Update RemoteSyncEngine to adopt a StateMachine to allow for easier control of start/stop/retry

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/Sync/RemoteSyncEngine+Action.swift

@@ -0,0 +1,57 @@
+//
+// Copyright 2018-2020 Amazon.com,
+// Inc. or its affiliates. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+import Amplify
+import Combine
+
+@available(iOS 13.0, *)
+extension RemoteSyncEngine {
+
+    /// Actions are declarative, they say what I just did
+    enum Action {
+        // Startup/config actions
+        case receivedStart
+
+        case pausedSubscriptions
+        case pausedMutationQueue(APICategoryGraphQLBehavior, StorageEngineAdapter)
+        case initializedSubscriptions
+        case performedInitialSync
+        case activatedCloudSubscriptions(APICategoryGraphQLBehavior, MutationEventPublisher)
+        case activatedMutationQueue
+        case notifiedSyncStarted
+
+        // Terminal actions
+        case receivedCancel
+        case errored(AmplifyError)
+
+        var displayName: String {
+            switch self {
+            case .receivedStart:
+                return "receivedStart"
+            case .pausedSubscriptions:
+                return "pausedSubscriptions"
+            case .pausedMutationQueue:
+                return "pausedMutationQueue"
+            case .initializedSubscriptions:
+                return "initializedSubscriptions"
+            case .performedInitialSync:
+                return "performedInitialSync"
+            case .activatedCloudSubscriptions:
+                return "activatedCloudSubscriptions"
+            case .activatedMutationQueue:
+                return "activatedMutationQueue"
+            case .notifiedSyncStarted:
+                return "notifiedSyncStarted"
+            case .receivedCancel:
+                return "receivedCancel"
+            case .errored:
+                return "errored"
+            }
+
+        }
+    }
+}

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/Sync/RemoteSyncEngine+IncomingEventReconciliationQueueEvent.swift

@@ -0,0 +1,41 @@
+//
+// Copyright 2018-2020 Amazon.com,
+// Inc. or its affiliates. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+import Amplify
+import Combine
+import Foundation
+
+@available(iOS 13.0, *)
+extension RemoteSyncEngine {
+    @available(iOS 13.0, *)
+    func onReceiveCompletion(receiveCompletion: Subscribers.Completion<DataStoreError>) {
+        if case .failure(let error) = receiveCompletion {
+            remoteSyncTopicPublisher.send(completion: .failure(error))
+        }
+        if case .finished = receiveCompletion {
+            let unexpectedFinishError = DataStoreError.unknown("ReconcilationQueue sent .finished message",
+                                                               AmplifyErrorMessages.shouldNotHappenReportBugToAWS(),
+                                                               nil)
+            remoteSyncTopicPublisher.send(completion: .failure(unexpectedFinishError))
+        }
+    }
+
+    @available(iOS 13.0, *)
+    func onReceive(receiveValue: IncomingEventReconciliationQueueEvent) {
+        switch receiveValue {
+        case .started:
+            remoteSyncTopicPublisher.send(.subscriptionsActivated)
+            if let api = self.api {
+                stateMachine.notify(action: .activatedCloudSubscriptions(api, mutationEventPublisher))
+            }
+        case .paused:
+            remoteSyncTopicPublisher.send(.subscriptionsPaused)
+        case .mutationEvent(let mutationEvent):
+            remoteSyncTopicPublisher.send(.mutationEvent(mutationEvent))
+        }
+    }
+}

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/Sync/RemoteSyncEngine+Resolver.swift

@@ -0,0 +1,53 @@
+//
+// Copyright 2018-2020 Amazon.com,
+// Inc. or its affiliates. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+import Amplify
+import Combine
+
+@available(iOS 13.0, *)
+extension RemoteSyncEngine {
+    struct Resolver {
+        static func resolve(currentState: State, action: Action) -> State {
+            switch (currentState, action) {
+            case (.notStarted, .receivedStart):
+                return .pauseSubscriptions
+
+            case (.pauseSubscriptions, .pausedSubscriptions):
+                return .pauseMutationQueue
+
+            case (.pauseMutationQueue, .pausedMutationQueue(let api, let storageEngineAdapter)):
+                return .initializeSubscriptions(api, storageEngineAdapter)
+
+            case (.initializeSubscriptions, .initializedSubscriptions):
+                return .performInitialSync
+
+            case (.performInitialSync, .performedInitialSync):
+                return .activateCloudSubscriptions
+            case (.performInitialSync, .errored(let error)):
+                return .cleanup(error)
+
+            case (.activateCloudSubscriptions, .activatedCloudSubscriptions(let api, let mutationEventPublisher)):
+                return .activateMutationQueue(api, mutationEventPublisher)
+            case (.activateCloudSubscriptions, .errored(let error)):
+                return .cleanup(error)
+
+            case (.activateMutationQueue, .activatedMutationQueue):
+                return .notifySyncStarted
+            case (.activateMutationQueue, .errored(let error)):
+                return .cleanup(error)
+
+            case (.notifySyncStarted, .notifiedSyncStarted):
+                return .syncEngineActive
+
+            default:
+                log.warn("Unexpected state transition. In \(currentState.displayName), got \(action.displayName)")
+                log.verbose("Unexpected state transition. In \(currentState), got \(action)")
+                return currentState
+            }
+        }
+    }
+}

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/Sync/RemoteSyncEngine+State.swift

@@ -0,0 +1,53 @@
+//
+// Copyright 2018-2020 Amazon.com,
+// Inc. or its affiliates. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+import Amplify
+import Combine
+@available(iOS 13.0, *)
+extension RemoteSyncEngine {
+
+    /// States are descriptive, they say what is happening in the system right now
+    enum State {
+        case notStarted
+
+        case pauseSubscriptions
+        case pauseMutationQueue
+        case initializeSubscriptions(APICategoryGraphQLBehavior, StorageEngineAdapter)
+        case performInitialSync
+        case activateCloudSubscriptions
+        case activateMutationQueue(APICategoryGraphQLBehavior, MutationEventPublisher)
+        case notifySyncStarted
+
+        case syncEngineActive
+
+        case cleanup(AmplifyError)
+        var displayName: String {
+            switch self {
+            case .notStarted:
+                return "notStarted"
+            case .pauseSubscriptions:
+                return "pauseCloudSubscriptions"
+            case .pauseMutationQueue:
+                return "pauseMutationQueue"
+            case .initializeSubscriptions:
+                return "initializeSubscriptions"
+            case .performInitialSync:
+                return "performInitialSync"
+            case .activateCloudSubscriptions:
+                return "activateCloudSubscriptions"
+            case .activateMutationQueue:
+                return "activateMutationQueue"
+            case .notifySyncStarted:
+                return "notifySyncStarted"
+            case .syncEngineActive:
+                return "syncEngineActive"
+            case .cleanup:
+                return "cleanup"
+            }
+        }
+    }
+}