feat: Implement XEP-0444

packages/moxxmpp/lib/src/xeps/xep_0444.dart

@@ -0,0 +1,68 @@
+import 'package:moxxmpp/src/managers/base.dart';
+import 'package:moxxmpp/src/managers/data.dart';
+import 'package:moxxmpp/src/managers/handlers.dart';
+import 'package:moxxmpp/src/managers/namespaces.dart';
+import 'package:moxxmpp/src/namespaces.dart';
+import 'package:moxxmpp/src/stanza.dart';
+import 'package:moxxmpp/src/stringxml.dart';
+
+class MessageReactions {
+  const MessageReactions(this.messageId, this.emojis);
+  final String messageId;
+  final List<String> emojis;
+
+  XMLNode toXml() {
+    return XMLNode.xmlns(
+      tag: 'reactions',
+      xmlns: messageReactionsXmlns,
+      attributes: <String, String>{
+        'id': messageId,
+      },
+      children: emojis.map((emoji) {
+        return XMLNode(
+          tag: 'reaction',
+          text: emoji,
+        );
+      }).toList(),
+    );
+  }
+}
+
+class MessageReactionsManager extends XmppManagerBase {
+  @override
+  List<String> getDiscoFeatures() => [ messageReactionsXmlns ];
+
+  @override
+  String getName() => 'MessageReactionsManager';
+
+  @override
+  String getId() => messageReactionsManager;
+
+  @override
+  List<StanzaHandler> getIncomingStanzaHandlers() => [
+    StanzaHandler(
+      stanzaTag: 'message',
+      tagName: 'reactions',
+      tagXmlns: messageReactionsXmlns,
+      callback: _onReactionsReceived,
+      // Before the message handler
+      priority: -99,
+    ),
+  ];
+
+  @override
+  Future<bool> isSupported() async => true;
+ 
+  Future<StanzaHandlerData> _onReactionsReceived(Stanza message, StanzaHandlerData state) async {
+    final reactionsElement = message.firstTag('reactions', xmlns: messageReactionsXmlns)!;
+    return state.copyWith(
+      messageReactions: MessageReactions(
+        reactionsElement.attributes['id']! as String,
+        reactionsElement.children
+          .where((c) => c.tag == 'reaction')
+          .map((c) => c.innerText())
+          .toList(),
+      ),
+    );
+  }
+}