rewrite using IoC and DI

model/playlist.go

@@ -0,0 +1,36 @@
+package model
+
+import "fmt"
+
+type PlaylistMode int
+
+const (
+	PlaylistModeNormal PlaylistMode = iota
+	PlaylistModeRandom
+)
+
+type Playlist struct {
+	Name   string
+	Medias []*Media
+	Mode   PlaylistMode
+	Meta   Meta
+}
+
+func (p Playlist) String() string {
+	return fmt.Sprintf("<Playlist %s>", p.Name)
+}
+
+func (p *Playlist) Size() int {
+	return len(p.Medias)
+}
+
+func (p *Playlist) Copy() *Playlist {
+	medias := make([]*Media, len(p.Medias))
+	copy(medias, p.Medias)
+	return &Playlist{
+		Name:   p.Name,
+		Medias: medias,
+		Mode:   p.Mode,
+		Meta:   p.Meta,
+	}
+}