[BUG] Fixed problem with unread marker wrongly positioned

Rocket.Chat/Controllers/Chat/MessagesViewController.swift

@@ -54,12 +54,15 @@ final class MessagesViewController: RocketChatViewController {
     var emptyStateImageView: UIImageView?
     var documentController: UIDocumentInteractionController?
 
+    var unmanagedSubscription: UnmanagedSubscription?
     var subscription: Subscription! {
         didSet {
             let sub: Subscription? = subscription
+            let unmanaged = sub?.unmanaged
 
             viewModel.subscription = sub
-            viewSubscriptionModel.subscription = sub?.unmanaged
+            viewSubscriptionModel.subscription = unmanaged
+            unmanagedSubscription = unmanaged
 
             recoverDraftMessage()
             updateEmptyState()
@@ -161,6 +164,7 @@ final class MessagesViewController: RocketChatViewController {
 
             // Update dataset with the new data normalized
             self.updateData(with: self.viewModel.dataNormalized)
+            self.markAsRead()
         }
 
         viewSubscriptionModel.onDataChanged = { [weak self] in
@@ -389,7 +393,7 @@ final class MessagesViewController: RocketChatViewController {
     // MARK: Reading Status
 
     private func markAsRead() {
-        guard let subscription = viewModel.subscription?.validated()?.unmanaged else { return }
+        guard let subscription = unmanagedSubscription else { return }
         API.current()?.client(SubscriptionsClient.self).markAsRead(subscription: subscription)
     }
 

Rocket.Chat/Controllers/Chat/MessagesViewModel.swift

@@ -36,7 +36,7 @@ final class MessagesViewModel {
     internal var subscription: Subscription? {
         didSet {
             guard let subscription = subscription?.validated() else { return }
-            lastSeen = subscription.lastSeen ?? Date()
+            lastSeen = lastSeen == nil ? subscription.lastSeen : lastSeen
             subscribe(for: subscription)
             messagesQuery = subscription.fetchMessagesQueryResults()
             messagesQueryToken = messagesQuery?.observe(handleDataUpdates)
@@ -59,8 +59,9 @@ final class MessagesViewModel {
     /**
      Last time user read the messages from the Subscription from this view model.
      */
-    internal var lastSeen = Date()
+    internal var lastSeen: Date?
     internal var hasUnreadMarker = false
+    internal var unreadMarkerObjectIdentifier: String?
 
     /**
      If the view model is requesting new data from the API.
@@ -391,6 +392,7 @@ final class MessagesViewModel {
                 self?.cacheDataSorted()
             }
 
+            self?.markUnreadMarkerIfNeeded()
             self?.normalizeDataSorted()
 
             if shouldUpdateUI {
@@ -415,23 +417,47 @@ final class MessagesViewModel {
         }
     }
 
+    /**
+     This method will mark the unread marker position
+     for this subscription state and won't change until
+     the user leaves the room.
+     */
+    internal func markUnreadMarkerIfNeeded() {
+        // Unread marker will remain on the same message
+        // all the time until user closes the screen.
+        if unreadMarkerObjectIdentifier == nil {
+            if let lastSeen = lastSeen {
+                for object in dataSorted.reversed() {
+                    guard let messageSection1 = object.object.base as? MessageSectionModel else { continue }
+
+                    let message = messageSection1.message
+                    let unreadMarker = !hasUnreadMarker && message.createdAt > lastSeen
+
+                    if unreadMarker {
+                        unreadMarkerObjectIdentifier = message.identifier
+                        hasUnreadMarker = true
+                        break
+                    }
+                }
+            }
+        }
+    }
+
     /**
      Anything related to the section that refers to sequential messages, day separators
      and unread marks is done on this method. A loop in the whole list of messages
      is executed on every update to make sure that there's no duplicated separators
      and everything looks good to the user on the final result.
      */
     internal func normalizeDataSorted() {
-        hasUnreadMarker = false
-
         let dataSortedMaxIndex = dataSorted.count - 1
 
         for (idx, object) in dataSorted.enumerated() {
             guard let messageSection1 = object.object.base as? MessageSectionModel else { continue }
 
             let message = messageSection1.message
             let collpsibleItemsState = (object.base as? MessageSection)?.collapsibleItemsState ?? [:]
-            let unreadMarker = !hasUnreadMarker && message.createdAt > lastSeen
+
             var separator: Date?
             var sequential = false
             var loader = false
@@ -449,7 +475,7 @@ final class MessagesViewModel {
                 message: message,
                 daySeparator: separator,
                 sequential: sequential,
-                unreadIndicator: unreadMarker,
+                unreadIndicator: unreadMarkerObjectIdentifier == message.identifier,
                 loader: loader,
                 header: header
             )
@@ -469,10 +495,6 @@ final class MessagesViewModel {
             // Cache the processed result of the message text
             // on this loop to avoid doing that in the main thread.
             MessageTextCacheManager.shared.message(for: message, with: currentTheme)
-
-            if unreadMarker {
-                hasUnreadMarker = true
-            }
         }
 
         dataNormalized = dataSorted.map({ ArraySection(model: $0, elements: $0.viewModels()) })

Rocket.ChatTests/Controllers/MessagesViewModelSpec.swift

@@ -115,9 +115,15 @@ final class MessagesViewModelSpec: XCTestCase {
     func testUnreadMarkerPresenceTrue() {
         let model = MessagesViewModel()
 
+        let first = Message.testInstance()
+        first.identifier = "message-identifier-1"
+
+        let second = Message.testInstance()
+        second.identifier = "message-identifier-2"
+
         guard
-            let messageFirst = Message.testInstance().validated()?.unmanaged,
-            var messageSecond = Message.testInstance().validated()?.unmanaged
+            let messageFirst = first.validated()?.unmanaged,
+            var messageSecond = second.validated()?.unmanaged
         else {
             return XCTFail("messages must be created")
         }
@@ -128,6 +134,7 @@ final class MessagesViewModelSpec: XCTestCase {
             model.lastSeen = Date().addingTimeInterval(-500)
             model.data = [section1, section2]
             model.cacheDataSorted()
+            model.markUnreadMarkerIfNeeded()
             model.normalizeDataSorted()
         }