add _refreshLastEvent to Thread

use Event.fromMatrixEvent instead of casting

lib/src/thread.dart

@@ -3,11 +3,13 @@ import 'package:matrix/matrix.dart';
 class Thread {
   final Room room;
   final Event rootEvent;
-  final Event? lastEvent;
+  Event? lastEvent;
+  final Client client;
 
   Thread({
     required this.room,
     required this.rootEvent,
+    required this.client,
     this.lastEvent,
   });
 
@@ -15,14 +17,63 @@ class Thread {
     final room = client.getRoomById(json['room_id']);
     if (room == null) throw Error();
     Event? lastEvent;
-    if (json['unsigned']?['m.relations']?['m.thread']?['latest_event'] != null) {
+    if (json['unsigned']?['m.relations']?['m.thread']?['latest_event'] !=
-      lastEvent = MatrixEvent.fromJson(json['unsigned']?['m.relations']?['m.thread']?['latest_event']) as Event;
+        null) {
+      lastEvent = Event.fromMatrixEvent(
+        MatrixEvent.fromJson(
+            json['unsigned']?['m.relations']?['m.thread']?['latest_event']),
+        room,
+      );
     }
     final thread = Thread(
       room: room,
-        rootEvent: MatrixEvent.fromJson(json) as Event,
+      client: client,
+      rootEvent: Event.fromMatrixEvent(
+        MatrixEvent.fromJson(json),
+        room,
+      ),
       lastEvent: lastEvent,
     );
     return thread;
   }
+
+  Future<Event?>? _refreshingLastEvent;
+
+  Future<Event?> _refreshLastEvent({
+    timeout = const Duration(seconds: 30),
+  }) async {
+    if (room.membership != Membership.join) return null;
+
+    final result = await client
+        .getRelatingEventsWithRelType(
+          room.id,
+          rootEvent.eventId,
+          'm.thread',
+        )
+        .timeout(timeout);
+    final matrixEvent = result.chunk.firstOrNull;
+    if (matrixEvent == null) {
+      if (lastEvent?.type == EventTypes.refreshingLastEvent) {
+        lastEvent = null;
+      }
+      Logs().d(
+        'No last event found for thread ${rootEvent.eventId} in ${rootEvent.roomId}',
+      );
+      return null;
+    }
+    var event = Event.fromMatrixEvent(
+      matrixEvent,
+      room,
+      status: EventStatus.synced,
+    );
+    if (event.type == EventTypes.Encrypted) {
+      final encryption = client.encryption;
+      if (encryption != null) {
+        event = await encryption.decryptRoomEvent(event);
+      }
+    }
+    lastEvent = event;
+
+    return event;
+  }
 }