Fix volume burst when call connects

By centralizing AudioSession management onto the AudioService, we can
avoid enabling the RTCAudioSession while we're mid-ring.

Also allows us to centralize and remove redundant audio session logic.

// FREEBIE

Signal/src/ViewControllers/CallViewController.swift

@@ -936,6 +936,11 @@ class CallViewController: OWSViewController, CallObserver, CallServiceObserver {
         self.updateCallUI(callState: call.state)
     }
 
+    func holdDidChange(call: SignalCall, isOnHold: Bool) {
+        AssertIsOnMainThread()
+        self.updateCallUI(callState: call.state)
+    }
+
     internal func audioSourceDidChange(call: SignalCall, audioSource: AudioSource?) {
         AssertIsOnMainThread()
         self.updateCallUI(callState: call.state)

Signal/src/call/CallAudioService.swift

@@ -137,10 +137,20 @@ struct AudioSource: Hashable {
     // `pulseDuration` is the small pause between the two vibrations in the pair.
     private let pulseDuration = 0.2
 
+    static private let sharedAudioSession = CallAudioSession()
+    var audioSession: CallAudioSession {
+        return type(of: self).sharedAudioSession
+    }
+
     // MARK: - Initializers
 
     init(handleRinging: Bool) {
         self.handleRinging = handleRinging
+
+        super.init()
+
+        // Configure audio session so we don't prompt user with Record permission until call is connected.
+        audioSession.configure()
     }
 
     // MARK: - CallObserver
@@ -152,7 +162,14 @@ struct AudioSource: Hashable {
 
     internal func muteDidChange(call: SignalCall, isMuted: Bool) {
         AssertIsOnMainThread()
-        Logger.verbose("\(TAG) in \(#function) is no-op")
+
+        ensureProperAudioSession(call: call)
+    }
+
+    internal func holdDidChange(call: SignalCall, isOnHold: Bool) {
+        AssertIsOnMainThread()
+
+        ensureProperAudioSession(call: call)
     }
 
     internal func audioSourceDidChange(call: SignalCall, audioSource: AudioSource?) {
@@ -219,7 +236,7 @@ struct AudioSource: Hashable {
                 try session.setPreferredInput(call.audioSource?.portDescription)
             }
 
-            if call.isSpeakerphoneEnabled || (call.hasLocalVideo && call.state != .connected)  {
+            if call.isSpeakerphoneEnabled || (call.hasLocalVideo && call.state != .connected) {
                 // We want consistent ringer-volume between speaker-phone and video chat.
                 // But because using VideoChat mode has noticeably higher output gain, we treat
                 // video chat like speakerphone mode until the call is connected.
@@ -232,6 +249,12 @@ struct AudioSource: Hashable {
         } catch {
             owsFail("\(TAG) failed setting audio source with error: \(error) isSpeakerPhoneEnabled: \(call.isSpeakerphoneEnabled)")
         }
+
+        if call.state == .connected, !call.isOnHold {
+            audioSession.isRTCAudioEnabled = true
+        } else {
+            audioSession.isRTCAudioEnabled = false
+        }
     }
 
     // MARK: - Service action handlers
@@ -290,7 +313,6 @@ struct AudioSource: Hashable {
         Logger.debug("\(TAG) \(#function)")
         AssertIsOnMainThread()
 
-        // FIXME if you toggled speakerphone before this point, the outgoing ring does not play through speaker. Why?
         self.play(sound: Sound.outgoingRing)
     }
 

Signal/src/call/CallAudioSession.swift

@@ -1,4 +1,5 @@
-//  Copyright © 2017 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
 //
 
 import Foundation
@@ -21,7 +22,6 @@ class CallAudioSession {
      */
     private let rtcAudioSession = RTCAudioSession.sharedInstance()
 
-
     /**
     * This must be called before any audio tracks are added to the peerConnection, else we'll start recording before all
     * our signaling is set up.
@@ -32,19 +32,15 @@ class CallAudioSession {
     }
 
     /**
-     * Because we useManualAudio with our RTCAudioSession, we have to start the recording audio session ourselves.
-     */
-    func start() {
-        Logger.info("\(TAG) in \(#function)")
-        rtcAudioSession.isAudioEnabled = true
-    }
-
-    /**
-     * Because we useManualAudio with our RTCAudioSession, we have to stop the recording audio session ourselves.
+     * Because we useManualAudio with our RTCAudioSession, we have to start/stop the recording audio session ourselves.
      * Else, we start recording before the next call is ringing.
      */
-    func stop() {
-        Logger.info("\(TAG) in \(#function)")
-        rtcAudioSession.isAudioEnabled = false
+    var isRTCAudioEnabled: Bool {
+        get {
+            return rtcAudioSession.isAudioEnabled
+        }
+        set {
+            rtcAudioSession.isAudioEnabled = newValue
+        }
     }
 }

Signal/src/call/CallService.swift

@@ -1441,7 +1441,6 @@ protocol CallServiceObserver: class {
         self.remoteVideoTrack = nil
         self.isRemoteVideoEnabled = false
 
-        PeerConnectionClient.stopAudioSession()
         self.peerConnectionClient?.terminate()
         Logger.debug("\(TAG) setting peerConnectionClient in \(#function)")
         self.peerConnectionClient = nil
@@ -1495,6 +1494,11 @@ protocol CallServiceObserver: class {
         // Do nothing
     }
 
