Fix operation tree bug

api/operation.py

@@ -12,10 +12,10 @@ def _update_current_operation(name: str, old_id: int, id: int) -> None:
 
 def _add_redo_undo(name: str, redo: str, undo: str) -> int:
     with conn[name].cursor(row_factory=dict_row) as cur:
-        cur.execute("select max(id) from operation")
-        parent = int(cur.fetchone()['max'])
+        parent = _get_current_operation(name)
         cur.execute(f"insert into operation (id, redo, undo, parent) values (default, '{redo}', '{undo}', {parent})")
-        return parent + 1
+        cur.execute("select max(id) from operation")
+        return int(cur.fetchone()['max'])
 
 # execute curr undo
 def _query_undo(name: str, id: str) -> dict[str, str]: