import json
import logging
import time

from sqlalchemy import text
from sqlalchemy.orm import sessionmaker

from app.models import MarketData, SymbolTimestamp

logger = logging.getLogger(__name__)

# Redis 缓存 TTL：30 天
CACHE_TTL_SECONDS = 30 * 24 * 60 * 60


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")

    def get_market_data(self, symbol, data_type, periods):
        """
        读取行情数据：Redis → MySQL → None（由调用方降级到 SQLite）。

        Args:
            symbol: 品种合约代码
            data_type: 数据类型，如 futures
            periods: 周期，如 5min（对应 Redis key 中的 period）

        Returns:
            dict 或 None
        """
        cache_key = f"market_data:{symbol}:{periods}"

        # 1. 检查 Redis 缓存
        if self.check_redis():
            try:
                raw = self.redis_client.get(cache_key)
                if raw:
                    return json.loads(raw)
            except Exception as e:
                logger.warning(f"Redis 读取失败 [{cache_key}]: {e}")

        # 2. Redis 未命中，检查 MySQL 可用性
        if not self.check_mysql():
            return None

        # 3. 从 MySQL 读取
        try:
            SessionLocal = sessionmaker(bind=self.mysql_engine)
            with SessionLocal() as db:
                record = (
                    db.query(MarketData)
                    .filter_by(symbol=symbol, data_type=data_type, period=periods)
                    .first()
                )
                if not record:
                    return None

                result = {
                    "current_price": record.current_price,
                    "timestamp": (
                        record.fetched_at.isoformat() if record.fetched_at else None
                    ),
                    "candles": (
                        json.loads(record.candles_json) if record.candles_json else []
                    ),
                }

                # 4. 回填 Redis（TTL 30 天）
                if self.check_redis():
                    try:
                        self.redis_client.setex(
                            cache_key,
                            CACHE_TTL_SECONDS,
                            json.dumps(result, ensure_ascii=False),
                        )
                    except Exception as e:
                        logger.warning(f"Redis 回填失败 [{cache_key}]: {e}")

                return result
        except Exception as e:
            logger.warning(f"MySQL 读取失败 [{cache_key}]: {e}")
            return None

    def get_symbol_timestamp(self, symbol, data_type):
        """
        读取合约时间戳：Redis → MySQL → None（由调用方降级到 SQLite）。

        Args:
            symbol: 品种合约代码
            data_type: 数据类型，如 futures

        Returns:
            dict 或 None
        """
        cache_key = f"symbol_timestamps:{symbol}"

        # 1. 检查 Redis 缓存
        if self.check_redis():
            try:
                raw = self.redis_client.get(cache_key)
                if raw:
                    return json.loads(raw)
            except Exception as e:
                logger.warning(f"Redis 读取失败 [{cache_key}]: {e}")

        # 2. Redis 未命中，检查 MySQL 可用性
        if not self.check_mysql():
            return None

        # 3. 从 MySQL 读取
        try:
            SessionLocal = sessionmaker(bind=self.mysql_engine)
            with SessionLocal() as db:
                record = (
                    db.query(SymbolTimestamp)
                    .filter_by(symbol=symbol, data_type=data_type)
                    .first()
                )
                if not record:
                    return None

                result = {
                    "last_refresh_at": (
                        record.last_refresh_at.isoformat()
                        if record.last_refresh_at
                        else None
                    ),
                    "refresh_count": record.refresh_count,
                }

                # 4. 回填 Redis（TTL 30 天）
                if self.check_redis():
                    try:
                        self.redis_client.setex(
                            cache_key,
                            CACHE_TTL_SECONDS,
                            json.dumps(result, ensure_ascii=False),
                        )
                    except Exception as e:
                        logger.warning(f"Redis 回填失败 [{cache_key}]: {e}")

                return result
        except Exception as e:
            logger.warning(f"MySQL 读取失败 [{cache_key}]: {e}")
            return None


_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