Add basic Playlist listener functionality

internal/playlist/playlist.go

@@ -9,7 +9,7 @@ import (
 const DefaultPlaylistDuration = 20 * time.Second
 
 type PlaylistListener interface {
-	OnUpdate(p *Playlist)
+	OnUpdate(p Playlist)
 }
 
 type Playlist interface {
@@ -18,16 +18,18 @@ type Playlist interface {
 	TargetDuration() time.Duration
 	AddSegment(s *segment.Segment) error
 	Render() string
-	//AddListener(l PlaylistListener)
+	AddListener(l PlaylistListener)
 }
 
 type MediaPlaylist struct {
 	Segments  []*segment.Segment
+	Listeners []PlaylistListener
 }
 
 func NewMediaPlaylist() *MediaPlaylist {
 	return &MediaPlaylist{
 		Segments:  make([]*segment.Segment, 0, 10),
+		Listeners: make([]PlaylistListener, 0),
 	}
 }
 
@@ -42,16 +44,16 @@ func (p *MediaPlaylist) TargetDuration() time.Duration {
 func (p *MediaPlaylist) AddSegment(s *segment.Segment) error {
 	p.Segments = append(p.Segments, s)
 
-	if len(p.Segments) == 1 {
+	if len(p.Segments) > 1 {
-		return nil
-	}
-
 		for {
 			if p.durationOf(p.Segments[1:]) > p.TargetDuration() {
 				p.Segments = p.Segments[1:]
 			}
 			break
 		}
+	}
+
+	p.updateListeners()
 
 	return nil
 }
@@ -77,6 +79,18 @@ func (p *MediaPlaylist) Render() string {
 	return r
 }
 
+// Listeners
+
+func (p *MediaPlaylist) AddListener(l PlaylistListener) {
+	p.Listeners = append(p.Listeners, l)
+}
+
+func (p *MediaPlaylist) updateListeners() {
+	for _, l := range p.Listeners {
+		l.OnUpdate(p)
+	}
+}
+
 func (p *MediaPlaylist) Run() error {
 	for {
 		// TODO block here and listen to the channel of incoming segments.

internal/playlist/playlist_test.go

@@ -46,3 +46,23 @@ func TestMediaPlaylistRender(t *testing.T) {
 	require.Equal(t, "#EXTINF:2.70000", lines[5])
 	require.Equal(t, "http://www.example.com/x.mp3", lines[6])
 }
+
+type listener struct {
+	count int
+}
+
+func (l *listener) OnUpdate(p playlist.Playlist) {
+	l.count++
+}
+
+func TestMediaPlaylistListener(t *testing.T) {
+	playlist := playlist.NewMediaPlaylist()
+	l := &listener{}
+	playlist.AddListener(l)
+
+	s := segment.NewSegment(3*time.Second, 0)
+	s.IncrementDuration(3 * time.Second)
+	playlist.AddSegment(s)
+
+	require.Equal(t, 1, l.count)
+}