added guardian letters with chat and multiple answer functionalities

lib/push/push_renderer.dart

@@ -12,6 +12,7 @@ import 'nid_store.dart';
 import 'push_actions.dart';
 import 'push_avatar.dart';
 import 'push_subject.dart';
+import 'push_target.dart';
 
 /// Renders decrypted push subjects (and plaintext Connect pushes) as local
 /// notifications. Talk messages of one chat stack into a SINGLE
@@ -23,6 +24,8 @@ class PushRenderer {
   static const talkChannelName = 'Talk-Nachrichten';
   static const generalChannelId = 'nextcloud_general';
   static const generalChannelName = 'Benachrichtigungen';
+  static const parentLettersChannelId = 'parent_letters';
+  static const parentLettersChannelName = 'Elternbriefe';
 
   static const String iosTalkCategory = 'TALK_MESSAGE';
 
@@ -67,6 +70,14 @@ class PushRenderer {
         description: 'Allgemeine Benachrichtigungen',
       ),
     );
+    await android.createNotificationChannel(
+      const AndroidNotificationChannel(
+        parentLettersChannelId,
+        parentLettersChannelName,
+        description: 'Neue Elternbriefe und Antworten der Schule',
+        importance: Importance.high,
+      ),
+    );
   }
 
   /// Renders a decrypted Nextcloud push subject.
@@ -350,23 +361,35 @@ class PushRenderer {
     required String body,
     Map<String, String>? data,
   }) async {
-    final id = _fallbackId('$title$body');
-    const androidDetails = AndroidNotificationDetails(
-      generalChannelId,
-      generalChannelName,
+    final parentLetterId = data?[parentLetterIdKey];
+    final isParentLetter =
+        data?['type'] == parentLetterPushType &&
+        parentLetterId != null &&
+        parentLetterId.isNotEmpty;
+    // One notification per letter: a reply replaces the letter's earlier one.
+    final id = isParentLetter
+        ? parentLetterNotificationId(parentLetterId)
+        : _fallbackId('$title$body');
+    final androidDetails = AndroidNotificationDetails(
+      isParentLetter ? parentLettersChannelId : generalChannelId,
+      isParentLetter ? parentLettersChannelName : generalChannelName,
       importance: Importance.high,
       priority: Priority.high,
       color: _accentColor,
+      styleInformation: isParentLetter ? BigTextStyleInformation(body) : null,
     );
     await _plugin.show(
       id: id,
       title: title,
       body: body,
-      notificationDetails: const NotificationDetails(android: androidDetails),
+      notificationDetails: NotificationDetails(android: androidDetails),
       payload: data == null ? null : jsonEncode(data),
     );
   }
 
+  static int parentLetterNotificationId(String letterId) =>
+      stableChatNotificationId('parent-letter:$letterId');
+
   String _payload({required String? chatToken, required int nid}) =>
       jsonEncode({'chatToken': ?chatToken, 'nid': nid});