Implement the ability to attach and detach a room

Based on the simplified requirements described in #19. This doesn’t
include the emission of a room status change; will do that in a separate
PR.

Example/AblyChatExample/Mocks/MockRealtime.swift

@@ -1,7 +1,8 @@
 import Ably
+import AblyChat
 
-/// A mock implementation of `ARTRealtimeProtocol`. It only exists so that we can construct an instance of `DefaultChatClient` without needing to create a proper `ARTRealtime` instance (which we can’t yet do because we don’t have a method for inserting an API key into the example app). TODO remove this once we start building the example app
-final class MockRealtime: NSObject, ARTRealtimeProtocol, Sendable {
+/// A mock implementation of `RealtimeClientProtocol`. It only exists so that we can construct an instance of `DefaultChatClient` without needing to create a proper `ARTRealtime` instance (which we can’t yet do because we don’t have a method for inserting an API key into the example app). TODO remove this once we start building the example app
+final class MockRealtime: NSObject, RealtimeClientProtocol, Sendable {
     var device: ARTLocalDevice {
         fatalError("Not implemented")
     }
@@ -10,6 +11,168 @@ final class MockRealtime: NSObject, ARTRealtimeProtocol, Sendable {
         fatalError("Not implemented")
     }
 
+    let channels = Channels()
+
+    final class Channels: RealtimeChannelsProtocol {
+        func get(_: String) -> Channel {
+            fatalError("Not implemented")
+        }
+
+        func exists(_: String) -> Bool {
+            fatalError("Not implemented")
+        }
+
+        func release(_: String, callback _: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func release(_: String) {
+            fatalError("Not implemented")
+        }
+    }
+
+    final class Channel: RealtimeChannelProtocol {
+        var state: ARTRealtimeChannelState {
+            fatalError("Not implemented")
+        }
+
+        var errorReason: ARTErrorInfo? {
+            fatalError("Not implemented")
+        }
+
+        var options: ARTRealtimeChannelOptions? {
+            fatalError("Not implemented")
+        }
+
+        func attach() {
+            fatalError("Not implemented")
+        }
+
+        func attach(_: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func detach() {
+            fatalError("Not implemented")
+        }
+
+        func detach(_: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func subscribe(_: @escaping ARTMessageCallback) -> ARTEventListener? {
+            fatalError("Not implemented")
+        }
+
+        func subscribe(attachCallback _: ARTCallback?, callback _: @escaping ARTMessageCallback) -> ARTEventListener? {
+            fatalError("Not implemented")
+        }
+
+        func subscribe(_: String, callback _: @escaping ARTMessageCallback) -> ARTEventListener? {
+            fatalError("Not implemented")
+        }
+
+        func subscribe(_: String, onAttach _: ARTCallback?, callback _: @escaping ARTMessageCallback) -> ARTEventListener? {
+            fatalError("Not implemented")
+        }
+
+        func unsubscribe() {
+            fatalError("Not implemented")
+        }
+
+        func unsubscribe(_: ARTEventListener?) {
+            fatalError("Not implemented")
+        }
+
+        func unsubscribe(_: String, listener _: ARTEventListener?) {
+            fatalError("Not implemented")
+        }
+
+        func history(_: ARTRealtimeHistoryQuery?, callback _: @escaping ARTPaginatedMessagesCallback) throws {
+            fatalError("Not implemented")
+        }
+
+        func setOptions(_: ARTRealtimeChannelOptions?, callback _: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func on(_: ARTChannelEvent, callback _: @escaping (ARTChannelStateChange) -> Void) -> ARTEventListener {
+            fatalError("Not implemented")
+        }
+
+        func on(_: @escaping (ARTChannelStateChange) -> Void) -> ARTEventListener {
+            fatalError("Not implemented")
+        }
+
+        func once(_: ARTChannelEvent, callback _: @escaping (ARTChannelStateChange) -> Void) -> ARTEventListener {
+            fatalError("Not implemented")
+        }
+
+        func once(_: @escaping (ARTChannelStateChange) -> Void) -> ARTEventListener {
+            fatalError("Not implemented")
+        }
+
+        func off(_: ARTChannelEvent, listener _: ARTEventListener) {
+            fatalError("Not implemented")
+        }
+
+        func off(_: ARTEventListener) {
+            fatalError("Not implemented")
+        }
+
+        func off() {
+            fatalError("Not implemented")
+        }
+
+        var name: String {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?, callback _: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?, clientId _: String) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?, clientId _: String, callback _: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?, extras _: (any ARTJsonCompatible)?) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?, extras _: (any ARTJsonCompatible)?, callback _: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?, clientId _: String, extras _: (any ARTJsonCompatible)?) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: String?, data _: Any?, clientId _: String, extras _: (any ARTJsonCompatible)?, callback _: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: [ARTMessage]) {
+            fatalError("Not implemented")
+        }
+
+        func publish(_: [ARTMessage], callback _: ARTCallback? = nil) {
+            fatalError("Not implemented")
+        }
+
+        func history(_: @escaping ARTPaginatedMessagesCallback) {
+            fatalError("Not implemented")
+        }
+    }
+
     required init(options _: ARTClientOptions) {}
 
