"""
元数据字段定义缓存服务
使用 Redis 缓存 metadata_field_definitions，减少数据库查询
"""

import json
import logging
from typing import Any

from app.core.config import get_settings

logger = logging.getLogger(__name__)


class MetadataCacheService:
    """
    元数据字段定义缓存服务
    
    缓存策略：
    - Key: metadata:fields:{tenant_id}
    - Value: JSON 序列化的字段定义列表
    - TTL: 1小时（3600秒）
    - 更新策略：写时更新 + 定时刷新
    """
    
    CACHE_KEY_PREFIX = "metadata:fields"
    DEFAULT_TTL = 3600  # 1小时
    
    def __init__(self):
        self._settings = get_settings()
        self._redis_client = None
        self._enabled = self._settings.redis_enabled
    
    async def _get_redis(self):
        """获取 Redis 连接（延迟初始化）"""
        if not self._enabled:
            return None
        
        if self._redis_client is None:
            try:
                import redis.asyncio as redis
                self._redis_client = redis.from_url(
                    self._settings.redis_url,
                    decode_responses=True
                )
            except Exception as e:
                logger.error(f"[MetadataCache] Failed to connect Redis: {e}")
                self._enabled = False
                return None
        
        return self._redis_client
    
    def _make_key(self, tenant_id: str) -> str:
        """生成缓存 key"""
        return f"{self.CACHE_KEY_PREFIX}:{tenant_id}"
    
    async def get_fields(self, tenant_id: str) -> list[dict[str, Any]] | None:
        """
        获取缓存的字段定义
        
        Args:
            tenant_id: 租户 ID
            
        Returns:
            字段定义列表，未缓存返回 None
        """
        if not self._enabled:
            return None
        
        try:
            redis = await self._get_redis()
            if not redis:
                return None
            
            key = self._make_key(tenant_id)
            cached_data = await redis.get(key)
            
            if cached_data:
                logger.info(f"[MetadataCache] Cache hit for tenant={tenant_id}")
                return json.loads(cached_data)
            
            logger.info(f"[MetadataCache] Cache miss for tenant={tenant_id}")
            return None
            
        except Exception as e:
            logger.error(f"[MetadataCache] Get cache error: {e}")
            return None
    
    async def set_fields(
        self,
        tenant_id: str,
        fields: list[dict[str, Any]],
        ttl: int | None = None
    ) -> bool:
        """
        缓存字段定义
        
        Args:
            tenant_id: 租户 ID
            fields: 字段定义列表
            ttl: 过期时间（秒），默认 1小时
            
        Returns:
            是否成功
        """
        if not self._enabled:
            return False
        
        try:
            redis = await self._get_redis()
            if not redis:
                return False
            
            key = self._make_key(tenant_id)
            ttl = ttl or self.DEFAULT_TTL
            
            await redis.setex(
                key,
                ttl,
                json.dumps(fields, ensure_ascii=False, default=str)
            )
            
            logger.info(
                f"[MetadataCache] Cached {len(fields)} fields for tenant={tenant_id}, "
                f"ttl={ttl}s"
            )
            return True
            
        except Exception as e:
            logger.error(f"[MetadataCache] Set cache error: {e}")
            return False
    
    async def invalidate(self, tenant_id: str) -> bool:
        """
        使缓存失效（字段定义更新时调用）
        
        Args:
            tenant_id: 租户 ID
            
        Returns:
            是否成功
        """
        if not self._enabled:
            return False
        
        try:
            redis = await self._get_redis()
            if not redis:
                return False
            
            key = self._make_key(tenant_id)
            result = await redis.delete(key)
            
            if result:
                logger.info(f"[MetadataCache] Invalidated cache for tenant={tenant_id}")
            return bool(result)
            
        except Exception as e:
            logger.error(f"[MetadataCache] Invalidate error: {e}")
            return False
    
    async def invalidate_all(self) -> bool:
        """
        使所有元数据缓存失效
        
        Returns:
            是否成功
        """
        if not self._enabled:
            return False
        
        try:
            redis = await self._get_redis()
            if not redis:
                return False
            
            # 查找所有元数据缓存 key
            pattern = f"{self.CACHE_KEY_PREFIX}:*"
            keys = []
            async for key in redis.scan_iter(match=pattern):
                keys.append(key)
            
            if keys:
                await redis.delete(*keys)
                logger.info(f"[MetadataCache] Invalidated {len(keys)} cache entries")
            return True
            
        except Exception as e:
            logger.error(f"[MetadataCache] Invalidate all error: {e}")
            return False


# 全局缓存服务实例
_metadata_cache_service: MetadataCacheService | None = None


async def get_metadata_cache_service() -> MetadataCacheService:
    """获取元数据缓存服务实例（单例）"""
    global _metadata_cache_service
    if _metadata_cache_service is None:
        _metadata_cache_service = MetadataCacheService()
    return _metadata_cache_service