more cleanup and commenting

// FREEBIE

Signal/src/ViewControllers/CallViewController.swift

@@ -354,13 +354,20 @@ class CallViewController: UIViewController, CallObserver, CallServiceObserver, R
 
     func didChangeAudioSession() {
         AssertIsOnMainThread()
-        // TODO unnecessary?
+
+        // Which sources are available depends on the state of your Session.
+        // When the audio session is not yet in PlayAndRecord none are available
+        // Then if we're in speakerphone, bluetooth isn't available. 
+        // So we acrew all possible audio sources in a set, and that list lives as longs as the CallViewController
+        // The downside of this is that if you e.g. unpair your bluetooth mid call, it will still appear as an option
+        // until your next call.
+        // FIXME: There's got to be a better way, but this is where I landed after a bit of work, and seems to work
+        // pretty well in practrice.
         let availableInputs = callUIAdapter.audioService.availableInputs
         self.allAudioSources.formUnion(availableInputs)
     }
 
     func presentAudioSourcePicker() {
-        Logger.info("\(TAG) in \(#function)")
         AssertIsOnMainThread()
 
         let actionSheetController = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)

Signal/src/call/CallAudioService.swift

@@ -407,16 +407,20 @@ struct AudioSource: Hashable {
     }
 
     func currentAudioSource(call: SignalCall) -> AudioSource? {
-        if call.isSpeakerphoneEnabled {
+        if let audioSource = call.audioSource {
-            return AudioSource.builtInSpeaker
+            return audioSource
-        } else {
+        }
-            let session = AVAudioSession.sharedInstance()
-            guard let portDescription = session.currentRoute.inputs.first else {
-                return nil
-            }
 
-            return AudioSource(portDescription: portDescription)
+        // Before the user has specified an audio source on the call, we rely on the existing
+        // system state to determine the current audio source.
+        // If a bluetooth is connected, this will be bluetooth, otherwise
+        // this will be the receiver.
+        let session = AVAudioSession.sharedInstance()
+        guard let portDescription = session.currentRoute.inputs.first else {
+            return nil
         }
+
+        return AudioSource(portDescription: portDescription)
     }
 
     public func setPreferredInput(call: SignalCall, audioSource: AudioSource?) {