Introduce CallService

Riot/Managers/Call/AsyncOperation.swift

@@ -0,0 +1,90 @@
+// 
+// Copyright 2020 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
+
+class AsyncOperation: Operation {
+    
+    @objc private enum State: Int {
+        case ready
+        case executing
+        case finished
+    }
+    
+    private var _state: State = .ready
+    private let stateQueue = DispatchQueue(label: "AsyncOpStateQueue_\(String.vc_unique)",
+                                           attributes: .concurrent)
+    
+    @objc private dynamic var state: State {
+        get {
+            return stateQueue.sync {
+                _state
+            }
+        } set {
+            stateQueue.sync(flags: .barrier) {
+                _state = newValue
+            }
+        }
+    }
+    
+    override var isAsynchronous: Bool {
+        return true
+    }
+    
+    override var isReady: Bool {
+        return super.isReady && state == .ready
+    }
+    
+    override var isExecuting: Bool {
+        return state == .executing
+    }
+    
+    override var isFinished: Bool {
+        return state == .finished
+    }
+    
+    override func start() {
+        if isCancelled {
+            finish()
+            return
+        }
+        self.state = .executing
+        main()
+    }
+    
+    override func main() {
+        fatalError("Subclasses must implement `main` without calling super.")
+    }
+    
+    @objc class var keyPathsForValuesAffectingIsReady: Set<String> {
+        return [#keyPath(state)]
+    }
+    
+    @objc class var keyPathsForValuesAffectingIsExecuting: Set<String> {
+        return [#keyPath(state)]
+    }
+    
+    @objc class var keyPathsForValuesAffectingIsFinished: Set<String> {
+        return [#keyPath(state)]
+    }
+    
+    func finish() {
+        if isExecuting {
+            self.state = .finished
+        }
+    }
+    
+}