feat(meta): add writing metadata by ffmpeg

internal/ffmpeg/ffmpeg.go

@@ -5,10 +5,14 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"os"
 	"os/exec"
+	"strings"
+
+	"unlock-music.dev/cli/algo/common"
 )
 
-func ExtractAlbumArt(ctx context.Context, rd io.Reader) (io.Reader, error) {
+func ExtractAlbumArt(ctx context.Context, rd io.Reader) (*bytes.Buffer, error) {
 	cmd := exec.CommandContext(ctx, "ffmpeg",
 		"-i", "pipe:0", // input from stdin
 		"-an",              // disable audio
@@ -21,13 +25,134 @@ func ExtractAlbumArt(ctx context.Context, rd io.Reader) (io.Reader, error) {
 	stdout, stderr := &bytes.Buffer{}, &bytes.Buffer{}
 	cmd.Stdout, cmd.Stderr = stdout, stderr
 
-	if err := cmd.Start(); err != nil {
+	if err := cmd.Run(); err != nil {
 		return nil, fmt.Errorf("ffmpeg run: %w", err)
 	}
 
-	if err := cmd.Wait(); err != nil {
-		return nil, fmt.Errorf("ffmpeg wait: %w: %s", err, stderr.String())
-	}
-
 	return stdout, nil
 }
+
+type UpdateMetadataParams struct {
+	Audio    io.Reader // required
+	AudioExt string    // required
+
+	Meta common.AudioMeta // required
+
+	AlbumArt    io.Reader // optional
+	AlbumArtExt string    // required if AlbumArt is not nil
+}
+
+func UpdateAudioMetadata(ctx context.Context, params *UpdateMetadataParams) (*bytes.Buffer, error) {
+	builder := newFFmpegBuilder()
+	builder.SetFlag("y") // overwrite output file
+
+	out := newOutputBuilder("pipe:1")                        // use stdout as output
+	out.AddOption("f", encodeFormatFromExt(params.AudioExt)) // use mp3 muxer
+	builder.AddOutput(out)
+
+	// since ffmpeg doesn't support multiple input streams,
+	// we need to write the audio to a temp file
+	audioPath, err := writeTempFile(params.Audio, params.AudioExt)
+	if err != nil {
+		return nil, fmt.Errorf("updateAudioMeta write temp file: %w", err)
+	}
+	defer os.Remove(audioPath)
+
+	// input audio -> output audio
+	builder.AddInput(newInputBuilder(audioPath)) // input 0: audio
+	out.AddOption("map", "0:a")
+	out.AddOption("codec:a", "copy")
+
+	// input cover -> output cover
+	if params.AlbumArt != nil &&
+		params.AudioExt != ".wav" /* wav doesn't support attached image */ {
+
+		// write cover to temp file
+		artPath, err := writeTempFile(params.AlbumArt, params.AlbumArtExt)
+		if err != nil {
+			return nil, fmt.Errorf("updateAudioMeta write temp file: %w", err)
+		}
+		defer os.Remove(artPath)
+
+		builder.AddInput(newInputBuilder(artPath)) // input 1: cover
+		out.AddOption("map", "1:v")
+
+		switch params.AudioExt {
+		case ".ogg": // ogg only supports theora codec
+			out.AddOption("codec:v", "libtheora")
+		case ".m4a": // .m4a(mp4) requires set codec, disposition, stream metadata
+			out.AddOption("codec:v", "mjpeg")
+			out.AddOption("disposition:v", "attached_pic")
+			out.AddMetadata("s:v", "title", "Album cover")
+			out.AddMetadata("s:v", "comment", "Cover (front)")
+		default: // other formats use default behavior
+		}
+	}
+
+	// set file metadata
+	album := params.Meta.GetAlbum()
+	if album != "" {
+		out.AddMetadata("", "album", album)
+	}
+
+	title := params.Meta.GetTitle()
+	if album != "" {
+		out.AddMetadata("", "title", title)
+	}
+
+	artists := params.Meta.GetArtists()
+	if len(artists) != 0 {
+		// TODO: it seems that ffmpeg doesn't support multiple artists
+		out.AddMetadata("", "artist", strings.Join(artists, " / "))
+	}
+
+	// execute ffmpeg
+	cmd := builder.Command(ctx)
+	stdout, stderr := &bytes.Buffer{}, &bytes.Buffer{}
+	cmd.Stdout, cmd.Stderr = stdout, stderr
+
+	if err := cmd.Run(); err != nil {
+		return nil, fmt.Errorf("ffmpeg run: %w", err)
+	}
+
+	return stdout, nil
+}
+
+func writeTempFile(rd io.Reader, ext string) (string, error) {
+	audioFile, err := os.CreateTemp("", "*"+ext)
+	if err != nil {
+		return "", fmt.Errorf("ffmpeg create temp file: %w", err)
+	}
+
+	if _, err := io.Copy(audioFile, rd); err != nil {
+		return "", fmt.Errorf("ffmpeg write temp file: %w", err)
+	}
+
+	if err := audioFile.Close(); err != nil {
+		return "", fmt.Errorf("ffmpeg close temp file: %w", err)
+	}
+
+	return audioFile.Name(), nil
+}
+
+// encodeFormatFromExt returns the file format name the recognized & supporting encoding by ffmpeg.
+func encodeFormatFromExt(ext string) string {
+	switch ext {
+	case ".flac":
+		return "flac" // raw FLAC
+	case ".mp3":
+		return "mp3" // MP3 (MPEG audio layer 3)
+	case ".ogg":
+		return "ogg" // Ogg
+	case ".m4a":
+		return "ipod" // iPod H.264 MP4 (MPEG-4 Part 14)
+	case ".wav":
+		return "wav" // WAV / WAVE (Waveform Audio)
+	case ".aac":
+		return "adts" // ADTS AAC (Advanced Audio Coding)
+	case ".wma":
+		return "asf" // ASF (Advanced / Active Streaming Format)
+	default:
+		return ""
+	}
+}