Merge pull request #20 from ably/groundwork-for-object-sync

Groundwork for object sync

Author: lawrence-forooghian

Sources/AblyLiveObjects/DefaultRealtimeObjects.swift

@@ -2,21 +2,22 @@ import Ably
 internal import AblyPlugin
 
 /// The class that provides the public API for interacting with LiveObjects, via the ``ARTRealtimeChannel/objects`` property.
-internal class DefaultRealtimeObjects: RealtimeObjects {
-    private weak var channel: ARTRealtimeChannel?
+internal final class DefaultRealtimeObjects: RealtimeObjects {
+    // Used for synchronizing access to all of this instance's mutable state. This is a temporary solution just to allow us to implement `Sendable`, and we'll revisit it in https://github.com/ably/ably-cocoa-liveobjects-plugin/issues/3.
+    private let mutex = NSLock()
+
+    private let coreSDK: CoreSDK
     private let logger: AblyPlugin.Logger
-    private let pluginAPI: AblyPlugin.PluginAPIProtocol
 
     // These drive the testsOnly_* properties that expose the received ProtocolMessages to the test suite.
     private let receivedObjectProtocolMessages: AsyncStream<[InboundObjectMessage]>
     private let receivedObjectProtocolMessagesContinuation: AsyncStream<[InboundObjectMessage]>.Continuation
     private let receivedObjectSyncProtocolMessages: AsyncStream<[InboundObjectMessage]>
     private let receivedObjectSyncProtocolMessagesContinuation: AsyncStream<[InboundObjectMessage]>.Continuation
 
-    internal init(channel: ARTRealtimeChannel, logger: AblyPlugin.Logger, pluginAPI: AblyPlugin.PluginAPIProtocol) {
-        self.channel = channel
+    internal init(coreSDK: CoreSDK, logger: AblyPlugin.Logger) {
+        self.coreSDK = coreSDK
         self.logger = logger
-        self.pluginAPI = pluginAPI
         (receivedObjectProtocolMessages, receivedObjectProtocolMessagesContinuation) = AsyncStream.makeStream()
         (receivedObjectSyncProtocolMessages, receivedObjectSyncProtocolMessagesContinuation) = AsyncStream.makeStream()
     }
@@ -27,23 +28,23 @@ internal class DefaultRealtimeObjects: RealtimeObjects {
         notYetImplemented()
     }
 
-    internal func createMap(entries _: any LiveMap) async throws(ARTErrorInfo) -> any LiveMap {
+    internal func createMap(entries _: [String: LiveMapValue]) async throws(ARTErrorInfo) -> any LiveMap {
         notYetImplemented()
     }
 
     internal func createMap() async throws(ARTErrorInfo) -> any LiveMap {
         notYetImplemented()
     }
 
-    internal func createCounter(count _: Int) async throws(ARTErrorInfo) -> any LiveCounter {
+    internal func createCounter(count _: Double) async throws(ARTErrorInfo) -> any LiveCounter {
         notYetImplemented()
     }
 
     internal func createCounter() async throws(ARTErrorInfo) -> any LiveCounter {
         notYetImplemented()
     }
 
-    internal func batch(callback _: (any BatchContext) -> Void) async throws {
+    internal func batch(callback _: sending (sending any BatchContext) -> Void) async throws {
         notYetImplemented()
     }
 
@@ -57,9 +58,17 @@ internal class DefaultRealtimeObjects: RealtimeObjects {
 
     // MARK: Handling channel events
 
-    internal private(set) var testsOnly_onChannelAttachedHasObjects: Bool?
+    private nonisolated(unsafe) var onChannelAttachedHasObjects: Bool?
+    internal var testsOnly_onChannelAttachedHasObjects: Bool? {
+        mutex.withLock {
+            onChannelAttachedHasObjects
+        }
+    }
+
     internal func onChannelAttached(hasObjects: Bool) {
-        testsOnly_onChannelAttachedHasObjects = hasObjects
+        mutex.withLock {
+            onChannelAttachedHasObjects = hasObjects
+        }
     }
 
     internal var testsOnly_receivedObjectProtocolMessages: AsyncStream<[InboundObjectMessage]> {
@@ -74,22 +83,14 @@ internal class DefaultRealtimeObjects: RealtimeObjects {
         receivedObjectSyncProtocolMessages
     }
 
-    internal func handleObjectSyncProtocolMessage(objectMessages: [InboundObjectMessage], protocolMessageChannelSerial _: String) {
+    internal func handleObjectSyncProtocolMessage(objectMessages: [InboundObjectMessage], protocolMessageChannelSerial _: String?) {
         receivedObjectSyncProtocolMessagesContinuation.yield(objectMessages)
     }
 
     // MARK: - Sending `OBJECT` ProtocolMessage
 
     // This is currently exposed so that we can try calling it from the tests in the early days of the SDK to check that we can send an OBJECT ProtocolMessage. We'll probably make it private later on.
     internal func testsOnly_sendObject(objectMessages: [OutboundObjectMessage]) async throws(InternalError) {
-        guard let channel else {
-            return
-        }
-
-        try await DefaultInternalPlugin.sendObject(
-            objectMessages: objectMessages,
-            channel: channel,
-            pluginAPI: pluginAPI,
-        )
+        try await coreSDK.sendObject(objectMessages: objectMessages)
     }
 }

Sources/AblyLiveObjects/Internal/CoreSDK.swift

@@ -0,0 +1,44 @@
+import Ably
+internal import AblyPlugin
+
+/// The API that the internal components of the SDK (that is, `DefaultLiveObjects` and down) use to interact with our core SDK (i.e. ably-cocoa).
+///
+/// This provides us with a mockable interface to ably-cocoa, and it also allows internal components and their tests not to need to worry about some of the boring details of how we bridge Swift types to AblyPlugin's Objective-C API (i.e. boxing).
+internal protocol CoreSDK: AnyObject, Sendable {
+    func sendObject(objectMessages: [OutboundObjectMessage]) async throws(InternalError)
+}
+
+internal final class DefaultCoreSDK: CoreSDK {
+    // We hold a weak reference to the channel so that `DefaultLiveObjects` can hold a strong reference to us without causing a strong reference cycle. We'll revisit this in https://github.com/ably/ably-cocoa-liveobjects-plugin/issues/9.
+    private let weakChannel: WeakRef<ARTRealtimeChannel>
+    private let pluginAPI: PluginAPIProtocol
+
+    internal init(
+        channel: ARTRealtimeChannel,
+        pluginAPI: PluginAPIProtocol
+    ) {
+        weakChannel = .init(referenced: channel)
+        self.pluginAPI = pluginAPI
+    }
+
+    // MARK: - Fetching channel
+
+    private var channel: ARTRealtimeChannel {
+        guard let channel = weakChannel.referenced else {
+            // It's currently completely possible that the channel _does_ become deallocated during the usage of the LiveObjects SDK; in https://github.com/ably/ably-cocoa-liveobjects-plugin/issues/9 we'll figure out how to prevent this.
+            preconditionFailure("Expected channel to not become deallocated during usage of LiveObjects SDK")
+        }
+
+        return channel
+    }
+
+    // MARK: - CoreSDK conformance
+
+    internal func sendObject(objectMessages: [OutboundObjectMessage]) async throws(InternalError) {
+        try await DefaultInternalPlugin.sendObject(
+            objectMessages: objectMessages,
+            channel: channel,
+            pluginAPI: pluginAPI,
+        )
+    }
+}

Sources/AblyLiveObjects/Internal/DefaultInternalPlugin.swift

@@ -37,7 +37,8 @@ internal final class DefaultInternalPlugin: NSObject, AblyPlugin.LiveObjectsInte
         let logger = pluginAPI.logger(for: channel)
 
         logger.log("LiveObjects.DefaultInternalPlugin received prepare(_:)", level: .debug)
-        let liveObjects = DefaultRealtimeObjects(channel: channel, logger: logger, pluginAPI: pluginAPI)
+        let coreSDK = DefaultCoreSDK(channel: channel, pluginAPI: pluginAPI)
+        let liveObjects = DefaultRealtimeObjects(coreSDK: coreSDK, logger: logger)
         pluginAPI.setPluginDataValue(liveObjects, forKey: Self.pluginDataKey, channel: channel)
     }
 
@@ -109,7 +110,7 @@ internal final class DefaultInternalPlugin: NSObject, AblyPlugin.LiveObjectsInte
         )
     }
 
-    internal func handleObjectSyncProtocolMessage(withObjectMessages publicObjectMessages: [any AblyPlugin.ObjectMessageProtocol], protocolMessageChannelSerial: String, channel: ARTRealtimeChannel) {
+    internal func handleObjectSyncProtocolMessage(withObjectMessages publicObjectMessages: [any AblyPlugin.ObjectMessageProtocol], protocolMessageChannelSerial: String?, channel: ARTRealtimeChannel) {
         guard let inboundObjectMessageBoxes = publicObjectMessages as? [ObjectMessageBox<InboundObjectMessage>] else {
             preconditionFailure("Expected to receive the same InboundObjectMessage type as we emit")
         }