Fixes #258 - Display an indicator if the network is currently unreachable (#379)

ElementX/Sources/Application/AppCoordinator.swift

@@ -47,6 +47,7 @@ class AppCoordinator: AppCoordinatorProtocol {
     private let bugReportService: BugReportServiceProtocol
     private let backgroundTaskService: BackgroundTaskServiceProtocol
 
+    private var userSessionCancellables = Set<AnyCancellable>()
     private var cancellables = Set<AnyCancellable>()
     private(set) var notificationManager: NotificationManagerProtocol?
 
@@ -79,9 +80,8 @@ class AppCoordinator: AppCoordinatorProtocol {
         
         Bundle.elementFallbackLanguage = "en"
 
-        startObservingApplicationState()
-        
-        // Benchmark.trackingEnabled = true
+        observeApplicationState()
+        observeNetworkState()
     }
     
     func start() {
@@ -101,6 +101,7 @@ class AppCoordinator: AppCoordinatorProtocol {
     private static func setupServiceLocator(navigationRootCoordinator: NavigationRootCoordinator) {
         ServiceLocator.shared.register(userNotificationController: UserNotificationController(rootCoordinator: navigationRootCoordinator))
         ServiceLocator.shared.register(appSettings: AppSettings())
+        ServiceLocator.shared.register(networkMonitor: NetworkMonitor())
     }
     
     private static func setupLogging() {
@@ -329,12 +330,11 @@ class AppCoordinator: AppCoordinatorProtocol {
                     break
                 }
             }
-            .store(in: &cancellables)
+            .store(in: &userSessionCancellables)
     }
 
     private func deobserveUserSessionChanges() {
-        cancellables.forEach { $0.cancel() }
-        cancellables.removeAll()
+        userSessionCancellables.removeAll()
     }
     
     // MARK: Toasts and loading indicators
@@ -366,7 +366,7 @@ class AppCoordinator: AppCoordinatorProtocol {
         userSession?.clientProxy.startSync()
     }
 
-    private func startObservingApplicationState() {
+    private func observeApplicationState() {
         NotificationCenter.default.addObserver(self,
                                                selector: #selector(applicationWillResignActive),
                                                name: UIApplication.willResignActiveNotification,
@@ -401,6 +401,19 @@ class AppCoordinator: AppCoordinatorProtocol {
             resume()
         }
     }
+    
+    private func observeNetworkState() {
+        let reachabilityNotificationIdentifier = "io.element.elementx.reachability.notification"
+        ServiceLocator.shared.networkMonitor.reachabilityPublisher.sink { reachable in
+            if reachable {
+                ServiceLocator.shared.userNotificationController.retractNotificationWithId(reachabilityNotificationIdentifier)
+            } else {
+                ServiceLocator.shared.userNotificationController.submitNotification(.init(id: reachabilityNotificationIdentifier,
+                                                                                          title: ElementL10n.a11yPresenceOffline,
+                                                                                          persistent: true))
+            }
+        }.store(in: &cancellables)
+    }
 }
 
 // MARK: - AuthenticationCoordinatorDelegate

ElementX/Sources/Application/ServiceLocator.swift

@@ -32,4 +32,10 @@ class ServiceLocator {
     func register(appSettings: AppSettings) {
         settings = appSettings
     }
+    
+    private(set) var networkMonitor: NetworkMonitor!
+    
+    func register(networkMonitor: NetworkMonitor) {
+        self.networkMonitor = networkMonitor
+    }
 }

ElementX/Sources/Other/NetworkMonitor.swift

@@ -0,0 +1,50 @@
+//
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Combine
+import Foundation
+import Network
+
+class NetworkMonitor {
+    private let pathMonitor: NWPathMonitor
+    private let queue: DispatchQueue
+    let reachabilityPublisher: CurrentValueSubject<Bool, Never>
+    
+    var isCurrentConnectionExpensive: Bool {
+        pathMonitor.currentPath.isExpensive
+    }
+    
+    var isCurrentConnectionConstrained: Bool {
+        pathMonitor.currentPath.isConstrained
+    }
+    
+    init() {
+        queue = DispatchQueue(label: "io.element.elementx.networkmonitor")
+        pathMonitor = NWPathMonitor()
+        reachabilityPublisher = CurrentValueSubject<Bool, Never>(pathMonitor.currentPath.status == .satisfied)
+        
+        pathMonitor.pathUpdateHandler = { [weak self] path in
+            DispatchQueue.main.async {
+                if path.status == .satisfied {
+                    self?.reachabilityPublisher.send(true)
+                } else {
+                    self?.reachabilityPublisher.send(false)
+                }
+            }
+        }
+        pathMonitor.start(queue: queue)
+    }
+}

ElementX/Sources/Screens/RoomScreen/RoomScreenViewModel.swift

@@ -120,7 +120,6 @@ class RoomScreenViewModel: RoomScreenViewModelType, RoomScreenViewModelProtocol
     }
 
     func stop() {
-        cancellables.forEach { $0.cancel() }
         cancellables.removeAll()
         state.contextMenuBuilder = nil
     }