From 543136e254f0f08854039bfa5f381be87f20ab1a Mon Sep 17 00:00:00 2001
From: Pol Quintana <pol.quintana1@gmail.com>
Date: Tue, 21 Nov 2023 12:47:00 +0100
Subject: [PATCH 1/6] Fix Mark As Unread in BG by introducing breaking changes

---
 .../ChannelController/ChannelController.swift | 160 ++++++++++--------
 .../Repositories/ChannelRepository.swift      |  12 +-
 .../StreamChat/Workers/ChannelUpdater.swift   |   2 +-
 .../ChatChannel/ChatChannelVC.swift           |  33 ++--
 4 files changed, 117 insertions(+), 90 deletions(-)

diff --git a/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift b/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
index d7b31463a47..00602624ae2 100644
--- a/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
+++ b/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
@@ -120,22 +120,12 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
     /// This is because we cannot calculate the accurate value until we have all he messages in memory.
     /// Paginate to get the most accurate value.
     public var firstUnreadMessageId: MessageId? {
-        getFirstUnreadMessageId()
+        getFirstUnreadMessageId(for: channel)
     }
 
     /// The id of the message which the current user last read.
     public var lastReadMessageId: MessageId? {
-        guard let currentUserRead = channel?.reads.first(where: {
-            $0.user.id == client.currentUserId
-        }) else {
-            return nil
-        }
-
-        guard let lastReadMessageId = currentUserRead.lastReadMessageId else {
-            return nil
-        }
-
-        return lastReadMessageId
+        channel?.lastReadMessageId(userId: client.currentUserId)
     }
 
     /// A boolean indicating if the user marked the channel as unread in the current session
@@ -909,22 +899,30 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
     /// - Parameters:
     ///   - messageId: The id of the first message id that will be marked as unread.
     ///   - completion: The completion will be called on a **callbackQueue** when the network request is finished.
-    public func markUnread(from messageId: MessageId, completion: ((Error?) -> Void)? = nil) {
+    public func markUnread(from messageId: MessageId, completion: ((Result<ChatChannel, Error>) -> Void)? = nil) {
         /// Perform action only if channel is already created on backend side and have a valid `cid`.
         guard let channel = channel else {
-            channelModificationFailed(completion)
+            let error = ClientError.ChannelNotCreatedYet()
+            log.error(error.localizedDescription)
+            callback {
+                completion?(.failure(error))
+            }
             return
         }
 
         /// Read events are not enabled for this channel
         guard channel.canReceiveReadEvents == true else {
-            channelFeatureDisabled(feature: "read events", completion: completion)
+            let error = ClientError.ChannelFeatureDisabled("Channel feature: read events is disabled for this channel.")
+            log.error(error.localizedDescription)
+            callback {
+                completion?(.failure(error))
+            }
             return
         }
 
         guard !markingRead, let currentUserId = client.currentUserId else {
             callback {
-                completion?(nil)
+                completion?(.success(channel))
             }
             return
         }
@@ -936,13 +934,13 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
             userId: currentUserId,
             from: messageId,
             lastReadMessageId: getLastReadMessageId(firstUnreadMessageId: messageId)
-        ) { [weak self] error in
+        ) { [weak self] result in
             self?.callback {
-                if error == nil {
+                if case .success = result {
                     self?.isMarkedAsUnread = true
                 }
                 self?.markingRead = false
-                completion?(error)
+                completion?(result)
             }
         }
     }
@@ -1219,6 +1217,60 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
         updater.deleteImage(in: cid, url: url, completion: completion)
     }
 
+    public func getFirstUnreadMessageId(for channel: ChatChannel?) -> MessageId? {
+        // Return the oldest regular message if all messages are unread in the message list.
+        let oldestRegularMessage: () -> MessageId? = { [weak self] in
+            guard self?.hasLoadedAllPreviousMessages == true else {
+                return nil
+            }
+            return self?.messages.last(where: { $0.type == .regular || $0.type == .reply })?.id
+        }
+
+        guard let currentUserRead = channel?.reads.first(where: {
+            $0.user.id == client.currentUserId
+        }) else {
+            return oldestRegularMessage()
+        }
+
+        // If there are no unreads, then return nil.
+        guard currentUserRead.unreadMessagesCount > 0 else {
+            return nil
+        }
+
+        // If there unreads but no `lastReadMessageId`, it means the whole message list is unread.
+        // So the top message (oldest one) is the first unread message id.
+        guard let lastReadMessageId = currentUserRead.lastReadMessageId else {
+            return oldestRegularMessage()
+        }
+
+        guard lastReadMessageId != messages.first?.id else {
+            return nil
+        }
+
+        guard let lastReadIndex = messages.firstIndex(where: { $0.id == lastReadMessageId }), lastReadIndex != 0 else {
+            // If there is a lastReadMessageId, and we loaded all messages, but can't find firstUnreadMessageId,
+            // then it means the lastReadMessageId is not reachable because the channel was truncated or hidden.
+            // So we return the oldest regular message already fetched.
+            if hasLoadedAllPreviousMessages {
+                return oldestRegularMessage()
+            }
+
+            return nil
+        }
+
+        let lookUpStartIndex = messages.index(before: lastReadIndex)
+
+        var id: MessageId?
+        for index in (0...lookUpStartIndex).reversed() {
+            let message = message(at: index)
+            guard message?.author.id != client.currentUserId, message?.deletedAt == nil else { continue }
+            id = message?.id
+            break
+        }
+
+        return id
+    }
+
     // MARK: - Internal
 
     func recoverWatchedChannel(completion: @escaping (Error?) -> Void) {
@@ -1507,60 +1559,6 @@ private extension ChatChannelController {
         return messageId(at: newLastReadMessageIndex)
     }
 
-    private func getFirstUnreadMessageId() -> MessageId? {
-        // Return the oldest regular message if all messages are unread in the message list.
-        let oldestRegularMessage: () -> MessageId? = { [weak self] in
-            guard self?.hasLoadedAllPreviousMessages == true else {
-                return nil
-            }
-            return self?.messages.last(where: { $0.type == .regular || $0.type == .reply })?.id
-        }
-
-        guard let currentUserRead = channel?.reads.first(where: {
-            $0.user.id == client.currentUserId
-        }) else {
-            return oldestRegularMessage()
-        }
-
-        // If there are no unreads, then return nil.
-        guard currentUserRead.unreadMessagesCount > 0 else {
-            return nil
-        }
-
-        // If there unreads but no `lastReadMessageId`, it means the whole message list is unread.
-        // So the top message (oldest one) is the first unread message id.
-        guard let lastReadMessageId = currentUserRead.lastReadMessageId else {
-            return oldestRegularMessage()
-        }
-
-        guard lastReadMessageId != messages.first?.id else {
-            return nil
-        }
-
-        guard let lastReadIndex = messages.firstIndex(where: { $0.id == lastReadMessageId }), lastReadIndex != 0 else {
-            // If there is a lastReadMessageId, and we loaded all messages, but can't find firstUnreadMessageId,
-            // then it means the lastReadMessageId is not reachable because the channel was truncated or hidden.
-            // So we return the oldest regular message already fetched.
-            if hasLoadedAllPreviousMessages {
-                return oldestRegularMessage()
-            }
-
-            return nil
-        }
-
-        let lookUpStartIndex = messages.index(before: lastReadIndex)
-
-        var id: MessageId?
-        for index in (0...lookUpStartIndex).reversed() {
-            let message = message(at: index)
-            guard message?.author.id != client.currentUserId, message?.deletedAt == nil else { continue }
-            id = message?.id
-            break
-        }
-
-        return id
-    }
-
     private func message(at index: Int) -> ChatMessage? {
         if !messages.indices.contains(index) {
             return nil
@@ -1678,3 +1676,19 @@ public extension ChatChannelController {
         }
     }
 }
+
+public extension ChatChannel {
+    func lastReadMessageId(userId: UserId?) -> MessageId? {
+        guard let currentUserRead = reads.first(where: {
+            $0.user.id == userId
+        }) else {
+            return nil
+        }
+
+        guard let lastReadMessageId = currentUserRead.lastReadMessageId else {
+            return nil
+        }
+
+        return lastReadMessageId
+    }
+}
diff --git a/Sources/StreamChat/Repositories/ChannelRepository.swift b/Sources/StreamChat/Repositories/ChannelRepository.swift
index f532febcf91..01924fb9acc 100644
--- a/Sources/StreamChat/Repositories/ChannelRepository.swift
+++ b/Sources/StreamChat/Repositories/ChannelRepository.swift
@@ -47,16 +47,17 @@ class ChannelRepository {
         userId: UserId,
         from messageId: MessageId,
         lastReadMessageId: MessageId?,
-        completion: ((Error?) -> Void)? = nil
+        completion: ((Result<ChatChannel, Error>) -> Void)? = nil
     ) {
         apiClient.request(
             endpoint: .markUnread(cid: cid, messageId: messageId, userId: userId)
         ) { [weak self] result in
             if let error = result.error {
-                completion?(error)
+                completion?(.failure(error))
                 return
             }
 
+            var channel: ChatChannel?
             self?.database.write({ session in
                 session.markChannelAsUnread(
                     for: cid,
@@ -66,8 +67,13 @@ class ChannelRepository {
                     lastReadAt: nil,
                     unreadMessagesCount: nil
                 )
+                channel = try session.channel(cid: cid)?.asModel()
             }, completion: { error in
-                completion?(error)
+                if let channel = channel, error == nil {
+                    completion?(.success(channel))
+                } else {
+                    completion?(.failure(error ?? ClientError.ChannelNotCreatedYet()))
+                }
             })
         }
     }
diff --git a/Sources/StreamChat/Workers/ChannelUpdater.swift b/Sources/StreamChat/Workers/ChannelUpdater.swift
index a0ee0542b1e..a960e93effe 100644
--- a/Sources/StreamChat/Workers/ChannelUpdater.swift
+++ b/Sources/StreamChat/Workers/ChannelUpdater.swift
@@ -441,7 +441,7 @@ class ChannelUpdater: Worker {
         userId: UserId,
         from messageId: MessageId,
         lastReadMessageId: MessageId?,
-        completion: ((Error?) -> Void)? = nil
+        completion: ((Result<ChatChannel, Error>) -> Void)? = nil
     ) {
         channelRepository.markUnread(
             for: cid,
diff --git a/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift b/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
index ac1047dc327..28cb9bbf72a 100644
--- a/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
+++ b/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
@@ -391,8 +391,10 @@ open class ChatChannelVC: _ViewController,
             }
         case is MarkUnreadActionItem:
             dismiss(animated: true) { [weak self] in
-                self?.channelController.markUnread(from: message.id) { _ in
-                    self?.updateAllUnreadMessagesRelatedComponents()
+                self?.channelController.markUnread(from: message.id) { result in
+                    if case let .success(channel) = result {
+                        self?.updateAllUnreadMessagesRelatedComponents(channel: channel)
+                    }
                 }
             }
         default:
@@ -576,27 +578,32 @@ private extension ChatChannelVC {
         )
     }
 
-    func updateAllUnreadMessagesRelatedComponents() {
-        updateScrollToBottomButtonCount()
-        updateJumpToUnreadRelatedComponents()
-        updateUnreadMessagesBannerRelatedComponents()
+    func updateAllUnreadMessagesRelatedComponents(channel: ChatChannel? = nil) {
+        let firstUnreadMessageId = channelController.getFirstUnreadMessageId(for: channel)
+        updateScrollToBottomButtonCount(channel: channel)
+        updateJumpToUnreadRelatedComponents(channel: channel)
+        updateUnreadMessagesBannerRelatedComponents(channel: channel)
     }
 
-    func updateScrollToBottomButtonCount() {
-        let channelUnreadCount = channelController.channel?.unreadCount ?? .noUnread
+    func updateScrollToBottomButtonCount(channel: ChatChannel? = nil) {
+        let channelUnreadCount = (channel ?? channelController.channel)?.unreadCount ?? .noUnread
         messageListVC.scrollToBottomButton.content = channelUnreadCount
     }
 
-    func updateJumpToUnreadRelatedComponents() {
+    func updateJumpToUnreadRelatedComponents(channel: ChatChannel? = nil) {
+        let firstUnreadMessageId = channelController.getFirstUnreadMessageId(for: channel) ?? channelController.firstUnreadMessageId
+        let lastReadMessageId = channel?.lastReadMessageId(userId: client.currentUserId) ?? channelController.lastReadMessageId
+
         messageListVC.updateJumpToUnreadMessageId(
-            channelController.firstUnreadMessageId,
-            lastReadMessageId: channelController.lastReadMessageId
+            firstUnreadMessageId,
+            lastReadMessageId: lastReadMessageId
         )
         messageListVC.updateJumpToUnreadButtonVisibility()
     }
 
-    func updateUnreadMessagesBannerRelatedComponents() {
-        firstUnreadMessageId = channelController.firstUnreadMessageId
+    func updateUnreadMessagesBannerRelatedComponents(channel: ChatChannel? = nil) {
+        let firstUnreadMessageId = channelController.getFirstUnreadMessageId(for: channel) ?? channelController.firstUnreadMessageId
+        self.firstUnreadMessageId = firstUnreadMessageId
         messageListVC.updateUnreadMessagesSeparator(at: firstUnreadMessageId)
     }
 }

From 652e303644d531561cef64b62d2b48befc91f218 Mon Sep 17 00:00:00 2001
From: Pol Quintana <pol.quintana1@gmail.com>
Date: Wed, 22 Nov 2023 15:15:01 +0100
Subject: [PATCH 2/6] Fix existing tests

---
 .../Repositories/ChannelRepository_Mock.swift |  6 ++--
 .../Workers/ChannelUpdater_Mock.swift         |  4 +--
 .../ChannelController_Tests.swift             | 36 +++++++++----------
 .../ChannelRepository_Tests.swift             | 16 ++++++---
 .../Workers/ChannelUpdater_Tests.swift        | 10 +++---
 5 files changed, 39 insertions(+), 33 deletions(-)

diff --git a/TestTools/StreamChatTestTools/Mocks/StreamChat/Repositories/ChannelRepository_Mock.swift b/TestTools/StreamChatTestTools/Mocks/StreamChat/Repositories/ChannelRepository_Mock.swift
index 539e2db6d72..123e9968e08 100644
--- a/TestTools/StreamChatTestTools/Mocks/StreamChat/Repositories/ChannelRepository_Mock.swift
+++ b/TestTools/StreamChatTestTools/Mocks/StreamChat/Repositories/ChannelRepository_Mock.swift
@@ -18,7 +18,7 @@ class ChannelRepository_Mock: ChannelRepository {
     var markUnreadUserId: UserId?
     var markUnreadMessageId: UserId?
     var markUnreadLastReadMessageId: UserId?
-    var markUnreadResult: Result<Void, Error>?
+    var markUnreadResult: Result<ChatChannel, Error>?
 
     override func markRead(cid: ChannelId, userId: UserId, completion: ((Error?) -> Void)? = nil) {
         markReadCid = cid
@@ -29,14 +29,14 @@ class ChannelRepository_Mock: ChannelRepository {
         }
     }
 
-    override func markUnread(for cid: ChannelId, userId: UserId, from messageId: MessageId, lastReadMessageId: MessageId?, completion: ((Error?) -> Void)? = nil) {
+    override func markUnread(for cid: ChannelId, userId: UserId, from messageId: MessageId, lastReadMessageId: MessageId?, completion: ((Result<ChatChannel, Error>) -> Void)? = nil) {
         markUnreadCid = cid
         markUnreadUserId = userId
         markUnreadMessageId = messageId
         markUnreadLastReadMessageId = lastReadMessageId
 
         markUnreadResult.map {
-            completion?($0.error)
+            completion?($0)
         }
     }
 }
diff --git a/TestTools/StreamChatTestTools/Mocks/StreamChat/Workers/ChannelUpdater_Mock.swift b/TestTools/StreamChatTestTools/Mocks/StreamChat/Workers/ChannelUpdater_Mock.swift
index 1ef73fb417e..c85e9fc6b2c 100644
--- a/TestTools/StreamChatTestTools/Mocks/StreamChat/Workers/ChannelUpdater_Mock.swift
+++ b/TestTools/StreamChatTestTools/Mocks/StreamChat/Workers/ChannelUpdater_Mock.swift
@@ -81,7 +81,7 @@ final class ChannelUpdater_Mock: ChannelUpdater {
     @Atomic var markUnread_userId: UserId?
     @Atomic var markUnread_messageId: MessageId?
     @Atomic var markUnread_lastReadMessageId: MessageId?
-    @Atomic var markUnread_completion: ((Error?) -> Void)?
+    @Atomic var markUnread_completion: ((Result<ChatChannel, Error>) -> Void)?
 
     @Atomic var enableSlowMode_cid: ChannelId?
     @Atomic var enableSlowMode_cooldownDuration: Int?
@@ -359,7 +359,7 @@ final class ChannelUpdater_Mock: ChannelUpdater {
         markRead_completion = completion
     }
 
-    override func markUnread(cid: ChannelId, userId: UserId, from messageId: MessageId, lastReadMessageId: MessageId?, completion: ((Error?) -> Void)? = nil) {
+    override func markUnread(cid: ChannelId, userId: UserId, from messageId: MessageId, lastReadMessageId: MessageId?, completion: ((Result<ChatChannel, Error>) -> Void)? = nil) {
         markUnread_cid = cid
         markUnread_userId = userId
         markUnread_messageId = messageId
diff --git a/Tests/StreamChatTests/Controllers/ChannelController/ChannelController_Tests.swift b/Tests/StreamChatTests/Controllers/ChannelController/ChannelController_Tests.swift
index d3e162435f9..649ebb11219 100644
--- a/Tests/StreamChatTests/Controllers/ChannelController/ChannelController_Tests.swift
+++ b/Tests/StreamChatTests/Controllers/ChannelController/ChannelController_Tests.swift
@@ -440,7 +440,7 @@ final class ChannelController_Tests: XCTestCase {
         let token = Token(rawValue: "", userId: userId, expiration: nil)
         controller.client.authenticationRepository.setMockToken(token)
 
-        try createChannel(oldestMessageId: oldestMessageId, newestMessageId: newestMessageId, channelReads: [channelRead])
+        createChannel(oldestMessageId: oldestMessageId, newestMessageId: newestMessageId, channelReads: [channelRead])
 
         try client.databaseContainer.writeSynchronously {
             try $0.saveCurrentUser(payload: .dummy(userId: userId, role: .user))
@@ -3958,8 +3958,8 @@ final class ChannelController_Tests: XCTestCase {
     func test_markUnread_whenChannelDoesNotExist() {
         var receivedError: Error?
         let expectation = self.expectation(description: "Mark Unread completes")
-        controller.markUnread(from: .unique) { error in
-            receivedError = error
+        controller.markUnread(from: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 
@@ -3979,8 +3979,8 @@ final class ChannelController_Tests: XCTestCase {
 
         var receivedError: Error?
         let expectation = self.expectation(description: "Mark Unread completes")
-        controller.markUnread(from: .unique) { error in
-            receivedError = error
+        controller.markUnread(from: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 
@@ -4034,8 +4034,8 @@ final class ChannelController_Tests: XCTestCase {
 
         var receivedError: Error?
         let expectation = self.expectation(description: "Mark Unread completes")
-        controller.markUnread(from: .unique) { error in
-            receivedError = error
+        controller.markUnread(from: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 
@@ -4055,8 +4055,8 @@ final class ChannelController_Tests: XCTestCase {
 
         var receivedError: Error?
         let expectation = self.expectation(description: "Mark Unread completes")
-        controller.markUnread(from: .unique) { error in
-            receivedError = error
+        controller.markUnread(from: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 
@@ -4076,12 +4076,12 @@ final class ChannelController_Tests: XCTestCase {
 
         var receivedError: Error?
         let expectation = self.expectation(description: "Mark Unread completes")
-        controller.markUnread(from: .unique) { error in
-            receivedError = error
+        controller.markUnread(from: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
         let mockedError = TestError()
-        env.channelUpdater?.markUnread_completion?(mockedError)
+        env.channelUpdater?.markUnread_completion?(.failure(mockedError))
 
         waitForExpectations(timeout: defaultTimeout)
 
@@ -4100,13 +4100,13 @@ final class ChannelController_Tests: XCTestCase {
         var receivedError: Error?
         let messageId = MessageId.unique
         let expectation = self.expectation(description: "Mark Unread completes")
-        controller.markUnread(from: messageId) { error in
-            receivedError = error
+        controller.markUnread(from: messageId) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
         let updater = try XCTUnwrap(env.channelUpdater)
 
-        updater.markUnread_completion?(nil)
+        updater.markUnread_completion?(.success(ChatChannel.mock(cid: .unique)))
 
         waitForExpectations(timeout: defaultTimeout)
 
@@ -4130,13 +4130,13 @@ final class ChannelController_Tests: XCTestCase {
 
         var receivedError: Error?
         let expectation = self.expectation(description: "Mark Unread completes")
-        controller.markUnread(from: messageId) { error in
-            receivedError = error
+        controller.markUnread(from: messageId) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
         let updater = try XCTUnwrap(env.channelUpdater)
 
-        updater.markUnread_completion?(nil)
+        updater.markUnread_completion?(.success(ChatChannel.mock(cid: .unique)))
 
         waitForExpectations(timeout: defaultTimeout)
 
diff --git a/Tests/StreamChatTests/Repositories/ChannelRepository_Tests.swift b/Tests/StreamChatTests/Repositories/ChannelRepository_Tests.swift
index a46f3aa68e1..b4d0a44d61a 100644
--- a/Tests/StreamChatTests/Repositories/ChannelRepository_Tests.swift
+++ b/Tests/StreamChatTests/Repositories/ChannelRepository_Tests.swift
@@ -72,15 +72,21 @@ final class ChannelRepository_Tests: XCTestCase {
 
     // MARK: - Mark as unread
 
-    func test_markUnread_successfulResponse() {
+    func test_markUnread_successfulResponse() throws {
         let cid = ChannelId.unique
         let userId = UserId.unique
         let messageId = MessageId.unique
 
+        try database.createCurrentUser()
+        try database.writeSynchronously {
+            try $0.saveChannel(payload: .dummy(channel: .dummy(cid: cid)))
+        }
+        database.writeSessionCounter = 0
+
         let expectation = self.expectation(description: "markUnread completes")
         var receivedError: Error?
-        repository.markUnread(for: cid, userId: userId, from: messageId, lastReadMessageId: .unique) { error in
-            receivedError = error
+        repository.markUnread(for: cid, userId: userId, from: messageId, lastReadMessageId: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 
@@ -100,8 +106,8 @@ final class ChannelRepository_Tests: XCTestCase {
 
         let expectation = self.expectation(description: "markUnread completes")
         var receivedError: Error?
-        repository.markUnread(for: cid, userId: userId, from: messageId, lastReadMessageId: .unique) { error in
-            receivedError = error
+        repository.markUnread(for: cid, userId: userId, from: messageId, lastReadMessageId: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 
diff --git a/Tests/StreamChatTests/Workers/ChannelUpdater_Tests.swift b/Tests/StreamChatTests/Workers/ChannelUpdater_Tests.swift
index e5609715731..13554772ed8 100644
--- a/Tests/StreamChatTests/Workers/ChannelUpdater_Tests.swift
+++ b/Tests/StreamChatTests/Workers/ChannelUpdater_Tests.swift
@@ -1472,9 +1472,9 @@ final class ChannelUpdater_Tests: XCTestCase {
         let expectation = self.expectation(description: "markUnread completes")
         var receivedError: Error?
 
-        channelRepository.markUnreadResult = .success(())
-        channelUpdater.markUnread(cid: .unique, userId: .unique, from: .unique, lastReadMessageId: .unique) { error in
-            receivedError = error
+        channelRepository.markUnreadResult = .success(.mock(cid: .unique))
+        channelUpdater.markUnread(cid: .unique, userId: .unique, from: .unique, lastReadMessageId: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 
@@ -1488,8 +1488,8 @@ final class ChannelUpdater_Tests: XCTestCase {
         var receivedError: Error?
 
         channelRepository.markUnreadResult = .failure(mockedError)
-        channelUpdater.markUnread(cid: .unique, userId: .unique, from: .unique, lastReadMessageId: .unique) { error in
-            receivedError = error
+        channelUpdater.markUnread(cid: .unique, userId: .unique, from: .unique, lastReadMessageId: .unique) { result in
+            receivedError = result.error
             expectation.fulfill()
         }
 

From dcae26ad4f727b4fd929e4e2dde34f51fa53549d Mon Sep 17 00:00:00 2001
From: Pol Quintana <pol.quintana1@gmail.com>
Date: Wed, 22 Nov 2023 16:03:39 +0100
Subject: [PATCH 3/6] Add tests for ChatChannel.lastReadMessageId

---
 .../ChannelController/ChannelController.swift |  4 +--
 .../Models/ChatChannel_Tests.swift            | 30 +++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift b/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
index 00602624ae2..57bae8d71d6 100644
--- a/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
+++ b/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
@@ -125,7 +125,7 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
 
     /// The id of the message which the current user last read.
     public var lastReadMessageId: MessageId? {
-        channel?.lastReadMessageId(userId: client.currentUserId)
+        client.currentUserId.flatMap { channel?.lastReadMessageId(userId: $0) }
     }
 
     /// A boolean indicating if the user marked the channel as unread in the current session
@@ -1678,7 +1678,7 @@ public extension ChatChannelController {
 }
 
 public extension ChatChannel {
-    func lastReadMessageId(userId: UserId?) -> MessageId? {
+    func lastReadMessageId(userId: UserId) -> MessageId? {
         guard let currentUserRead = reads.first(where: {
             $0.user.id == userId
         }) else {
diff --git a/Tests/StreamChatTests/Models/ChatChannel_Tests.swift b/Tests/StreamChatTests/Models/ChatChannel_Tests.swift
index f3d3aff79f1..7efaa4d41e1 100644
--- a/Tests/StreamChatTests/Models/ChatChannel_Tests.swift
+++ b/Tests/StreamChatTests/Models/ChatChannel_Tests.swift
@@ -285,6 +285,36 @@ final class ChatChannel_Tests: XCTestCase {
         XCTAssertEqual(channelWithoutCapability.isSlowMode, false)
     }
 
+    func test_lastReadMessageId_readsDontContainUser() {
+        let userId: UserId = "current"
+        let channel = ChatChannel.mock(cid: .unique, reads: [
+            .init(lastReadAt: Date(), lastReadMessageId: .unique, unreadMessagesCount: 3, user: .mock(id: "other"))
+        ])
+
+        XCTAssertNil(channel.lastReadMessageId(userId: userId))
+    }
+
+    func test_lastReadMessageId_userReadDoesNotHaveLastRead() {
+        let userId: UserId = "current"
+        let channel = ChatChannel.mock(cid: .unique, reads: [
+            .init(lastReadAt: Date(), lastReadMessageId: nil, unreadMessagesCount: 3, user: .mock(id: userId)),
+            .init(lastReadAt: Date(), lastReadMessageId: .unique, unreadMessagesCount: 3, user: .mock(id: "other"))
+        ])
+
+        XCTAssertNil(channel.lastReadMessageId(userId: userId))
+    }
+
+    func test_lastReadMessageId_userReadHasLastRead() {
+        let userId: UserId = "current"
+        let lastReadId = MessageId.unique
+        let channel = ChatChannel.mock(cid: .unique, reads: [
+            .init(lastReadAt: Date(), lastReadMessageId: lastReadId, unreadMessagesCount: 3, user: .mock(id: userId)),
+            .init(lastReadAt: Date(), lastReadMessageId: .unique, unreadMessagesCount: 3, user: .mock(id: "other"))
+        ])
+
+        XCTAssertEqual(channel.lastReadMessageId(userId: userId), lastReadId)
+    }
+
     private func setupChannel(withCapabilities capabilities: Set<ChannelCapability>) -> ChatChannel {
         .mock(
             cid: .unique,

From c0228db3b8fa8b079d1f485d1eb9721a11cdd0b6 Mon Sep 17 00:00:00 2001
From: Pol Quintana <pol.quintana1@gmail.com>
Date: Wed, 22 Nov 2023 16:16:58 +0100
Subject: [PATCH 4/6] Fix compilation issue

---
 Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift b/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
index 28cb9bbf72a..7efc9c0bc13 100644
--- a/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
+++ b/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
@@ -579,7 +579,6 @@ private extension ChatChannelVC {
     }
 
     func updateAllUnreadMessagesRelatedComponents(channel: ChatChannel? = nil) {
-        let firstUnreadMessageId = channelController.getFirstUnreadMessageId(for: channel)
         updateScrollToBottomButtonCount(channel: channel)
         updateJumpToUnreadRelatedComponents(channel: channel)
         updateUnreadMessagesBannerRelatedComponents(channel: channel)
@@ -592,7 +591,7 @@ private extension ChatChannelVC {
 
     func updateJumpToUnreadRelatedComponents(channel: ChatChannel? = nil) {
         let firstUnreadMessageId = channelController.getFirstUnreadMessageId(for: channel) ?? channelController.firstUnreadMessageId
-        let lastReadMessageId = channel?.lastReadMessageId(userId: client.currentUserId) ?? channelController.lastReadMessageId
+        let lastReadMessageId = client.currentUserId.flatMap { channel?.lastReadMessageId(userId: $0) } ?? channelController.lastReadMessageId
 
         messageListVC.updateJumpToUnreadMessageId(
             firstUnreadMessageId,

From 588edb448133c25dc3760d37ea65119a1cd0ab00 Mon Sep 17 00:00:00 2001
From: Pol Quintana <pol.quintana1@gmail.com>
Date: Wed, 22 Nov 2023 17:53:05 +0100
Subject: [PATCH 5/6] Make sure we don't fallback into oldestRegularMessageId
 if channel is nil

