msglist: Support data model for edited/moved marker

.vscode/settings.json

@@ -17,4 +17,7 @@
 
   // This much more focused automatic fix is helpful, though.
   "files.trimTrailingWhitespace": true,
+
+  // Suppress the warnings that appear for TODOs throughout the codebase.
+  "dart.showTodos": false,
 }

lib/api/model/model.dart

@@ -464,6 +464,9 @@ sealed class Message {
   final String contentType;
 
   // final List<MessageEditHistory> editHistory; // TODO handle
+  @JsonKey(readValue: MessageEditState._readFromMessage, fromJson: Message._messageEditStateFromJson)
+  MessageEditState editState;
+
   final int id;
   bool isMeMessage;
   int? lastEditTimestamp;
@@ -490,6 +493,12 @@ sealed class Message {
   @JsonKey(name: 'match_subject')
   final String? matchTopic;
 
+  static MessageEditState _messageEditStateFromJson(dynamic json) {
+    // This is a no-op so that [MessageEditState._readFromMessage]
+    // can return the enum value directly.
+    return json as MessageEditState;
+  }
+
   static Reactions? _reactionsFromJson(dynamic json) {
     final list = (json as List<dynamic>);
     return list.isNotEmpty ? Reactions.fromJson(list) : null;
@@ -508,6 +517,7 @@ sealed class Message {
     required this.client,
     required this.content,
     required this.contentType,
+    required this.editState,
     required this.id,
     required this.isMeMessage,
     required this.lastEditTimestamp,
@@ -573,6 +583,7 @@ class StreamMessage extends Message {
     required super.client,
     required super.content,
     required super.contentType,
+    required super.editState,
     required super.id,
     required super.isMeMessage,
     required super.lastEditTimestamp,
@@ -675,6 +686,7 @@ class DmMessage extends Message {
     required super.client,
     required super.content,
     required super.contentType,
+    required super.editState,
     required super.id,
     required super.isMeMessage,
     required super.lastEditTimestamp,
@@ -698,3 +710,78 @@ class DmMessage extends Message {
   @override
   Map<String, dynamic> toJson() => _$DmMessageToJson(this);
 }
+
+enum MessageEditState {
+  none,
+  edited,
+  moved;
+
+  // Adapted from the shared code:
+  //   https://github.com/zulip/zulip/blob/1fac99733/web/shared/src/resolved_topic.ts
+  // The canonical resolved-topic prefix.
+  static const String _resolvedTopicPrefix = '✔ ';
+
+  /// Whether the given topic move reflected either a "resolve topic"
+  /// or "unresolve topic" operation.
+  ///
+  /// The Zulip "resolved topics" feature is implemented by renaming the topic;
+  /// but for purposes of [Message.editState], we want to ignore such renames.
+  /// This method identifies topic moves that should be ignored in that context.
+  static bool topicMoveWasResolveOrUnresolve(String topic, String prevTopic) {
+    if (topic.startsWith(_resolvedTopicPrefix)
+        && topic.substring(_resolvedTopicPrefix.length) == prevTopic) {
+      return true;
+    }
+
+    if (prevTopic.startsWith(_resolvedTopicPrefix)
+        && prevTopic.substring(_resolvedTopicPrefix.length) == topic) {
+      return true;
+    }
+
+    return false;
+  }
+
+  static MessageEditState _readFromMessage(Map<dynamic, dynamic> json, String key) {
+    // Adapted from `analyze_edit_history` in the web app:
+    //   https://github.com/zulip/zulip/blob/c31cebbf68a93927d41e9947427c2dd4d46503e3/web/src/message_list_view.js#L68-L118
+    final editHistory = json['edit_history'] as List<dynamic>?;
+    final lastEditTimestamp = json['last_edit_timestamp'] as int?;
+    if (editHistory == null) {
+      return (lastEditTimestamp != null)
+        ? MessageEditState.edited
+        : MessageEditState.none;
+    }
+
+    // Edit history should never be empty whenever it is present
+    assert(editHistory.isNotEmpty);
+
+    bool hasMoved = false;
+    for (final entry in editHistory) {
+      if (entry['prev_content'] != null) {
+        return MessageEditState.edited;
+      }
+
+      if (entry['prev_stream'] != null) {
+        hasMoved = true;
+        continue;
+      }
+
+      // TODO(server-5) prev_subject was the old name of prev_topic on pre-5.0 servers
+      final prevTopic = (entry['prev_topic'] ?? entry['prev_subject']) as String?;
+      final topic = entry['topic'] as String?;
+      if (prevTopic != null) {
+        // TODO(server-5) pre-5.0 servers do not have the 'topic' field
+        if (topic == null) {
+          hasMoved = true;
+        } else {
+          hasMoved |= !topicMoveWasResolveOrUnresolve(topic, prevTopic);
+        }
+      }
+    }
+
+    if (hasMoved) return MessageEditState.moved;
+
+    // This can happen when a topic is resolved but nothing else has been edited
+    return MessageEditState.none;
+  }
+}

