SpotiFLAC/backend/metadata.go

package backend

import (
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	pathfilepath "path/filepath"
	"strconv"
	"strings"

	id3v2 "github.com/bogem/id3v2/v2"
	"github.com/go-flac/flacpicture"
	"github.com/go-flac/flacvorbis"
	"github.com/go-flac/go-flac"
)

type Metadata struct {
	Title       string
	Artist      string
	Album       string
	AlbumArtist string
	Date        string
	ReleaseDate string
	TrackNumber int
	TotalTracks int
	DiscNumber  int
	TotalDiscs  int
	URL         string
	Copyright   string
	Publisher   string
	Lyrics      string
	Description string
}

func EmbedMetadata(filepath string, metadata Metadata, coverPath string) error {
	f, err := flac.ParseFile(filepath)
	if err != nil {
		return fmt.Errorf("failed to parse FLAC file: %w", err)
	}

	var cmtIdx = -1
	for idx, block := range f.Meta {
		if block.Type == flac.VorbisComment {
			cmtIdx = idx
			break
		}
	}

	cmt := flacvorbis.New()

	if metadata.Title != "" {
		_ = cmt.Add(flacvorbis.FIELD_TITLE, metadata.Title)
	}
	if metadata.Artist != "" {
		_ = cmt.Add(flacvorbis.FIELD_ARTIST, metadata.Artist)
	}
	if metadata.Album != "" {
		_ = cmt.Add(flacvorbis.FIELD_ALBUM, metadata.Album)
	}
	if metadata.AlbumArtist != "" {
		_ = cmt.Add("ALBUMARTIST", metadata.AlbumArtist)
	}
	if metadata.Date != "" {
		_ = cmt.Add(flacvorbis.FIELD_DATE, metadata.Date)
	}
	if metadata.TrackNumber > 0 {
		_ = cmt.Add(flacvorbis.FIELD_TRACKNUMBER, strconv.Itoa(metadata.TrackNumber))
	}
	if metadata.TotalTracks > 0 {
		_ = cmt.Add("TOTALTRACKS", strconv.Itoa(metadata.TotalTracks))
	}
	if metadata.DiscNumber > 0 {
		_ = cmt.Add("DISCNUMBER", strconv.Itoa(metadata.DiscNumber))
	}
	if metadata.TotalDiscs > 0 {
		_ = cmt.Add("TOTALDISCS", strconv.Itoa(metadata.TotalDiscs))
	}
	if metadata.Copyright != "" {
		_ = cmt.Add("COPYRIGHT", metadata.Copyright)
	}
	if metadata.Publisher != "" {
		_ = cmt.Add("PUBLISHER", metadata.Publisher)
	}
	if metadata.Description != "" {
		_ = cmt.Add("DESCRIPTION", metadata.Description)
	}

	if metadata.Lyrics != "" {
		_ = cmt.Add("LYRICS", metadata.Lyrics)
	}

	cmtBlock := cmt.Marshal()
	if cmtIdx < 0 {
		f.Meta = append(f.Meta, &cmtBlock)
	} else {
		f.Meta[cmtIdx] = &cmtBlock
	}

	if coverPath != "" && fileExists(coverPath) {
		if err := embedCoverArt(f, coverPath); err != nil {
			fmt.Printf("Warning: Failed to embed cover art: %v\n", err)
		}
	}

	if err := f.Save(filepath); err != nil {
		return fmt.Errorf("failed to save FLAC file: %w", err)
	}

	return nil
}

func embedCoverArt(f *flac.File, coverPath string) error {
	imgData, err := os.ReadFile(coverPath)
	if err != nil {
		return fmt.Errorf("failed to read cover image: %w", err)
	}

	picture, err := flacpicture.NewFromImageData(
		flacpicture.PictureTypeFrontCover,
		"Cover",
		imgData,
		"image/jpeg",
	)
	if err != nil {
		return fmt.Errorf("failed to create picture block: %w", err)
	}

	pictureBlock := picture.Marshal()

	for i := len(f.Meta) - 1; i >= 0; i-- {
		if f.Meta[i].Type == flac.Picture {
			f.Meta = append(f.Meta[:i], f.Meta[i+1:]...)
		}
	}

