unreads: Handle updates when there are moved messages

Signed-off-by: Zixuan James Li <zixuan@zulip.com>

Author: PIG208

lib/model/unreads.dart

@@ -296,13 +296,38 @@ class Unreads extends ChangeNotifier {
         madeAnyUpdate |= mentions.add(messageId);
     }
 
-    // TODO(#901) handle moved messages
+    madeAnyUpdate |= _handleMessageMove(event);
 
     if (madeAnyUpdate) {
       notifyListeners();
     }
   }
 
+  bool _handleMessageMove(UpdateMessageEvent event) {
+    final messageMove = event.moveData;
+    if (messageMove == null) {
+      // No moved messages or malformed event.
+      return false;
+    }
+
+    final topics = streams[messageMove.origStreamId];
+    if (topics == null || topics[messageMove.origTopic] == null) {
+      // No known unreads affected by move; nothing to do.
+      return false;
+    }
+
+    final messageToMoveIds = _removeAllInStreamTopic(
+      event.messageIds.toSet(),
+      messageMove.origStreamId, messageMove.origTopic);
+    if (messageToMoveIds.isEmpty) {
+      return false;
+    }
+    _addAllInStreamTopic(
+      messageToMoveIds..sort(),
+      messageMove.newStreamId, messageMove.newTopic);
+    return true;
+  }
+
   void handleDeleteMessageEvent(DeleteMessageEvent event) {
     mentions.removeAll(event.messageIds);
     final messageIdsSet = Set.of(event.messageIds);

test/model/unreads_test.dart

@@ -469,6 +469,128 @@ void main() {
         }
       }
     });
+
+    group('moves', () {
+      final origChannel = eg.stream();
+      const origTopic = 'origTopic';
+      const newTopic = 'newTopic';
+
+      group('move read messages', () {
+        final readMessages = List<StreamMessage>.generate(10,
+          (_) => eg.streamMessage(
+            stream: origChannel, topic: origTopic, flags: [MessageFlag.read]));
+
+        test('to new topic', () {
+          prepare();
+          fillWithMessages(readMessages);
+
+          model.handleUpdateMessageEvent(eg.updateMessageEventMoveFrom(
+            origMessages: readMessages,
+            newTopicStr: newTopic));
+          checkNotNotified();
+          checkMatchesMessages([]);
+        });
+
+        test('from topic with unreads', () {
+          prepare();
+          final unreadMessage = eg.streamMessage(
+            stream: origChannel, topic: origTopic);
+          fillWithMessages([...readMessages, unreadMessage]);
+
+          model.handleUpdateMessageEvent(eg.updateMessageEventMoveFrom(
+            origMessages: readMessages,
+            newTopicStr: newTopic));
+          checkNotNotified();
+          checkMatchesMessages([unreadMessage]);
+        });
+
+        test('to topic with unreads', () {
+          prepare();
+          final unreadMessage = eg.streamMessage(
+            stream: origChannel, topic: newTopic);
+          fillWithMessages([...readMessages, unreadMessage]);
+
+          model.handleUpdateMessageEvent(eg.updateMessageEventMoveFrom(
+            origMessages: readMessages,
+            newTopicStr: newTopic,
+          ));
+          checkNotNotified();
+          checkMatchesMessages([unreadMessage]);
+        });
+      });
+
+      group('move unread messages', () {
+        final unreadMessages = List<StreamMessage>.generate(10,
+          (_) => eg.streamMessage(stream: origChannel, topic: origTopic));
+
+        test('to new topic', () {
+          prepare();
+          fillWithMessages(unreadMessages);
+
+          model.handleUpdateMessageEvent(eg.updateMessageEventMoveFrom(
+            origMessages: unreadMessages,
+            newTopicStr: newTopic));
+          checkNotifiedOnce();
+          checkMatchesMessages([
+            for (final message in unreadMessages)
+              Message.fromJson(message.toJson()..['subject'] = newTopic),
+          ]);
+        });
+
+        test('from topic with unreads', () {
+          prepare();
+          final unreadMessage = eg.streamMessage(
+            stream: origChannel, topic: origTopic);
+          fillWithMessages([...unreadMessages, unreadMessage]);
+
+          model.handleUpdateMessageEvent(eg.updateMessageEventMoveFrom(
+            origMessages: unreadMessages,
+            newTopicStr: newTopic));
+          checkNotifiedOnce();
+          checkMatchesMessages([
+            for (final message in unreadMessages)
+              Message.fromJson(message.toJson()..['subject'] = newTopic),
+            unreadMessage,
+          ]);
+        });
+
+        test('to topic with unreads', () {
+          prepare();
+          final unreadMessage = eg.streamMessage(
+            stream: origChannel, topic: newTopic);
+          fillWithMessages([...unreadMessages, unreadMessage]);
+
+          model.handleUpdateMessageEvent(eg.updateMessageEventMoveFrom(
+            origMessages: unreadMessages,
+            newTopicStr: newTopic));
+          checkNotifiedOnce();
+          checkMatchesMessages([
+            for (final message in unreadMessages)
+              Message.fromJson(message.toJson()..['subject'] = newTopic),
+            unreadMessage,
+          ]);
+        });
+
+        test('to new channel', () {
+          final message = eg.streamMessage(
+            id: 1, stream: origChannel, topic: origTopic);
+          final newChannel = eg.stream();
+          prepare();
+          fillWithMessages([message]);
+
+          model.handleUpdateMessageEvent(eg.updateMessageEventMoveFrom(
+            origMessages: [message],
+            newStreamId: newChannel.streamId,
+            newTopicStr: newTopic));
+          checkNotifiedOnce();
+          checkMatchesMessages([
+            Message.fromJson(message.toJson()
+              ..['stream_id'] = newChannel.streamId
+              ..['subject'] = newTopic),
+          ]);
+        });
+      });
+    });
   });