auto-refresh message-list on FB message receive

flutter/lib/state/app_events.dart

@@ -0,0 +1,47 @@
+import 'package:simplecloudnotifier/models/scn_message.dart';
+import 'package:simplecloudnotifier/state/application_log.dart';
+
+class AppEvents {
+  static AppEvents? _singleton = AppEvents._internal();
+
+  factory AppEvents() {
+    return _singleton ?? (_singleton = AppEvents._internal());
+  }
+
+  AppEvents._internal() {}
+
+  List<void Function(String)> _searchListeners = [];
+  List<void Function(SCNMessage)> _messageReceivedListeners = [];
+
+  void subscribeSearchListener(void Function(String) listener) {
+    _searchListeners.add(listener);
+  }
+
+  void unsubscribeSearchListener(void Function(String) listener) {
+    _searchListeners.remove(listener);
+  }
+
+  void notifySearchListeners(String query) {
+    ApplicationLog.debug('[AppEvents] onSearch: $query');
+
+    for (var listener in _searchListeners) {
+      listener(query);
+    }
+  }
+
+  void subscribeMessageReceivedListener(void Function(SCNMessage) listener) {
+    _messageReceivedListeners.add(listener);
+  }
+
+  void unsubscribeMessageReceivedListener(void Function(SCNMessage) listener) {
+    _messageReceivedListeners.remove(listener);
+  }
+
+  void notifyMessageReceivedListeners(SCNMessage msg) {
+    ApplicationLog.debug('[AppEvents] onMessageReceived: ${msg.messageID}');
+
+    for (var listener in _messageReceivedListeners) {
+      listener(msg);
+    }
+  }
+}