refactor api_server and post_parser: implement asynchronous JSON file operations with locking mechanism to ensure thread safety, and streamline media file ID persistence logic

file_io.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+# flake8: noqa
+# pylint: disable=missing-function-docstring
+
+import os
+import json
+import asyncio
+from typing import Any, List
+
+
+# One shared lock for operations that write to media_file_ids.json
+_media_file_ids_lock: asyncio.Lock | None = None
+
+
+def get_media_file_ids_lock() -> asyncio.Lock:
+    global _media_file_ids_lock
+    if _media_file_ids_lock is None:
+        _media_file_ids_lock = asyncio.Lock()
+    return _media_file_ids_lock
+
+
+def read_json_file_sync(file_path: str) -> List[dict[str, Any]]:
+    with open(file_path, 'r', encoding='utf-8') as f:
+        return json.load(f)
+
+
+def write_json_file_sync(file_path: str, data: List[dict[str, Any]]) -> None:
+    temp_path = f"{file_path}.tmp"
+    with open(temp_path, 'w', encoding='utf-8') as f:
+        json.dump(data, f, ensure_ascii=False, indent=2)
+    os.replace(temp_path, file_path)
+
+