ym-dl-watcher/internal/storage/storage.go

package storage

import (
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/bogem/id3v2"
	_ "modernc.org/sqlite"
	"gitea.mrixs.me/Mrixs/yandex-music-api-go/yandexmusic"
)

// TrackMeta holds metadata for a downloaded track
type TrackMeta struct {
	TrackID        string   `json:"track_id"`
	AlbumID        string   `json:"album_id"`
	ArtistID       string   `json:"artist_id"`
	Title          string   `json:"title"`
	ArtistName     string   `json:"artist_name"`      // Primary artist (first)
	ArtistNames    []string `json:"artist_names"`     // All artists
	AlbumTitle     string   `json:"album_title"`
	AlbumArtist    string   `json:"album_artist"`     // Album artist (may differ from track artist)
	AlbumArtistID  string   `json:"album_artist_id"`  // Album artist ID
	Year           int      `json:"year"`             // Release year from album
	TrackNumber    int      `json:"track_number"`
	DiscNumber     int      `json:"disc_number"`
	DurationMs     int64    `json:"duration_ms"`
	Bitrate        int      `json:"bitrate"`
	Codec          string   `json:"codec"`
	FilePath       string   `json:"file_path"`
	FileSize       int64    `json:"file_size"`
	DownloadedAt   string   `json:"downloaded_at"`

	// Extended metadata from Yandex Music API
	Genre       string `json:"genre"`                // Track or album genre
	Comment     string `json:"comment"`              // Album description / comments
	Lyrics      string `json:"lyrics"`               // Track lyrics text
	Publisher   string `json:"publisher"`            // Album label / publisher
	EncodedBy   string `json:"encoded_by"`           // Encoder name
	OriginalYear string `json:"original_year"`        // Original release year
	Composer    string `json:"composer"`             // Composer
	ISRC        string `json:"isrc"`                 // International Standard Recording Code
	Copyright   string `json:"copyright"`            // Copyright information
}

// AlbumMeta holds metadata for a downloaded album
type AlbumMeta struct {
	AlbumID    string     `json:"album_id"`
	ArtistID   string     `json:"artist_id"`
	Title      string     `json:"title"`
	ArtistName string     `json:"artist_name"`
	Year       int        `json:"year"`
	TrackCount int        `json:"track_count"`
	CoverPath  string     `json:"cover_path"`
	Tracks     []TrackMeta `json:"tracks"`
	DownloadedAt string   `json:"downloaded_at"`
}

// Storage manages local file storage for downloaded music
type Storage struct {
	rootPath string
	organize bool
	mu       sync.RWMutex
	db       *sql.DB
}

// NewStorage creates a new storage instance with SQLite backend
func NewStorage(rootPath string, organize bool) (*Storage, error) {
	if err := os.MkdirAll(rootPath, 0755); err != nil {
		return nil, fmt.Errorf("create root path: %w", err)
	}

	dbPath := filepath.Join(rootPath, "index.db")
	db, err := sql.Open("sqlite", dbPath)
	if err != nil {
		return nil, fmt.Errorf("open sqlite db: %w", err)
	}

	// Configure connection pool for single-writer SQLite
	db.SetMaxOpenConns(1)

	if err := createSchema(db); err != nil {
		db.Close()
		return nil, fmt.Errorf("create schema: %w", err)
	}

	s := &Storage{
		rootPath: rootPath,
		organize: organize,
		db:       db,
	}

	// Migrate from old JSON index if it exists
	if err := s.migrateFromJSON(); err != nil {
		// Log but don't fail — migration is best-effort
		fmt.Printf("Warning: JSON index migration: %v\n", err)
	}

	return s, nil
}

// createSchema creates the tracks table if it doesn't exist
func createSchema(db *sql.DB) error {
	schema := `
	CREATE TABLE IF NOT EXISTS tracks (
		track_id      TEXT PRIMARY KEY,
		album_id      TEXT,
		artist_id     TEXT,
		title         TEXT,
		artist_name   TEXT,
		artist_names  TEXT,
		album_title   TEXT,
		album_artist  TEXT,
		album_artist_id TEXT,
		year          INTEGER,
		track_number  INTEGER,
		disc_number   INTEGER,
		duration_ms   INTEGER,
		bitrate       INTEGER,
		codec         TEXT,
		file_path     TEXT,
		file_size     INTEGER,
		downloaded_at TEXT,
		genre         TEXT,
		comment       TEXT,
		lyrics        TEXT,
		publisher     TEXT,
		encoded_by    TEXT,
		original_year TEXT,
		composer      TEXT,
		isrc          TEXT,
		copyright     TEXT
	);
	CREATE INDEX IF NOT EXISTS idx_tracks_album_id ON tracks(album_id);
	`
	_, err := db.Exec(schema)
	return err
}

// migrateFromJSON imports the old .index.json into SQLite if it exists
func (s *Storage) migrateFromJSON() error {
	jsonPath := filepath.Join(s.rootPath, ".index.json")
	data, err := os.ReadFile(jsonPath)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil // No old index, nothing to migrate
		}
		return err
	}

	var oldIndex map[string]TrackMeta
	if err := json.Unmarshal(data, &oldIndex); err != nil {
		return fmt.Errorf("parse old index: %w", err)
	}

	if len(oldIndex) == 0 {
		return nil
	}

	// Check if SQLite already has data (avoid double-migration)
	var count int
	err = s.db.QueryRow("SELECT COUNT(*) FROM tracks").Scan(&count)
	if err != nil {
		return err
	}
	if count > 0 {
		return nil // Already migrated
	}

	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	stmt, err := tx.Prepare(insertTrackSQL())
	if err != nil {
		tx.Rollback()
		return err
	}
	defer stmt.Close()

	for _, meta := range oldIndex {
		if _, err := stmt.Exec(
			meta.TrackID, meta.AlbumID, meta.ArtistID, meta.Title, meta.ArtistName,
			serializeStrings(meta.ArtistNames), meta.AlbumTitle, meta.AlbumArtist,
			meta.AlbumArtistID, meta.Year, meta.TrackNumber, meta.DiscNumber,
			meta.DurationMs, meta.Bitrate, meta.Codec, meta.FilePath, meta.FileSize,
			meta.DownloadedAt, meta.Genre, meta.Comment, meta.Lyrics, meta.Publisher,
			meta.EncodedBy, meta.OriginalYear, meta.Composer, meta.ISRC, meta.Copyright,
		); err != nil {
			tx.Rollback()
			return err
		}
	}

	if err := tx.Commit(); err != nil {
		return err
	}

	// Remove the old JSON file after successful migration
	if err := os.Remove(jsonPath); err != nil && !errors.Is(err, os.ErrNotExist) {
		return err
	}

	return nil
}

// insertTrackSQL returns the parameterized INSERT OR REPLACE statement
func insertTrackSQL() string {
	return `
	INSERT OR REPLACE INTO tracks (
		track_id, album_id, artist_id, title, artist_name, artist_names,
		album_title, album_artist, album_artist_id, year, track_number,
		disc_number, duration_ms, bitrate, codec, file_path, file_size,
		downloaded_at, genre, comment, lyrics, publisher, encoded_by,
		original_year, composer, isrc, copyright
	) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
`
}

// scanTrackMeta reads a TrackMeta from a sql.Row
func scanTrackMeta(row *sql.Row) (TrackMeta, error) {
	var m TrackMeta
	var artistNamesStr string
	var downloadedAt sql.NullString
	var genre sql.NullString
	var comment sql.NullString
	var lyrics sql.NullString
	var publisher sql.NullString
	var encodedBy sql.NullString
	var originalYear sql.NullString
	var composer sql.NullString
	var isrc sql.NullString
	var copyright sql.NullString

	err := row.Scan(
		&m.TrackID, &m.AlbumID, &m.ArtistID, &m.Title, &m.ArtistName,
		&artistNamesStr, &m.AlbumTitle, &m.AlbumArtist, &m.AlbumArtistID,
		&m.Year, &m.TrackNumber, &m.DiscNumber, &m.DurationMs, &m.Bitrate,
		&m.Codec, &m.FilePath, &m.FileSize, &downloadedAt, &genre, &comment,
		&lyrics, &publisher, &encodedBy, &originalYear, &composer, &isrc,
		&copyright,
	)
	if err != nil {
		return m, err
	}

	if downloadedAt.Valid {
		m.DownloadedAt = downloadedAt.String
	}
	m.ArtistNames = deserializeStrings(artistNamesStr)
	if genre.Valid {
		m.Genre = genre.String
	}
	if comment.Valid {
		m.Comment = comment.String
	}
	if lyrics.Valid {
		m.Lyrics = lyrics.String
	}
	if publisher.Valid {
		m.Publisher = publisher.String
	}
	if encodedBy.Valid {
		m.EncodedBy = encodedBy.String
	}
	if originalYear.Valid {
		m.OriginalYear = originalYear.String
	}
	if composer.Valid {
		m.Composer = composer.String
	}
	if isrc.Valid {
		m.ISRC = isrc.String
	}
	if copyright.Valid {
		m.Copyright = copyright.String
	}

	return m, nil
}

// serializeStrings converts a []string to a JSON string for storage
func serializeStrings(strs []string) string {
	if strs == nil {
		return "[]"
	}
	b, _ := json.Marshal(strs)
	return string(b)
}

// deserializeStrings converts a JSON string back to []string
func deserializeStrings(s string) []string {
	if s == "" || s == "[]" {
		return nil
	}
	var strs []string
	if err := json.Unmarshal([]byte(s), &strs); err != nil {
		return nil
	}
	return strs
}

// IsTrackDownloaded checks if a track has already been downloaded
func (s *Storage) IsTrackDownloaded(trackID string) bool {
	s.mu.RLock()
	defer s.mu.RUnlock()

	var count int
	err := s.db.QueryRow("SELECT COUNT(*) FROM tracks WHERE track_id = ?", trackID).Scan(&count)
	if err != nil {
		return false
	}
	return count > 0
}

// GetTrackMeta returns metadata for a downloaded track
func (s *Storage) GetTrackMeta(trackID string) (TrackMeta, bool) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	m, err := scanTrackMeta(s.db.QueryRow("SELECT * FROM tracks WHERE track_id = ?", trackID))
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return TrackMeta{}, false
		}
		return TrackMeta{}, false
	}
	return m, true
}

// SaveTrack saves a track file and its metadata
func (s *Storage) SaveTrack(trackMeta TrackMeta, data []byte, coverData []byte) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	// Determine file path
	var filePath string
	if s.organize {
		// Artist/Album/TrackNumber - Title.ext
		artistDir := sanitizeFilename(trackMeta.ArtistName)
		albumDir := sanitizeFilename(trackMeta.AlbumTitle)
		trackFilename := fmt.Sprintf("%02d - %s.%s", trackMeta.TrackNumber, sanitizeFilename(trackMeta.Title), trackMeta.Codec)
		filePath = filepath.Join(s.rootPath, artistDir, albumDir, trackFilename)
	} else {
		// Flat structure: Artist - Title.ext
		trackFilename := fmt.Sprintf("%s - %s.%s", sanitizeFilename(trackMeta.ArtistName), sanitizeFilename(trackMeta.Title), trackMeta.Codec)
		filePath = filepath.Join(s.rootPath, trackFilename)
	}

	// Create directory
	dir := filepath.Dir(filePath)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("create directory: %w", err)
	}

	// Write file
	if err := os.WriteFile(filePath, data, 0644); err != nil {
		return fmt.Errorf("write track file: %w", err)
	}

	// Write ID3 tags (only for MP3)
	if strings.EqualFold(trackMeta.Codec, "mp3") {
		if err := writeID3Tags(filePath, trackMeta, coverData); err != nil {
			// Log error but don't fail the download
			fmt.Printf("Warning: failed to write ID3 tags: %v\n", err)
		}
	}

	// Update metadata
	trackMeta.FilePath = filePath
	trackMeta.FileSize = int64(len(data))
	trackMeta.DownloadedAt = time.Now().Format(time.RFC3339)

	_, err := s.db.Exec(insertTrackSQL(),
		trackMeta.TrackID, trackMeta.AlbumID, trackMeta.ArtistID, trackMeta.Title,
		trackMeta.ArtistName, serializeStrings(trackMeta.ArtistNames),
		trackMeta.AlbumTitle, trackMeta.AlbumArtist, trackMeta.AlbumArtistID,
		trackMeta.Year, trackMeta.TrackNumber, trackMeta.DiscNumber,
		trackMeta.DurationMs, trackMeta.Bitrate, trackMeta.Codec,
		trackMeta.FilePath, trackMeta.FileSize, trackMeta.DownloadedAt,
		trackMeta.Genre, trackMeta.Comment, trackMeta.Lyrics, trackMeta.Publisher,
		trackMeta.EncodedBy, trackMeta.OriginalYear, trackMeta.Composer,
		trackMeta.ISRC, trackMeta.Copyright,
	)
	if err != nil {
		return fmt.Errorf("save track meta: %w", err)
	}

	return nil
}

// SaveAlbum saves album cover and metadata
func (s *Storage) SaveAlbum(albumMeta AlbumMeta, coverData []byte) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	var coverPath string
	if s.organize && len(albumMeta.Tracks) > 0 {
		artistDir := sanitizeFilename(albumMeta.ArtistName)
		albumDir := sanitizeFilename(albumMeta.Title)
		coverPath = filepath.Join(s.rootPath, artistDir, albumDir, "cover.jpg")
	} else {
		coverPath = filepath.Join(s.rootPath, fmt.Sprintf("%s - %s_cover.jpg", sanitizeFilename(albumMeta.ArtistName), sanitizeFilename(albumMeta.Title)))
	}

	dir := filepath.Dir(coverPath)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("create directory: %w", err)
	}

	if len(coverData) > 0 {
		if err := os.WriteFile(coverPath, coverData, 0644); err != nil {
			return fmt.Errorf("write cover file: %w", err)
		}
	}

	albumMeta.CoverPath = coverPath
	// Update track metas with album info
	for i := range albumMeta.Tracks {
		if _, err := s.db.Exec(insertTrackSQL(),
			albumMeta.Tracks[i].TrackID, albumMeta.Tracks[i].AlbumID,
			albumMeta.Tracks[i].ArtistID, albumMeta.Tracks[i].Title,
			albumMeta.Tracks[i].ArtistName,
			serializeStrings(albumMeta.Tracks[i].ArtistNames),
			albumMeta.Tracks[i].AlbumTitle, albumMeta.Tracks[i].AlbumArtist,
			albumMeta.Tracks[i].AlbumArtistID, albumMeta.Tracks[i].Year,
			albumMeta.Tracks[i].TrackNumber, albumMeta.Tracks[i].DiscNumber,
			albumMeta.Tracks[i].DurationMs, albumMeta.Tracks[i].Bitrate,
			albumMeta.Tracks[i].Codec, albumMeta.Tracks[i].FilePath,
			albumMeta.Tracks[i].FileSize, albumMeta.Tracks[i].DownloadedAt,
			albumMeta.Tracks[i].Genre, albumMeta.Tracks[i].Comment,
			albumMeta.Tracks[i].Lyrics, albumMeta.Tracks[i].Publisher,
			albumMeta.Tracks[i].EncodedBy, albumMeta.Tracks[i].OriginalYear,
			albumMeta.Tracks[i].Composer, albumMeta.Tracks[i].ISRC,
			albumMeta.Tracks[i].Copyright,
		); err != nil {
			return fmt.Errorf("save album track meta: %w", err)
		}
	}

	return nil
}

// GetDownloadedTracks returns all downloaded track IDs
func (s *Storage) GetDownloadedTracks() []string {
	s.mu.RLock()
	defer s.mu.RUnlock()

	rows, err := s.db.Query("SELECT track_id FROM tracks")
	if err != nil {
		return nil
	}
	defer rows.Close()

	var tracks []string
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			continue
		}
		tracks = append(tracks, id)
	}
	return tracks
}

// GetDownloadedAlbums returns all downloaded album IDs
func (s *Storage) GetDownloadedAlbums() []string {
	s.mu.RLock()
	defer s.mu.RUnlock()

	rows, err := s.db.Query("SELECT DISTINCT album_id FROM tracks WHERE album_id != '' AND album_id IS NOT NULL")
	if err != nil {
		return nil
	}
	defer rows.Close()

	var albums []string
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			continue
		}
		albums = append(albums, id)
	}
	return albums
}

// Close closes the database connection
func (s *Storage) Close() error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.db != nil {
		return s.db.Close()
	}
	return nil
}