---
 .../Controllers/ChannelController/ChannelController.swift   | 6 +++---
 Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift        | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift b/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
index 57bae8d71d6..784c18745b1 100644
--- a/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
+++ b/Sources/StreamChat/Controllers/ChannelController/ChannelController.swift
@@ -120,7 +120,7 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
     /// This is because we cannot calculate the accurate value until we have all he messages in memory.
     /// Paginate to get the most accurate value.
     public var firstUnreadMessageId: MessageId? {
-        getFirstUnreadMessageId(for: channel)
+        channel.flatMap { getFirstUnreadMessageId(for: $0) }
     }
 
     /// The id of the message which the current user last read.
@@ -1217,7 +1217,7 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
         updater.deleteImage(in: cid, url: url, completion: completion)
     }
 
-    public func getFirstUnreadMessageId(for channel: ChatChannel?) -> MessageId? {
+    public func getFirstUnreadMessageId(for channel: ChatChannel) -> MessageId? {
         // Return the oldest regular message if all messages are unread in the message list.
         let oldestRegularMessage: () -> MessageId? = { [weak self] in
             guard self?.hasLoadedAllPreviousMessages == true else {
@@ -1226,7 +1226,7 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
             return self?.messages.last(where: { $0.type == .regular || $0.type == .reply })?.id
         }
 
-        guard let currentUserRead = channel?.reads.first(where: {
+        guard let currentUserRead = channel.reads.first(where: {
             $0.user.id == client.currentUserId
         }) else {
             return oldestRegularMessage()
diff --git a/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift b/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
index 7efc9c0bc13..f284a23ae93 100644
--- a/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
+++ b/Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift
@@ -590,7 +590,7 @@ private extension ChatChannelVC {
     }
 
     func updateJumpToUnreadRelatedComponents(channel: ChatChannel? = nil) {
-        let firstUnreadMessageId = channelController.getFirstUnreadMessageId(for: channel) ?? channelController.firstUnreadMessageId
+        let firstUnreadMessageId = channel.flatMap { channelController.getFirstUnreadMessageId(for: $0) } ?? channelController.firstUnreadMessageId
         let lastReadMessageId = client.currentUserId.flatMap { channel?.lastReadMessageId(userId: $0) } ?? channelController.lastReadMessageId
 
         messageListVC.updateJumpToUnreadMessageId(
@@ -601,7 +601,7 @@ private extension ChatChannelVC {
     }
 
     func updateUnreadMessagesBannerRelatedComponents(channel: ChatChannel? = nil) {
-        let firstUnreadMessageId = channelController.getFirstUnreadMessageId(for: channel) ?? channelController.firstUnreadMessageId
+        let firstUnreadMessageId = channel.flatMap { channelController.getFirstUnreadMessageId(for: $0) } ?? channelController.firstUnreadMessageId
         self.firstUnreadMessageId = firstUnreadMessageId
         messageListVC.updateUnreadMessagesSeparator(at: firstUnreadMessageId)
     }

From e9c1ef1f5512a990fc2198309ebe44296d97effc Mon Sep 17 00:00:00 2001
From: Pol Quintana <pol.quintana1@gmail.com>
Date: Thu, 23 Nov 2023 16:21:14 +0100
Subject: [PATCH 6/6] Update CHANGELOG

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d4445a5eb18..68abb659c5c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,9 +3,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 # Upcoming
 
+## StreamChatUI
 ### 🐞 Fixed
 - Fix skip slow mode capability not handled [#2904](https://github.com/GetStream/stream-chat-swift/pull/2904)
 
+### 🔄 Changed
+- `ChannelController.markUnread`'s `completion`'s argument is now a `(Result<ChatChannel, Error>` instead of `Error?`
+
 # [4.43.0](https://github.com/GetStream/stream-chat-swift/releases/tag/4.43.0)
 _November 17, 2023_