"""Redis 分布式锁（SET NX EX）。"""
import secrets
import time

import redis.asyncio as aioredis

from app.config import settings


class Lock:
    def __init__(self, redis: aioredis.Redis, name: str, timeout: int = settings.lock_timeout):
        self.redis = redis
        self.name = name
        self.timeout = timeout
        self._token = secrets.token_hex(8)

    async def acquire(self) -> bool:
        ok = await self.redis.set(self.name, self._token, nx=True, ex=self.timeout)
        return bool(ok)

    async def release(self) -> None:
        # 仅在持有相同 token 时释放，避免误删他人锁
        val = await self.redis.get(self.name)
        if val == self._token:
            await self.redis.delete(self.name)

    async def guarded(self, fn):
        """上下文封装：获取锁执行，释放锁。"""
        if not await self.acquire():
            return False
        try:
            await fn()
            return True
        finally:
            await self.release()