// sanitizeFilename removes invalid characters from filenames
func sanitizeFilename(name string) string {
	replacer := strings.NewReplacer(
		"/", "_",
		"\\", "_",
		":", "_",
		"*", "_",
		"?", "_",
		"\"", "_",
		"<", "_",
		">", "_",
		"|", "_",
		"\n", "_",
		"\r", "_",
	)
	return replacer.Replace(name)
}

// BuildTrackMetaFromYandex creates TrackMeta from Yandex API data
func BuildTrackMetaFromYandex(track *yandexmusic.Track, album *yandexmusic.Album, trackNum, discNum int, downloadInfo yandexmusic.DownloadInfo) TrackMeta {
	artistNames := make([]string, 0, len(track.Artists))
	for _, a := range track.Artists {
		artistNames = append(artistNames, a.Name)
	}
	artistName := ""
	if len(artistNames) > 0 {
		artistName = artistNames[0]
	}

	albumTitle := ""
	albumID := ""
	year := 0
	var albumGenre, albumLabel, albumDesc, albumReleaseDate, albumCopyright string
	if album != nil {
		albumTitle = album.Title
		albumID = album.ID
		year = album.Year
		albumGenre = album.Genre
		albumLabel = album.Label
		albumDesc = album.Description
		albumReleaseDate = album.ReleaseDate
		if len(album.CatalogNumber) > 0 {
			albumCopyright = album.CatalogNumber
		}
	} else if len(track.Albums) > 0 {
		albumTitle = track.Albums[0].Title
		albumID = track.Albums[0].ID
		year = track.Albums[0].Year
	}

	artistID := ""
	if len(track.Artists) > 0 {
		artistID = track.Artists[0].ID
	}

	albumArtist := ""
	albumArtistID := ""
	if album != nil && len(album.Artists) > 0 {
		albumArtist = album.Artists[0].Name
		albumArtistID = album.Artists[0].ID
	} else if len(track.Albums) > 0 && len(track.Albums[0].Artists) > 0 {
		albumArtist = track.Albums[0].Artists[0].Name
		albumArtistID = track.Albums[0].Artists[0].ID
	}

	// Genre: prefer track genre, fallback to album genre
	genre := track.Genre
	if genre == "" {
		genre = albumGenre
	}

	// Publisher: album label
	publisher := albumLabel

	// Original year from release date
	var originalYear string
	if albumReleaseDate != "" {
		if len(albumReleaseDate) >= 4 {
			originalYear = albumReleaseDate[:4]
		}
	}

	// Lyrics
	var lyrics string
	if track.Lyrics != nil && track.Lyrics.HasText {
		lyrics = track.Lyrics.Text
	}

	return TrackMeta{
		TrackID:       track.ID,
		AlbumID:       albumID,
		ArtistID:      artistID,
		Title:         track.Title,
		ArtistName:    artistName,
		ArtistNames:   artistNames,
		AlbumTitle:    albumTitle,
		AlbumArtist:   albumArtist,
		AlbumArtistID: albumArtistID,
		Year:          year,
		TrackNumber:   trackNum,
		DiscNumber:    discNum,
		DurationMs:    int64(track.DurationMs),
		Bitrate:       downloadInfo.Bitrate,
		Codec:         downloadInfo.Codec,
		DownloadedAt:  "",

		// Extended metadata
		Genre:       genre,
		Comment:     albumDesc,
		Lyrics:      lyrics,
		Publisher:   publisher,
		EncodedBy:   "ym-dl",
		OriginalYear: originalYear,
		Composer:    "",
		ISRC:        "",
		Copyright:   albumCopyright,
	}
}

// BuildAlbumMetaFromYandex creates AlbumMeta from Yandex API data
func BuildAlbumMetaFromYandex(album *yandexmusic.Album, tracks []TrackMeta) AlbumMeta {
	artistName := ""
	artistID := ""
	if len(album.Artists) > 0 {
		artistName = album.Artists[0].Name
		artistID = album.Artists[0].ID
	}

	return AlbumMeta{
		AlbumID:      album.ID,
		ArtistID:     artistID,
		Title:        album.Title,
		ArtistName:   artistName,
		Year:         album.Year,
		TrackCount:   len(tracks),
		Tracks:       tracks,
		DownloadedAt: "",
	}
}

