn(7) + 530     // 530-536
+	webkitMinor := c.rng.Intn(7) + 30      // 30-36
+	chromeMajor := c.rng.Intn(25) + 80     // 80-104
+	chromeBuild := c.rng.Intn(1500) + 3000 // 3000-4499
+	chromePatch := c.rng.Intn(65) + 60     // 60-124
+	safariMajor := c.rng.Intn(7) + 530     // 530-536
+	safariMinor := c.rng.Intn(6) + 30      // 30-35
 
 	return fmt.Sprintf(
-		"Mozilla/5.0 (Linux; Android 12) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Mobile Safari/537.36",
+		"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,
 	)
 }
 

ios/Runner.xcodeproj/project.pbxproj

@@ -427,7 +427,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = YES;
+				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = AppIcon;
 				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
@@ -484,7 +484,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = YES;
+				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = AppIcon;
 				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";

ios/Runner/AppDelegate.swift

@@ -181,6 +181,383 @@ import Gobackend  // Import Go framework
             GobackendCleanupConnections()
             return nil
             
+        case "readFileMetadata":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let response = GobackendReadFileMetadata(filePath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "searchDeezerAll":
+            let args = call.arguments as! [String: Any]
+            let query = args["query"] as! String
+            let trackLimit = args["track_limit"] as? Int ?? 15
+            let artistLimit = args["artist_limit"] as? Int ?? 3
+            let response = GobackendSearchDeezerAll(query, Int(trackLimit), Int(artistLimit), &error)
+            if let error = error { throw error }
+            return response
+
+        case "getDeezerMetadata":
+            let args = call.arguments as! [String: Any]
+            let resourceType = args["resource_type"] as! String
+            let resourceId = args["resource_id"] as! String
+            let response = GobackendGetDeezerMetadata(resourceType, resourceId, &error)
+            if let error = error { throw error }
+            return response
+
+        case "parseDeezerUrl":
+            let args = call.arguments as! [String: Any]
+            let url = args["url"] as! String
+            let response = GobackendParseDeezerURLExport(url, &error)
+            if let error = error { throw error }
+            return response
+
+        case "searchDeezerByISRC":
+            let args = call.arguments as! [String: Any]
+            let isrc = args["isrc"] as! String
+            let response = GobackendSearchDeezerByISRC(isrc, &error)
+            if let error = error { throw error }
+            return response
+
+        case "convertSpotifyToDeezer":
+            let args = call.arguments as! [String: Any]
+            let resourceType = args["resource_type"] as! String
+            let spotifyId = args["spotify_id"] as! String
+            let response = GobackendConvertSpotifyToDeezer(resourceType, spotifyId, &error)
+            if let error = error { throw error }
+            return response
+
+        case "getSpotifyMetadataWithFallback":
+            let args = call.arguments as! [String: Any]
+            let url = args["url"] as! String
+            let response = GobackendGetSpotifyMetadataWithDeezerFallback(url, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "preWarmTrackCache":
+            let args = call.arguments as! [String: Any]
+            let tracksJson = args["tracks"] as! String
+            let _ = GobackendPreWarmTrackCacheJSON(tracksJson, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getTrackCacheSize":
+            let response = GobackendGetTrackCacheSize()
+            return response
+            
+        case "clearTrackCache":
+            GobackendClearTrackCache()
+            return nil
+            
+        case "setSpotifyCredentials":
+            let args = call.arguments as! [String: Any]
+            let clientId = args["client_id"] as! String
+            let clientSecret = args["client_secret"] as! String
+            GobackendSetSpotifyAPICredentials(clientId, clientSecret)
+            return nil
+            
+        case "hasSpotifyCredentials":
+            let hasCredentials = GobackendCheckSpotifyCredentials()
+            return hasCredentials
+            
+        // Log methods
+        case "getLogs":
+            let response = GobackendGetLogs()
+            return response
+            
+        case "getLogsSince":
+            let args = call.arguments as! [String: Any]
+            let index = args["index"] as? Int ?? 0
+            let response = GobackendGetLogsSince(Int(index))
+            return response
+            
+        case "clearLogs":
+            GobackendClearLogs()
+            return nil
+            
+        case "getLogCount":
+            let response = GobackendGetLogCount()
+            return response
+            
+        case "setLoggingEnabled":
+            let args = call.arguments as! [String: Any]
+            let enabled = args["enabled"] as? Bool ?? false
+            GobackendSetLoggingEnabled(enabled)
+            return nil
+            
+        // Extension System methods
+        case "initExtensionSystem":
+            let args = call.arguments as! [String: Any]
+            let extensionsDir = args["extensions_dir"] as! String
+            let dataDir = args["data_dir"] as! String
+            GobackendInitExtensionSystem(extensionsDir, dataDir, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "loadExtensionsFromDir":
+            let args = call.arguments as! [String: Any]
+            let dirPath = args["dir_path"] as! String
+            let response = GobackendLoadExtensionsFromDir(dirPath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "loadExtensionFromPath":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let response = GobackendLoadExtensionFromPath(filePath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "unloadExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            GobackendUnloadExtensionByID(extensionId, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getInstalledExtensions":
+            let response = GobackendGetInstalledExtensions(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "setExtensionEnabled":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let enabled = args["enabled"] as? Bool ?? false
+            GobackendSetExtensionEnabledByID(extensionId, enabled, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "setProviderPriority":
+            let args = call.arguments as! [String: Any]
+            let priorityJson = args["priority"] as! String
+            GobackendSetProviderPriorityJSON(priorityJson, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getProviderPriority":
+            let response = GobackendGetProviderPriorityJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "setMetadataProviderPriority":
+            let args = call.arguments as! [String: Any]
+            let priorityJson = args["priority"] as! String
+            GobackendSetMetadataProviderPriorityJSON(priorityJson, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getMetadataProviderPriority":
