import asyncio
import aiomysql
from contextlib import asynccontextmanager
from typing import  Dict,Optional, AsyncGenerator
from foundation.observability.logger.loggering import server_logger
from foundation.utils.common import handler_err
from foundation.infrastructure.config import config_handler

# 异步数据库连接池
class AsyncMySQLPool:
    _instance = None

    def __new__(cls, *args, **kwargs):
        if not cls._instance:
            cls._instance = super().__new__(cls)
        return cls._instance

    def __init__(self):
        if not hasattr(self, '_pool'):
            self._pool = None
            self._initialized = False

    async def initialize(self, max_retries=3, retry_delay=2):
        """初始化连接池，支持重试。已初始化且连接池健康时直接返回。"""
        if self._initialized and self._pool and not self._pool._closed:
            if self._pool._loop and not self._pool._loop.is_closed():
                return
            server_logger.info("事件循环已关闭，丢弃旧连接池引用...")
            self._pool = None
            self._initialized = False

        # 关闭旧池（如果有，且事件循环仍存活）
        if self._pool and not self._pool._closed:
            if self._pool._loop and self._pool._loop.is_closed():
                server_logger.info("旧连接池的事件循环已关闭，丢弃引用...")
                self._pool = None
                self._initialized = False
            else:
                server_logger.info("关闭旧连接池...")
                self._pool.close()
                await self._pool.wait_closed()
                self._pool = None
                self._initialized = False

        last_error = None

        for attempt in range(1, max_retries + 1):
            try:
                server_logger.info(f"尝试初始化MySQL连接池 (第{attempt}/{max_retries}次)...")

                self._pool = await aiomysql.create_pool(
                    host=config_handler.get("mysql", "MYSQL_HOST" , "localhost"),
                    port=int(config_handler.get("mysql", "MYSQL_PORT" , "3306")),
                    user=config_handler.get("mysql", "MYSQL_USER"),
                    password=config_handler.get("mysql", "MYSQL_PASSWORD"),
                    db=config_handler.get("mysql", "MYSQL_DB"),
                    minsize=int(config_handler.get("mysql", "MYSQL_MIN_SIZE" , "1")),
                    maxsize=int(config_handler.get("mysql", "MYSQL_MAX_SIZE" , "2")),
                    autocommit=config_handler.get("mysql", "MYSQL_AUTO_COMMIT"),
                    connect_timeout=int(config_handler.get("mysql", "MYSQL_CONNECT_TIMEOUT", "30")),
                    pool_recycle=1800
                )
                self._initialized = True
                server_logger.info("异步MySQL连接池初始化成功")
                return
            except Exception as e:
                last_error = e
                server_logger.warning(f"连接池初始化失败 (第{attempt}次): {e}")
                if attempt < max_retries:
                    server_logger.info(f"{retry_delay}秒后重试...")
                    await asyncio.sleep(retry_delay)

        server_logger.error(f"连接池初始化失败，已重试{max_retries}次: {last_error}")
        raise last_error
    
    async def close(self):
        """关闭连接池"""
        if self._pool:
            self._pool.close()
            await self._pool.wait_closed()
            server_logger.info("异步MySQL连接池已关闭")
    
    @asynccontextmanager
    async def get_connection(self) -> AsyncGenerator[aiomysql.Connection, None]:
        """获取数据库连接的上下文管理器，带连接健康检查"""
        if not self._initialized or not self._pool or self._pool._closed:
            await self.initialize()

        async with self._pool.acquire() as conn:
            try:
                await conn.ping()
            except Exception:
                server_logger.warning("连接已失效，尝试重新初始化连接池")
                await self.initialize()
                async with self._pool.acquire() as new_conn:
                    try:
                        yield new_conn
                    except Exception as e:
                        server_logger.error(f"数据库连接操作失败: {e}")
                        raise
                return
            try:
                yield conn
            except Exception as e:
                server_logger.error(f"数据库连接操作失败: {e}")
                raise
    
    @asynccontextmanager
    async def get_cursor(self, connection: Optional[aiomysql.Connection] = None) -> AsyncGenerator[aiomysql.Cursor, None]:
        """获取游标的上下文管理器"""
        if connection:
            # 使用提供的连接
            async with connection.cursor(aiomysql.DictCursor) as cursor:
                try:
                    yield cursor
                except Exception as e:
                    server_logger.error(f"游标操作失败: {e}")
                    raise
        else:
            # 创建新连接
            async with self.get_connection() as conn:
                async with conn.cursor(aiomysql.DictCursor) as cursor:
                    try:
                        yield cursor
                    except Exception as e:
                        server_logger.error(f"游标操作失败: {e}")
                        raise


# 全局数据库连接池实例
#async_db_pool = AsyncMySQLPool()