Add GStreamer player state machine

internal/player/gstreamer_player.go

@@ -84,6 +84,7 @@ var gstInitOnce sync.Once
 
 type GStreamerPlayer struct {
 	mu       sync.Mutex
+	seekMu   sync.Mutex
 	pipeline *C.GstElement
 	appsink  *C.GstElement
 	bus      *C.GstBus
@@ -101,6 +102,7 @@ type GStreamerPlayer struct {
 	eos      bool
 	state    C.GstState
 	duration time.Duration
+	mode     PlayerState
 }
 
 type busEvent struct {
@@ -109,6 +111,20 @@ type busEvent struct {
 	State C.GstState
 }
 
+type PlayerState int
+
+const (
+	StateIdle PlayerState = iota
+	StateLoading
+	StatePaused
+	StatePlaying
+	StateSeeking
+	StateStepping
+	StateStopped
+	StateError
+	StateEOS
+)
+
 func NewGStreamerPlayer(config Config) (*GStreamerPlayer, error) {
 	var initErr error
 	gstInitOnce.Do(func() {
@@ -125,6 +141,7 @@ func NewGStreamerPlayer(config Config) (*GStreamerPlayer, error) {
 		paused:  true,
 		volume:  config.Volume,
 		preview: config.PreviewMode,
+		mode:    StateIdle,
 	}, nil
 }
 
@@ -224,9 +241,11 @@ func (p *GStreamerPlayer) Load(path string, offset time.Duration) error {
 	p.paused = true
 	p.eos = false
 	p.lastErr = ""
+	p.mode = StateLoading
 
 	// Set to PAUSED to preroll (loads first frame)
 	if C.gst_element_set_state(playbin, C.GST_STATE_PAUSED) == C.GST_STATE_CHANGE_FAILURE {
+		p.mode = StateError
 		p.closeLocked()
 		return errors.New("gstreamer failed to enter paused state")
 	}
@@ -244,8 +263,10 @@ func (p *GStreamerPlayer) Load(path string, offset time.Duration) error {
 				p.closeLocked()
 				if errMsg != nil {
 					defer C.vt_gst_free_error(errMsg)
+					p.mode = StateError
 					return errors.New(C.GoString(errMsg))
 				}
+				p.mode = StateError
 				return errors.New("gstreamer error while loading")
 			}
 			C.gst_message_unref(msg)
@@ -256,6 +277,7 @@ func (p *GStreamerPlayer) Load(path string, offset time.Duration) error {
 		_ = p.seekLocked(offset)
 	}
 
+	p.mode = StatePaused
 	p.startBusLoopLocked()
 	return nil
 }
@@ -268,9 +290,11 @@ func (p *GStreamerPlayer) Play() error {
 		return errors.New("no pipeline loaded")
 	}
 	if C.gst_element_set_state(p.pipeline, C.GST_STATE_PLAYING) == C.GST_STATE_CHANGE_FAILURE {
+		p.mode = StateError
 		return errors.New("gstreamer failed to enter playing state")
 	}
 	p.paused = false
+	p.mode = StatePlaying
 	return nil
 }
 
@@ -282,16 +306,33 @@ func (p *GStreamerPlayer) Pause() error {
 		return errors.New("no pipeline loaded")
 	}
 	if C.gst_element_set_state(p.pipeline, C.GST_STATE_PAUSED) == C.GST_STATE_CHANGE_FAILURE {
+		p.mode = StateError
 		return errors.New("gstreamer failed to enter paused state")
 	}
 	p.paused = true
+	p.mode = StatePaused
 	return nil
 }
 
 func (p *GStreamerPlayer) SeekToTime(offset time.Duration) error {
+	p.seekMu.Lock()
+	defer p.seekMu.Unlock()
+
 	p.mu.Lock()
-	defer p.mu.Unlock()
+	prevMode := p.mode
-	return p.seekLocked(offset)
+	p.mode = StateSeeking
+	p.mu.Unlock()
+
+	err := p.seekLocked(offset)
+
+	p.mu.Lock()
+	if err != nil {
+		p.mode = StateError
+	} else {
+		p.mode = prevMode
+	}
+	p.mu.Unlock()
+	return err
 }
 
 func (p *GStreamerPlayer) seekLocked(offset time.Duration) error {
@@ -311,14 +352,30 @@ func (p *GStreamerPlayer) seekLockedWithFlags(offset time.Duration, flags C.GstS
 }
 
 func (p *GStreamerPlayer) SeekToFrame(frame int64) error {
+	p.seekMu.Lock()
+	defer p.seekMu.Unlock()
+
 	p.mu.Lock()
-	defer p.mu.Unlock()
 	if p.fps <= 0 {
+		p.mu.Unlock()
 		return nil
 	}
+	prevMode := p.mode
+	p.mode = StateStepping
 	seconds := float64(frame) / p.fps
+	p.mu.Unlock()
+
 	flags := C.GstSeekFlags(C.GST_SEEK_FLAG_FLUSH | C.GST_SEEK_FLAG_ACCURATE)
-	return p.seekLockedWithFlags(time.Duration(seconds*float64(time.Second)), flags)
+	err := p.seekLockedWithFlags(time.Duration(seconds*float64(time.Second)), flags)
+
+	p.mu.Lock()
+	if err != nil {
+		p.mode = StateError
+	} else {
+		p.mode = prevMode
+	}
+	p.mu.Unlock()
+	return err
 }
 
 func (p *GStreamerPlayer) GetCurrentTime() time.Duration {
@@ -472,12 +529,14 @@ func (p *GStreamerPlayer) Stop() error {
 	if p.pipeline != nil {
 		C.gst_element_set_state(p.pipeline, C.GST_STATE_NULL)
 	}
+	p.mode = StateStopped
 	return nil
 }
 
 func (p *GStreamerPlayer) Close() {
 	p.mu.Lock()
 	defer p.mu.Unlock()
+	p.mode = StateStopped
 	p.closeLocked()
 }
 
@@ -485,6 +544,12 @@ func (p *GStreamerPlayer) Events() <-chan busEvent {
 	return p.events
 }
 
+func (p *GStreamerPlayer) State() PlayerState {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.mode
+}
+
 func (p *GStreamerPlayer) closeLocked() {
 	p.stopBusLoopLocked()
 	if p.pipeline != nil {
@@ -568,12 +633,14 @@ func (p *GStreamerPlayer) busLoop() {
 			} else {
 				p.lastErr = "gstreamer error"
 			}
+			p.mode = StateError
 			evt := busEvent{Kind: "error", Info: p.lastErr}
 			p.mu.Unlock()
 			p.pushEvent(evt)
 		case C.GST_MESSAGE_EOS:
 			p.mu.Lock()
 			p.eos = true
+			p.mode = StateEOS
 			p.mu.Unlock()
 			p.pushEvent(busEvent{Kind: "eos"})
 		case C.GST_MESSAGE_STATE_CHANGED: