refactor: decouple tag writers from deezer models

internal/tag/tag.go

@@ -0,0 +1,69 @@
+package tag
+
+import (
+	"path"
+
+	"github.com/bogem/id3v2/v2"
+	"github.com/go-flac/flacvorbis/v2"
+	"github.com/go-flac/go-flac/v2"
+)
+
+type AlbumMetadata struct {
+	Artist              string
+	Title               string
+	Label               string
+	OriginalReleaseDate string
+	ReleaseDate         string
+	ProducerLine        string
+	Copyright           string
+}
+
+type Metadata struct {
+	Title       string
+	Artists     string
+	Composers   string
+	Lyricists   string
+	Genre       string
+	BPM         string
+	Key         string
+	TrackNumber string
+	Duration    string
+	Gain        string
+	ISRC        string
+	Cover       []byte
+	Album       *AlbumMetadata
+}
+
+type tagger interface {
+	write(m Metadata) error
+}
+
+func newTagger(filePath string) (tagger, error) {
+	if path.Ext(filePath) == ".mp3" {
+		tag, err := id3v2.Open(filePath, id3v2.Options{Parse: true})
+		if err != nil {
+			return nil, err
+		}
+		return &id3v2Tagger{tag: tag}, nil
+	}
+
+	file, err := flac.ParseFile(filePath)
+	if err != nil {
+		return nil, err
+	}
+
+	cmts, idx := extractFLACComment(file)
+	if cmts == nil {
+		cmts = flacvorbis.New()
+	}
+
+	return &flacTagger{file: file, cmts: cmts, index: idx, path: filePath}, nil
+}
+
+func Write(filePath string, m Metadata) error {
+	t, err := newTagger(filePath)
+	if err != nil {
+		return err
+	}
+	return t.write(m)
+}