from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker
from config import settings
from utils.logger import session_logger
import asyncio
import urllib.parse

class DatabaseManager:
    _instance = None
    _lock = asyncio.Lock()
    
    def __init__(self):
        self.engine = None
        self.async_session = None
        self._initialized = False
    
    @classmethod
    async def get_instance(cls):
        async with cls._lock:
            if cls._instance is None:
                cls._instance = DatabaseManager()
            
            if not cls._instance._initialized:
                await cls._instance.initialize()
                
            return cls._instance
    
    async def initialize(self):
        if self._initialized:
            return
            
        try:
            encoded_password = urllib.parse.quote_plus(settings.db_password)
            connection_string = f"mysql+aiomysql://{settings.db_user}:{encoded_password}@{settings.db_host}:{settings.db_port}/{settings.db_name}?charset=utf8mb4"
            self.engine = create_async_engine(
                connection_string,
                echo=settings.db_echo,
                pool_pre_ping=True,
                pool_recycle=3600,
            )
            
            self.async_session = sessionmaker(
                self.engine, expire_on_commit=False, class_=AsyncSession
            )
            
            self._initialized = True
            session_logger.info("system", "database", f"数据库连接初始化成功: {settings.db_host}:{settings.db_port}/{settings.db_name}")
        except Exception as e:
            session_logger.error("system", "database", f"数据库连接初始化失败: {str(e)}")
            raise
    
    async def get_session(self):
        """获取数据库会话"""
        if not self._initialized:
            await self.initialize()
        return self.async_session()
    
    async def close(self):
        """关闭数据库连接"""
        if self.engine:
            await self.engine.dispose()
            self._initialized = False
            session_logger.info("system", "database", "数据库连接已关闭")

db_manager = None

async def get_db_manager():
    global db_manager
    if db_manager is None:
        db_manager = await DatabaseManager.get_instance()
    return db_manager