message: Create an outbox message on send; manage its states

While we do create outbox messages, there are in no way user-visible
changes since the outbox messages don't end up in message list views.
We create skeletons for helpers needed from message list view, but don't
implement them yet, to make the diff smaller.

For testing, similar to TypingNotifier.debugEnable, we add
MessageStoreImpl.debugOutboxEnable for tests that do not intend to
cover outbox messages.

Some of the delays to fake responses added in tests are not necessary
because the future of sendMessage is not completed immediately, but we
still add them to keep the tests realistic.

Author: PIG208

lib/model/message.dart

@@ -10,6 +10,7 @@ import '../api/route/messages.dart';
 import 'algorithms.dart';
 import 'channel.dart';
 import 'content.dart';
+import 'message.dart';
 import 'narrow.dart';
 import 'store.dart';
 
@@ -626,6 +627,17 @@ class MessageListView with ChangeNotifier, _MessageSequence {
     }
   }
 
+  void handleOutboxMessage(OutboxMessage outboxMessage) {
+    // TODO(#1441) implement this
+  }
+
+  /// Remove the [outboxMessage] from the view.
+  ///
+  /// This is a no-op if the message is not found.
+  void removeOutboxMessageIfExists(OutboxMessage outboxMessage) {
+    // TODO(#1441) implement this
+  }
+
   void handleUserTopicEvent(UserTopicEvent event) {
     switch (_canAffectVisibility(event)) {
       case VisibilityEffect.none:
@@ -787,6 +799,11 @@ class MessageListView with ChangeNotifier, _MessageSequence {
     }
   }
 
+  /// Notify listeners if the given outbox message is present in this view.
+  void notifyListenersIfOutboxMessagePresent(int localMessageId) {
+    // TODO(#1441) implement this
+  }
+
   /// 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/message_list.dart

@@ -494,7 +494,8 @@ class PerAccountStore extends PerAccountStoreBase with ChangeNotifier, EmojiStor
         typingStartedExpiryPeriod: Duration(milliseconds: initialSnapshot.serverTypingStartedExpiryPeriodMilliseconds),
       ),
       channels: channels,
-      messages: MessageStoreImpl(core: core),
+      messages: MessageStoreImpl(core: core,
+        realmEmptyTopicDisplayName: initialSnapshot.realmEmptyTopicDisplayName),
       unreads: Unreads(
         initial: initialSnapshot.unreadMsgs,
         core: core,
@@ -725,6 +726,8 @@ class PerAccountStore extends PerAccountStoreBase with ChangeNotifier, EmojiStor
   @override
   Map<int, Message> get messages => _messages.messages;
   @override
+  Map<int, OutboxMessage> get outboxMessages => _messages.outboxMessages;
+  @override
   void registerMessageList(MessageListView view) =>
     _messages.registerMessageList(view);
   @override
@@ -904,6 +907,9 @@ class PerAccountStore extends PerAccountStoreBase with ChangeNotifier, EmojiStor
     return _messages.sendMessage(destination: destination, content: content);
   }
 
+  @override
+  void removeOutboxMessage(int localMessageId) => _messages.removeOutboxMessage(localMessageId);
+
   static List<CustomProfileField> _sortCustomProfileFields(List<CustomProfileField> initialCustomProfileFields) {
     // TODO(server): The realm-wide field objects have an `order` property,
     //   but the actual API appears to be that the fields should be shown in

lib/model/store.dart

@@ -30,6 +30,7 @@ extension TopicNameChecks on Subject<TopicName> {
 }
 
 extension StreamConversationChecks on Subject<StreamConversation> {
+  Subject<TopicName> get topic => has((x) => x.topic, 'topic');
   Subject<String?> get displayRecipient => has((x) => x.displayRecipient, 'displayRecipient');
 }
 

test/api/model/model_checks.dart

@@ -622,8 +622,8 @@ UserTopicEvent userTopicEvent(
   );
 }
 
-MessageEvent messageEvent(Message message) =>
-  MessageEvent(id: 0, message: message, localMessageId: null);
+MessageEvent messageEvent(Message message, {int? localMessageId}) =>
+  MessageEvent(id: 0, message: message, localMessageId: localMessageId?.toString());
 
 DeleteMessageEvent deleteMessageEvent(List<StreamMessage> messages) {
   assert(messages.isNotEmpty);

test/example_data.dart

@@ -0,0 +1,6 @@
+import 'package:checks/checks.dart';
+import 'package:fake_async/fake_async.dart';
+
+extension FakeTimerChecks on Subject<FakeTimer> {
+  Subject<Duration> get duration => has((t) => t.duration, 'duration');
+}

test/fake_async_checks.dart

@@ -0,0 +1,9 @@
+import 'package:checks/checks.dart';
+import 'package:zulip/api/model/model.dart';
+import 'package:zulip/model/message.dart';
+
+extension OutboxMessageChecks<T extends Conversation> on Subject<OutboxMessage<T>> {
+  Subject<int> get localMessageId => has((x) => x.localMessageId, 'localMessageId');
+  Subject<OutboxMessageLifecycle> get state => has((x) => x.state, 'state');
+  Subject<bool> get hidden => has((x) => x.hidden, 'hidden');
+}