+    internal func holdDidChange(call: SignalCall, isOnHold: Bool) {
+        AssertIsOnMainThread()
+        // Do nothing
+    }
+
     internal func audioSourceDidChange(call: SignalCall, audioSource: AudioSource?) {
         AssertIsOnMainThread()
         // Do nothing

Signal/src/call/NonCallKitCallUIAdaptee.swift

@@ -81,7 +81,6 @@ class NonCallKitCallUIAdaptee: CallUIAdaptee {
             return
         }
 
-        PeerConnectionClient.startAudioSession()
         self.callService.handleAnswerCall(call)
     }
 
@@ -114,8 +113,7 @@ class NonCallKitCallUIAdaptee: CallUIAdaptee {
 
     func recipientAcceptedCall(_ call: SignalCall) {
         AssertIsOnMainThread()
-
-        PeerConnectionClient.startAudioSession()
+        // no-op
     }
 
     func localHangupCall(_ call: SignalCall) {

Signal/src/call/PeerConnectionClient.swift

@@ -104,7 +104,6 @@ class PeerConnectionClient: NSObject, RTCPeerConnectionDelegate, RTCDataChannelD
     private var audioSender: RTCRtpSender?
     private var audioTrack: RTCAudioTrack?
     private var audioConstraints: RTCMediaConstraints
-    static private let sharedAudioSession = CallAudioSession()
 
     // Video
 
@@ -146,8 +145,6 @@ class PeerConnectionClient: NSObject, RTCPeerConnectionDelegate, RTCDataChannelD
 
         super.init()
 
-        // Configure audio session so we don't prompt user with Record permission until call is connected.
-        type(of: self).configureAudioSession()
         peerConnection = factory.peerConnection(with: configuration,
                                                 constraints: connectionConstraints,
                                                 delegate: self)
@@ -703,20 +700,6 @@ class PeerConnectionClient: NSObject, RTCPeerConnectionDelegate, RTCDataChannelD
         }
     }
 
-    // Mark: Audio Session
-
-    class func configureAudioSession() {
-        sharedAudioSession.configure()
-    }
-
-    class func startAudioSession() {
-        sharedAudioSession.start()
-    }
-
-    class func stopAudioSession() {
-        sharedAudioSession.stop()
-    }
-
     // MARK: Helpers
 
     /**

Signal/src/call/SignalCall.swift

@@ -26,6 +26,7 @@ protocol CallObserver: class {
     func stateDidChange(call: SignalCall, state: CallState)
     func hasLocalVideoDidChange(call: SignalCall, hasLocalVideo: Bool)
     func muteDidChange(call: SignalCall, isMuted: Bool)
+    func holdDidChange(call: SignalCall, isOnHold: Bool)
     func audioSourceDidChange(call: SignalCall, audioSource: AudioSource?)
 }
 
@@ -123,7 +124,16 @@ protocol CallObserver: class {
         return audioSource.isBuiltInSpeaker
     }
 
-    var isOnHold = false
+    var isOnHold = false {
+        didSet {
+            AssertIsOnMainThread()
+            Logger.debug("\(TAG) isOnHold changed: \(oldValue) -> \(self.isOnHold)")
+
+            for observer in observers {
+                observer.value?.holdDidChange(call: self, isOnHold: isOnHold)
+            }
+        }
+    }
 
     var connectedDate: NSDate?
 

Signal/src/call/Speakerbox/CallKitCallUIAdaptee.swift

@@ -217,9 +217,6 @@ final class CallKitCallUIAdaptee: NSObject, CallUIAdaptee, CXProviderDelegate {
         AssertIsOnMainThread()
         Logger.info("\(self.TAG) \(#function)")
 
-        // Stop any in-progress WebRTC related audio.
-        PeerConnectionClient.stopAudioSession()
-
         // End any ongoing calls if the provider resets, and remove them from the app's list of calls,
         // since they are no longer valid.
         callService.handleFailedCurrentCall(error: .providerReset)
@@ -302,16 +299,6 @@ final class CallKitCallUIAdaptee: NSObject, CallUIAdaptee, CXProviderDelegate {
         // Update the SignalCall's underlying hold state.
         call.isOnHold = action.isOnHold
 
-        // Stop or start audio in response to holding or unholding the call.
-        if call.isOnHold {
-            // stopAudio() <-- SpeakerBox
-            PeerConnectionClient.stopAudioSession()
-        } else {
-            // startAudio() <-- SpeakerBox
-            // This is redundant with what happens in `provider(_:didActivate:)`
-            //PeerConnectionClient.startAudioSession()
-        }
-
         // Signal to the system that the action has been successfully performed.
         action.fulfill()
     }
@@ -355,8 +342,8 @@ final class CallKitCallUIAdaptee: NSObject, CallUIAdaptee, CXProviderDelegate {
 
         Logger.debug("\(TAG) Received \(#function)")
 
-        // Start recording
-        PeerConnectionClient.startAudioSession()
+        // Audio Session is managed by CallAudioService, which observes changes on the
+        // SignalCall directly.
     }
 
     func provider(_ provider: CXProvider, didDeactivate audioSession: AVAudioSession) {
@@ -364,10 +351,8 @@ final class CallKitCallUIAdaptee: NSObject, CallUIAdaptee, CXProviderDelegate {
 
         Logger.debug("\(TAG) Received \(#function)")
 
-        /*
-         Restart any non-call related audio now that the app's audio session has been
-         de-activated after having its priority restored to normal.
-         */
+        // Audio Session is managed by CallAudioService, which observes changes on the
+        // SignalCall directly.
     }
 
     // MARK: - Util