optimitic update in flutter

packages/z-timeline/lib/main.dart

@@ -122,21 +122,41 @@ class _MainAppState extends State<MainApp> {
     String newGroupId,
     int newLane,
   ) {
-    final payload = <String, Object?>{
+    final duration = entry.end.difference(entry.start);
+    final newEnd = entry.hasEnd ? newStart.add(duration) : null;
+
+    // Optimistic update – apply locally before the host round-trips.
+    if (_state case final state?) {
+      final oldItem = state.items[entry.id];
+      if (oldItem != null) {
+        final updatedItems = Map<String, TimelineItemData>.of(state.items);
+        updatedItems[entry.id] = TimelineItemData(
+          id: oldItem.id,
+          groupId: newGroupId,
+          title: oldItem.title,
+          description: oldItem.description,
+          start: newStart.toIso8601String(),
+          end: newEnd?.toIso8601String(),
+          lane: newLane,
+        );
+        final updatedState = TimelineState(
+          timeline: state.timeline,
+          groups: state.groups,
+          items: updatedItems,
+          groupOrder: state.groupOrder,
+          selectedItemId: state.selectedItemId,
+        );
+        _applyState(updatedState);
+      }
+    }
+
+    emitEvent('entry_moved', <String, Object?>{
       'entryId': entry.id,
       'newStart': newStart.toIso8601String(),
       'newGroupId': newGroupId,
       'newLane': newLane,
-    };
+      'newEnd': newEnd?.toIso8601String(),
-
+    });
-    if (entry.hasEnd) {
-      final duration = entry.end.difference(entry.start);
-      payload['newEnd'] = newStart.add(duration).toIso8601String();
-    } else {
-      payload['newEnd'] = null;
-    }
-
-    emitEvent('entry_moved', payload);
   }
 
   void _emitContentHeight() {