Fix state machine crashes & background tasks (#343)

* Fix `UIApplication.shared` after moving to SwiftUI app

* Do not autoplay videos on background

* Move app state changes into the app coordinator

* Add application background task, move into the suspended state more accurately

* Add changelog

* Fix most of the linter errors

* Strip suspended state from state machine

* Fix build

* Clear audio session warning

* Update AppCoordinator.swift

* Update AppCoordinator.swift

* Swift format

ElementX/Sources/Application/AppCoordinator.swift

@@ -22,6 +22,14 @@ class AppCoordinator: AppCoordinatorProtocol {
     private let stateMachine: AppCoordinatorStateMachine
     private let navigationController: NavigationController
     private let userSessionStore: UserSessionStoreProtocol
+    /// Common background task to resume long-running tasks in the background.
+    /// When this task expiring, we'll try to suspend the state machine by `suspend` event.
+    private var backgroundTask: BackgroundTaskProtocol?
+    private var isSuspended = false {
+        didSet {
+            MXLog.debug("didSet to: \(isSuspended)")
+        }
+    }
     
     private var userSession: UserSessionProtocol! {
         didSet {
@@ -52,7 +60,9 @@ class AppCoordinator: AppCoordinatorProtocol {
 
         ServiceLocator.shared.register(userNotificationController: UserNotificationController(rootCoordinator: navigationController))
 
-        backgroundTaskService = UIKitBackgroundTaskService(withApplication: UIApplication.shared)
+        backgroundTaskService = UIKitBackgroundTaskService {
+            UIApplication.shared
+        }
 
         userSessionStore = UserSessionStore(backgroundTaskService: backgroundTaskService)
         
@@ -61,6 +71,8 @@ class AppCoordinator: AppCoordinatorProtocol {
         setupLogging()
         
         Bundle.elementFallbackLanguage = "en"
+
+        startObservingApplicationState()
         
         // Benchmark.trackingEnabled = true
     }
@@ -324,6 +336,52 @@ class AppCoordinator: AppCoordinatorProtocol {
     private func showLoginErrorToast() {
         ServiceLocator.shared.userNotificationController.submitNotification(UserNotification(title: "Failed logging in"))
     }
+
+    // MARK: - Application State
+
+    private func pause() {
+        userSession?.clientProxy.stopSync()
+    }
+
+    private func resume() {
+        userSession?.clientProxy.startSync()
+    }
+
+    private func startObservingApplicationState() {
+        NotificationCenter.default.addObserver(self,
+                                               selector: #selector(applicationWillResignActive),
+                                               name: UIApplication.willResignActiveNotification,
+                                               object: nil)
+        NotificationCenter.default.addObserver(self,
+                                               selector: #selector(applicationDidBecomeActive),
+                                               name: UIApplication.didBecomeActiveNotification,
+                                               object: nil)
+    }
+
+    @objc
+    private func applicationWillResignActive() {
+        guard backgroundTask == nil else {
+            return
+        }
+
+        backgroundTask = backgroundTaskService.startBackgroundTask(withName: "SuspendApp: \(UUID().uuidString)") { [weak self] in
+            self?.pause()
+            
+            self?.backgroundTask = nil
+            self?.isSuspended = true
+        }
+    }
+
+    @objc
+    private func applicationDidBecomeActive() {
+        backgroundTask?.stop()
+        backgroundTask = nil
+
+        if isSuspended {
+            isSuspended = false
+            resume()
+        }
+    }
 }
 
