Fix more call state edge cases.

Signal/src/call/CallService.swift

@@ -244,10 +244,11 @@ private class SignalCallData: NSObject {
                 if let oldValue = oldValue {
                     DeviceSleepManager.sharedInstance.removeBlock(blockObject: oldValue)
                 }
-                stopAnyCallTimer()
                 if let callData = callData {
                     DeviceSleepManager.sharedInstance.addBlock(blockObject: callData)
                     self.startCallTimer()
+                } else {
+                    stopAnyCallTimer()
                 }
             }
 
@@ -1233,9 +1234,9 @@ private class SignalCallData: NSObject {
         SwiftAssertIsOnMainThread(#function)
 
         guard let call = self.call else {
-            // This can happen if you tap the video button right after the other
-            // user hangs up.
-            Logger.warn("\(self.logTag) ignoring local video change; no call.")
+            // This can happen if you toggle local video right after
+            // the other user ends the call.
+            Logger.debug("\(self.logTag) \(#function) Ignoring event from obsolete call")
             return
         }
 
@@ -1526,6 +1527,14 @@ private class SignalCallData: NSObject {
         terminateCall()
     }
 
+    public func terminateCallDueToCriticalError() {
+        SwiftAssertIsOnMainThread(#function)
+
+        owsFail("\(logTag) \(#function)")
+
+        terminateCall()
+    }
+
     /**
      * Clean up any existing call state and get ready to receive a new call.
      */
@@ -1665,11 +1674,8 @@ private class SignalCallData: NSObject {
     func startCallTimer() {
         SwiftAssertIsOnMainThread(#function)
 
-        if self.activeCallTimer != nil {
-            owsFail("\(self.logTag) activeCallTimer should only be set once per call")
-            self.activeCallTimer!.invalidate()
-            self.activeCallTimer = nil
-        }
+        stopAnyCallTimer()
+        assert(self.activeCallTimer == nil)
 
         self.activeCallTimer = WeakTimer.scheduledTimer(timeInterval: 1, target: self, userInfo: nil, repeats: true) { [weak self] timer in
             guard let strongSelf = self else {
@@ -1687,6 +1693,15 @@ private class SignalCallData: NSObject {
     }
 
     func ensureCallScreenPresented(call: SignalCall) {
+        guard let currentCall = self.call else {
+            owsFail("\(self.logTag) obsolete call: \(call.identifiersForLogs) in \(#function)")
+            return
+        }
+        guard currentCall == call else {
+            owsFail("\(self.logTag) obsolete call: \(call.identifiersForLogs) in \(#function)")
+            return
+        }
+
         guard let connectedDate = call.connectedDate else {
             // Ignore; call hasn't connected yet.
             return

Signal/src/call/UserInterface/CallUIAdapter.swift

@@ -67,8 +67,8 @@ extension CallUIAdaptee {
         SwiftAssertIsOnMainThread(#function)
 
         guard self.callService.call == nil else {
-            Logger.info("unexpectedly found an existing call when trying to start outgoing call: \(recipientId)")
-            //TODO terminate existing call.
+            owsFail("unexpectedly found an existing call when trying to start outgoing call: \(recipientId)")
+            self.callService.terminateCallDueToCriticalError()
             return
         }