add poll support

Fixes #130

lib/models/content/content.dart

@@ -17,6 +17,9 @@ import "package:nexus/models/content/topic.dart";
 import "package:nexus/models/content/sticker.dart";
 import "package:nexus/models/content/history_visibility.dart";
 import "package:nexus/models/content/image_pack.dart";
+import "package:nexus/models/content/poll_end.dart";
+import "package:nexus/models/content/poll_response.dart";
+import "package:nexus/models/content/poll_start.dart";
 
 class const Content({final String? parseError, final StackTrace? stackTrace}) {
   factory Content.fromJson(Map<String, dynamic> json) => const Content();
@@ -64,5 +67,11 @@ enum EventType(
   pinnedEvents("m.room.pinned_events", PinnedEventsContent.fromJson),
   imagePack("m.room.image_pack", ImagePackContent.fromJson),
   legacyImagePack("im.ponies.room_emotes", ImagePackContent.fromJson),
+  pollStart("org.matrix.msc3381.poll.start", PollStartContent.fromJson),
+  pollResponse(
+    "org.matrix.msc3381.poll.response",
+    PollResponseContent.fromJson,
+  ),
+  pollEnd("org.matrix.msc3381.poll.end", PollEndContent.fromJson),
   message("m.room.message", MessageContent.fromJson),
 }

lib/models/content/poll_end.dart

@@ -0,0 +1,12 @@
+import "package:nexus/models/content/content.dart";
+
+class const PollEndContent() extends Content {
+  factory PollEndContent.fromJson(Map<String, dynamic> json) =>
+      const PollEndContent();
+
+  @override
+  Map<String, dynamic> toJson() => {
+    "org.matrix.msc3381.poll.end": {},
+    "org.matrix.msc1767.text": "Ended the poll",
+  };
+}

lib/models/content/poll_response.dart

@@ -0,0 +1,23 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:freezed_annotation/freezed_annotation.dart";
+import "package:nexus/models/content/content.dart";
+part "poll_response.freezed.dart";
+part "poll_response.g.dart";
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable(createToJson: false)
+class const PollResponseContent({
+  @JsonKey(readValue: PollResponseContent.answersFromJson)
+  final IList<String> answers = const .empty(),
+}) extends Content with _$PollResponseContent {
+  static List<dynamic>? answersFromJson(Map<dynamic, dynamic> json, _) =>
+      json["org.matrix.msc3381.poll.response"]?["answers"];
+
+  @override
+  Map<String, Object?> toJson() => {
+    "org.matrix.msc3381.poll.response": {"answers": answers.toList()},
+  };
+
+  factory PollResponseContent.fromJson(Map<String, Object?> json) =>
+      _$PollResponseContentFromJson(json);
+}

lib/models/content/poll_start.dart

@@ -0,0 +1,90 @@
+import "dart:math";
+
+import "package:collection/collection.dart";
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:freezed_annotation/freezed_annotation.dart";
+import "package:nexus/models/content/content.dart";
+part "poll_start.freezed.dart";
+part "poll_start.g.dart";
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable(createToJson: false)
+class const PollStartContent({
+  @JsonKey(name: "org.matrix.msc3381.poll.start") required final PollStart poll,
+}) extends Content with _$PollStartContent {
+  @override
+  Map<String, Object?> toJson() => {
+    "org.matrix.msc3381.poll.start": poll.toJson(),
+    // Shown by clients without poll support
+    "org.matrix.msc1767.text": [
+      poll.question,
+      ...poll.answers.mapIndexed(
+        (index, answer) => "${index + 1}. ${answer.text}",
+      ),
+    ].join("\n"),
+  };
+
+  factory PollStartContent.fromJson(Map<String, Object?> json) =>
+      _$PollStartContentFromJson(json);
+}
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const PollStart({
+  @JsonKey(readValue: PollStart.questionFromJson) final String question = "",
+  final int? maxSelections,
+  @JsonKey(readValue: PollStart.answersFromJson)
+  final IList<PollAnswer> answers = const .empty(),
+}) with _$PollStart {
+  static const maxAnswers = 20;
+
+  static String? extensibleTextFromJson(Object? json) => switch (json) {
+    {"org.matrix.msc1767.text": final String text} => text,
+    {"body": final String body} => body,
+    {"org.matrix.msc1767.message": final List message} =>
+      message
+          .whereType<Map>()
+          .map((part) => part["body"])
+          .whereType<String>()
+          .firstOrNull,
+    _ => null,
+  };
+
+  static String? questionFromJson(Map<dynamic, dynamic> json, String key) =>
+      PollStart.extensibleTextFromJson(json[key]);
+
+  static List<dynamic>? answersFromJson(
+    Map<dynamic, dynamic> json,
+    String key,
+  ) => (json[key] as List?)?.take(maxAnswers).toList();
+
+  /// [maxSelections], defaulting to 1, and at most the number of answers
+  int get selectionLimit =>
+      (maxSelections ?? 1).clamp(1, max(answers.length, 1));
+
+  Map<String, Object?> toJson() => {
+    ..._$PollStartToJson(this),
+    // We don't allow undisclosed polls as they make no sense
+    "kind": "org.matrix.msc3381.poll.disclosed",
+    "question": {"org.matrix.msc1767.text": question},
+    "answers": answers.map((answer) => answer.toJson()).toList(),
+  };
+
+  factory PollStart.fromJson(Map<String, Object?> json) =>
+      _$PollStartFromJson(json);
+}
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable(createToJson: false)
+class const PollAnswer({
+  required final String id,
+  @JsonKey(readValue: PollAnswer.textFromJson) final String text = "",
+}) with _$PollAnswer {
+  static String? textFromJson(Map<dynamic, dynamic> json, _) =>
+      PollStart.extensibleTextFromJson(json);
+
+  Map<String, Object?> toJson() => {"id": id, "org.matrix.msc1767.text": text};
+
+  factory PollAnswer.fromJson(Map<String, Object?> json) =>
+      _$PollAnswerFromJson(json);
+}