refactor: decouple tag writers from deezer models

internal/tag/flac.go

@@ -0,0 +1,84 @@
+package tag
+
+import (
+	"os"
+	"strings"
+
+	"github.com/go-flac/flacpicture/v2"
+	"github.com/go-flac/flacvorbis/v2"
+	"github.com/go-flac/go-flac/v2"
+)
+
+type flacTagger struct {
+	file  *flac.File
+	cmts  *flacvorbis.MetaDataBlockVorbisComment
+	index int
+	path  string
+}
+
+func (t *flacTagger) write(m Metadata) error {
+	if m.Album != nil {
+		date := m.Album.ReleaseDate
+		if parts := strings.Split(date, "-"); len(parts) == 3 {
+			date = parts[0]
+		}
+
+		t.addTag("TRACKNUMBER", m.TrackNumber)
+		t.addTag("ALBUMARTIST", m.Album.Artist)
+		t.addTag("ALBUM", m.Album.Title)
+		t.addTag("PUBLISHER", m.Album.Label)
+		t.addTag("ORIGINALDATE", m.Album.OriginalReleaseDate)
+		t.addTag("DATE", date)
+		t.addTag("COMMENT", m.Album.ProducerLine)
+		t.addTag("COPYRIGHT", m.Album.Copyright)
+	}
+
+	t.addTag("ARTIST", m.Artists)
+	t.addTag("TITLE", m.Title)
+	t.addTag("COMPOSER", m.Composers)
+	t.addTag("LYRICIST", m.Lyricists)
+	t.addTag("GENRE", m.Genre)
+	t.addTag("REPLAYGAIN_TRACK_GAIN", m.Gain)
+	t.addTag("ISRC", m.ISRC)
+	t.addTag("BPM", m.BPM)
+	t.addTag("KEY", m.Key)
+	t.addTag("INITIALKEY", m.Key)
+
+	cmtsMeta := t.cmts.Marshal()
+	if t.index > 0 {
+		t.file.Meta[t.index] = &cmtsMeta
+	} else {
+		t.file.Meta = append(t.file.Meta, &cmtsMeta)
+	}
+
+	picture, err := flacpicture.NewFromImageData(flacpicture.PictureTypeFrontCover, "Front cover", m.Cover, "image/jpeg")
+	if err != nil {
+		return err
+	}
+	pictureMeta := picture.Marshal()
+	t.file.Meta = append(t.file.Meta, &pictureMeta)
+
+	tmpPath := t.path + ".tmp"
+	if err := t.file.Save(tmpPath); err != nil {
+		return err
+	}
+	return os.Rename(tmpPath, t.path)
+}
+
+func (t *flacTagger) addTag(name, value string) {
+	if value != "" {
+		t.cmts.Add(name, value)
+	}
+}
+
+func extractFLACComment(file *flac.File) (*flacvorbis.MetaDataBlockVorbisComment, int) {
+	for idx, meta := range file.Meta {
+		if meta.Type == flac.VorbisComment {
+			cmt, err := flacvorbis.ParseFromMetaDataBlock(*meta)
+			if err == nil {
+				return cmt, idx
+			}
+		}
+	}
+	return nil, 0
+}