+            let response = GobackendGetMetadataProviderPriorityJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "getExtensionSettings":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let response = GobackendGetExtensionSettingsJSON(extensionId, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "setExtensionSettings":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let settingsJson = args["settings"] as! String
+            GobackendSetExtensionSettingsJSON(extensionId, settingsJson, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "searchTracksWithExtensions":
+            let args = call.arguments as! [String: Any]
+            let query = args["query"] as! String
+            let limit = args["limit"] as? Int ?? 20
+            let response = GobackendSearchTracksWithExtensionsJSON(query, Int(limit), &error)
+            if let error = error { throw error }
+            return response
+            
+        case "downloadWithExtensions":
+            let requestJson = call.arguments as! String
+            let response = GobackendDownloadWithExtensionsJSON(requestJson, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "removeExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            GobackendRemoveExtensionByID(extensionId, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "upgradeExtension":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let response = GobackendUpgradeExtensionFromPath(filePath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "checkExtensionUpgrade":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let response = GobackendCheckExtensionUpgradeFromPath(filePath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "cleanupExtensions":
+            GobackendCleanupExtensions()
+            return nil
+            
+        // Extension Auth API
+        case "getExtensionPendingAuth":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let response = GobackendGetExtensionPendingAuthJSON(extensionId, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "setExtensionAuthCode":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let authCode = args["auth_code"] as! String
+            GobackendSetExtensionAuthCodeByID(extensionId, authCode)
+            return nil
+            
+        case "setExtensionTokens":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let accessToken = args["access_token"] as! String
+            let refreshToken = args["refresh_token"] as? String ?? ""
+            let expiresIn = args["expires_in"] as? Int ?? 0
+            GobackendSetExtensionTokensByID(extensionId, accessToken, refreshToken, Int(expiresIn))
+            return nil
+            
+        case "clearExtensionPendingAuth":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            GobackendClearExtensionPendingAuthByID(extensionId)
+            return nil
+            
+        case "isExtensionAuthenticated":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let response = GobackendIsExtensionAuthenticatedByID(extensionId)
+            return response
+            
+        case "getAllPendingAuthRequests":
+            let response = GobackendGetAllPendingAuthRequestsJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension FFmpeg API
+        case "getPendingFFmpegCommand":
+            let args = call.arguments as! [String: Any]
+            let commandId = args["command_id"] as! String
+            let response = GobackendGetPendingFFmpegCommandJSON(commandId, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "setFFmpegCommandResult":
+            let args = call.arguments as! [String: Any]
+            let commandId = args["command_id"] as! String
+            let success = args["success"] as? Bool ?? false
+            let output = args["output"] as? String ?? ""
+            let errorMsg = args["error"] as? String ?? ""
+            GobackendSetFFmpegCommandResult(commandId, success, output, errorMsg)
+            return nil
+            
+        case "getAllPendingFFmpegCommands":
+            let response = GobackendGetAllPendingFFmpegCommandsJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension Custom Search API
+        case "customSearchWithExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let query = args["query"] as! String
+            let optionsJson = args["options"] as? String ?? ""
+            let response = GobackendCustomSearchWithExtensionJSON(extensionId, query, optionsJson, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "getSearchProviders":
+            let response = GobackendGetSearchProvidersJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension URL Handler API
+        case "handleURLWithExtension":
+            let args = call.arguments as! [String: Any]
+            let url = args["url"] as! String
+            let response = GobackendHandleURLWithExtensionJSON(url, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "findURLHandler":
+            let args = call.arguments as! [String: Any]
+            let url = args["url"] as! String
+            let response = GobackendFindURLHandlerJSON(url)
+            return response
+            
+        case "getURLHandlers":
+            let response = GobackendGetURLHandlersJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension Post-Processing API
+        case "runPostProcessing":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let metadataJson = args["metadata"] as? String ?? ""
+            let response = GobackendRunPostProcessingJSON(filePath, metadataJson, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "getPostProcessingProviders":
+            let response = GobackendGetPostProcessingProvidersJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension Store
+        case "initExtensionStore":
+            let args = call.arguments as! [String: Any]
+            let cacheDir = args["cache_dir"] as! String
+            GobackendInitExtensionStoreJSON(cacheDir, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getStoreExtensions":
+            let args = call.arguments as! [String: Any]
+            let forceRefresh = args["force_refresh"] as? Bool ?? false
+            let response = GobackendGetStoreExtensionsJSON(forceRefresh, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "searchStoreExtensions":
+            let args = call.arguments as! [String: Any]
+            let query = args["query"] as? String ?? ""
+            let category = args["category"] as? String ?? ""
+            let response = GobackendSearchStoreExtensionsJSON(query, category, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "getStoreCategories":
+            let response = GobackendGetStoreCategoriesJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "downloadStoreExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let destDir = args["dest_dir"] as! String
+            let response = GobackendDownloadStoreExtensionJSON(extensionId, destDir, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "clearStoreCache":
+            GobackendClearStoreCacheJSON(&error)
+            if let error = error { throw error }
+            return nil
+            
         default:
             throw NSError(
                 domain: "SpotiFLAC",