	f.Meta = append(f.Meta, &pictureBlock)

	return nil
}

func fileExists(path string) bool {
	_, err := os.Stat(path)
	return err == nil
}

func extractYear(releaseDate string) string {
	if releaseDate == "" {
		return ""
	}

	if len(releaseDate) >= 4 {
		return releaseDate[:4]
	}
	return releaseDate
}

func EmbedLyricsOnly(filepath string, lyrics string) error {
	if lyrics == "" {
		return nil
	}
	f, err := flac.ParseFile(filepath)
	if err != nil {
		return fmt.Errorf("failed to parse FLAC file: %w", err)
	}

	var cmtIdx = -1
	var existingCmt *flacvorbis.MetaDataBlockVorbisComment
	for idx, block := range f.Meta {
		if block.Type == flac.VorbisComment {
			cmtIdx = idx
			existingCmt, err = flacvorbis.ParseFromMetaDataBlock(*block)
			if err != nil {
				existingCmt = nil
			}
			break
		}
	}

	cmt := flacvorbis.New()

	if existingCmt != nil {
		for _, comment := range existingCmt.Comments {
			parts := strings.SplitN(comment, "=", 2)
			if len(parts) == 2 {
				fieldName := strings.ToUpper(parts[0])
				if fieldName != "LYRICS" && fieldName != "UNSYNCEDLYRICS" && fieldName != "SYNCEDLYRICS" {
					_ = cmt.Add(parts[0], parts[1])
				}
			}
		}
	}

	_ = cmt.Add("LYRICS", lyrics)

	cmtBlock := cmt.Marshal()
	if cmtIdx < 0 {
		f.Meta = append(f.Meta, &cmtBlock)
	} else {
		f.Meta[cmtIdx] = &cmtBlock
	}

	if err := f.Save(filepath); err != nil {
		return fmt.Errorf("failed to save FLAC file: %w", err)
	}

	return nil
}

func ExtractCoverArt(filePath string) (string, error) {
	ext := strings.ToLower(pathfilepath.Ext(filePath))

	switch ext {
	case ".mp3":
		return extractCoverFromMp3(filePath)
	case ".m4a", ".flac":
		return extractCoverFromM4AOrFlac(filePath)
	default:
		return "", fmt.Errorf("unsupported file format: %s", ext)
	}
}

func extractCoverFromMp3(filePath string) (string, error) {
	tag, err := id3v2.Open(filePath, id3v2.Options{Parse: true})
	if err != nil {
		return "", fmt.Errorf("failed to open MP3 file: %w", err)
	}
	defer tag.Close()

	pictures := tag.GetFrames(tag.CommonID("Attached picture"))
	if len(pictures) == 0 {
		return "", fmt.Errorf("no cover art found")
	}

	pic, ok := pictures[0].(id3v2.PictureFrame)
	if !ok {
		return "", fmt.Errorf("invalid picture frame")
	}

	tmpFile, err := os.CreateTemp("", "cover-*.jpg")
	if err != nil {
		return "", fmt.Errorf("failed to create temp file: %w", err)
	}
	defer tmpFile.Close()

	if _, err := tmpFile.Write(pic.Picture); err != nil {
		os.Remove(tmpFile.Name())
		return "", fmt.Errorf("failed to write cover art: %w", err)
	}

	return tmpFile.Name(), nil
}

func extractCoverFromM4AOrFlac(filePath string) (string, error) {
	ext := strings.ToLower(pathfilepath.Ext(filePath))

	if ext == ".flac" {
		f, err := flac.ParseFile(filePath)
		if err != nil {
			return "", fmt.Errorf("failed to parse FLAC file: %w", err)
		}

		for _, block := range f.Meta {
			if block.Type == flac.Picture {
				pic, err := flacpicture.ParseFromMetaDataBlock(*block)
				if err != nil {
					continue
				}

				tmpFile, err := os.CreateTemp("", "cover-*.jpg")
				if err != nil {
					return "", fmt.Errorf("failed to create temp file: %w", err)
				}
				defer tmpFile.Close()

				if _, err := tmpFile.Write(pic.ImageData); err != nil {
					os.Remove(tmpFile.Name())
					return "", fmt.Errorf("failed to write cover art: %w", err)
				}

