unreads [nfc]: Enhance performance in _isPresentInStreams

Author: Khader-1

lib/model/unreads.dart

@@ -257,7 +257,7 @@ class Unreads extends ChangeNotifier {
     final bool isRead = event.flags.contains(MessageFlag.read);
     assert(() {
       if (!oldUnreadsMissing && !event.messageIds.every((messageId) {
-        final isUnreadLocally = _slowIsPresentInDms(messageId) || _slowIsPresentInStreams(messageId);
+        final isUnreadLocally = _slowIsPresentInDms(messageId) || _isPresentInStreams(messageId);
         return isUnreadLocally == !isRead;
       })) {
         // If this happens, then either:
@@ -333,7 +333,7 @@ class Unreads extends ChangeNotifier {
           case UpdateMessageFlagsAddEvent():
             mentions.addAll(
               event.messages.where(
-                (messageId) => _slowIsPresentInStreams(messageId) || _slowIsPresentInDms(messageId),
+                (messageId) => _isPresentInStreams(messageId) || _slowIsPresentInDms(messageId),
               ),
             );
 
@@ -432,13 +432,8 @@ class Unreads extends ChangeNotifier {
     notifyListeners();
   }
 
-  // TODO use efficient lookups
-  bool _slowIsPresentInStreams(int messageId) {
-    return streams.values.any(
-      (topics) => topics.values.any(
-        (messageIds) => messageIds.contains(messageId),
-      ),
-    );
+  bool _isPresentInStreams(int messageId) {
+    return _reverseStreamsLookup.containsKey(messageId);
   }
 
   void _addLastInStreamTopic(int messageId, int streamId, String topic) {