ios/Runner/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -1,122 +1 @@
-{
+{"images":[{"size":"20x20","idiom":"iphone","filename":"Icon-App-20x20@2x.png","scale":"2x"},{"size":"20x20","idiom":"iphone","filename":"Icon-App-20x20@3x.png","scale":"3x"},{"size":"29x29","idiom":"iphone","filename":"Icon-App-29x29@1x.png","scale":"1x"},{"size":"29x29","idiom":"iphone","filename":"Icon-App-29x29@2x.png","scale":"2x"},{"size":"29x29","idiom":"iphone","filename":"Icon-App-29x29@3x.png","scale":"3x"},{"size":"40x40","idiom":"iphone","filename":"Icon-App-40x40@2x.png","scale":"2x"},{"size":"40x40","idiom":"iphone","filename":"Icon-App-40x40@3x.png","scale":"3x"},{"size":"57x57","idiom":"iphone","filename":"Icon-App-57x57@1x.png","scale":"1x"},{"size":"57x57","idiom":"iphone","filename":"Icon-App-57x57@2x.png","scale":"2x"},{"size":"60x60","idiom":"iphone","filename":"Icon-App-60x60@2x.png","scale":"2x"},{"size":"60x60","idiom":"iphone","filename":"Icon-App-60x60@3x.png","scale":"3x"},{"size":"20x20","idiom":"ipad","filename":"Icon-App-20x20@1x.png","scale":"1x"},{"size":"20x20","idiom":"ipad","filename":"Icon-App-20x20@2x.png","scale":"2x"},{"size":"29x29","idiom":"ipad","filename":"Icon-App-29x29@1x.png","scale":"1x"},{"size":"29x29","idiom":"ipad","filename":"Icon-App-29x29@2x.png","scale":"2x"},{"size":"40x40","idiom":"ipad","filename":"Icon-App-40x40@1x.png","scale":"1x"},{"size":"40x40","idiom":"ipad","filename":"Icon-App-40x40@2x.png","scale":"2x"},{"size":"50x50","idiom":"ipad","filename":"Icon-App-50x50@1x.png","scale":"1x"},{"size":"50x50","idiom":"ipad","filename":"Icon-App-50x50@2x.png","scale":"2x"},{"size":"72x72","idiom":"ipad","filename":"Icon-App-72x72@1x.png","scale":"1x"},{"size":"72x72","idiom":"ipad","filename":"Icon-App-72x72@2x.png","scale":"2x"},{"size":"76x76","idiom":"ipad","filename":"Icon-App-76x76@1x.png","scale":"1x"},{"size":"76x76","idiom":"ipad","filename":"Icon-App-76x76@2x.png","scale":"2x"},{"size":"83.5x83.5","idiom":"ipad","filename":"Icon-App-83.5x83.5@2x.png","scale":"2x"},{"size":"1024x1024","idiom":"ios-marketing","filename":"Icon-App-1024x1024@1x.png","scale":"1x"}],"info":{"version":1,"author":"xcode"}}
-  "images" : [
-    {
-      "size" : "20x20",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-20x20@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "20x20",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-20x20@3x.png",
-      "scale" : "3x"
-    },
-    {
-      "size" : "29x29",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-29x29@1x.png",
-      "scale" : "1x"
-    },
-    {
-      "size" : "29x29",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-29x29@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "29x29",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-29x29@3x.png",
-      "scale" : "3x"
-    },
-    {
-      "size" : "40x40",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-40x40@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "40x40",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-40x40@3x.png",
-      "scale" : "3x"
-    },
-    {
-      "size" : "60x60",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-60x60@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "60x60",
-      "idiom" : "iphone",
-      "filename" : "Icon-App-60x60@3x.png",
-      "scale" : "3x"
-    },
-    {
-      "size" : "20x20",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-20x20@1x.png",
-      "scale" : "1x"
-    },
-    {
-      "size" : "20x20",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-20x20@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "29x29",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-29x29@1x.png",
-      "scale" : "1x"
-    },
-    {
-      "size" : "29x29",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-29x29@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "40x40",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-40x40@1x.png",
-      "scale" : "1x"
-    },
-    {
-      "size" : "40x40",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-40x40@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "76x76",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-76x76@1x.png",
-      "scale" : "1x"
-    },
-    {
-      "size" : "76x76",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-76x76@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "83.5x83.5",
-      "idiom" : "ipad",
-      "filename" : "Icon-App-83.5x83.5@2x.png",
-      "scale" : "2x"
-    },
-    {
-      "size" : "1024x1024",
-      "idiom" : "ios-marketing",
-      "filename" : "Icon-App-1024x1024@1x.png",
-      "scale" : "1x"
-    }
-  ],
-  "info" : {
-    "version" : 1,
-    "author" : "xcode"
-  }
-}

