event: Handle submessage event for polls.

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

Author: PIG208

lib/api/model/events.dart

@@ -2,6 +2,7 @@ import 'package:json_annotation/json_annotation.dart';
 
 import 'json.dart';
 import 'model.dart';
+import 'submessage.dart';
 
 part 'events.g.dart';
 
@@ -62,6 +63,7 @@ sealed class Event {
           case 'remove': return UpdateMessageFlagsRemoveEvent.fromJson(json);
           default: return UnexpectedEvent.fromJson(json);
         }
+      case 'submessage': return SubmessageEvent.fromJson(json);
       case 'typing': return TypingEvent.fromJson(json);
       case 'reaction': return ReactionEvent.fromJson(json);
       case 'heartbeat': return HeartbeatEvent.fromJson(json);
@@ -873,6 +875,37 @@ class UpdateMessageFlagsMessageDetail {
   Map<String, dynamic> toJson() => _$UpdateMessageFlagsMessageDetailToJson(this);
 }
 
+/// A Zulip event of type `submessage`: https://zulip.com/api/get-events#submessage
+@JsonSerializable(fieldRename: FieldRename.snake)
+class SubmessageEvent extends Event {
+  @override
+  @JsonKey(includeToJson: true)
+  String get type => 'submessage';
+
+  @JsonKey(unknownEnumValue: SubmessageType.unknown)
+  final SubmessageType msgType;
+  @JsonKey(readValue: Submessage.readContent)
+  final Object? content;
+  final int messageId;
+  final int senderId;
+  final int submessageId;
+
+  SubmessageEvent({
+    required super.id,
+    required this.msgType,
+    required this.content,
+    required this.messageId,
+    required this.senderId,
+    required this.submessageId,
+  });
+
+  factory SubmessageEvent.fromJson(Map<String, dynamic> json) =>
+    _$SubmessageEventFromJson(json);
+
+  @override
+  Map<String, dynamic> toJson() => _$SubmessageEventToJson(this);
+}
+
 /// A Zulip event of type `typing`:
 ///   https://zulip.com/api/get-events#typing-start
 ///   https://zulip.com/api/get-events#typing-stop

lib/api/model/events.g.dart

@@ -482,7 +482,10 @@ sealed class Message {
   final String senderRealmStr;
   @JsonKey(name: 'subject')
   final String topic;
-  final List<Submessage> submessages;
+  // Only null when processed by store.
+  // See [Polls].
+  @JsonKey(disallowNullValue: true, required: true)
+  List<Submessage>? submessages;
   @JsonKey(readValue: WidgetData.readFromMessage)
   WidgetData? widgetData;
   final int timestamp;

lib/api/model/model.dart

@@ -17,13 +17,14 @@ class Submessage {
 
   @JsonKey(unknownEnumValue: SubmessageType.unknown)
   final SubmessageType msgType;
-  @JsonKey(readValue: _readContent, toJson: _contentToJson)
+  /// JSON-encoded [SubmessageData].
+  @JsonKey(readValue: readContent, toJson: _contentToJson)
   final Object? content;
   final int messageId;
   final int senderId;
   final int id;
 
-  static Object? _readContent(Map<Object?, Object?> json, String key) {
+  static Object? readContent(Map<Object?, Object?> json, String key) {
     try {
       return (const JsonDecoder().convert(json[key] as String)) as Object?;
     }
@@ -59,7 +60,7 @@ sealed class WidgetData extends SubmessageData {
   static Object? readFromMessage(Map<Object?, Object?> json, String key) {
     final submessages = json['submessages'] as List<Object?>;
     if (submessages.isEmpty) return null;
-    return Submessage._readContent(submessages[0] as Map<String, Object?>, 'content');
+    return Submessage.readContent(submessages[0] as Map<String, Object?>, 'content');
   }
 
   factory WidgetData.fromJson(Object? json) {