Check network reachability before attempting to restart the sync service

ElementX/Sources/Other/NetworkMonitor/NetworkMonitor.swift

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+//
+// 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: NetworkMonitorProtocol {
+    private let pathMonitor: NWPathMonitor
+    private let queue: DispatchQueue
+    
+    private let reachabilitySubject: CurrentValueSubject<NetworkMonitorReachability, Never>
+    var reachabilityPublisher: CurrentValuePublisher<NetworkMonitorReachability, Never> {
+        reachabilitySubject.asCurrentValuePublisher()
+    }
+    
+    var isCurrentConnectionExpensive: Bool {
+        pathMonitor.currentPath.isExpensive
+    }
+    
+    var isCurrentConnectionConstrained: Bool {
+        pathMonitor.currentPath.isConstrained
+    }
+    
+    init() {
+        queue = DispatchQueue(label: "io.element.elementx.networkmonitor", qos: .background)
+        pathMonitor = NWPathMonitor()
+        reachabilitySubject = CurrentValueSubject<NetworkMonitorReachability, Never>(.reachable)
+        
+        pathMonitor.pathUpdateHandler = { [weak self] path in
+            DispatchQueue.main.async {
+                if path.status == .satisfied {
+                    self?.reachabilitySubject.send(.reachable)
+                } else {
+                    self?.reachabilitySubject.send(.unreachable)
+                }
+            }
+        }
+        pathMonitor.start(queue: queue)
+    }
+}

ElementX/Sources/Other/NetworkMonitor/NetworkMonitorProtocol.swift

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+//
+// Copyright 2023 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 Foundation
+
+enum NetworkMonitorReachability {
+    case reachable
+    case unreachable
+}
+
+protocol NetworkMonitorProtocol {
+    var reachabilityPublisher: CurrentValuePublisher<NetworkMonitorReachability, Never> { get }
+    var isCurrentConnectionExpensive: Bool { get }
+    var isCurrentConnectionConstrained: Bool { get }
+}