feat: add extended metadata (genre, label, copyright) support

- Add genre, label, copyright fields to ExtTrackMetadata and DownloadResponse
- Add utils.randomUserAgent() for extensions to get random User-Agent strings
- Fix VM race condition panic by adding mutex locks to all provider methods
- Fix Tidal release date fallback when req.ReleaseDate is empty
- Display genre, label, copyright in track metadata screen
- Store extended metadata in download history for persistence
- Add trackGenre, trackLabel, trackCopyright localization strings

go_backend/exports.go

@@ -186,6 +186,10 @@ type DownloadResponse struct {
 	DiscNumber       int    `json:"disc_number,omitempty"`
 	ISRC             string `json:"isrc,omitempty"`
 	CoverURL         string `json:"cover_url,omitempty"`
+	// Extended metadata for FLAC tagging (passed to Flutter for M4A->FLAC conversion)
+	Genre     string `json:"genre,omitempty"`     // Music genre(s)
+	Label     string `json:"label,omitempty"`     // Record label
+	Copyright string `json:"copyright,omitempty"` // Copyright info
 	// If true, skip metadata enrichment from Deezer/Spotify (extension already provides metadata)
 	SkipMetadataEnrichment bool `json:"skip_metadata_enrichment,omitempty"`
 }

go_backend/extension_manager.go

@@ -51,6 +51,7 @@ type LoadedExtension struct {
 	ID        string             `json:"id"`
 	Manifest  *ExtensionManifest `json:"manifest"`
 	VM        *goja.Runtime      `json:"-"`
+	VMMu      sync.Mutex         `json:"-"` // Mutex to prevent concurrent VM access
 	Enabled   bool               `json:"enabled"`
 	Error     string             `json:"error,omitempty"`
 	DataDir   string             `json:"data_dir"`

go_backend/extension_providers.go

@@ -38,6 +38,10 @@ type ExtTrackMetadata struct {
 	DeezerID      string            `json:"deezer_id,omitempty"`
 	SpotifyID     string            `json:"spotify_id,omitempty"`
 	ExternalLinks map[string]string `json:"external_links,omitempty"` // service -> URL mapping
+	// Extended metadata from enrichment (can come from Deezer, Spotify, etc.)
+	Label     string `json:"label,omitempty"`     // Record label
+	Copyright string `json:"copyright,omitempty"` // Copyright information
+	Genre     string `json:"genre,omitempty"`     // Music genre(s)
 }
 
 // ResolvedCoverURL returns the cover URL, checking both CoverURL and Images fields
@@ -144,6 +148,10 @@ func (p *ExtensionProviderWrapper) SearchTracks(query string, limit int) (*ExtSe
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	// Call extension's searchTracks function
 	script := fmt.Sprintf(`
 		(function() {
@@ -206,6 +214,10 @@ func (p *ExtensionProviderWrapper) GetTrack(trackID string) (*ExtTrackMetadata,
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.getTrack === 'function') {
@@ -252,6 +264,10 @@ func (p *ExtensionProviderWrapper) GetAlbum(albumID string) (*ExtAlbumMetadata,
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.getAlbum === 'function') {
@@ -301,6 +317,10 @@ func (p *ExtensionProviderWrapper) GetArtist(artistID string) (*ExtArtistMetadat
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.getArtist === 'function') {
@@ -349,6 +369,10 @@ func (p *ExtensionProviderWrapper) EnrichTrack(track *ExtTrackMetadata) (*ExtTra
 		return track, nil // Extension disabled, return as-is
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	// Convert track to JSON for passing to JS
 	trackJSON, err := json.Marshal(track)
 	if err != nil {
@@ -415,6 +439,10 @@ func (p *ExtensionProviderWrapper) CheckAvailability(isrc, trackName, artistName
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.checkAvailability === 'function') {
@@ -460,6 +488,10 @@ func (p *ExtensionProviderWrapper) GetDownloadURL(trackID, quality string) (*Ext
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.getDownloadUrl === 'function') {
@@ -508,6 +540,10 @@ func (p *ExtensionProviderWrapper) Download(trackID, quality, outputPath string,
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	// Set up progress callback in VM
 	p.vm.Set("__onProgress", func(call goja.FunctionCall) goja.Value {
 		if len(call.Arguments) > 0 {
@@ -758,6 +794,23 @@ func DownloadWithExtensionFallback(req DownloadRequest) (*DownloadResponse, erro
 				if enrichedTrack.Artists != "" {
 					req.ArtistName = enrichedTrack.Artists
 				}
+				// Copy extended metadata from enrichment (label, copyright, genre, release_date)
+				if enrichedTrack.Label != "" && req.Label == "" {
+					GoLog("[DownloadWithExtensionFallback] Label from enrichment: %s\n", enrichedTrack.Label)
+					req.Label = enrichedTrack.Label
+				}
+				if enrichedTrack.Copyright != "" && req.Copyright == "" {
+					GoLog("[DownloadWithExtensionFallback] Copyright from enrichment: %s\n", enrichedTrack.Copyright)
+					req.Copyright = enrichedTrack.Copyright
+				}
+				if enrichedTrack.Genre != "" && req.Genre == "" {
+					GoLog("[DownloadWithExtensionFallback] Genre from enrichment: %s\n", enrichedTrack.Genre)
+					req.Genre = enrichedTrack.Genre
+				}
+				if enrichedTrack.ReleaseDate != "" && req.ReleaseDate == "" {
+					GoLog("[DownloadWithExtensionFallback] ReleaseDate from enrichment: %s\n", enrichedTrack.ReleaseDate)
+					req.ReleaseDate = enrichedTrack.ReleaseDate
+				}
 			}
 		}
 	}
@@ -891,6 +944,19 @@ func DownloadWithExtensionFallback(req DownloadRequest) (*DownloadResponse, erro
 			result, err := tryBuiltInProvider(providerID, req)
 			if err == nil && result.Success {
 				result.Service = providerID
+				// Copy enriched metadata to response for Flutter (needed for M4A->FLAC conversion)
+				if req.Label != "" {
+					result.Label = req.Label
+				}
+				if req.Copyright != "" {
+					result.Copyright = req.Copyright
+				}
+				if req.Genre != "" {
+					result.Genre = req.Genre
+				}
+				if req.ReleaseDate != "" && result.ReleaseDate == "" {
+					result.ReleaseDate = req.ReleaseDate
+				}
 				return result, nil
 			}
 			if err != nil {
@@ -1138,6 +1204,10 @@ func (p *ExtensionProviderWrapper) CustomSearch(query string, options map[string
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	// Convert options to JSON
 	optionsJSON, _ := json.Marshal(options)
 
