ios, core: better notifications processing to avoid contention for database (#3485)

* core: forward notifications about message processing (for iOS notifications)

* simplexmq

* the option to keep database key, to allow re-opening the database

* export new init with keepKey and reopen DB api

* stop remote ctrl when suspending chat

* ios: close/re-open db on suspend/activate

* allow activating chat without restoring (for NSE)

* update NSE to suspend/activate (does not work)

* simplexmq

* suspend chat and close database when last notification in the process is processed

* stop reading notifications on message markers

* replace async stream with cancellable concurrent queue

* better synchronization of app and NSE

* remove outside of task

* remove unused var

* whitespace

* more debug logging, handle cancelled read after dequeue

* comments

* more comments

apps/ios/Shared/Model/BGManager.swift

@@ -15,7 +15,7 @@ private let receiveTaskId = "chat.simplex.app.receive"
 // TCP timeout + 2 sec
 private let waitForMessages: TimeInterval = 6
 
-private let bgRefreshInterval: TimeInterval = 450
+private let bgRefreshInterval: TimeInterval = 600
 
 private let maxTimerCount = 9
 
@@ -55,7 +55,7 @@ class BGManager {
         }
         logger.debug("BGManager.handleRefresh")
         schedule()
-        if appStateGroupDefault.get().inactive {
+        if allowBackgroundRefresh() {
             let completeRefresh = completionHandler {
                 task.setTaskCompleted(success: true)
             }
@@ -92,18 +92,19 @@ class BGManager {
         DispatchQueue.main.async {
             let m = ChatModel.shared
             if (!m.chatInitialized) {
+                setAppState(.bgRefresh)
                 do {
                     try initializeChat(start: true)
                 } catch let error {
                     fatalError("Failed to start or load chats: \(responseError(error))")
                 }
             }
+            activateChat(appState: .bgRefresh)
             if m.currentUser == nil {
                 completeReceiving("no current user")
                 return
             }
             logger.debug("BGManager.receiveMessages: starting chat")
-            activateChat(appState: .bgRefresh)
             let cr = ChatReceiver()
             self.chatReceiver = cr
             cr.start()

apps/ios/Shared/Model/ChatModel.swift

@@ -105,11 +105,13 @@ final class ChatModel: ObservableObject {
     static var ok: Bool { ChatModel.shared.chatDbStatus == .ok }
 
     var ntfEnableLocal: Bool {
-        notificationMode == .off || ntfEnableLocalGroupDefault.get()
+        true
+//        notificationMode == .off || ntfEnableLocalGroupDefault.get()
     }
 
     var ntfEnablePeriodic: Bool {
-        notificationMode == .periodic || ntfEnablePeriodicGroupDefault.get()
+        notificationMode != .off
+//        notificationMode == .periodic || ntfEnablePeriodicGroupDefault.get()
     }
 
     var activeRemoteCtrl: Bool {

apps/ios/Shared/Model/SimpleXAPI.swift

@@ -228,7 +228,8 @@ func apiStopChat() async throws {
 }
 
 func apiActivateChat() {
-    let r = chatSendCmdSync(.apiActivateChat)
+    chatReopenStore()
+    let r = chatSendCmdSync(.apiActivateChat(restoreChat: true))
     if case .cmdOk = r { return }
     logger.error("apiActivateChat error: \(String(describing: r))")
 }

apps/ios/Shared/Model/SuspendChat.swift

@@ -18,6 +18,8 @@ let bgSuspendTimeout: Int = 5 // seconds
 
 let terminationTimeout: Int = 3 // seconds
 
+let activationDelay: Double = 1.5 // seconds
+
 private func _suspendChat(timeout: Int) {
     // this is a redundant check to prevent logical errors, like the one fixed in this PR
     let state = appStateGroupDefault.get()
@@ -47,8 +49,6 @@ func suspendBgRefresh() {
     }
 }
 
-private var terminating = false
-
 func terminateChat() {
     logger.debug("terminateChat")
     suspendLockQueue.sync {
@@ -64,7 +64,6 @@ func terminateChat() {
         case .stopped:
             chatCloseStore()
         default:
-            terminating = true
             // the store will be closed in _chatSuspended when event is received
             _suspendChat(timeout: terminationTimeout)
         }
@@ -85,14 +84,17 @@ private func _chatSuspended() {
     if ChatModel.shared.chatRunning == true {
         ChatReceiver.shared.stop()
     }
-    if terminating {
-         chatCloseStore()
+    chatCloseStore()
+}
+
+func setAppState(_ appState: AppState) {
+    suspendLockQueue.sync {
+        appStateGroupDefault.set(appState)
     }
 }
 
 func activateChat(appState: AppState = .active) {
     logger.debug("DEBUGGING: activateChat")
-    terminating = false
     suspendLockQueue.sync {
         appStateGroupDefault.set(appState)
         if ChatModel.ok { apiActivateChat() }
@@ -101,7 +103,6 @@ func activateChat(appState: AppState = .active) {
 }
 
 func initChatAndMigrate(refreshInvitations: Bool = true) {
-    terminating = false
     let m = ChatModel.shared
     if (!m.chatInitialized) {
         do {
@@ -113,16 +114,32 @@ func initChatAndMigrate(refreshInvitations: Bool = true) {
     }
 }
 
-func startChatAndActivate() {
-    terminating = false
+func startChatAndActivate(dispatchQueue: DispatchQueue = DispatchQueue.main, _ completion: @escaping () -> Void) {
     logger.debug("DEBUGGING: startChatAndActivate")
     if ChatModel.shared.chatRunning == true {
         ChatReceiver.shared.start()
         logger.debug("DEBUGGING: startChatAndActivate: after ChatReceiver.shared.start")
     }
-    if .active != appStateGroupDefault.get()  {
+    if .active == appStateGroupDefault.get() {
+        completion()
+    } else if nseStateGroupDefault.get().inactive {
+        activate()
+    } else {
+        suspendLockQueue.sync {
+            appStateGroupDefault.set(.activating)
+        }
+        // TODO can be replaced with Mach messenger to notify the NSE to terminate and continue after reply, with timeout
+        dispatchQueue.asyncAfter(deadline: .now() + activationDelay) {
+            if appStateGroupDefault.get() == .activating {
+                activate()
+            }
+        }
+    }
+
+    func activate() {
         logger.debug("DEBUGGING: startChatAndActivate: before activateChat")
         activateChat()
+        completion()
         logger.debug("DEBUGGING: startChatAndActivate: after activateChat")
     }
 }