from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from alien_gateway.config import settings

# 数据库引擎配置 (异步)
# 注意：aiomysql 用于异步 MySQL 驱动
DATABASE_URL = settings.SQLALCHEMY_DATABASE_URI.replace("mysql+pymysql", "mysql+aiomysql")

engine = create_async_engine(
    DATABASE_URL,
    echo=True,  # 开发环境开启 SQL 日志
    pool_pre_ping=True,
    pool_size=10,
    max_overflow=20
)

# 创建异步 Session 工厂
AsyncSessionLocal = async_sessionmaker(
    bind=engine,
    class_=AsyncSession,
    expire_on_commit=False,
)

async def get_db():
    """
    FastAPI 依赖注入项，用于获取数据库 Session。
    """
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()