"""异步数据库会话，DATABASE_URL 来自环境变量。"""
from collections.abc import AsyncGenerator

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

from app.config import settings

engine = create_async_engine(
    settings.database_url,
    echo=False,
    pool_pre_ping=True,
)
async_session_factory = async_sessionmaker(
    engine, class_=AsyncSession, expire_on_commit=False, autoflush=False
)


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()