// writeID3Tags writes ID3v2 tags to an MP3 file
func writeID3Tags(filePath string, meta TrackMeta, coverData []byte) error {
	tag, err := id3v2.Open(filePath, id3v2.Options{Parse: true})
	if err != nil {
		// Create new tag if file doesn't have one
		tag = id3v2.NewEmptyTag()
	}
	defer tag.Close()

	// Join all artists with "; " for the artist tag
	artistString := strings.Join(meta.ArtistNames, "; ")

	// Set basic tags
	tag.SetTitle(meta.Title)
	tag.SetArtist(artistString)
	tag.SetAlbum(meta.AlbumTitle)
	// Album artist (TPE2 frame) - use album artist if different from track artist
	if meta.AlbumArtist != "" && meta.AlbumArtist != meta.ArtistName {
		tag.AddTextFrame("TPE2", id3v2.EncodingUTF8, meta.AlbumArtist)
	}
	// Use album year from metadata, fallback to current year
	year := meta.Year
	if year == 0 {
		year = time.Now().Year()
	}
	tag.SetYear(fmt.Sprintf("%d", year))

	if meta.TrackNumber > 0 {
		// Track number via TRCK frame
		tag.AddTextFrame("TRCK", id3v2.EncodingUTF8, fmt.Sprintf("%d", meta.TrackNumber))
	}

	if meta.DiscNumber > 0 {
		// Disc number via TPOS frame
		tag.AddTextFrame("TPOS", id3v2.EncodingUTF8, fmt.Sprintf("%d", meta.DiscNumber))
	}

	// Genre (TCON)
	if meta.Genre != "" {
		tag.SetGenre(meta.Genre)
	}

	// Composer (TCOM)
	if meta.Composer != "" {
		tag.AddTextFrame("TCOM", id3v2.EncodingUTF8, meta.Composer)
	}

	// Publisher (TPUB)
	if meta.Publisher != "" {
		tag.AddTextFrame("TPUB", id3v2.EncodingUTF8, meta.Publisher)
	}

	// Encoded by (TENC)
	if meta.EncodedBy != "" {
		tag.AddTextFrame("TENC", id3v2.EncodingUTF8, meta.EncodedBy)
	}

	// Copyright (TCOP)
	if meta.Copyright != "" {
		tag.AddTextFrame("TCOP", id3v2.EncodingUTF8, meta.Copyright)
	}

	// Original year (TORY)
	if meta.OriginalYear != "" {
		tag.AddTextFrame("TORY", id3v2.EncodingUTF8, meta.OriginalYear)
	}

	// ISRC (TSRC)
	if meta.ISRC != "" {
		tag.AddTextFrame("TSRC", id3v2.EncodingUTF8, meta.ISRC)
	}

	// Comment (COMM)
	if meta.Comment != "" {
		tag.AddCommentFrame(id3v2.CommentFrame{
			Encoding:    id3v2.EncodingUTF8,
			Language:    "eng",
			Description: "Comment",
			Text:        meta.Comment,
		})
	}

	// Lyrics (USLT)
	if meta.Lyrics != "" {
		tag.AddUnsynchronisedLyricsFrame(id3v2.UnsynchronisedLyricsFrame{
			Encoding:          id3v2.EncodingUTF8,
			Language:          "eng",
			ContentDescriptor: "Lyrics",
			Lyrics:            meta.Lyrics,
		})
	}

	// Add cover art (APIC frame)
	if len(coverData) > 0 {
		tag.AddAttachedPicture(id3v2.PictureFrame{
			Encoding:   id3v2.EncodingUTF8,
			MimeType:   "image/jpeg",
			PictureType: id3v2.PTFrontCover,
			Description: "Cover",
			Picture:    coverData,
		})
	}

	// Add custom TXXX frames for Yandex IDs
	tag.AddTextFrame("TXXX", id3v2.EncodingUTF8, "YANDEX_TRACK_ID: "+meta.TrackID)
	tag.AddTextFrame("TXXX", id3v2.EncodingUTF8, "YANDEX_ALBUM_ID: "+meta.AlbumID)
	tag.AddTextFrame("TXXX", id3v2.EncodingUTF8, "YANDEX_ARTIST_ID: "+meta.ArtistID)

	// Save tag
	return tag.Save()
}