api: Add delete_message events

lib/api/model/events.dart

@@ -32,6 +32,7 @@ sealed class Event {
         }
       case 'message': return MessageEvent.fromJson(json);
       case 'update_message': return UpdateMessageEvent.fromJson(json);
+      case 'delete_message': return DeleteMessageEvent.fromJson(json);
       case 'heartbeat': return HeartbeatEvent.fromJson(json);
       // TODO add many more event types
       default: return UnexpectedEvent.fromJson(json);
@@ -344,6 +345,51 @@ enum PropagateMode {
   };
 }
 
+/// A Zulip event of type `delete_message`.
+@JsonSerializable(fieldRename: FieldRename.snake)
+class DeleteMessageEvent extends Event {
+  @override
+  String get type => 'delete_message';
+
+  final List<int> messageIds;
+  // final int messageId; // Not present; we support the bulk_message_deletion capability
+  @JsonKey(fromJson: MessageType.fromJson, toJson: MessageType.toJson)
+  final MessageType messageType;
+  final int? streamId;
+  final String? topic;
+
+  DeleteMessageEvent({
+    required super.id,
+    required this.messageIds,
+    required this.messageType,
+    this.streamId,
+    this.topic,
+  });
+
+  factory DeleteMessageEvent.fromJson(Map<String, dynamic> json) =>
+    _$DeleteMessageEventFromJson(json);
+
+  @override
+  Map<String, dynamic> toJson() => _$DeleteMessageEventToJson(this);
+}
+
+/// As in [DeleteMessageEvent.messageType].
+enum MessageType {
+  stream,
+  private;
+
+  factory MessageType.fromJson(dynamic json) => switch (json) {
+    'stream'  => MessageType.stream,
+    'private' => MessageType.private,
+    _         => throw Exception("MessageType.fromJson: unexpected message type $json"),
+  };
+
+  static String toJson(MessageType value) => switch (value) {
+    MessageType.stream  => 'stream',
+    MessageType.private => 'private',
+  };
+}
+
 @JsonSerializable(fieldRename: FieldRename.snake)
 class HeartbeatEvent extends Event {
   @override

lib/model/store.dart

@@ -259,6 +259,8 @@ class PerAccountStore extends ChangeNotifier {
       }
     } else if (event is UpdateMessageEvent) {
       // TODO handle
+    } else if (event is DeleteMessageEvent) {
+      // TODO handle
     } else if (event is UnexpectedEvent) {
       assert(debugLog("server event: ${jsonEncode(event.toJson())}")); // TODO log better
     } else {