 // MARK: - AuthenticationCoordinatorDelegate

ElementX/Sources/Application/AppCoordinatorStateMachine.swift

@@ -62,27 +62,38 @@ class AppCoordinatorStateMachine {
     private let stateMachine: StateMachine<State, Event>
     
     init() {
-        stateMachine = StateMachine(state: .initial) { machine in
+        stateMachine = StateMachine(state: .initial)
-            machine.addRoutes(event: .startWithAuthentication, transitions: [.initial => .signedOut])
+        configure()
-            machine.addRoutes(event: .succeededSigningIn, transitions: [.signedOut => .signedIn])
+    }
-            
+
-            machine.addRoutes(event: .startWithExistingSession, transitions: [.initial => .restoringSession])
+    private func configure() {
-            machine.addRoutes(event: .succeededRestoringSession, transitions: [.restoringSession => .signedIn])
+        stateMachine.addRoutes(event: .startWithAuthentication, transitions: [.initial => .signedOut])
-            machine.addRoutes(event: .failedRestoringSession, transitions: [.restoringSession => .signedOut])
+        stateMachine.addRoutes(event: .succeededSigningIn, transitions: [.signedOut => .signedIn])
-            
+
-            machine.addRoutes(event: .signOut, transitions: [.any => .signingOut])
+        stateMachine.addRoutes(event: .startWithExistingSession, transitions: [.initial => .restoringSession])
-            machine.addRoutes(event: .completedSigningOut, transitions: [.signingOut => .signedOut])
+        stateMachine.addRoutes(event: .succeededRestoringSession, transitions: [.restoringSession => .signedIn])
-                        
+        stateMachine.addRoutes(event: .failedRestoringSession, transitions: [.restoringSession => .signedOut])
-            // Transitions with associated values need to be handled through `addRouteMapping`
+
-            machine.addRouteMapping { event, fromState, _ in
+        stateMachine.addRoutes(event: .signOut, transitions: [.any => .signingOut])
-                switch (event, fromState) {
+        stateMachine.addRoutes(event: .completedSigningOut, transitions: [.signingOut => .signedOut])
-                case (.remoteSignOut(let isSoft), _):
+
-                    return .remoteSigningOut(isSoft: isSoft)
+        // Transitions with associated values need to be handled through `addRouteMapping`
-                case (.completedSigningOut, .remoteSigningOut):
+        stateMachine.addRouteMapping { event, fromState, _ in
-                    return .signedOut
+            switch (event, fromState) {
-                default:
+            case (.remoteSignOut(let isSoft), _):
-                    return nil
+                return .remoteSigningOut(isSoft: isSoft)
-                }
+            case (.completedSigningOut, .remoteSigningOut):
+                return .signedOut
+            default:
+                return nil
+            }
+        }
+
+        addTransitionHandler { context in
+            if let event = context.event {
+                MXLog.info("Transitioning from `\(context.fromState)` to `\(context.toState)` with event `\(event)`")
+            } else {
+                MXLog.info("Transitioning from \(context.fromState)` to `\(context.toState)`")
             }
         }
     }

ElementX/Sources/Screens/Other/ActivityCoordinator.swift

@@ -20,7 +20,7 @@ struct ActivityCoordinator: CoordinatorProtocol {
     let items: [Any]
     
     func toPresentable() -> AnyView {
-        return AnyView(UIActivityViewControllerWrapper(activityItems: items)
+        AnyView(UIActivityViewControllerWrapper(activityItems: items)
             .presentationDetents([.medium])
             .ignoresSafeArea())
     }

ElementX/Sources/Screens/VideoPlayer/VideoPlayerCoordinator.swift

@@ -36,6 +36,7 @@ final class VideoPlayerCoordinator: CoordinatorProtocol {
         self.parameters = parameters
         
         viewModel = VideoPlayerViewModel(videoURL: parameters.videoURL,
+                                         autoplay: UIApplication.shared.applicationState == .active,
                                          isModallyPresented: parameters.isModallyPresented)
     }
     
@@ -67,8 +68,7 @@ final class VideoPlayerCoordinator: CoordinatorProtocol {
     private func configureAudioSession(_ session: AVAudioSession) {
         do {
             try session.setCategory(.playback,
-                                    mode: .default,
+                                    mode: .default)
-                                    options: [.allowBluetooth, .allowBluetoothA2DP])
             try session.setActive(true)
         } catch {
             MXLog.debug("Configure audio session failed: \(error)")

ElementX/Sources/Services/Background/UIKitBackgroundTask.swift

@@ -53,6 +53,7 @@ class UIKitBackgroundTask: BackgroundTaskProtocol {
         // attempt to start
         identifier = application.beginBackgroundTask(withName: name) { [weak self] in
             guard let self else { return }
+            self.stop()
             self.expirationHandler?(self)
         }
 

ElementX/Sources/Services/Background/UIKitBackgroundTaskService.swift

@@ -19,13 +19,17 @@ import UIKit
 
 /// /// UIKitBackgroundTaskService is a concrete implementation of BackgroundTaskServiceProtocol using a given `ApplicationProtocol`  instance.
 class UIKitBackgroundTaskService: BackgroundTaskServiceProtocol {
-    private let application: ApplicationProtocol?
+    private let applicationBlock: () -> ApplicationProtocol?
     private var reusableTasks: WeakDictionary<String, UIKitBackgroundTask> = WeakDictionary()
 
+    private var application: ApplicationProtocol? {
+        applicationBlock()
+    }
+
     /// Initializer
-    /// - Parameter application: application instance to use. Defaults to `UIApplication.extensionSafeShared`.
+    /// - Parameter applicationBlock: block returning the application instance to use. Defaults to a block returning `UIApplication.extensionSafeShared`.
-    init(withApplication application: ApplicationProtocol? = UIApplication.extensionSafeShared) {
+    init(withApplicationBlock applicationBlock: @escaping () -> ApplicationProtocol? = { UIApplication.extensionSafeShared }) {
-        self.application = application
+        self.applicationBlock = applicationBlock
     }
 
     func startBackgroundTask(withName name: String,

ElementX/Sources/Services/UserSession/UserSessionFlowCoordinator.swift

@@ -36,7 +36,6 @@ class UserSessionFlowCoordinator: CoordinatorProtocol {
         self.bugReportService = bugReportService
         
         setupStateMachine()
-        startObservingApplicationState()
     }
     
     func start() {
@@ -84,11 +83,6 @@ class UserSessionFlowCoordinator: CoordinatorProtocol {
             case (.feedbackScreen, .dismissedFeedbackScreen, .homeScreen):
                 break
                 
-            case (_, .resignActive, .suspended):
-                self.pause()
-            case (_, .becomeActive, _):
-                self.resume()
-                
             default:
                 fatalError("Unknown transition: \(context)")
             }
@@ -98,17 +92,6 @@ class UserSessionFlowCoordinator: CoordinatorProtocol {
             fatalError("Failed transition with context: \(context)")
         }
     }
-
-    private func startObservingApplicationState() {
-        NotificationCenter.default.addObserver(self,
-                                               selector: #selector(applicationWillResignActive),
-                                               name: UIApplication.willResignActiveNotification,
-                                               object: nil)
-        NotificationCenter.default.addObserver(self,
-                                               selector: #selector(applicationDidBecomeActive),
-                                               name: UIApplication.didBecomeActiveNotification,
-                                               object: nil)
-    }
     
     private func presentHomeScreen() {
         userSession.clientProxy.startSync()
@@ -247,24 +230,4 @@ class UserSessionFlowCoordinator: CoordinatorProtocol {
             self?.stateMachine.processEvent(.dismissedFeedbackScreen)
         }
     }
-    
-    // MARK: - Application State
-
-    private func pause() {
-        userSession.clientProxy.stopSync()
-    }
-
-    private func resume() {
-        userSession.clientProxy.startSync()
-    }
-
-    @objc
-    private func applicationWillResignActive() {
-        stateMachine.processEvent(.resignActive)
-    }
-
-    @objc
-    private func applicationDidBecomeActive() {
-        stateMachine.processEvent(.becomeActive)
-    }
 }

ElementX/Sources/Services/UserSession/UserSessionFlowCoordinatorStateMachine.swift

@@ -38,9 +38,6 @@ class UserSessionFlowCoordinatorStateMachine {
         
         /// Showing the settings screen
         case settingsScreen
-
-        /// Application has been suspended
-        case suspended
     }
 
     /// Events that can be triggered on the AppCoordinator state machine
@@ -68,22 +65,15 @@ class UserSessionFlowCoordinatorStateMachine {
         case showSessionVerificationScreen
         /// Session verification has finished
         case dismissedSessionVerificationScreen
-
-        /// Application goes into inactive state
-        case resignActive
-        /// Application goes into active state
-        case becomeActive
     }
     
     private let stateMachine: StateMachine<State, Event>
-    private var stateBeforeSuspension: State?
     
     init() {
         stateMachine = StateMachine(state: .initial)
         configure()
     }
 
-    // swiftlint:disable:next cyclomatic_complexity
     private func configure() {
         stateMachine.addRoutes(event: .start, transitions: [.initial => .homeScreen])
 
@@ -109,18 +99,6 @@ class UserSessionFlowCoordinatorStateMachine {
             case (.dismissedSessionVerificationScreen, .sessionVerificationScreen):
                 return .homeScreen
                 
-            case (.resignActive, _):
-                self.stateBeforeSuspension = fromState
-                return .suspended
-            case (.becomeActive, _):
-                // Cannot become active if not previously suspended
-                // Happens when the app is backgrounded before the session is setup
-                guard let previousState = self.stateBeforeSuspension else {
-                    return self.stateMachine.state
-                }
-                
-                return previousState
-                
             default:
                 return nil
             }

UnitTests/Sources/BackgroundTaskTests.swift

@@ -25,14 +25,18 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testInAnExtension() {
-        let service = UIKitBackgroundTaskService(withApplication: nil)
+        let service = UIKitBackgroundTaskService {
+            nil
+        }
         let task = service.startBackgroundTask(withName: Constants.bgTaskName)
 
         XCTAssertNil(task, "Task should not be created")
     }
 
     func testInitAndStop() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockHealty)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockHealty
+        }
         guard let task = service.startBackgroundTask(withName: Constants.bgTaskName) else {
             XCTFail("Failed to setup test conditions")
             return
@@ -48,7 +52,9 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testNotReusableInit() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockHealty)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockHealty
+        }
 
         //  create two not reusable task with the same name
         guard let task1 = service.startBackgroundTask(withName: Constants.bgTaskName),
@@ -63,7 +69,9 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testReusableInit() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockHealty)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockHealty
+        }
 
         //  create two reusable task with the same name
         guard let task1 = service.startBackgroundTask(withName: Constants.bgTaskName, isReusable: true),
@@ -82,7 +90,9 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testMultipleStops() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockHealty)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockHealty
+        }
 
         //  create two reusable task with the same name
         guard let task = service.startBackgroundTask(withName: Constants.bgTaskName, isReusable: true),
@@ -103,7 +113,9 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testNotValidReuse() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockHealty)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockHealty
+        }
 
         //  create two reusable task with the same name
         guard let task = service.startBackgroundTask(withName: Constants.bgTaskName, isReusable: true) else {
@@ -123,7 +135,9 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testValidReuse() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockHealty)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockHealty
+        }
 
         //  create two reusable task with the same name
         guard let task = service.startBackgroundTask(withName: Constants.bgTaskName, isReusable: true) else {
@@ -147,7 +161,9 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testBrokenApp() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockBroken)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockBroken
+        }
 
         //  create two reusable task with the same name
         let task = service.startBackgroundTask(withName: Constants.bgTaskName)
@@ -156,7 +172,9 @@ class BackgroundTaskTests: XCTestCase {
     }
 
     func testNoTimeApp() {
-        let service = UIKitBackgroundTaskService(withApplication: UIApplication.mockAboutToSuspend)
+        let service = UIKitBackgroundTaskService {
+            UIApplication.mockAboutToSuspend
+        }
 
         //  create two reusable task with the same name
         let task = service.startBackgroundTask(withName: Constants.bgTaskName)

changelog.d/341.bugfix

@@ -0,0 +1 @@
+Application: Fix background tasks & state machine crashes.