"""Simple thread-safe in-memory session state for storing sess_key.

提供 set_sess_key/get_sess_key/clear_sess_key 接口，供其他模块在调用 API 时获取会话 key。
"""
from threading import Lock
from typing import Optional

_lock = Lock()
_sess_key: Optional[str] = None


def set_sess_key(key: str) -> None:
    """设置全局 sess_key（线程安全）。"""
    global _sess_key
    with _lock:
        _sess_key = key


def get_sess_key() -> Optional[str]:
    """获取当前的 sess_key，如果没有则返回 None（线程安全）。"""
    with _lock:
        return _sess_key


def clear_sess_key() -> None:
    """清除当前 sess_key（线程安全）。"""
    global _sess_key
    with _lock:
        _sess_key = None