Release fix: Truncation related fixes for mark as/jump to unread (#2806)

* Reset read for truncated messages

* Allow automatic marking as read when discarding unread messages

* Make sure we can mark as read if the last message was seen or is currently on screen

Author: polqf

Sources/StreamChat/Controllers/ChannelController/ChannelController.swift

@@ -861,6 +861,7 @@ public class ChatChannelController: DataController, DelegateCallable, DataStoreP
         updater.markRead(cid: channel.cid, userId: currentUserId) { error in
             self.callback {
                 self.markingRead = false
+                self.isMarkedAsUnread = false
                 completion?(error)
             }
         }

Sources/StreamChat/WebSocketClient/EventMiddlewares/ChannelTruncatedEventMiddleware.swift

@@ -14,10 +14,18 @@ struct ChannelTruncatedEventMiddleware: EventMiddleware {
         }
 
         do {
-            if let channelDTO = session.channel(cid: truncatedEvent.channel.cid) {
-                channelDTO.truncatedAt = truncatedEvent.channel.truncatedAt?.bridgeDate
-            } else {
-                throw ClientError.ChannelDoesNotExist(cid: truncatedEvent.channel.cid)
+            let cid = truncatedEvent.channel.cid
+            guard let channelDTO = session.channel(cid: cid) else {
+                throw ClientError.ChannelDoesNotExist(cid: cid)
+            }
+
+            channelDTO.truncatedAt = truncatedEvent.channel.truncatedAt?.bridgeDate
+
+            // Until BE returns valid values for user's read after truncation, we are clearing them.
+            if let userId = truncatedEvent.user?.id, let read = session.loadChannelRead(cid: cid, userId: userId) {
+                read.lastReadMessageId = nil
+                read.lastReadAt = truncatedEvent.channel.truncatedAt?.bridgeDate ?? DBDate()
+                read.unreadMessageCount = 0
             }
         } catch {
             log.error("Failed to write the `truncatedAt` field update in the database, error: \(error)")

Sources/StreamChatUI/ChatChannel/ChatChannelVC.swift

@@ -90,7 +90,11 @@ open class ChatChannelVC: _ViewController,
             return false
         }
 
-        return hasSeenLastMessage && hasSeenFirstUnreadMessage && channelController.hasLoadedAllNextMessages && !hasMarkedMessageAsUnread
+        return isLastMessageVisibleOrSeen && hasSeenFirstUnreadMessage && channelController.hasLoadedAllNextMessages && !hasMarkedMessageAsUnread
+    }
+
+    private var isLastMessageVisibleOrSeen: Bool {
+        hasSeenLastMessage || isLastMessageFullyVisible
     }
 
     /// A component responsible to handle when to load new or old messages.
@@ -106,7 +110,7 @@ open class ChatChannelVC: _ViewController,
     /// Determines whether first unread message has been seen
     private var hasSeenFirstUnreadMessage: Bool = false
 
-    /// Determines whether last cell has been seen
+    /// Determines whether last cell has been seen since the last time it was marked as read
     private var hasSeenLastMessage: Bool = false
 
     /// The id of the first unread message

Sources/StreamChatUI/ChatMessageList/ChatMessageListVC.swift

@@ -1039,8 +1039,6 @@ private extension ChatMessageListVC {
                 self?.adjustContentOffset(oldContentOffset: oldContentOffset, oldContentSize: oldContentSize)
             }
 
-            self?.updateScrollDependentButtonsVisibility()
-
             UIView.performWithoutAnimation {
                 self?.scrollToBottomIfNeeded(with: changes, newestChange: newestChange)
                 self?.reloadMovedMessage(newestChange: newestChange)