from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.orm import declarative_base
from .settings import get_settings

settings = get_settings()

DATABASE_URL = (
    f"mysql+aiomysql://{settings.DB_USER}:{settings.DB_PASSWORD}"
    f"@{settings.DB_HOST}:{settings.DB_PORT}/{settings.DB_NAME}"
    f"?charset={settings.DB_CHARSET}"
)

engine = create_async_engine(DATABASE_URL, echo=settings.DEBUG, future=True)

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

Base = declarative_base()


async def get_db():
    """获取数据库会话的依赖项函数

    用于FastAPI依赖注入，自动管理数据库会话的生命周期
    成功时自动提交，异常时自动回滚，最后确保关闭会话
    """
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def init_db():
    """初始化数据库，创建所有表结构"""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)