wip api: Add unreadMsgs in initial snapshot

TODO resolve two #api documentation discussions:
  https://chat.zulip.org/#narrow/stream/412-api-documentation/topic/register.3A.20.60unread_msgs.2Epms.5B.5D.2Eunread_message_ids.60/near/1623940
  https://chat.zulip.org/#narrow/stream/412-api-documentation/topic/register.3A.20When.20was.20.60unread_msgs.2Epms.5B.5D.2Eother_user_id.60.20added.3F/near/1623961

Our own data structure in PerAccountStore will be constructed from
this value, and it will probably have quite a different shape; for
example, we're likely to want to collapse the distinction between
1:1 and group DMs.

But now we're validating this part of the /register response and
making it available to feed into those new internal data structures.

Related: #253

Author: chrisbobbe

lib/api/model/initial_snapshot.dart

@@ -28,6 +28,8 @@ class InitialSnapshot {
 
   final List<Subscription> subscriptions;
 
+  final UnreadMessagesSnapshot unreadMsgs;
+
   final List<ZulipStream> streams;
 
   final int maxFileUploadSizeMib;
@@ -70,6 +72,7 @@ class InitialSnapshot {
     required this.customProfileFields,
     required this.recentPrivateConversations,
     required this.subscriptions,
+    required this.unreadMsgs,
     required this.streams,
     required this.maxFileUploadSizeMib,
     required this.realmUsers,
@@ -102,3 +105,98 @@ class RecentDmConversation {
 
   Map<String, dynamic> toJson() => _$RecentDmConversationToJson(this);
 }
+
+/// The `unread_msgs` snapshot.
+///
+/// For docs, search for "unread_msgs:"
+/// in <https://zulip.com/api/register-queue>.
+@JsonSerializable(fieldRename: FieldRename.snake)
+class UnreadMessagesSnapshot {
+  final int count;
+
+  @JsonKey(name: 'pms')
+  final List<UnreadDmSnapshot> dms;
+
+  final List<UnreadStreamSnapshot> streams;
+  final List<UnreadHuddleSnapshot> huddles;
+  final List<int> mentions;
+  final bool oldUnreadsMissing;
+
+  UnreadMessagesSnapshot({
+    required this.count,
+    required this.dms,
+    required this.streams,
+    required this.huddles,
+    required this.mentions,
+    required this.oldUnreadsMissing,
+  });
+
+  factory UnreadMessagesSnapshot.fromJson(Map<String, dynamic> json) =>
+    _$UnreadMessagesSnapshotFromJson(json);
+
+  Map<String, dynamic> toJson() => _$UnreadMessagesSnapshotToJson(this);
+}
+
+/// An item in `unread_msgs.pms`.
+///
+/// For docs, search for "unread_msgs:" and see "pms:"
+/// in <https://zulip.com/api/register-queue>.
+@JsonSerializable(fieldRename: FieldRename.snake)
+class UnreadDmSnapshot {
+  final int otherUserId;
+  // final int senderId; // deprecated; ignore
+  final List<int> unreadMessageIds;
+
+  UnreadDmSnapshot({
+    required this.otherUserId,
+    required this.unreadMessageIds,
+  });
+
+  factory UnreadDmSnapshot.fromJson(Map<String, dynamic> json) =>
+    _$UnreadDmSnapshotFromJson(json);
+
+  Map<String, dynamic> toJson() => _$UnreadDmSnapshotToJson(this);
+}
+
+/// An item in `unread_msgs.streams`.
+///
+/// For docs, search for "unread_msgs:" and see "streams:"
+/// in <https://zulip.com/api/register-queue>.
+@JsonSerializable(fieldRename: FieldRename.snake)
+class UnreadStreamSnapshot {
+  final String topic;
+  final int streamId;
+  final List<int> unreadMessageIds;
+  // final List<int> senderIds; // deprecated; ignore
+
+  UnreadStreamSnapshot({
+    required this.topic,
+    required this.streamId,
+    required this.unreadMessageIds,
+  });
+
+  factory UnreadStreamSnapshot.fromJson(Map<String, dynamic> json) =>
+    _$UnreadStreamSnapshotFromJson(json);
+
+  Map<String, dynamic> toJson() => _$UnreadStreamSnapshotToJson(this);
+}
+
+/// An item in `unread_msgs.huddles`.
+///
+/// For docs, search for "unread_msgs:" and see "huddles:"
+/// in <https://zulip.com/api/register-queue>.
+@JsonSerializable(fieldRename: FieldRename.snake)
+class UnreadHuddleSnapshot {
+  final String userIdsString;
+  final List<int> unreadMessageIds;
+
+  UnreadHuddleSnapshot({
+    required this.userIdsString,
+    required this.unreadMessageIds,
+  });
+
+  factory UnreadHuddleSnapshot.fromJson(Map<String, dynamic> json) =>
+    _$UnreadHuddleSnapshotFromJson(json);
+
+  Map<String, dynamic> toJson() => _$UnreadHuddleSnapshotToJson(this);
+}

lib/api/model/initial_snapshot.g.dart

@@ -92,6 +92,25 @@ ZulipStream stream({
   );
 }
 
+UnreadMessagesSnapshot unreadMsgs({
+  int? count,
+  List<UnreadDmSnapshot>? dms,
+  List<UnreadStreamSnapshot>? streams,
+  List<UnreadHuddleSnapshot>? huddles,
+  List<int>? mentions,
+  bool? oldUnreadsMissing,
+}) {
+  return UnreadMessagesSnapshot(
+    count: count ?? 0,
+    dms: dms ?? [],
+    streams: streams ?? [],
+    huddles: huddles ?? [],
+    mentions: mentions ?? [],
+    oldUnreadsMissing: oldUnreadsMissing ?? false,
+  );
+}
+const _unreadMsgs = unreadMsgs;
+
 final _messagePropertiesBase = {
   'is_me_message': false,
   'recipient_id': 32, // obsolescent in API, and ignored
@@ -207,6 +226,7 @@ InitialSnapshot initialSnapshot({
   List<CustomProfileField>? customProfileFields,
   List<RecentDmConversation>? recentPrivateConversations,
   List<Subscription>? subscriptions,
+  UnreadMessagesSnapshot? unreadMsgs,
   List<ZulipStream>? streams,
   int? maxFileUploadSizeMib,
   List<User>? realmUsers,
@@ -223,6 +243,7 @@ InitialSnapshot initialSnapshot({
     customProfileFields: customProfileFields ?? [],
     recentPrivateConversations: recentPrivateConversations ?? [],
     subscriptions: subscriptions ?? [], // TODO add subscriptions to default
+    unreadMsgs: unreadMsgs ?? _unreadMsgs(),
     streams: streams ?? [], // TODO add streams to default
     maxFileUploadSizeMib: maxFileUploadSizeMib ?? 25,
     realmUsers: realmUsers ?? [],