message: Handle UpdateMessageEvent for moving.

When a channel (a.k.a stream) or a topic gets updated on a message, we
get a UpdateMessageEvent from the server.

This updates the edit state to show the "edited" or "moved" marker
properly on the messages affected, and leave other move related states
(like streamId) untouched until we get to #150.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/model/message.dart

@@ -142,7 +142,10 @@ class MessageStoreImpl with MessageStore {
     // The interaction between the fields of these events are a bit tricky.
     // For reference, see: https://zulip.com/api/get-events#update_message
 
-    if (event.origTopic == null) {
+    final bool isChannelMoved = event.newStreamId != null;
+    bool isTopicMoved = event.origTopic != null;
+
+    if (!isTopicMoved && !isChannelMoved) {
       // There was no move.
       assert(() {
         if (event.newStreamId != null && event.origStreamId != null
@@ -167,10 +170,27 @@ class MessageStoreImpl with MessageStore {
       return;
     }
 
+    if (isTopicMoved) {
+      // Eliminate the case when the topic is updated but resolved/unresolved.
+      isTopicMoved = MessageEditState.areSameTopic(event.origTopic!, event.newTopic!);
+    }
+
+    // When nothing has been moved,
+    // return early as the messages' editStates need no update.
+    if (!isTopicMoved && !isChannelMoved) return;
+
     // final newStreamId = event.newStreamId; // null if topic-only move
     // final newTopic = event.newTopic!;
     // TODO(#150): Handle message moves.  The views' recipient headers
     //   may need updating, and consequently showSender too.
+    //   Currently only editState gets updated.
+    for (final messageId in event.messageIds) {
+      final message = messages[messageId];
+      if (message == null) continue;
+      // Do not override the edited marker if the message has also been moved.
+      if (message.editState == MessageEditState.edited) continue;
+      message.editState = MessageEditState.moved;
+    }
   }
 
   void handleDeleteMessageEvent(DeleteMessageEvent event) {

test/example_data.dart

@@ -420,6 +420,35 @@ UpdateMessageEvent updateMessageEditEvent(
   );
 }
 
+UpdateMessageEvent updateMessageMoveEvent(
+  Message origMessage, {
+  int? messageId,
+  int? newStreamId,
+  String? origTopic,
+  String? newTopic,
+}) {
+  messageId ??= origMessage.id;
+  return UpdateMessageEvent(
+    id: 0,
+    userId: selfUser.userId,
+    renderingOnly: false,
+    messageId: messageId,
+    messageIds: [messageId],
+    flags: origMessage.flags,
+    editTimestamp: 1234567890, // TODO generate timestamp
+    origStreamId: origMessage is StreamMessage ? origMessage.streamId : null,
+    newStreamId: newStreamId,
+    propagateMode: null,
+    origTopic: origTopic,
+    newTopic: newTopic,
+    origContent: 'some probably-mismatched old Markdown',
+    origRenderedContent: origMessage.content,
+    content: 'some probably-mismatched new Markdown',
+    renderedContent: origMessage.content,
+    isMeMessage: false,
+  );
+}
+
 UpdateMessageFlagsRemoveEvent updateMessageFlagsRemoveEvent(
   MessageFlag flag,
   Iterable<Message> messages, {

test/model/message_test.dart

@@ -269,6 +269,48 @@ void main() {
     test('rendering-only update does not change timestamp (for old server versions)', () async {
       await checkRenderingOnly(legacy: true);
     });
+
+    group('Handle message edit state update', () {
+      final message = eg.streamMessage();
+
+      Future<void> sendEvent(Message message, UpdateMessageEvent event) async {
+        await prepare();
+        await prepareMessages([message]);
+
+        await store.handleEvent(event);
+        checkNotifiedOnce();
+      }
+
+      test('message not moved update', () async {
+        await sendEvent(message, eg.updateMessageMoveEvent(message));
+        check(store).messages.values.single.editState.equals(MessageEditState.none);
+      });
+
+      test('message topic moved update', () async {
+        await sendEvent(message, eg.updateMessageMoveEvent(message,
+          origTopic: 'old topic',
+          newTopic:  'new topic',
+        ));
+        check(store).messages.values.single.editState.equals(MessageEditState.moved);
+      });
+
+      test('message topic resolved update', () async {
+        await sendEvent(message, eg.updateMessageMoveEvent(message,
+          origTopic: 'new topic',
+          newTopic:  '✔ new topic',
+        ));
+        check(store).messages.values.single.editState.equals(MessageEditState.none);
+      });
+
+      test('message stream moved update', () async {
+        await sendEvent(message, eg.updateMessageMoveEvent(message,
+          origTopic: 'topic',
+          newTopic: 'topic',
+          newStreamId:  20,
+        ));
+        check(store).messages.values.single.editState.equals(MessageEditState.moved);
+      });
+    });
   });
 
   group('handleUpdateMessageFlagsEvent', () {