				return tmpFile.Name(), nil
			}
		}
		return "", fmt.Errorf("no cover art found")
	}

	return "", nil
}

func ExtractLyrics(filePath string) (string, error) {
	ext := strings.ToLower(pathfilepath.Ext(filePath))

	switch ext {
	case ".mp3":
		return extractLyricsFromMp3(filePath)
	case ".flac":
		return extractLyricsFromFlac(filePath)
	case ".m4a":

		return "", nil
	default:
		return "", fmt.Errorf("unsupported file format: %s", ext)
	}
}

func extractLyricsFromMp3(filePath string) (string, error) {
	tag, err := id3v2.Open(filePath, id3v2.Options{Parse: true})
	if err != nil {
		return "", fmt.Errorf("failed to open MP3 file: %w", err)
	}
	defer tag.Close()

	usltFrames := tag.GetFrames(tag.CommonID("Unsynchronised lyrics/text transcription"))
	if len(usltFrames) == 0 {
		fmt.Printf("[ExtractLyrics] No USLT frames found in MP3: %s\n", filePath)
		return "", nil
	}

	uslt, ok := usltFrames[0].(id3v2.UnsynchronisedLyricsFrame)
	if !ok {
		fmt.Printf("[ExtractLyrics] USLT frame type assertion failed in MP3: %s\n", filePath)
		return "", nil
	}

	if uslt.Lyrics == "" {
		fmt.Printf("[ExtractLyrics] USLT frame has empty lyrics in MP3: %s\n", filePath)
		return "", nil
	}

	fmt.Printf("[ExtractLyrics] Successfully extracted lyrics from MP3: %s (%d characters)\n", filePath, len(uslt.Lyrics))
	return uslt.Lyrics, nil
}

func extractLyricsFromFlac(filePath string) (string, error) {
	f, err := flac.ParseFile(filePath)
	if err != nil {
		return "", fmt.Errorf("failed to parse FLAC file: %w", err)
	}

	for _, block := range f.Meta {
		if block.Type == flac.VorbisComment {
			cmt, err := flacvorbis.ParseFromMetaDataBlock(*block)
			if err != nil {
				continue
			}

			for _, comment := range cmt.Comments {
				parts := strings.SplitN(comment, "=", 2)
				if len(parts) == 2 {
					fieldName := strings.ToUpper(parts[0])
					if fieldName == "LYRICS" || fieldName == "UNSYNCEDLYRICS" {
						lyrics := parts[1]
						fmt.Printf("[ExtractLyrics] Successfully extracted lyrics from FLAC: %s (%d characters)\n", filePath, len(lyrics))
						return lyrics, nil
					}
				}
			}
		}
	}

	fmt.Printf("[ExtractLyrics] No lyrics found in FLAC: %s\n", filePath)
	return "", nil
}

func EmbedCoverArtOnly(filePath string, coverPath string) error {
	if coverPath == "" || !fileExists(coverPath) {
		return nil
	}

	ext := strings.ToLower(pathfilepath.Ext(filePath))

	switch ext {
	case ".mp3":
		return embedCoverToMp3(filePath, coverPath)
	case ".m4a":

		return nil
	default:
		return fmt.Errorf("unsupported file format: %s", ext)
	}
}

func embedCoverToMp3(filePath string, coverPath string) error {
	tag, err := id3v2.Open(filePath, id3v2.Options{Parse: true})
	if err != nil {
		return fmt.Errorf("failed to open MP3 file: %w", err)
	}
	defer tag.Close()

	tag.DeleteFrames(tag.CommonID("Attached picture"))

	artwork, err := os.ReadFile(coverPath)
	if err != nil {
		return fmt.Errorf("failed to read cover art: %w", err)
	}

	pic := id3v2.PictureFrame{
		Encoding:    id3v2.EncodingUTF8,
		MimeType:    "image/jpeg",
		PictureType: id3v2.PTFrontCover,
		Description: "Front cover",
		Picture:     artwork,
	}
	tag.AddAttachedPicture(pic)

	if err := tag.Save(); err != nil {
		return fmt.Errorf("failed to save MP3 tags: %w", err)
	}

