Local track subscribed event (#467)

Fired when the first remote participant has subscribed to the
localParticipant's track.

Sources/LiveKit/Core/Room+SignalClientDelegate.swift

@@ -345,4 +345,22 @@ extension Room: SignalClientDelegate {
         // update token
         _state.mutate { $0.token = token }
     }
+
+    func signalClient(_: SignalClient, didSubscribeTrack trackSid: Track.Sid) async {
+        // Find the local track publication.
+        guard let track = localParticipant.trackPublications[trackSid] as? LocalTrackPublication else {
+            log("Could not find local track publication for subscribed event")
+            return
+        }
+
+        // Notify Room.
+        delegates.notify {
+            $0.room?(self, participant: self.localParticipant, remoteDidSubscribeTrack: track)
+        }
+
+        // Notify LocalParticipant.
+        localParticipant.delegates.notify {
+            $0.participant?(self.localParticipant, remoteDidSubscribeTrack: track)
+        }
+    }
 }

Sources/LiveKit/Core/SignalClient.swift

@@ -341,8 +341,8 @@ private extension SignalClient {
         case .requestResponse:
             log("Received requestResponse message")
 
-        case .trackSubscribed:
-            log("Received trackSubscribed message")
+        case let .trackSubscribed(trackSubscribed):
+            _delegate.notifyDetached { await $0.signalClient(self, didSubscribeTrack: Track.Sid(from: trackSubscribed.trackSid)) }
         }
     }
 }

Sources/LiveKit/Protocols/ParticipantDelegate.swift

@@ -79,6 +79,10 @@ public protocol ParticipantDelegate: AnyObject {
     @objc(localParticipant:didUnpublishTrack:) optional
     func participant(_ participant: LocalParticipant, didUnpublishTrack publication: LocalTrackPublication)
 
+    /// Fired when the first remote participant has subscribed to the localParticipant's track.
+    @objc(localParticipant:remoteDidSubscribeTrack:) optional
+    func participant(_ participant: LocalParticipant, remoteDidSubscribeTrack publication: LocalTrackPublication)
+
     // MARK: - RemoteTrackPublication
 
     /// When a new ``RemoteTrackPublication`` is published to ``Room`` after the ``LocalParticipant`` has joined.

Sources/LiveKit/Protocols/RoomDelegate.swift

@@ -120,6 +120,10 @@ public protocol RoomDelegate: AnyObject {
     @objc(room:localParticipant:didUnpublishTrack:) optional
     func room(_ room: Room, participant: LocalParticipant, didUnpublishTrack publication: LocalTrackPublication)
 
+    /// Fired when the first remote participant has subscribed to the localParticipant's track.
+    @objc(room:localParticipant:remoteDidSubscribeTrack:) optional
+    func room(_ room: Room, participant: LocalParticipant, remoteDidSubscribeTrack publication: LocalTrackPublication)
+
     /// A ``RemoteParticipant`` has un-published a ``RemoteTrack``.
     @objc(room:remoteParticipant:didUnpublishTrack:) optional
     func room(_ room: Room, participant: RemoteParticipant, didUnpublishTrack publication: RemoteTrackPublication)

Sources/LiveKit/Protocols/SignalClientDelegate.swift

@@ -39,4 +39,5 @@ protocol SignalClientDelegate: AnyObject {
     func signalClient(_ signalClient: SignalClient, didUpdateSubscriptionPermission permission: Livekit_SubscriptionPermissionUpdate) async
     func signalClient(_ signalClient: SignalClient, didUpdateToken token: String) async
     func signalClient(_ signalClient: SignalClient, didReceiveLeave canReconnect: Bool, reason: Livekit_DisconnectReason) async
+    func signalClient(_ signalClient: SignalClient, didSubscribeTrack trackSid: Track.Sid) async
 }