lib/constants/app_info.dart

@@ -1,8 +1,8 @@
 /// App version and info constants
 /// Update version here only - all other files will reference this
 class AppInfo {
-  static const String version = '2.0.7-preview';
+  static const String version = '3.0.0';
-  static const String buildNumber = '37';
+  static const String buildNumber = '57';
   static const String fullVersion = '$version+$buildNumber';
   
   
@@ -15,4 +15,6 @@ class AppInfo {
   static const String githubRepo = 'zarzet/SpotiFLAC-Mobile';
   static const String githubUrl = 'https://github.com/$githubRepo';
   static const String originalGithubUrl = 'https://github.com/afkarxyz/SpotiFLAC';
+  
+  static const String kofiUrl = 'https://ko-fi.com/zarzet';
 }

lib/main.dart

@@ -1,7 +1,10 @@
+import 'dart:io';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:path_provider/path_provider.dart';
 import 'package:spotiflac_android/app.dart';
 import 'package:spotiflac_android/providers/download_queue_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/services/notification_service.dart';
 import 'package:spotiflac_android/services/share_intent_service.dart';
 
@@ -24,14 +27,42 @@ void main() async {
 }
 
 /// Widget to eagerly initialize providers that need to load data on startup
-class _EagerInitialization extends ConsumerWidget {
+class _EagerInitialization extends ConsumerStatefulWidget {
   const _EagerInitialization({required this.child});
   final Widget child;
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  ConsumerState<_EagerInitialization> createState() => _EagerInitializationState();
+}
+
+class _EagerInitializationState extends ConsumerState<_EagerInitialization> {
+  @override
+  void initState() {
+    super.initState();
+    _initializeExtensions();
+  }
+
+  Future<void> _initializeExtensions() async {
+    try {
+      final appDir = await getApplicationDocumentsDirectory();
+      final extensionsDir = '${appDir.path}/extensions';
+      final dataDir = '${appDir.path}/extension_data';
+      
+      // Create directories if needed
+      await Directory(extensionsDir).create(recursive: true);
+      await Directory(dataDir).create(recursive: true);
+      
+      // Initialize extension system
+      await ref.read(extensionProvider.notifier).initialize(extensionsDir, dataDir);
+    } catch (e) {
+      debugPrint('Failed to initialize extensions: $e');
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
     // Eagerly initialize download history provider to load from storage
     ref.watch(downloadHistoryProvider);
-    return child;
+    return widget.child;
   }
 }

lib/models/download_item.dart

@@ -13,6 +13,15 @@ enum DownloadStatus {
   skipped,
 }
 
+/// Error type enum for better error handling
+enum DownloadErrorType {
+  unknown,
+  notFound,    // Track not found on any service
+  rateLimit,   // Rate limited by service
+  network,     // Network/connection error
+  permission,  // File/folder permission error
+}
+
 @JsonSerializable()
 class DownloadItem {
   final String id;
@@ -20,8 +29,10 @@ class DownloadItem {
   final String service;
   final DownloadStatus status;
   final double progress;
+  final double speedMBps; // Download speed in MB/s
   final String? filePath;
   final String? error;
+  final DownloadErrorType? errorType;
   final DateTime createdAt;
   final String? qualityOverride; // Override quality for this specific download
 
@@ -31,8 +42,10 @@ class DownloadItem {
     required this.service,
     this.status = DownloadStatus.queued,
     this.progress = 0.0,
+    this.speedMBps = 0.0,
     this.filePath,
     this.error,
+    this.errorType,
     required this.createdAt,
     this.qualityOverride,
   });
@@ -43,8 +56,10 @@ class DownloadItem {
     String? service,
     DownloadStatus? status,
     double? progress,
+    double? speedMBps,
     String? filePath,
     String? error,
+    DownloadErrorType? errorType,
     DateTime? createdAt,
     String? qualityOverride,
   }) {
@@ -54,13 +69,33 @@ class DownloadItem {
       service: service ?? this.service,
       status: status ?? this.status,
       progress: progress ?? this.progress,
+      speedMBps: speedMBps ?? this.speedMBps,
       filePath: filePath ?? this.filePath,
       error: error ?? this.error,
+      errorType: errorType ?? this.errorType,
       createdAt: createdAt ?? this.createdAt,
       qualityOverride: qualityOverride ?? this.qualityOverride,
     );
   }
 
+  /// Get user-friendly error message based on error type
+  String get errorMessage {
+    if (error == null) return '';
+    
+    switch (errorType) {
+      case DownloadErrorType.notFound:
+        return 'Song not found on any service';
+      case DownloadErrorType.rateLimit:
+        return 'Rate limit reached, try again later';
+      case DownloadErrorType.network:
+        return 'Connection failed, check your internet';
+      case DownloadErrorType.permission:
+        return 'Cannot write to folder, check storage permission';
+      default:
+        return error ?? 'An error occurred';
+    }
+  }
+
   factory DownloadItem.fromJson(Map<String, dynamic> json) =>
       _$DownloadItemFromJson(json);
   Map<String, dynamic> toJson() => _$DownloadItemToJson(this);

lib/models/download_item.g.dart

@@ -14,8 +14,10 @@ DownloadItem _$DownloadItemFromJson(Map<String, dynamic> json) => DownloadItem(
       $enumDecodeNullable(_$DownloadStatusEnumMap, json['status']) ??
       DownloadStatus.queued,
   progress: (json['progress'] as num?)?.toDouble() ?? 0.0,
+  speedMBps: (json['speedMBps'] as num?)?.toDouble() ?? 0.0,
   filePath: json['filePath'] as String?,
   error: json['error'] as String?,
+  errorType: $enumDecodeNullable(_$DownloadErrorTypeEnumMap, json['errorType']),
   createdAt: DateTime.parse(json['createdAt'] as String),
   qualityOverride: json['qualityOverride'] as String?,
 );
@@ -27,8 +29,10 @@ Map<String, dynamic> _$DownloadItemToJson(DownloadItem instance) =>
       'service': instance.service,
       'status': _$DownloadStatusEnumMap[instance.status]!,
       'progress': instance.progress,
+      'speedMBps': instance.speedMBps,
       'filePath': instance.filePath,
       'error': instance.error,
+      'errorType': _$DownloadErrorTypeEnumMap[instance.errorType],
       'createdAt': instance.createdAt.toIso8601String(),
       'qualityOverride': instance.qualityOverride,
     };
@@ -41,3 +45,11 @@ const _$DownloadStatusEnumMap = {
   DownloadStatus.failed: 'failed',
   DownloadStatus.skipped: 'skipped',
 };
+
+const _$DownloadErrorTypeEnumMap = {
+  DownloadErrorType.unknown: 'unknown',
+  DownloadErrorType.notFound: 'notFound',
+  DownloadErrorType.rateLimit: 'rateLimit',
+  DownloadErrorType.network: 'network',
+  DownloadErrorType.permission: 'permission',
+};

lib/models/settings.dart

@@ -14,13 +14,22 @@ class AppSettings {
   final bool isFirstLaunch;
   final int concurrentDownloads; // 1 = sequential (default), max 3
   final bool checkForUpdates; // Check for updates on app start
+  final String updateChannel; // stable, preview
   final bool hasSearchedBefore; // Hide helper text after first search
   final String folderOrganization; // none, artist, album, artist_album
   final String historyViewMode; // list, grid
+  final String historyFilterMode; // all, albums, singles
   final bool askQualityBeforeDownload; // Show quality picker before each download
   final String spotifyClientId; // Custom Spotify client ID (empty = use default)
   final String spotifyClientSecret; // Custom Spotify client secret (empty = use default)
   final bool useCustomSpotifyCredentials; // Whether to use custom credentials (if set)
+  final String metadataSource; // spotify, deezer - source for search and metadata
+  final bool enableLogging; // Enable detailed logging for debugging
+  final bool useExtensionProviders; // Use extension providers for downloads when available
+  final String? searchProvider; // null/empty = default (Deezer/Spotify), otherwise extension ID
+  final bool separateSingles; // Separate singles/EPs into their own folder
+  final String albumFolderStructure; // artist_album or album_only
+  final bool showExtensionStore; // Show Extension Store tab in navigation
 
