fix(ui): microseconds diffs result in wrong unread indicator (#1932)

Take into account the lastReadMessageId property

Author: esarbanis

packages/stream_chat_flutter/CHANGELOG.md

@@ -3,6 +3,9 @@
 ✅ Added
 - Added `VoiceRecordingAttachmentBuilder`, for displaying voice recording attachments in the chat.
 
+🐞 Fixed
+- Fixed wrong calculation of the last unread message indicator.
+
 ## 7.2.0-hotfix.1
 
   🔄 Changed

packages/stream_chat_flutter/lib/src/message_list_view/message_list_view.dart

@@ -520,17 +520,7 @@ class _StreamMessageListViewState extends State<StreamMessageListView> {
   Widget _buildListView(List<Message> data) {
     messages = data;
 
-    if (_userRead != null &&
-        messages.isNotEmpty &&
-        messages.first.createdAt.isAfter(_userRead!.lastRead) &&
-        messages.last.createdAt.isBefore(_userRead!.lastRead)) {
-      _oldestUnreadMessage = messages.lastWhereOrNull(
-        (it) =>
-            it.user?.id !=
-                streamChannel?.channel.client.state.currentUser?.id &&
-            it.createdAt.compareTo(_userRead!.lastRead) > 0,
-      );
-    }
+    _oldestUnreadMessage = messages.lastUnreadMessage(_userRead);
 
     for (var index = 0; index < messages.length; index++) {
       messagesIndex[messages[index].id] = index;

packages/stream_chat_flutter/lib/src/utils/extensions.dart

@@ -1,6 +1,7 @@
 import 'dart:io';
 import 'dart:math';
 
+import 'package:collection/collection.dart';
 import 'package:diacritic/diacritic.dart';
 import 'package:file_picker/file_picker.dart';
 import 'package:flutter/foundation.dart';
@@ -563,3 +564,29 @@ extension OriginalSizeX on Attachment {
     return Size(width.toDouble(), height.toDouble());
   }
 }
+
+/// Useful extensions on [List<Message>].
+extension MessageListX on Iterable<Message> {
+  /// Returns the last unread message in the list.
+  /// Returns null if the list is empty or the userRead is null.
+  ///
+  /// The [userRead] is the last read message by the user.
+  ///
+  /// The last unread message is the last message in the list that is not
+  /// sent by the current user and is sent after the last read message.
+  Message? lastUnreadMessage(Read? userRead) {
+    if (isEmpty || userRead == null) return null;
+
+    if (first.createdAt.isAfter(userRead.lastRead) &&
+        last.createdAt.isBefore(userRead.lastRead)) {
+      return lastWhereOrNull(
+        (it) =>
+            it.user?.id != userRead.user.id &&
+            it.id != userRead.lastReadMessageId &&
+            it.createdAt.compareTo(userRead.lastRead) > 0,
+      );
+    }
+
+    return null;
+  }
+}

packages/stream_chat_flutter/test/src/utils/extension_test.dart

@@ -270,4 +270,124 @@ void main() {
       expect(modifiedMessage.text, isNot(contains('@Alice')));
     });
   });
+
+  group('Message List Extension Tests', () {
+    group('lastUnreadMessage', () {
+      test('should return null when list is empty', () {
+        final messages = <Message>[];
+        final userRead = Read(
+          lastRead: DateTime.now(),
+          user: User(id: 'user1'),
+        );
+        expect(messages.lastUnreadMessage(userRead), isNull);
+      });
+
+      test('should return null when userRead is null', () {
+        final messages = <Message>[
+          Message(id: '1'),
+          Message(id: '2'),
+        ];
+        expect(messages.lastUnreadMessage(null), isNull);
+      });
+
+      test('should return null when all messages are read', () {
+        final lastRead = DateTime.now();
+        final messages = <Message>[
+          Message(
+              id: '1',
+              createdAt: lastRead.subtract(const Duration(seconds: 1))),
+          Message(id: '2', createdAt: lastRead),
+        ];
+        final userRead = Read(
+          lastRead: lastRead,
+          user: User(id: 'user1'),
+        );
+        expect(messages.lastUnreadMessage(userRead), isNull);
+      });
+
+      test('should return null when all messages are mine', () {
+        final lastRead = DateTime.now();
+        final userRead = Read(
+          lastRead: lastRead,
+          user: User(id: 'user1'),
+        );
+        final messages = <Message>[
+          Message(
+              id: '1',
+              user: userRead.user,
+              createdAt: lastRead.add(const Duration(seconds: 1))),
+          Message(id: '2', user: userRead.user, createdAt: lastRead),
+        ];
+        expect(messages.lastUnreadMessage(userRead), isNull);
+      });
+
+      test('should return the message', () {
+        final lastRead = DateTime.now();
+        final otherUser = User(id: 'user2');
+        final userRead = Read(
+          lastRead: lastRead,
+          user: User(id: 'user1'),
+        );
+
+        final messages = <Message>[
+          Message(
+            id: '1',
+            user: otherUser,
+            createdAt: lastRead.add(const Duration(seconds: 2)),
+          ),
+          Message(
+            id: '2',
+            user: otherUser,
+            createdAt: lastRead.add(const Duration(seconds: 1)),
+          ),
+          Message(
+            id: '3',
+            user: otherUser,
+            createdAt: lastRead.subtract(const Duration(seconds: 1)),
+          ),
+        ];
+
+        final lastUnreadMessage = messages.lastUnreadMessage(userRead);
+        expect(lastUnreadMessage, isNotNull);
+        expect(lastUnreadMessage!.id, '2');
+      });
+
+      test('should not return the last message read', () {
+        final lastRead = DateTime.timestamp();
+        final otherUser = User(id: 'user2');
+        final userRead = Read(
+          lastRead: lastRead,
+          user: User(id: 'user1'),
+          lastReadMessageId: '3',
+        );
+
+        final messages = <Message>[
+          Message(
+            id: '1',
+            user: otherUser,
+            createdAt: lastRead.add(const Duration(seconds: 2)),
+          ),
+          Message(
+            id: '2',
+            user: otherUser,
+            createdAt: lastRead.add(const Duration(milliseconds: 1)),
+          ),
+          Message(
+            id: '3',
+            user: otherUser,
+            createdAt: lastRead.add(const Duration(microseconds: 1)),
+          ),
+          Message(
+            id: '4',
+            user: otherUser,
+            createdAt: lastRead.subtract(const Duration(seconds: 1)),
+          ),
+        ];
+
+        final lastUnreadMessage = messages.lastUnreadMessage(userRead);
+        expect(lastUnreadMessage, isNotNull);
+        expect(lastUnreadMessage!.id, '2');
+      });
+    });
+  });
 }