Ignore CallService events related to obsolete calls.

// FREEBIE

Signal/src/call/CallService.swift

@@ -75,6 +75,7 @@ enum CallError: Error {
     case disconnected
     case externalError(underlyingError: Error)
     case timeout(description: String)
+    case unexpected(description: String)
 }
 
 // FIXME TODO do we need to timeout?
@@ -123,7 +124,7 @@ protocol CallServiceObserver: class {
         didSet {
             AssertIsOnMainThread()
 
-            Logger.debug("\(self.TAG) .peerConnectionClient setter: \(oldValue != nil) -> \(peerConnectionClient != nil)")
+            Logger.debug("\(self.TAG) .peerConnectionClient setter: \(oldValue != nil) -> \(peerConnectionClient != nil) \(peerConnectionClient)")
         }
     }
 
@@ -138,6 +139,8 @@ protocol CallServiceObserver: class {
 
             updateIsVideoEnabled()
 
+            Logger.debug("\(self.TAG) .call setter: \(oldValue != nil) -> \(call != nil) \(call)")
+
             for observer in observers {
                 observer.value?.didUpdateCall(call:call)
             }
@@ -424,6 +427,9 @@ protocol CallServiceObserver: class {
         let backgroundTask = UIApplication.shared.beginBackgroundTask {
             let timeout = CallError.timeout(description: "background task time ran out before call connected.")
             DispatchQueue.main.async {
+                guard self.call == newCall else {
+                    return
+                }
                 self.handleFailedCall(error: timeout)
             }
         }
@@ -433,6 +439,9 @@ protocol CallServiceObserver: class {
         }.then { (iceServers: [RTCIceServer]) -> Promise<HardenedRTCSessionDescription> in
             // FIXME for first time call recipients I think we'll see mic/camera permission requests here,
             // even though, from the users perspective, no incoming call is yet visible.
+            guard self.call == newCall else {
+                throw CallError.unexpected(description: "getIceServers() response for obsolete call")
+            }
             assert(self.peerConnectionClient == nil, "Unexpected PeerConnectionClient instance")
             Logger.debug("\(self.self.TAG) setting peerConnectionClient in \(#function)")
             self.peerConnectionClient = PeerConnectionClient(iceServers: iceServers, delegate: self, callType: .Incoming)
@@ -443,6 +452,9 @@ protocol CallServiceObserver: class {
             // Find a sessionDescription compatible with my constraints and the remote sessionDescription
             return self.peerConnectionClient!.negotiateSessionDescription(remoteDescription: offerSessionDescription, constraints: constraints)
         }.then { (negotiatedSessionDescription: HardenedRTCSessionDescription) in
+            guard self.call == newCall else {
+                throw CallError.unexpected(description: "negotiateSessionDescription() response for obsolete call")
+            }
             Logger.debug("\(self.TAG) set the remote description")
 
             let answerMessage = OWSCallAnswerMessage(callId: newCall.signalingId, sessionDescription: negotiatedSessionDescription.sdp)
@@ -450,6 +462,9 @@ protocol CallServiceObserver: class {
 
             return self.messageSender.sendCallMessage(callAnswerMessage)
         }.then {
+            guard self.call == newCall else {
+                throw CallError.unexpected(description: "sendCallMessage() response for obsolete call")
+            }
             Logger.debug("\(self.TAG) successfully sent callAnswerMessage")
 
             let (promise, fulfill, _) = Promise<Void>.pending()
@@ -464,6 +479,10 @@ protocol CallServiceObserver: class {
 
             return race(promise, timeout)
         }.catch { error in
+            guard self.call == newCall else {
+                Logger.debug("\(self.TAG) error for obsolete call: \(error)")
+                return
+            }
             if let callError = error as? CallError {
                 self.handleFailedCall(error: callError)
             } else {