msglist: Handle updated events in MessageListView (zulip#118).

Processes an UpdateMessageEvent and hands it off to the MessageListView to update, if the message is visible in the MessageListView. This completes the changes required for issue zulip#118.

lib/api/model/model.dart

@@ -250,13 +250,13 @@ class Subscription {
 sealed class Message {
   final String? avatarUrl;
   final String client;
-  final String content;
+  String content;
   final String contentType;
 
   // final List<MessageEditHistory> editHistory; // TODO handle
   final int id;
-  final bool isMeMessage;
-  final int? lastEditTimestamp;
+  bool isMeMessage;
+  int? lastEditTimestamp;
 
   // final List<Reaction> reactions; // TODO handle
   final int recipientId;
@@ -271,7 +271,7 @@ sealed class Message {
 
   // final List<TopicLink> topicLinks; // TODO handle
   // final string type; // handled by runtime type of object
-  final List<String> flags; // TODO enum
+  List<String> flags; // TODO enum
   final String? matchContent;
   final String? matchSubject;
 

lib/model/message_list.dart

@@ -1,5 +1,7 @@
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 
+import '../api/model/events.dart';
 import '../api/model/model.dart';
 import '../api/route/messages.dart';
 import 'content.dart';
@@ -86,6 +88,67 @@ class MessageListView extends ChangeNotifier {
     notifyListeners();
   }
 
+  applyChangesToMessage(UpdateMessageEvent event, Message message) {
+    if (event.renderingOnly != null && event.renderingOnly == true) {
+      //TODO update inline preview
+      return;
+    }
+
+    if (!event.flags.equals(message.flags)) {
+      message.flags = event.flags;
+    }
+
+    if (event.renderedContent != null) {
+      assert(message.contentType == 'text/html', "Expected message to have html contentType. Instead, got ${message.contentType}");
+      message.content = event.renderedContent!;
+    }
+
+    if (event.editTimestamp != null) {
+      message.lastEditTimestamp = event.editTimestamp;
+    }
+
+    if (event.isMeMessage != null) {
+      message.isMeMessage = event.isMeMessage!;
+    }
+
+  }
+
+  ///This is almost directly copied from package:collection/algorithms.dart.
+  ///The way that package was set up doesn't allow us to search
+  ///for a message ID among a bunch of message objects - this is a quick
+  ///modification of that method to work here for us.
+  int findMessageWithId(int messageId) {
+    var min = 0;
+    var max = messages.length;
+
+    while (min < max) {
+      var mid = min + ((max - min) >> 1);
+      Message message = messages[mid];
+      var comp = message.id.compareTo(messageId);
+      if (comp == 0) return mid;
+      if (comp < 0) {
+        min = mid + 1;
+      } else {
+        max = mid;
+      }
+    }
+    return -1;
+  }
+
+  void maybeUpdateMessage(UpdateMessageEvent event) {
+    int idx = findMessageWithId(event.messageId);
+
+    if (idx == -1)  {
+      return;
+    }
+
+    Message message = messages[idx];
+    applyChangesToMessage(event, message);
+
+    contents[idx] = parseContent(message.content);
+    notifyListeners();
+  }
+
   /// Called when the app is reassembled during debugging, e.g. for hot reload.
   ///
   /// This will redo from scratch any computations we can, such as parsing

lib/model/store.dart

@@ -272,7 +272,9 @@ class PerAccountStore extends ChangeNotifier {
       }
     } else if (event is UpdateMessageEvent) {
       assert(debugLog("server event: update_message ${event.messageId}"));
-      // TODO handle
+      for (final view in _messageListViews) {
+        view.maybeUpdateMessage(event);
+      }
     } else if (event is DeleteMessageEvent) {
       assert(debugLog("server event: delete_message ${event.messageIds}"));
       // TODO handle

test/model/message_list_test.dart

@@ -0,0 +1,103 @@
+import 'package:checks/checks.dart';
+import 'package:test/scaffolding.dart';
+import 'package:zulip/api/model/events.dart';
+import 'package:zulip/api/model/model.dart';
+import 'package:zulip/api/route/messages.dart';
+import 'package:zulip/model/message_list.dart';
+import 'package:zulip/model/narrow.dart';
+import 'package:zulip/model/store.dart';
+import '../api/fake_api.dart';
+import '../model/binding.dart';
+import '../model/test_store.dart';
+import '../example_data.dart' as eg;
+
+const int userId = 1;
+const int streamId = 2;
+
+Future<PerAccountStore> setupStore(ZulipStream stream) async {
+  await TestZulipBinding.instance.globalStore.add(eg.selfAccount, eg.initialSnapshot());
+  PerAccountStore store = await TestZulipBinding.instance.globalStore.perAccount(eg.selfAccount.id);
+  store.addUser(eg.user(userId: userId));
+  store.addStream(stream);
+  return store;
+}
+
+void main() async {
+  TestZulipBinding.ensureInitialized();
+  const narrow = StreamNarrow(streamId);
+
+  final ZulipStream stream = eg.stream(streamId: streamId);
+  PerAccountStore store = await setupStore(stream);
+
+  group('update message tests', () {
+
+    test('find message in message list returns index of message', () async {
+      MessageListView messageList = MessageListView.init(store: store, narrow: narrow);
+
+      final connection = store.connection as FakeApiConnection;
+      Message m1 = eg.streamMessage(id: 792, stream: stream);
+      Message m2 = eg.streamMessage(id: 793, stream: stream);
+      Message m3 = eg.streamMessage(id: 794, stream: stream);
+
+      connection.prepare(json: GetMessagesResult(
+        anchor: m1.id,
+        foundNewest: true,
+        foundOldest: true,
+        foundAnchor: true,
+        historyLimited: false,
+        messages: [m1, m2, m3],
+      ).toJson());
+
+      await messageList.fetch();
+
+      check(messageList.messages.length).equals(3);
+
+      int idx = messageList.findMessageWithId(793);
+      check(idx).equals(1);
+
+      idx = messageList.findMessageWithId(999);
+      check(idx).equals(-1);
+    });
+
+    test('update events are correctly applied to message', () async {
+      MessageListView messageList = MessageListView.init(store: store, narrow: narrow);
+
+      final connection = store.connection as FakeApiConnection;
+      String oldContent = "<p>Hello, world</p>";
+      String newContent = "<p>Hello, edited</p>";
+      int newTimestamp = 99999;
+
+      Message m = eg.streamMessage(id: 243, stream: stream, content: oldContent);
+      connection.prepare(json: GetMessagesResult(
+        anchor: m.id,
+        foundNewest: true,
+        foundOldest: true,
+        foundAnchor: true,
+        historyLimited: false,
+        messages: [m],
+      ).toJson());
+
+      await messageList.fetch();
+
+      UpdateMessageEvent updateEvent = UpdateMessageEvent(
+        id: 1,
+        messageId: m.id,
+        messageIds: [m.id],
+        flags: m.flags,
+        renderedContent: newContent,
+        editTimestamp: newTimestamp
+      );
+
+      Message oldMessage = messageList.messages[0];
+      check(oldMessage.content).equals(oldContent);
+
+      messageList.maybeUpdateMessage(updateEvent);
+
+      Message updatedMessage = messageList.messages[0];
+
+      check(updatedMessage.content).equals(newContent);
+      check(updatedMessage.lastEditTimestamp).equals(newTimestamp);
+
+    });
+  });
+}