	return nil
}

func EmbedLyricsOnlyMP3(filepath string, lyrics string) error {
	if lyrics == "" {
		return nil
	}

	validatedLyrics, err := validateLyricsDuration(lyrics, filepath)
	if err != nil {
		fmt.Printf("[EmbedLyricsOnlyMP3] Warning: Failed to validate lyrics duration: %v, using original lyrics\n", err)
		validatedLyrics = lyrics
	}
	lyrics = validatedLyrics

	tag, err := id3v2.Open(filepath, id3v2.Options{Parse: true})
	if err != nil {
		return fmt.Errorf("failed to open MP3 file: %w", err)
	}
	defer tag.Close()

	tag.DeleteFrames(tag.CommonID("Unsynchronised lyrics/text transcription"))

	usltFrame := id3v2.UnsynchronisedLyricsFrame{
		Encoding:          id3v2.EncodingUTF8,
		Language:          "eng",
		ContentDescriptor: "",
		Lyrics:            lyrics,
	}
	tag.AddUnsynchronisedLyricsFrame(usltFrame)

	if err := tag.Save(); err != nil {
		return fmt.Errorf("failed to save MP3 tags: %w", err)
	}

	return nil
}

func embedLyricsToM4A(filepath string, lyrics string) error {

	validatedLyrics, err := validateLyricsDuration(lyrics, filepath)
	if err != nil {
		fmt.Printf("[embedLyricsToM4A] Warning: Failed to validate lyrics duration: %v, using original lyrics\n", err)
		validatedLyrics = lyrics
	}
	lyrics = validatedLyrics

	ffmpegPath, err := GetFFmpegPath()
	if err != nil {
		return fmt.Errorf("ffmpeg not found: %w", err)
	}

	if err := ValidateExecutable(ffmpegPath); err != nil {
		return fmt.Errorf("invalid ffmpeg executable: %w", err)
	}

	tmpOutputFile := strings.TrimSuffix(filepath, pathfilepath.Ext(filepath)) + ".tmp" + pathfilepath.Ext(filepath)
	defer func() {

		if _, err := os.Stat(tmpOutputFile); err == nil {
			os.Remove(tmpOutputFile)
		}
	}()

	cmd := exec.Command(ffmpegPath,
		"-i", filepath,
		"-map", "0",
		"-map_metadata", "0",
		"-metadata", "lyrics-eng="+lyrics,
		"-metadata", "lyrics="+lyrics,
		"-codec", "copy",
		"-f", "ipod",
		"-y",
		tmpOutputFile,
	)

	setHideWindow(cmd)

	output, err := cmd.CombinedOutput()
	if err != nil {
		fmt.Printf("[FFmpeg] Error embedding lyrics to M4A: %s\n", string(output))
		return fmt.Errorf("ffmpeg failed to embed lyrics: %s - %w", string(output), err)
	}

	if err := os.Rename(tmpOutputFile, filepath); err != nil {
		return fmt.Errorf("failed to replace original file: %w", err)
	}

	fmt.Printf("[FFmpeg] Lyrics embedded to M4A successfully: %d characters\n", len(lyrics))
	return nil
}

func EmbedLyricsOnlyUniversal(filepath string, lyrics string) error {
	if lyrics == "" {
		return nil
	}

	ext := strings.ToLower(pathfilepath.Ext(filepath))
	switch ext {
	case ".mp3":
		return EmbedLyricsOnlyMP3(filepath, lyrics)
	case ".flac":
		return EmbedLyricsOnly(filepath, lyrics)
	case ".m4a":
		return embedLyricsToM4A(filepath, lyrics)
	default:
		return fmt.Errorf("unsupported file format for lyrics embedding: %s", ext)
	}
}

func GetAudioDuration(filepath string) (float64, error) {
	ext := strings.ToLower(pathfilepath.Ext(filepath))

	if ext == ".flac" {
		duration, err := getFlacDuration(filepath)
		if err == nil && duration > 0 {
			return duration, nil
		}
	}

	return getDurationWithFFprobe(filepath)
}

func getFlacDuration(filepath string) (float64, error) {
	f, err := flac.ParseFile(filepath)
	if err != nil {
		return 0, err
	}