   const AppSettings({
     this.defaultService = 'tidal',
@@ -33,13 +42,22 @@ class AppSettings {
     this.isFirstLaunch = true,
     this.concurrentDownloads = 1, // Default: sequential (off)
     this.checkForUpdates = true, // Default: enabled
+    this.updateChannel = 'stable', // Default: stable releases only
     this.hasSearchedBefore = false, // Default: show helper text
     this.folderOrganization = 'none', // Default: no folder organization
     this.historyViewMode = 'grid', // Default: grid view
+    this.historyFilterMode = 'all', // Default: show all
     this.askQualityBeforeDownload = true, // Default: ask quality before download
     this.spotifyClientId = '', // Default: use built-in credentials
     this.spotifyClientSecret = '', // Default: use built-in credentials
     this.useCustomSpotifyCredentials = true, // Default: use custom if set
+    this.metadataSource = 'deezer', // Default: Deezer (no rate limit)
+    this.enableLogging = false, // Default: disabled for performance
+    this.useExtensionProviders = true, // Default: use extensions when available
+    this.searchProvider, // Default: null (use Deezer/Spotify)
+    this.separateSingles = false, // Default: disabled
+    this.albumFolderStructure = 'artist_album', // Default: Albums/Artist/Album
+    this.showExtensionStore = true, // Default: show store
   });
 
   AppSettings copyWith({
@@ -53,13 +71,23 @@ class AppSettings {
     bool? isFirstLaunch,
     int? concurrentDownloads,
     bool? checkForUpdates,
+    String? updateChannel,
     bool? hasSearchedBefore,
     String? folderOrganization,
     String? historyViewMode,
+    String? historyFilterMode,
     bool? askQualityBeforeDownload,
     String? spotifyClientId,
     String? spotifyClientSecret,
     bool? useCustomSpotifyCredentials,
+    String? metadataSource,
+    bool? enableLogging,
+    bool? useExtensionProviders,
+    String? searchProvider,
+    bool clearSearchProvider = false, // Set to true to clear searchProvider to null
+    bool? separateSingles,
+    String? albumFolderStructure,
+    bool? showExtensionStore,
   }) {
     return AppSettings(
       defaultService: defaultService ?? this.defaultService,
@@ -72,13 +100,22 @@ class AppSettings {
       isFirstLaunch: isFirstLaunch ?? this.isFirstLaunch,
       concurrentDownloads: concurrentDownloads ?? this.concurrentDownloads,
       checkForUpdates: checkForUpdates ?? this.checkForUpdates,
+      updateChannel: updateChannel ?? this.updateChannel,
       hasSearchedBefore: hasSearchedBefore ?? this.hasSearchedBefore,
       folderOrganization: folderOrganization ?? this.folderOrganization,
       historyViewMode: historyViewMode ?? this.historyViewMode,
+      historyFilterMode: historyFilterMode ?? this.historyFilterMode,
       askQualityBeforeDownload: askQualityBeforeDownload ?? this.askQualityBeforeDownload,
       spotifyClientId: spotifyClientId ?? this.spotifyClientId,
       spotifyClientSecret: spotifyClientSecret ?? this.spotifyClientSecret,
       useCustomSpotifyCredentials: useCustomSpotifyCredentials ?? this.useCustomSpotifyCredentials,
+      metadataSource: metadataSource ?? this.metadataSource,
+      enableLogging: enableLogging ?? this.enableLogging,
+      useExtensionProviders: useExtensionProviders ?? this.useExtensionProviders,
+      searchProvider: clearSearchProvider ? null : (searchProvider ?? this.searchProvider),
+      separateSingles: separateSingles ?? this.separateSingles,
+      albumFolderStructure: albumFolderStructure ?? this.albumFolderStructure,
+      showExtensionStore: showExtensionStore ?? this.showExtensionStore,
     );
   }
 

