msglist: Add message to mentions if mentioned

Fixes: zulip#649

Author: Khader-1

lib/model/store.dart

@@ -375,7 +375,7 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
   @override
   void reconcileMessages(List<Message> messages) {
     _messages.reconcileMessages(messages);
-    // TODO(#649) notify [unreads] of the just-fetched messages
+    unreads.onMessagesFetched(messages);
     // TODO(#650) notify [recentDmConversationsView] of the just-fetched messages
   }
 

lib/model/unreads.dart

@@ -32,8 +32,6 @@ import 'channel.dart';
 /// unsubscribed streams and messages sent by muted users.
 // TODO When [oldUnreadsMissing], if you load a message list with very old unreads,
 //   sync to those unreads, because the user has shown an interest in them.
-// TODO When loading a message list with stream messages, check all the stream
-//   messages and refresh [mentions] (see [mentions] dartdoc).
 class Unreads extends ChangeNotifier {
   factory Unreads({
     required UnreadMessagesSnapshot initial,
@@ -103,7 +101,7 @@ class Unreads extends ChangeNotifier {
   ///   a) the message is edited at all ([UpdateMessageEvent]),
   ///      assuming it still has a direct or wildcard mention after the edit, or
   ///   b) the message gains a direct @-mention ([UpdateMessageFlagsEvent]), or
-  ///   c) TODO unimplemented: the user loads the message in the message list
+  ///   c) the user loads the message in the message list
   /// But otherwise, assume its unread state remains unknown to [mentions].
   ///
   /// [1] This item applies verbatim at Server 8.0+. For older servers, the
@@ -236,6 +234,19 @@ class Unreads extends ChangeNotifier {
     notifyListeners();
   }
 
+  void onMessagesFetched(List<Message> messages) {
+    messages.forEach(_addMessageToMentionsIfMentioned);
+  }
+
+  void _addMessageToMentionsIfMentioned(Message message) {
+    if (message.flags.contains(MessageFlag.read)) return;
+    if (!message.flags.contains(MessageFlag.mentioned)
+      && !message.flags.contains(MessageFlag.wildcardMentioned)) return;
+
+    mentions.add(message.id);
+  }
+
+
   void handleUpdateMessageEvent(UpdateMessageEvent event) {
     final messageId = event.messageId;
 

test/model/unreads_test.dart

@@ -240,6 +240,23 @@ void main() {
     });
   });
 
+  group('onMessagesFetched', () {
+    test('messages are added to mentions when they are not read and include mention', () async {
+      final stream = eg.stream();
+      prepare();
+      await channelStore.addStream(stream);
+      check(model.mentions).isEmpty();
+      fillWithMessages([
+        eg.streamMessage(stream: stream, flags: []),
+        eg.streamMessage(stream: stream, flags: [MessageFlag.mentioned, MessageFlag.read]),
+        eg.streamMessage(stream: stream, flags: [MessageFlag.mentioned]),
+        eg.streamMessage(stream: stream, flags: [MessageFlag.wildcardMentioned]),
+      ]);
+
+      check(model.mentions.length).equals(2);
+    });
+  });
+
   group('handleMessageEvent', () {
     for (final (isUnread, isStream, isDirectMentioned, isWildcardMentioned) in [
       (true,  true,  true,  true ),