simplify and fix background loading (#288)

* simplify and fix background loading

* start receive loop in the main chat

apps/ios/Shared/Model/BGManager.swift

@@ -14,22 +14,25 @@ private let receiveTaskId = "chat.simplex.app.receive"
 // TCP timeout + 2 sec
 private let waitForMessages: TimeInterval = 6
 
-class BGManager {
-    private var bgTimer: Timer?
+private let bgRefreshInterval: TimeInterval = 450
 
+class BGManager {
     static let shared = BGManager()
+    var chatReceiver: ChatReceiver?
+    var bgTimer: Timer?
+    var completed = false
 
     func register() {
         logger.debug("BGManager.register")
         BGTaskScheduler.shared.register(forTaskWithIdentifier: receiveTaskId, using: nil) { task in
-            self.handleRefresh(RefreshTask(task as! BGAppRefreshTask))
+            self.handleRefresh(task as! BGAppRefreshTask)
         }
     }
 
     func schedule() {
         logger.debug("BGManager.schedule")
         let request = BGAppRefreshTaskRequest(identifier: receiveTaskId)
-        request.earliestBeginDate = Date(timeIntervalSinceNow: 10 * 60)
+        request.earliestBeginDate = Date(timeIntervalSinceNow: bgRefreshInterval)
         do {
             try BGTaskScheduler.shared.submit(request)
         } catch {
@@ -37,61 +40,41 @@ class BGManager {
         }
     }
 
-    private func handleRefresh(_ task: RefreshTask) {
+    private func handleRefresh(_ task: BGAppRefreshTask) {
         logger.debug("BGManager.handleRefresh")
         schedule()
-        task.expirationHandler = {
-            logger.debug("BGManager.handleRefresh expirationHandler")
-            ChatReceiver.shared.stop()
-            task.setTaskCompleted(success: true)
+        self.completed = false
+
+        let completeTask: (String) -> Void = { reason in
+            logger.debug("BGManager.handleRefresh completeTask: \(reason)")
+            if !self.completed {
+                self.completed = true
+                self.chatReceiver?.stop()
+                self.chatReceiver = nil
+                self.bgTimer?.invalidate()
+                self.bgTimer = nil
+                task.setTaskCompleted(success: true)
+            }
         }
+
+        task.expirationHandler = { completeTask("expirationHandler") }
         DispatchQueue.main.async {
             initializeChat()
             if ChatModel.shared.currentUser == nil {
-                task.setTaskCompleted(success: true)
+                completeTask("no current user")
                 return
             }
             logger.debug("BGManager.handleRefresh: starting chat")
-            ChatReceiver.shared.start(bgTask: task)
+            let cr = ChatReceiver()
+            self.chatReceiver = cr
+            cr.start()
             RunLoop.current.add(Timer(timeInterval: 2, repeats: true) { timer in
-                self.bgTimer = timer
                 logger.debug("BGManager.handleRefresh: timer")
-                if ChatReceiver.shared.lastMsgTime.distance(to: Date.now) >= waitForMessages {
-                    logger.debug("BGManager.handleRefresh: timer: stopping")
-                    ChatReceiver.shared.stop()
-                    task.setTaskCompleted(success: true)
-                    timer.invalidate()
-                    self.bgTimer = nil
+                self.bgTimer = timer
+                if cr.lastMsgTime.distance(to: Date.now) >= waitForMessages {
+                    completeTask("timer (no messages after \(waitForMessages) seconds)")
                 }
             }, forMode: .default)
         }
     }
-
-    func invalidateStopTimer() {
-        logger.debug("BGManager.invalidateStopTimer?")
-        if let timer = bgTimer {
-            timer.invalidate()
-            bgTimer = nil
-            logger.debug("BGManager.invalidateStopTimer: done")
-        }
-    }
-
-    class RefreshTask {
-        private let task: BGAppRefreshTask
-        var completed = false
-
-        internal init(_ task: BGAppRefreshTask) {
-            self.task = task
-        }
-
-        var expirationHandler: (() -> Void)? {
-            set { task.expirationHandler = newValue }
-            get { task.expirationHandler }
-        }
-
-        func setTaskCompleted(success: Bool) {
-            if !completed { task.setTaskCompleted(success: success) }
-            completed = true
-        }
-    }
 }

apps/ios/Shared/Model/SimpleXAPI.swift

@@ -345,19 +345,15 @@ func initializeChat() {
 class ChatReceiver {
     private var receiveLoop: DispatchWorkItem?
     private var receiveMessages = true
-    private var wasStarted = false
-    private var _canStop = false
     private var _lastMsgTime = Date.now
 
     static let shared = ChatReceiver()
 
     var lastMsgTime: Date { get { _lastMsgTime } }
 
-    func start(bgTask: BGManager.RefreshTask? = nil) {
+    func start() {
         logger.debug("ChatReceiver.start")
-        wasStarted = true
         receiveMessages = true
-        _canStop = true
         _lastMsgTime = .now
         if receiveLoop != nil { return }
         let loop = DispatchWorkItem(qos: .default, flags: []) {
@@ -369,25 +365,16 @@ class ChatReceiver {
                     logger.error("ChatReceiver.start chatRecvMsg error: \(error.localizedDescription)")
                 }
             }
-            if let task = bgTask { task.setTaskCompleted(success: true) }
         }
         receiveLoop = loop
         DispatchQueue.global().async(execute: loop)
     }
 
     func stop() {
-        logger.debug("ChatReceiver.stop?")
-        if !_canStop { return }
+        logger.debug("ChatReceiver.stop")
         receiveMessages = false
         receiveLoop?.cancel()
         receiveLoop = nil
-        logger.debug("ChatReceiver.stop: done")
-    }
-
-    func restart() {
-        logger.debug("ChatReceiver.restart?")
-        if wasStarted && receiveLoop == nil { start() }
-        _canStop = false
     }
 }
 

apps/ios/Shared/SimpleXApp.swift

@@ -36,9 +36,6 @@ struct SimpleXApp: App {
                 .onChange(of: scenePhase) { phase in
                     if phase == .background {
                         BGManager.shared.schedule()
-                    } else {
-                        BGManager.shared.invalidateStopTimer()
-                        ChatReceiver.shared.restart()
                     }
                 }
         }