add SDP answer.

internal/types/webrtc.go

@@ -19,9 +19,10 @@ type ICEServer struct {
 
 type WebRTCPeer interface {
 	CreateOffer(ICERestart bool) (*webrtc.SessionDescription, error)
-	SignalOffer(sdp string) error
+	CreateAnswer() (*webrtc.SessionDescription, error)
-	SignalAnswer(sdp string) error
+	SetOffer(sdp string) error
-	SignalCandidate(candidate webrtc.ICECandidateInit) error
+	SetAnswer(sdp string) error
+	SetCandidate(candidate webrtc.ICECandidateInit) error
 
 	SetVideoID(videoID string) error
 	SendCursorPosition(x, y int) error
@@ -36,5 +37,5 @@ type WebRTCManager interface {
 
 	ICEServers() []ICEServer
 
-	CreatePeer(session Session, videoID string) (*webrtc.SessionDescription, error)
+	CreatePeer(session Session, videoID string) (WebRTCPeer, error)
 }

internal/webrtc/manager.go

@@ -73,7 +73,7 @@ func (manager *WebRTCManagerCtx) ICEServers() []types.ICEServer {
 	return manager.config.ICEServers
 }
 
-func (manager *WebRTCManagerCtx) CreatePeer(session types.Session, videoID string) (*webrtc.SessionDescription, error) {
+func (manager *WebRTCManagerCtx) CreatePeer(session types.Session, videoID string) (types.WebRTCPeer, error) {
 	// add session id to logger context
 	logger := manager.logger.With().Str("session_id", session.ID()).Logger()
 	logger.Info().Msg("creating webrtc peer")
@@ -238,5 +238,5 @@ func (manager *WebRTCManagerCtx) CreatePeer(session types.Session, videoID strin
 	})
 
 	session.SetWebRTCPeer(peer)
-	return peer.CreateOffer(false)
+	return peer, nil
 }

internal/webrtc/peer.go

@@ -27,17 +27,33 @@ func (peer *WebRTCPeerCtx) CreateOffer(ICERestart bool) (*webrtc.SessionDescript
 		return nil, err
 	}
 
+	return peer.setLocalDescription(offer)
+}
+
+func (peer *WebRTCPeerCtx) CreateAnswer() (*webrtc.SessionDescription, error) {
+	peer.mu.Lock()
+	defer peer.mu.Unlock()
+
+	answer, err := peer.connection.CreateAnswer(nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return peer.setLocalDescription(answer)
+}
+
+func (peer *WebRTCPeerCtx) setLocalDescription(description webrtc.SessionDescription) (*webrtc.SessionDescription, error) {
 	if !peer.iceTrickle {
 		// Create channel that is blocked until ICE Gathering is complete
 		gatherComplete := webrtc.GatheringCompletePromise(peer.connection)
 
-		if err := peer.connection.SetLocalDescription(offer); err != nil {
+		if err := peer.connection.SetLocalDescription(description); err != nil {
 			return nil, err
 		}
 
 		<-gatherComplete
 	} else {
-		if err := peer.connection.SetLocalDescription(offer); err != nil {
+		if err := peer.connection.SetLocalDescription(description); err != nil {
 			return nil, err
 		}
 	}
@@ -45,21 +61,30 @@ func (peer *WebRTCPeerCtx) CreateOffer(ICERestart bool) (*webrtc.SessionDescript
 	return peer.connection.LocalDescription(), nil
 }
 
-func (peer *WebRTCPeerCtx) SignalOffer(sdp string) error {
+func (peer *WebRTCPeerCtx) SetOffer(sdp string) error {
+	peer.mu.Lock()
+	defer peer.mu.Unlock()
+
 	return peer.connection.SetRemoteDescription(webrtc.SessionDescription{
 		SDP:  sdp,
 		Type: webrtc.SDPTypeOffer,
 	})
 }
 
-func (peer *WebRTCPeerCtx) SignalAnswer(sdp string) error {
+func (peer *WebRTCPeerCtx) SetAnswer(sdp string) error {
+	peer.mu.Lock()
+	defer peer.mu.Unlock()
+
 	return peer.connection.SetRemoteDescription(webrtc.SessionDescription{
 		SDP:  sdp,
 		Type: webrtc.SDPTypeAnswer,
 	})
 }
 
-func (peer *WebRTCPeerCtx) SignalCandidate(candidate webrtc.ICECandidateInit) error {
+func (peer *WebRTCPeerCtx) SetCandidate(candidate webrtc.ICECandidateInit) error {
+	peer.mu.Lock()
+	defer peer.mu.Unlock()
+
 	return peer.connection.AddICECandidate(candidate)
 }
 

internal/websocket/handler/signal.go

@@ -19,7 +19,12 @@ func (h *MessageHandlerCtx) signalRequest(session types.Session, payload *messag
 		payload.Video = videos[0]
 	}
 
-	offer, err := h.webrtc.CreatePeer(session, payload.Video)
+	peer, err := h.webrtc.CreatePeer(session, payload.Video)
+	if err != nil {
+		return err
+	}
+
+	offer, err := peer.CreateOffer(false)
 	if err != nil {
 		return err
 	}
@@ -46,6 +51,7 @@ func (h *MessageHandlerCtx) signalRestart(session types.Session) error {
 		return err
 	}
 
+	// TODO: Use offer event intead.
 	session.Send(
 		event.SIGNAL_RESTART,
 		message.SignalDescription{
@@ -61,7 +67,23 @@ func (h *MessageHandlerCtx) signalOffer(session types.Session, payload *message.
 		return errors.New("webRTC peer does not exist")
 	}
 
-	return peer.SignalOffer(payload.SDP)
+	err := peer.SetOffer(payload.SDP)
+	if err != nil {
+		return err
+	}
+
+	answer, err := peer.CreateAnswer()
+	if err != nil {
+		return err
+	}
+
+	session.Send(
+		event.SIGNAL_ANSWER,
+		message.SignalDescription{
+			SDP: answer.SDP,
+		})
+
+	return nil
 }
 
 func (h *MessageHandlerCtx) signalAnswer(session types.Session, payload *message.SignalDescription) error {
@@ -70,7 +92,7 @@ func (h *MessageHandlerCtx) signalAnswer(session types.Session, payload *message
 		return errors.New("webRTC peer does not exist")
 	}
 
-	return peer.SignalAnswer(payload.SDP)
+	return peer.SetAnswer(payload.SDP)
 }
 
 func (h *MessageHandlerCtx) signalCandidate(session types.Session, payload *message.SignalCandidate) error {
@@ -79,7 +101,7 @@ func (h *MessageHandlerCtx) signalCandidate(session types.Session, payload *mess
 		return errors.New("webRTC peer does not exist")
 	}
 
-	return peer.SignalCandidate(payload.ICECandidateInit)
+	return peer.SetCandidate(payload.ICECandidateInit)
 }
 
 func (h *MessageHandlerCtx) signalVideo(session types.Session, payload *message.SignalVideo) error {