     required init(key _: String) {}

Sources/AblyChat/AblyCocoaExtensions/Ably+Concurrency.swift

@@ -0,0 +1,30 @@
+import Ably
+
+// This file contains extensions to ably-cocoa’s types, to make them easier to use in Swift concurrency.
+// TODO: remove once we improve this experience in ably-cocoa (https://github.com/ably/ably-cocoa/issues/1967)
+
+internal extension ARTRealtimeChannelProtocol {
+    func attachAsync() async throws {
+        try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Swift.Error>) in
+            attach { error in
+                if let error {
+                    continuation.resume(throwing: error)
+                } else {
+                    continuation.resume()
+                }
+            }
+        }
+    }
+
+    func detachAsync() async throws {
+        try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Swift.Error>) in
+            detach { error in
+                if let error {
+                    continuation.resume(throwing: error)
+                } else {
+                    continuation.resume()
+                }
+            }
+        }
+    }
+}

Sources/AblyChat/AblyCocoaExtensions/Ably+Dependencies.swift

@@ -0,0 +1,18 @@
+import Ably
+
+// TODO: remove "@unchecked Sendable" once https://github.com/ably/ably-cocoa/issues/1962 done
+
+#if swift(>=6)
+    // This @retroactive is needed to silence the Swift 6 compiler error "extension declares a conformance of imported type 'ARTRealtimeChannels' to imported protocol 'Sendable'; this will not behave correctly if the owners of 'Ably' introduce this conformance in the future (…) add '@retroactive' to silence this warning". I don’t fully understand the implications of this but don’t really mind since both libraries are in our control.
+    extension ARTRealtime: RealtimeClientProtocol, @retroactive @unchecked Sendable {}
+
+    extension ARTRealtimeChannels: RealtimeChannelsProtocol, @retroactive @unchecked Sendable {}
+
+    extension ARTRealtimeChannel: RealtimeChannelProtocol, @retroactive @unchecked Sendable {}
+#else
+    extension ARTRealtime: RealtimeClientProtocol, @unchecked Sendable {}
+
+    extension ARTRealtimeChannels: RealtimeChannelsProtocol, @unchecked Sendable {}
+
+    extension ARTRealtimeChannel: RealtimeChannelProtocol, @unchecked Sendable {}
+#endif

Sources/AblyChat/ChatClient.swift

@@ -8,7 +8,7 @@ public protocol ChatClient: AnyObject, Sendable {
     var clientOptions: ClientOptions { get }
 }
 
-public typealias RealtimeClient = any(ARTRealtimeProtocol & Sendable)
+public typealias RealtimeClient = any RealtimeClientProtocol
 
 public actor DefaultChatClient: ChatClient {
     public let realtime: RealtimeClient

Sources/AblyChat/Dependencies.swift

@@ -0,0 +1,22 @@
+import Ably
+
+/// Expresses the requirements of the Ably realtime client that is supplied to the Chat SDK.
+///
+/// The `ARTRealtime` class from the ably-cocoa SDK implements this protocol.
+public protocol RealtimeClientProtocol: ARTRealtimeProtocol, Sendable {
+    associatedtype Channels: RealtimeChannelsProtocol
+
+    // It’s not clear to me why ARTRealtimeProtocol doesn’t include this property. I briefly tried adding it but ran into compilation failures that it wasn’t immediately obvious how to fix.
+    var channels: Channels { get }
+}
+
+/// Expresses the requirements of the object returned by ``RealtimeClientProtocol.channels``.
+public protocol RealtimeChannelsProtocol: ARTRealtimeChannelsProtocol, Sendable {
+    associatedtype Channel: RealtimeChannelProtocol
+
+    // It’s not clear to me why ARTRealtimeChannelsProtocol doesn’t include this property (https://github.com/ably/ably-cocoa/issues/1968).
+    func get(_ name: String) -> Channel
+}
+
+/// Expresses the requirements of the object returned by ``RealtimeChannelsProtocol.get(_:)``.
+public protocol RealtimeChannelProtocol: ARTRealtimeChannelProtocol, Sendable {}

Sources/AblyChat/Room.swift

@@ -54,11 +54,26 @@ internal actor DefaultRoom: Room {
         fatalError("Not yet implemented")
     }
 
+    /// Fetches the channels that contribute to this room.
+    private func channels() -> [any RealtimeChannelProtocol] {
+        [
+            "chatMessages",
+            "typingIndicators",
+            "reactions",
+        ].map { suffix in
+            realtime.channels.get("\(roomID)::$chat::$\(suffix)")
+        }
+    }
+
     public func attach() async throws {
-        fatalError("Not yet implemented")
+        for channel in channels() {
+            try await channel.attachAsync()
+        }
     }
 
     public func detach() async throws {
-        fatalError("Not yet implemented")
+        for channel in channels() {
+            try await channel.detachAsync()
+        }
     }
 }