import time
from functools import wraps
import json

class MemoryCache:
    _instance = None

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super(MemoryCache, cls).__new__(cls)
            cls._instance.cache = {}
            cls._instance.timestamps = {}
        return cls._instance

    def get(self, key):
        """获取缓存，检查是否过期"""
        if key in self.cache:
            timestamp = self.timestamps.get(key, 0)
            if timestamp > time.time():
                return self.cache[key]
            else:
                # 过期则删除
                self.delete(key)
        return None

    def set(self, key, value, expiration=86400):
        """设置缓存，带过期时间"""
        self.cache[key] = value
        self.timestamps[key] = time.time() + expiration

    def delete(self, key):
        """删除缓存"""
        if key in self.cache:
            del self.cache[key]
        if key in self.timestamps:
            del self.timestamps[key]

    def clear_by_prefix(self, prefix):
        """按前缀清除缓存"""
        to_delete = [k for k in self.cache.keys() if k.startswith(prefix)]
        for key in to_delete:
            self.delete(key)

    def get_cache_info(self, key):
        """获取缓存信息"""
        if key in self.cache and key in self.timestamps:
            return {
                "exists": True,
                "expires_at": self.timestamps[key],
                "expires_in": int(self.timestamps[key] - time.time())
            }
        return {"exists": False}

    def clear_all(self):
        """清除所有缓存"""
        self.cache.clear()
        self.timestamps.clear()

# 创建缓存实例
cache = MemoryCache()