properly persist decryption of events

lib/src/event.dart

@@ -425,6 +425,25 @@ class Event {
   /// if it fails and does nothing if the event was not encrypted.
   Event get decrypted => room.decryptGroupMessage(this);
 
+  /// Trys to decrypt this event and persists it in the database afterwards
+  Future<Event> decryptAndStore([String updateType = 'timeline']) async {
+    final newEvent = decrypted;
+    if (newEvent.type == EventTypes.Encrypted || room.client.database == null) {
+      return newEvent; // decryption failed or we don't have a database
+    }
+    await room.client.database.storeEventUpdate(
+      room.client.id,
+      EventUpdate(
+        eventType: newEvent.typeKey,
+        content: newEvent.toJson(),
+        roomID: newEvent.roomId,
+        type: updateType,
+        sortOrder: newEvent.sortOrder,
+      ),
+    );
+    return newEvent;
+  }
+
   /// If this event is encrypted and the decryption was not successful because
   /// the session is unknown, this requests the session key from other devices
   /// in the room. If the event is not encrypted or the decryption failed because

lib/src/room.dart

@@ -271,9 +271,9 @@ class Room {
     onSessionKeyReceived.add(sessionId);
   }
 
-  void _tryAgainDecryptLastMessage() {
+  Future<void> _tryAgainDecryptLastMessage() async {
     if (getState('m.room.encrypted') != null) {
-      final decrypted = getState('m.room.encrypted').decrypted;
+      final decrypted = await getState('m.room.encrypted').decryptAndStore();
       if (decrypted.type != EventTypes.Encrypted) {
         setState(decrypted);
       }
@@ -1207,19 +1207,7 @@ class Room {
           if (events[i].type == EventTypes.Encrypted &&
               events[i].content['body'] == DecryptError.UNKNOWN_SESSION) {
             await events[i].loadSession();
-            events[i] = events[i].decrypted;
-            if (events[i].type != EventTypes.Encrypted) {
-              await client.database.storeEventUpdate(
-                client.id,
-                EventUpdate(
-                  eventType: events[i].typeKey,
-                  content: events[i].toJson(),
-                  roomID: events[i].roomId,
-                  type: 'timeline',
-                  sortOrder: events[i].sortOrder,
-                ),
-              );
-            }
+            events[i] = await events[i].decryptAndStore();
           }
         }
       });

lib/src/timeline.dart

@@ -97,19 +97,26 @@ class Timeline {
     sessionIdReceivedSub?.cancel();
   }
 
-  void _sessionKeyReceived(String sessionId) {
+  void _sessionKeyReceived(String sessionId) async {
     var decryptAtLeastOneEvent = false;
+    final decryptFn = () async {
       for (var i = 0; i < events.length; i++) {
         if (events[i].type == EventTypes.Encrypted &&
             events[i].messageType == MessageTypes.BadEncrypted &&
             events[i].content['body'] == DecryptError.UNKNOWN_SESSION &&
             events[i].content['session_id'] == sessionId) {
-        events[i] = events[i].decrypted;
+          events[i] = await events[i].decryptAndStore();
           if (events[i].type != EventTypes.Encrypted) {
             decryptAtLeastOneEvent = true;
           }
         }
       }
+    };
+    if (room.client.database != null) {
+      await room.client.database.transaction(decryptFn);
+    } else {
+      await decryptFn();
+    }
     if (decryptAtLeastOneEvent) onUpdate();
   }