lib/models/settings.g.dart

@@ -17,14 +17,23 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
   isFirstLaunch: json['isFirstLaunch'] as bool? ?? true,
   concurrentDownloads: (json['concurrentDownloads'] as num?)?.toInt() ?? 1,
   checkForUpdates: json['checkForUpdates'] as bool? ?? true,
+  updateChannel: json['updateChannel'] as String? ?? 'stable',
   hasSearchedBefore: json['hasSearchedBefore'] as bool? ?? false,
   folderOrganization: json['folderOrganization'] as String? ?? 'none',
   historyViewMode: json['historyViewMode'] as String? ?? 'grid',
+  historyFilterMode: json['historyFilterMode'] as String? ?? 'all',
   askQualityBeforeDownload: json['askQualityBeforeDownload'] as bool? ?? true,
   spotifyClientId: json['spotifyClientId'] as String? ?? '',
   spotifyClientSecret: json['spotifyClientSecret'] as String? ?? '',
   useCustomSpotifyCredentials:
       json['useCustomSpotifyCredentials'] as bool? ?? true,
+  metadataSource: json['metadataSource'] as String? ?? 'deezer',
+  enableLogging: json['enableLogging'] as bool? ?? false,
+  useExtensionProviders: json['useExtensionProviders'] as bool? ?? true,
+  searchProvider: json['searchProvider'] as String?,
+  separateSingles: json['separateSingles'] as bool? ?? false,
+  albumFolderStructure: json['albumFolderStructure'] as String? ?? 'artist_album',
+  showExtensionStore: json['showExtensionStore'] as bool? ?? true,
 );
 
 Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
@@ -39,11 +48,20 @@ Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
       'isFirstLaunch': instance.isFirstLaunch,
       'concurrentDownloads': instance.concurrentDownloads,
       'checkForUpdates': instance.checkForUpdates,
+      'updateChannel': instance.updateChannel,
       'hasSearchedBefore': instance.hasSearchedBefore,
       'folderOrganization': instance.folderOrganization,
       'historyViewMode': instance.historyViewMode,
+      'historyFilterMode': instance.historyFilterMode,
       'askQualityBeforeDownload': instance.askQualityBeforeDownload,
       'spotifyClientId': instance.spotifyClientId,
       'spotifyClientSecret': instance.spotifyClientSecret,
       'useCustomSpotifyCredentials': instance.useCustomSpotifyCredentials,
+      'metadataSource': instance.metadataSource,
+      'enableLogging': instance.enableLogging,
+      'useExtensionProviders': instance.useExtensionProviders,
+      'searchProvider': instance.searchProvider,
+      'separateSingles': instance.separateSingles,
+      'albumFolderStructure': instance.albumFolderStructure,
+      'showExtensionStore': instance.showExtensionStore,
     };

lib/models/theme_settings.dart

@@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
 const String kThemeModeKey = 'theme_mode';
 const String kUseDynamicColorKey = 'use_dynamic_color';
 const String kSeedColorKey = 'seed_color';
+const String kUseAmoledKey = 'use_amoled';
 
 /// Default Spotify green color for fallback
 const int kDefaultSeedColor = 0xFF1DB954;
@@ -13,11 +14,13 @@ class ThemeSettings {
   final ThemeMode themeMode;
   final bool useDynamicColor;
   final int seedColorValue;
+  final bool useAmoled; // Pure black background for OLED screens
 
   const ThemeSettings({
     this.themeMode = ThemeMode.system,
     this.useDynamicColor = true,
     this.seedColorValue = kDefaultSeedColor,
+    this.useAmoled = false,
   });
 
   /// Get seed color as Color object
@@ -28,11 +31,13 @@ class ThemeSettings {
     ThemeMode? themeMode,
     bool? useDynamicColor,
     int? seedColorValue,
+    bool? useAmoled,
   }) {
     return ThemeSettings(
       themeMode: themeMode ?? this.themeMode,
       useDynamicColor: useDynamicColor ?? this.useDynamicColor,
       seedColorValue: seedColorValue ?? this.seedColorValue,
+      useAmoled: useAmoled ?? this.useAmoled,
     );
   }
 
@@ -41,6 +46,7 @@ class ThemeSettings {
         kThemeModeKey: themeMode.name,
         kUseDynamicColorKey: useDynamicColor,
         kSeedColorKey: seedColorValue,
+        kUseAmoledKey: useAmoled,
       };
 
   /// Create from JSON map
@@ -49,6 +55,7 @@ class ThemeSettings {
       themeMode: _themeModeFromString(json[kThemeModeKey] as String?),
       useDynamicColor: json[kUseDynamicColorKey] as bool? ?? true,
       seedColorValue: json[kSeedColorKey] as int? ?? kDefaultSeedColor,
+      useAmoled: json[kUseAmoledKey] as bool? ?? false,
     );
   }
 
@@ -58,12 +65,13 @@ class ThemeSettings {
     return other is ThemeSettings &&
         other.themeMode == themeMode &&
         other.useDynamicColor == useDynamicColor &&
-        other.seedColorValue == seedColorValue;
+        other.seedColorValue == seedColorValue &&
+        other.useAmoled == useAmoled;
   }
 
