"""数据库连接管理。

提供 SQLAlchemy 异步 engine 和 session 工厂。
"""

from collections.abc import AsyncGenerator

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

from app.core.config import settings

engine = create_async_engine(
    settings.database_url,
    echo=settings.app_debug,
    pool_size=10,
    max_overflow=20,
)

async_session_factory = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
)


class Base(DeclarativeBase):
    """SQLAlchemy ORM 基类。"""

    pass


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """获取数据库 session 的依赖注入函数。"""
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()