	if len(f.Meta) > 0 {
		streamInfo := f.Meta[0]
		if streamInfo.Type == flac.StreamInfo {
			data := streamInfo.Data
			if len(data) >= 18 {

				sampleRate := uint32(data[10])<<12 | uint32(data[11])<<4 | uint32(data[12])>>4

				totalSamples := uint64(data[13]&0x0F)<<32 |
					uint64(data[14])<<24 |
					uint64(data[15])<<16 |
					uint64(data[16])<<8 |
					uint64(data[17])

				if sampleRate > 0 {
					return float64(totalSamples) / float64(sampleRate), nil
				}
			}
		}
	}

	return 0, fmt.Errorf("could not extract duration from FLAC file")
}

func getDurationWithFFprobe(filepath string) (float64, error) {
	ffprobePath, err := GetFFprobePath()
	if err != nil {
		return 0, err
	}

	if err := ValidateExecutable(ffprobePath); err != nil {
		return 0, fmt.Errorf("invalid ffprobe executable: %w", err)
	}

	cmd := exec.Command(ffprobePath,
		"-v", "quiet",
		"-print_format", "json",
		"-show_format",
		filepath,
	)

	setHideWindow(cmd)

	output, err := cmd.Output()
	if err != nil {
		return 0, err
	}

	var result struct {
		Format struct {
			Duration string `json:"duration"`
		} `json:"format"`
	}

	if err := json.Unmarshal(output, &result); err != nil {
		return 0, err
	}

	if result.Format.Duration == "" {
		return 0, fmt.Errorf("duration not found in ffprobe output")
	}

	duration, err := strconv.ParseFloat(result.Format.Duration, 64)
	if err != nil {
		return 0, err
	}

	return duration, nil
}

func validateLyricsDuration(lyrics string, filepath string) (string, error) {

	duration, err := GetAudioDuration(filepath)
	if err != nil {

		fmt.Printf("[ValidateLyrics] Warning: Could not get audio duration: %v, skipping validation\n", err)
		return lyrics, nil
	}

	if duration <= 0 {

		fmt.Printf("[ValidateLyrics] Warning: Invalid duration (%f seconds), skipping validation\n", duration)
		return lyrics, nil
	}

	durationMs := int64(duration * 1000)

	lines := strings.Split(lyrics, "\n")
	var validLines []string

	for _, line := range lines {
		trimmedLine := strings.TrimSpace(line)
		if trimmedLine == "" {
			validLines = append(validLines, line)
			continue
		}

		if strings.HasPrefix(trimmedLine, "[") {

			if strings.Index(trimmedLine, ":") > 0 {

				validLines = append(validLines, line)
				continue
			}

			closeBracket := strings.Index(trimmedLine, "]")
			if closeBracket > 0 {
				timestampStr := trimmedLine[1:closeBracket]

				ms := parseLRCTimestamp(timestampStr)
				if ms >= 0 && ms <= durationMs {

					validLines = append(validLines, line)
				} else {

					fmt.Printf("[ValidateLyrics] Filtered out line with timestamp %s (exceeds duration %d ms): %s\n", timestampStr, durationMs, trimmedLine)
				}
			} else {

				validLines = append(validLines, line)
			}
		} else {

			validLines = append(validLines, line)
		}
	}

	return strings.Join(validLines, "\n"), nil
}

func parseLRCTimestamp(timestamp string) int64 {
	var minutes, seconds, centiseconds int64
	n, _ := fmt.Sscanf(timestamp, "%d:%d.%d", &minutes, &seconds, &centiseconds)
	if n >= 2 {
		return minutes*60*1000 + seconds*1000 + centiseconds*10
	}
	return -1
}

func ExtractFullMetadataFromFile(filePath string) (Metadata, error) {
	var metadata Metadata

	ffprobePath, err := GetFFprobePath()
	if err != nil {
		return metadata, err
	}

	if err := ValidateExecutable(ffprobePath); err != nil {
		return metadata, fmt.Errorf("invalid ffprobe executable: %w", err)
	}

	cmd := exec.Command(ffprobePath,
		"-v", "quiet",
		"-print_format", "json",
		"-show_format",
		"-show_streams",
		filePath,
	)