   @override
   int get hashCode =>
-      themeMode.hashCode ^ useDynamicColor.hashCode ^ seedColorValue.hashCode;
+      themeMode.hashCode ^ useDynamicColor.hashCode ^ seedColorValue.hashCode ^ useAmoled.hashCode;
 }
 
 /// Helper to convert string to ThemeMode

lib/models/track.dart

@@ -16,7 +16,10 @@ class Track {
   final int? trackNumber;
   final int? discNumber;
   final String? releaseDate;
+  final String? deezerId;
   final ServiceAvailability? availability;
+  final String? source; // Extension ID that provided this track (null for built-in sources)
+  final String? albumType; // album, single, ep, compilation (from metadata API)
 
   const Track({
     required this.id,
@@ -30,11 +33,20 @@ class Track {
     this.trackNumber,
     this.discNumber,
     this.releaseDate,
+    this.deezerId,
     this.availability,
+    this.source,
+    this.albumType,
   });
 
+  /// Check if this track is a single (based on album_type metadata)
+  bool get isSingle => albumType == 'single' || albumType == 'ep';
+
   factory Track.fromJson(Map<String, dynamic> json) => _$TrackFromJson(json);
   Map<String, dynamic> toJson() => _$TrackToJson(this);
+  
+  /// Check if this track is from an extension
+  bool get isFromExtension => source != null && source!.isNotEmpty;
 }
 
 @JsonSerializable()
@@ -42,17 +54,23 @@ class ServiceAvailability {
   final bool tidal;
   final bool qobuz;
   final bool amazon;
+  final bool deezer;
   final String? tidalUrl;
   final String? qobuzUrl;
   final String? amazonUrl;
+  final String? deezerUrl;
+  final String? deezerId;
 
   const ServiceAvailability({
     this.tidal = false,
     this.qobuz = false,
     this.amazon = false,
+    this.deezer = false,
     this.tidalUrl,
     this.qobuzUrl,
     this.amazonUrl,
+    this.deezerUrl,
+    this.deezerId,
   });
 
   factory ServiceAvailability.fromJson(Map<String, dynamic> json) =>

lib/models/track.g.dart

@@ -18,11 +18,14 @@ Track _$TrackFromJson(Map<String, dynamic> json) => Track(
   trackNumber: (json['trackNumber'] as num?)?.toInt(),
   discNumber: (json['discNumber'] as num?)?.toInt(),
   releaseDate: json['releaseDate'] as String?,
+  deezerId: json['deezerId'] as String?,
   availability: json['availability'] == null
       ? null
       : ServiceAvailability.fromJson(
           json['availability'] as Map<String, dynamic>,
         ),
+  source: json['source'] as String?,
+  albumType: json['albumType'] as String?,
 );
 
 Map<String, dynamic> _$TrackToJson(Track instance) => <String, dynamic>{
@@ -37,7 +40,10 @@ Map<String, dynamic> _$TrackToJson(Track instance) => <String, dynamic>{
   'trackNumber': instance.trackNumber,
   'discNumber': instance.discNumber,
   'releaseDate': instance.releaseDate,
+  'deezerId': instance.deezerId,
   'availability': instance.availability,
+  'source': instance.source,
+  'albumType': instance.albumType,
 };
 
 ServiceAvailability _$ServiceAvailabilityFromJson(Map<String, dynamic> json) =>
@@ -45,9 +51,12 @@ ServiceAvailability _$ServiceAvailabilityFromJson(Map<String, dynamic> json) =>
       tidal: json['tidal'] as bool? ?? false,
       qobuz: json['qobuz'] as bool? ?? false,
       amazon: json['amazon'] as bool? ?? false,
+      deezer: json['deezer'] as bool? ?? false,
       tidalUrl: json['tidalUrl'] as String?,
       qobuzUrl: json['qobuzUrl'] as String?,
       amazonUrl: json['amazonUrl'] as String?,
+      deezerUrl: json['deezerUrl'] as String?,
+      deezerId: json['deezerId'] as String?,
     );
 
 Map<String, dynamic> _$ServiceAvailabilityToJson(
@@ -56,7 +65,10 @@ Map<String, dynamic> _$ServiceAvailabilityToJson(
   'tidal': instance.tidal,
   'qobuz': instance.qobuz,
   'amazon': instance.amazon,
+  'deezer': instance.deezer,
   'tidalUrl': instance.tidalUrl,
   'qobuzUrl': instance.qobuzUrl,
   'amazonUrl': instance.amazonUrl,
+  'deezerUrl': instance.deezerUrl,
+  'deezerId': instance.deezerId,
 };