@@ -1209,6 +1279,10 @@ func (p *ExtensionProviderWrapper) HandleURL(url string) (*ExtURLHandleResult, e
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.handleUrl === 'function') {
@@ -1290,6 +1364,10 @@ func (p *ExtensionProviderWrapper) MatchTrack(sourceTrack map[string]interface{}
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	sourceJSON, _ := json.Marshal(sourceTrack)
 	candidatesJSON, _ := json.Marshal(candidates)
 
@@ -1353,6 +1431,10 @@ func (p *ExtensionProviderWrapper) PostProcess(filePath string, metadata map[str
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
 
+	// Lock VM to prevent concurrent access
+	p.extension.VMMu.Lock()
+	defer p.extension.VMMu.Unlock()
+
 	metadataJSON, _ := json.Marshal(metadata)
 
 	script := fmt.Sprintf(`

go_backend/extension_runtime.go

@@ -299,6 +299,7 @@ func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
 	utilsObj.Set("encrypt", r.cryptoEncrypt)
 	utilsObj.Set("decrypt", r.cryptoDecrypt)
 	utilsObj.Set("generateKey", r.cryptoGenerateKey)
+	utilsObj.Set("randomUserAgent", r.randomUserAgent)
 	vm.Set("utils", utilsObj)
 
 	// Log object (already set in extension_manager.go, but we can enhance it)

go_backend/extension_runtime_utils.go

@@ -268,6 +268,11 @@ func (r *ExtensionRuntime) cryptoGenerateKey(call goja.FunctionCall) goja.Value
 	})
 }
 
+// randomUserAgent returns a random Chrome User-Agent string
+func (r *ExtensionRuntime) randomUserAgent(call goja.FunctionCall) goja.Value {
+	return r.vm.ToValue(getRandomUserAgent())
+}
+
 // ==================== Logging Functions ====================
 
 func (r *ExtensionRuntime) logDebug(call goja.FunctionCall) goja.Value {

go_backend/httputil.go

@@ -18,17 +18,16 @@ import (
 // HTTP utility functions for consistent request handling across all downloaders
 
 // getRandomUserAgent generates a random Windows Chrome User-Agent string
-// Uses same format as PC version (referensi/backend/spotify_metadata.go) for better API compatibility
+// Uses modern Chrome format with build and patch numbers
+// Windows 11 still reports as "Windows NT 10.0" for compatibility
 func getRandomUserAgent() string {
-	winMajor := rand.Intn(2) + 10
-
-	chromeVersion := rand.Intn(25) + 100
-	chromeBuild := rand.Intn(1500) + 3000
-	chromePatch := rand.Intn(65) + 60
+	// Chrome version 120-145 (modern range)
+	chromeVersion := rand.Intn(26) + 120
+	chromeBuild := rand.Intn(1500) + 6000
+	chromePatch := rand.Intn(200) + 100
 
 	return fmt.Sprintf(
-		"Mozilla/5.0 (Windows NT %d.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/537.36",
-		winMajor,
+		"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/537.36",
 		chromeVersion,
 		chromeBuild,
 		chromePatch,

go_backend/tidal.go

@@ -1706,12 +1706,19 @@ func downloadFromTidal(req DownloadRequest) (TidalDownloadResult, error) {
 	}
 
 	// Embed metadata using parallel-fetched cover data
+	// Use release date from Tidal API if not provided in request
+	releaseDate := req.ReleaseDate
+	if releaseDate == "" && track.Album.ReleaseDate != "" {
+		releaseDate = track.Album.ReleaseDate
+		GoLog("[Tidal] Using release date from Tidal API: %s\n", releaseDate)
+	}
+
 	metadata := Metadata{
 		Title:       req.TrackName,
 		Artist:      req.ArtistName,
 		Album:       req.AlbumName,
 		AlbumArtist: req.AlbumArtist,
-		Date:        req.ReleaseDate,
+		Date:        releaseDate,
 		TrackNumber: track.TrackNumber, // Use actual track number from Tidal
 		TotalTracks: req.TotalTracks,
 		DiscNumber:  track.VolumeNumber, // Use actual disc number from Tidal