wip discontinuities

TODO test
TODO test figure out internal interface
TODO see if there are any spec points to do

TODO if Umair merges reactions before this, we need to incorporate here.

Resolves #47.

Sources/AblyChat/DefaultMessages.swift

@@ -13,16 +13,16 @@ private struct MessageSubscriptionWrapper {
 @MainActor
 internal final class DefaultMessages: Messages, EmitsDiscontinuities {
     private let roomID: String
-    public nonisolated let channel: RealtimeChannelProtocol
+    public nonisolated let featureChannel: FeatureChannel
     private let chatAPI: ChatAPI
     private let clientID: String
 
     // TODO: https://github.com/ably-labs/ably-chat-swift/issues/36 - Handle unsubscribing in line with CHA-M4b
     // UUID acts as a unique identifier for each listener/subscription. MessageSubscriptionWrapper houses the subscription and the timeserial of when it was attached or resumed.
     private var subscriptionPoints: [UUID: MessageSubscriptionWrapper] = [:]
 
-    internal nonisolated init(channel: RealtimeChannelProtocol, chatAPI: ChatAPI, roomID: String, clientID: String) async {
-        self.channel = channel
+    internal nonisolated init(featureChannel: FeatureChannel, chatAPI: ChatAPI, roomID: String, clientID: String) async {
+        self.featureChannel = featureChannel
         self.chatAPI = chatAPI
         self.roomID = roomID
         self.clientID = clientID
@@ -32,6 +32,10 @@ internal final class DefaultMessages: Messages, EmitsDiscontinuities {
         await handleChannelEvents(roomId: roomID)
     }
 
+    internal nonisolated var channel: any RealtimeChannelProtocol {
+        featureChannel.channel
+    }
+
     // (CHA-M4) Messages can be received via a subscription in realtime.
     internal func subscribe(bufferingPolicy: BufferingPolicy) async throws -> MessageSubscription {
         let uuid = UUID()
@@ -100,8 +104,9 @@ internal final class DefaultMessages: Messages, EmitsDiscontinuities {
     }
 
     // TODO: (CHA-M7) Users may subscribe to discontinuity events to know when there’s been a break in messages that they need to resolve. Their listener will be called when a discontinuity event is triggered from the room lifecycle. - https://github.com/ably-labs/ably-chat-swift/issues/47
-    internal nonisolated func subscribeToDiscontinuities() -> Subscription<ARTErrorInfo> {
-        fatalError("not implemented")
+    internal func subscribeToDiscontinuities() async -> Subscription<ARTErrorInfo> {
+        // TODO: test
+        await featureChannel.subscribeToDiscontinuities()
     }
 
     private func getBeforeSubscriptionStart(_ uuid: UUID, params: QueryOptions) async throws -> any PaginatedResult<Message> {

Sources/AblyChat/DefaultRoomLifecycleContributor.swift

@@ -1,8 +1,9 @@
 import Ably
 
-internal actor DefaultRoomLifecycleContributor: RoomLifecycleContributor {
+internal actor DefaultRoomLifecycleContributor: RoomLifecycleContributor, EmitsDiscontinuities {
     internal let channel: DefaultRoomLifecycleContributorChannel
     internal let feature: RoomFeature
+    private var discontinuitySubscriptions: [Subscription<ARTErrorInfo>] = []
 
     internal init(channel: DefaultRoomLifecycleContributorChannel, feature: RoomFeature) {
         self.channel = channel
@@ -11,8 +12,17 @@ internal actor DefaultRoomLifecycleContributor: RoomLifecycleContributor {
 
     // MARK: - Discontinuities
 
-    internal func emitDiscontinuity(_: ARTErrorInfo) {
-        // TODO: https://github.com/ably-labs/ably-chat-swift/issues/47
+    internal func emitDiscontinuity(_ error: ARTErrorInfo) {
+        for subscription in discontinuitySubscriptions {
+            subscription.emit(error)
+        }
+    }
+
+    internal func subscribeToDiscontinuities() -> Subscription<ARTErrorInfo> {
+        let subscription = Subscription<ARTErrorInfo>(bufferingPolicy: .unbounded)
+        // TODO: clean up old subscriptions (https://github.com/ably-labs/ably-chat-swift/issues/36)
+        discontinuitySubscriptions.append(subscription)
+        return subscription
     }
 }
 

Sources/AblyChat/RoomFeature.swift

@@ -1,3 +1,5 @@
+import Ably
+
 /// The features offered by a chat room.
 internal enum RoomFeature {
     case messages
@@ -21,3 +23,17 @@ internal enum RoomFeature {
         }
     }
 }
+
+// TODO: what's this?
+internal protocol FeatureChannel: Sendable, EmitsDiscontinuities {
+    var channel: RealtimeChannelProtocol { get }
+}
+
+internal struct DefaultFeatureChannel: FeatureChannel {
+    internal var channel: RealtimeChannelProtocol
+    internal var contributor: DefaultRoomLifecycleContributor
+
+    internal func subscribeToDiscontinuities() async -> Subscription<ARTErrorInfo> {
+        await contributor.subscribeToDiscontinuities()
+    }
+}

Tests/AblyChatTests/Mocks/MockFeatureChannel.swift

@@ -0,0 +1,14 @@
+import Ably
+@testable import AblyChat
+
+final class MockFeatureChannel: FeatureChannel {
+    let channel: RealtimeChannelProtocol
+
+    init(channel: RealtimeChannelProtocol) {
+        self.channel = channel
+    }
+
+    func subscribeToDiscontinuities() async -> Subscription<ARTErrorInfo> {
+        fatalError("TODO")
+    }
+}