lib/model/message.dart

@@ -125,6 +125,11 @@ class MessageStoreImpl with MessageStore {
     if (message == null) return;
 
     message.flags = event.flags;
+    if (event.origContent != null) {
+      // The message is guaranteed to be edited.
+      // See also: https://zulip.com/api/get-events#update_message
+      message.editState = MessageEditState.edited;
+    }
     if (event.renderedContent != null) {
       assert(message.contentType == 'text/html',
         "Message contentType was ${message.contentType}; expected text/html.");
@@ -168,10 +173,26 @@ class MessageStoreImpl with MessageStore {
       return;
     }
 
-    // final newStreamId = event.newStreamId; // null if topic-only move
-    // final newTopic = event.newTopic!;
+    final newTopic = event.newTopic!;
+    final newChannelId = event.newStreamId; // null if topic-only move
+
+    if (newChannelId == null
+        && MessageEditState.topicMoveWasResolveOrUnresolve(event.origTopic!, newTopic)) {
+      // The topic was only resolved/unresolved.
+      // No change to the messages' editState.
+      return;
+    }
+
     // 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/api/model/model_checks.dart

@@ -34,6 +34,7 @@ extension MessageChecks on Subject<Message> {
   Subject<int> get id => has((e) => e.id, 'id');
   Subject<bool> get isMeMessage => has((e) => e.isMeMessage, 'isMeMessage');
   Subject<int?> get lastEditTimestamp => has((e) => e.lastEditTimestamp, 'lastEditTimestamp');
+  Subject<MessageEditState> get editState => has((e) => e.editState, 'editState');
   Subject<Reactions?> get reactions => has((e) => e.reactions, 'reactions');
   Subject<int> get recipientId => has((e) => e.recipientId, 'recipientId');
   Subject<String> get senderEmail => has((e) => e.senderEmail, 'senderEmail');

test/api/model/model_test.dart

@@ -148,6 +148,9 @@ void main() {
       );
       check(m2).flags.deepEquals([MessageFlag.read, MessageFlag.unknown]);
     });
+
+    // Code relevant to messageEditState is tested separately in the
+    // MessageEditState group.
   });
 