	setHideWindow(cmd)

	output, err := cmd.Output()
	if err != nil {
		return metadata, err
	}

	var result struct {
		Format struct {
			Tags map[string]string `json:"tags"`
		} `json:"format"`
		Streams []struct {
			Tags map[string]string `json:"tags"`
		} `json:"streams"`
	}

	if err := json.Unmarshal(output, &result); err != nil {
		return metadata, err
	}

	allTags := make(map[string]string)

	for _, stream := range result.Streams {
		for key, value := range stream.Tags {
			allTags[strings.ToLower(key)] = value
		}
	}

	for key, value := range result.Format.Tags {
		allTags[strings.ToLower(key)] = value
	}

	for key, value := range allTags {
		switch key {
		case "title":
			metadata.Title = value
		case "artist":
			metadata.Artist = value
		case "album":
			metadata.Album = value
		case "album_artist", "albumartist":
			metadata.AlbumArtist = value
		case "date", "year":
			if metadata.Date == "" || len(value) > len(metadata.Date) {
				metadata.Date = value
			}
		case "track":

			parts := strings.Split(value, "/")
			if len(parts) > 0 {
				if num, err := strconv.Atoi(parts[0]); err == nil {
					metadata.TrackNumber = num
				}
			}
			if len(parts) > 1 {
				if num, err := strconv.Atoi(parts[1]); err == nil {
					metadata.TotalTracks = num
				}
			}
		case "disc":

			parts := strings.Split(value, "/")
			if len(parts) > 0 {
				if num, err := strconv.Atoi(parts[0]); err == nil {
					metadata.DiscNumber = num
				}
			}
			if len(parts) > 1 {
				if num, err := strconv.Atoi(parts[1]); err == nil {
					metadata.TotalDiscs = num
				}
			}
		case "copyright", "tcop":
			metadata.Copyright = value
		case "publisher", "tpub", "label":
			metadata.Publisher = value
		case "url":
			metadata.URL = value
		case "description", "comment":
			if metadata.Description == "" {
				metadata.Description = value
			}
		}
	}

	return metadata, nil
}

func EmbedMetadataToConvertedFile(filePath string, metadata Metadata, coverPath string) error {
	ext := strings.ToLower(pathfilepath.Ext(filePath))

	switch ext {
	case ".flac":

		return EmbedMetadata(filePath, metadata, coverPath)
	case ".mp3":
		return embedMetadataToMP3(filePath, metadata, coverPath)
	case ".m4a":
		return embedMetadataToM4A(filePath, metadata, coverPath)
	default:
		return fmt.Errorf("unsupported file format: %s", ext)
	}
}

func embedMetadataToMP3(filePath string, metadata Metadata, coverPath string) error {
	tag, err := id3v2.Open(filePath, id3v2.Options{Parse: true})
	if err != nil {
		return fmt.Errorf("failed to open MP3 file: %w", err)
	}
	defer tag.Close()

	tag.DeleteFrames("TXXX")

	if metadata.Title != "" {
		tag.SetTitle(metadata.Title)
	}
	if metadata.Artist != "" {
		tag.SetArtist(metadata.Artist)
	}
	if metadata.Album != "" {
		tag.SetAlbum(metadata.Album)
	}
	if metadata.Date != "" {
		year := metadata.Date
		if len(year) >= 4 {
			year = year[:4]
		}
		tag.SetYear(year)
	}

	if metadata.AlbumArtist != "" {
		tag.DeleteFrames("TPE2")
		tag.AddTextFrame("TPE2", id3v2.EncodingUTF8, metadata.AlbumArtist)
	}

	if metadata.TrackNumber > 0 {
		tag.DeleteFrames(tag.CommonID("Track number/Position in set"))
		trackStr := strconv.Itoa(metadata.TrackNumber)
		if metadata.TotalTracks > 0 {
			trackStr = fmt.Sprintf("%d/%d", metadata.TrackNumber, metadata.TotalTracks)
		}
		tag.AddTextFrame(tag.CommonID("Track number/Position in set"), id3v2.EncodingUTF8, trackStr)
	}

	if metadata.DiscNumber > 0 {
		tag.DeleteFrames(tag.CommonID("Part of a set"))
		discStr := strconv.Itoa(metadata.DiscNumber)
		if metadata.TotalDiscs > 0 {
			discStr = fmt.Sprintf("%d/%d", metadata.DiscNumber, metadata.TotalDiscs)
		}
		tag.AddTextFrame(tag.CommonID("Part of a set"), id3v2.EncodingUTF8, discStr)
	}

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

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

	if coverPath != "" && fileExists(coverPath) {

		tag.DeleteFrames(tag.CommonID("Attached picture"))

		artwork, err := os.ReadFile(coverPath)
		if err == nil {
			pic := id3v2.PictureFrame{
				Encoding:    id3v2.EncodingUTF8,
				MimeType:    "image/jpeg",
				PictureType: id3v2.PTFrontCover,
				Description: "Cover",
				Picture:     artwork,
			}
			tag.AddAttachedPicture(pic)
		} else {
			fmt.Printf("[EmbedMetadataToMP3] Warning: Failed to read cover art file: %v\n", err)
		}
	}

	if err := tag.Save(); err != nil {
		return fmt.Errorf("failed to save MP3 tags: %w", err)
	}

	return nil
}

func embedMetadataToM4A(filePath string, metadata Metadata, coverPath string) error {
	ffmpegPath, err := GetFFmpegPath()
	if err != nil {
		return fmt.Errorf("ffmpeg not found: %w", err)
	}

	if err := ValidateExecutable(ffmpegPath); err != nil {
		return fmt.Errorf("invalid ffmpeg executable: %w", err)
	}

	args := []string{
		"-i", filePath,
		"-y",
	}

	if coverPath != "" && fileExists(coverPath) {
		args = append(args, "-i", coverPath)
		args = append(args, "-map", "0:a", "-map", "1", "-c:a", "copy", "-c:v", "copy", "-disposition:v:0", "attached_pic")
	} else {
		args = append(args, "-map", "0", "-codec", "copy")
	}

	if metadata.Title != "" {
		args = append(args, "-metadata", "title="+metadata.Title)
	}
	if metadata.Artist != "" {
		args = append(args, "-metadata", "artist="+metadata.Artist)
	}
	if metadata.Album != "" {
		args = append(args, "-metadata", "album="+metadata.Album)
	}
	if metadata.AlbumArtist != "" {
		args = append(args, "-metadata", "album_artist="+metadata.AlbumArtist)
	}
	if metadata.Date != "" {
		args = append(args, "-metadata", "date="+metadata.Date)
	}
	if metadata.TrackNumber > 0 {
		trackStr := strconv.Itoa(metadata.TrackNumber)
		if metadata.TotalTracks > 0 {
			trackStr = fmt.Sprintf("%d/%d", metadata.TrackNumber, metadata.TotalTracks)
		}
		args = append(args, "-metadata", "track="+trackStr)
	}
	if metadata.DiscNumber > 0 {
		discStr := strconv.Itoa(metadata.DiscNumber)
		if metadata.TotalDiscs > 0 {
			discStr = fmt.Sprintf("%d/%d", metadata.DiscNumber, metadata.TotalDiscs)
		}
		args = append(args, "-metadata", "disk="+discStr)
	}
	if metadata.Copyright != "" {
		args = append(args, "-metadata", "copyright="+metadata.Copyright)
	}
	if metadata.Publisher != "" {
		args = append(args, "-metadata", "publisher="+metadata.Publisher)
	}

	tmpOutputFile := strings.TrimSuffix(filePath, pathfilepath.Ext(filePath)) + ".tmp" + pathfilepath.Ext(filePath)
	defer func() {
		if _, err := os.Stat(tmpOutputFile); err == nil {
			os.Remove(tmpOutputFile)
		}
	}()

	args = append(args, "-f", "ipod", tmpOutputFile)

	cmd := exec.Command(ffmpegPath, args...)
	setHideWindow(cmd)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("ffmpeg failed to embed metadata: %s - %w", string(output), err)
	}

	if err := os.Rename(tmpOutputFile, filePath); err != nil {
		return fmt.Errorf("failed to replace original file: %w", err)
	}

	return nil
}