import logging
import time

from sqlalchemy import text

logger = logging.getLogger(__name__)


class StorageManager:
    """存储管理器骨架，封装 Redis / MySQL 可用性检测与三级降级状态。"""

    def __init__(self, redis_client=None, mysql_engine=None, check_interval=30):
        self.redis_client = redis_client
        self.mysql_engine = mysql_engine
        self.check_interval = check_interval

        self.redis_available = False
        self.mysql_available = False
        self.last_redis_check = 0
        self.last_mysql_check = 0

    def check_redis(self):
        """惰性检测 Redis 可用性，30 秒间隔内返回缓存结果。"""
        now = time.time()
        if now - self.last_redis_check < self.check_interval:
            return self.redis_available

        if self.redis_client is None:
            self.redis_available = False
        else:
            try:
                self.redis_client.ping()
                self.redis_available = True
            except Exception as e:
                self.redis_available = False

        self.last_redis_check = now
        return self.redis_available

    def check_mysql(self):
        """惰性检测 MySQL 可用性，30 秒间隔内返回缓存结果。"""
        now = time.time()
        if now - self.last_mysql_check < self.check_interval:
            return self.mysql_available

        if self.mysql_engine is None:
            self.mysql_available = False
        else:
            try:
                with self.mysql_engine.connect() as conn:
                    conn.execute(text("SELECT 1"))
                self.mysql_available = True
            except Exception as e:
                self.mysql_available = False

        self.last_mysql_check = now
        return self.mysql_available

    def is_available(self):
        """判断 Redis 或 MySQL 至少一个可用。"""
        return self.check_redis() or self.check_mysql()

    def initialize(self):
        """启动时调用，检测各后端可用性并输出日志。"""
        redis_ok = self.check_redis()
        mysql_ok = self.check_mysql()

        if redis_ok:
            logger.info("Redis 可用")
        else:
            logger.warning("Redis 不可用")

        if mysql_ok:
            logger.info("MySQL 可用")
        else:
            logger.warning("MySQL 不可用")


_storage_manager = None


def get_storage_manager():
    """获取全局 StorageManager 单例。"""
    global _storage_manager
    if _storage_manager is None:
        _storage_manager = StorageManager()
    return _storage_manager