   group('DmMessage', () {
@@ -212,4 +215,110 @@ void main() {
         .deepEquals([2, 3, 11]);
     });
   });
+
+  group('MessageEditState', () {
+    Map<String, dynamic> baseJson() => deepToJson(eg.streamMessage()) as Map<String, dynamic>;
+
+    group('Edit history is absent', () {
+      test('Message with no evidence of an edit history -> none', () {
+        check(Message.fromJson(baseJson()..['edit_history'] = null))
+          .editState.equals(MessageEditState.none);
+      });
+
+      test('Message without edit history has last edit timestamp -> edited', () {
+        check(Message.fromJson(baseJson()
+            ..['edit_history'] = null
+            ..['last_edit_timestamp'] = 1678139636))
+          .editState.equals(MessageEditState.edited);
+      });
+    });
+
+    void checkEditState(MessageEditState editState, List<Map<String, dynamic>> editHistory){
+      check(Message.fromJson(baseJson()..['edit_history'] = editHistory))
+        .editState.equals(editState);
+    }
+
+    group('edit history exists', () {
+      test('Moved message has last edit timestamp but no actual edits -> moved', () {
+        check(Message.fromJson(baseJson()
+            ..['edit_history'] = [{'prev_stream': 5, 'stream': 7}]
+            ..['last_edit_timestamp'] = 1678139636))
+          .editState.equals(MessageEditState.moved);
+      });
+
+      test('Channel change only -> moved', () {
+        checkEditState(MessageEditState.moved,
+          [{'prev_stream': 5, 'stream': 7}]);
+      });
+
+      test('Topic name change only -> moved', () {
+        checkEditState(MessageEditState.moved,
+          [{'prev_topic': 'old_topic', 'topic': 'new_topic'}]);
+      });
+
+      test('Both topic and content changed -> edited', () {
+        checkEditState(MessageEditState.edited, [
+          {'prev_topic': 'old_topic', 'topic': 'new_topic'},
+          {'prev_content': 'old_content'},
+        ]);
+        checkEditState(MessageEditState.edited, [
+          {'prev_content': 'old_content'},
+          {'prev_topic': 'old_topic', 'topic': 'new_topic'},
+        ]);
+      });
+
+      test('Both topic and content changed in a single edit -> edited', () {
+        checkEditState(MessageEditState.edited,
+          [{'prev_topic': 'old_topic', 'topic': 'new_topic', 'prev_content': 'old_content'}]);
+      });
+
+      test('Content change only -> edited', () {
+        checkEditState(MessageEditState.edited,
+          [{'prev_content': 'old_content'}]);
+      });
+
+      test("'prev_topic' present without the 'topic' field -> moved", () {
+        checkEditState(MessageEditState.moved,
+          [{'prev_topic': 'old_topic'}]);
+      });
+
+      test("'prev_subject' present from a pre-5.0 server -> moved", () {
+        checkEditState(MessageEditState.moved,
+          [{'prev_subject': 'old_topic'}]);
+      });
+    });
+
+    group('topic resolved in edit history', () {
+      test('Topic was only resolved -> none', () {
+        checkEditState(MessageEditState.none,
+          [{'prev_topic': 'old_topic', 'topic': '✔ old_topic'}]);
+      });
+
+      test('Topic was resolved but the content changed in the history -> edited', () {
+        checkEditState(MessageEditState.edited, [
+          {'prev_topic': 'old_topic', 'topic': '✔ old_topic'},
+          {'prev_content': 'old_content'},
+        ]);
+      });
+
+      test('Topic was resolved but it also moved in the history -> moved', () {
+        checkEditState(MessageEditState.moved, [
+          {'prev_topic': 'old_topic', 'topic': 'new_topic'},
+          {'prev_topic': '✔ old_topic', 'topic': 'old_topic'},
+        ]);
+      });
+
+      test('Topic was moved but it also was resolved in the history -> moved', () {
+        checkEditState(MessageEditState.moved, [
+          {'prev_topic': '✔ old_topic', 'topic': 'old_topic'},
+          {'prev_topic': 'old_topic', 'topic': 'new_topic'},
+        ]);
+      });
+
+      test('Unresolving topic with a weird prefix -> moved', () {
+          checkEditState(MessageEditState.moved,
+            [{'prev_topic': '✔ ✔old_topic', 'topic': 'old_topic'}]);
+      });
+    });
+  });
 }

test/example_data.dart

@@ -437,6 +437,38 @@ UpdateMessageEvent updateMessageEditEvent(
   );
 }
 
+UpdateMessageEvent updateMessageMoveEvent(
+  List<Message> messages, {
+  int? newStreamId,
+  String? origTopic,
+  String? newTopic,
+  String? origContent,
+  String? newContent,
+}) {
+  assert(messages.isNotEmpty);
+  final origMessage = messages[0];
+  final messageId = origMessage.id;
+  return UpdateMessageEvent(
+    id: 0,
+    userId: selfUser.userId,
+    renderingOnly: false,
+    messageId: messageId,
+    messageIds: messages.map((message) => message.id).toList(),
+    flags: origMessage.flags,
+    editTimestamp: 1234567890, // TODO generate timestamp
+    origStreamId: origMessage is StreamMessage ? origMessage.streamId : null,
+    newStreamId: newStreamId,
+    propagateMode: null,
+    origTopic: origTopic,
+    newTopic: newTopic,
+    origContent: origContent,
+    origRenderedContent: origContent,
+    content: newContent,
+    renderedContent: newContent,
+    isMeMessage: false,
+  );
+}
+
 UpdateMessageFlagsRemoveEvent updateMessageFlagsRemoveEvent(
   MessageFlag flag,
   Iterable<Message> messages, {