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

# 创建异步数据库引擎
engine = create_async_engine(settings.database_url, echo=False)

# 异步 Session 工厂
async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)


async def get_db():
    """FastAPI 依赖注入，提供数据库 Session"""
    async with async_session() as session:
        yield session


async def create_tables():
    """开发环境：通过 SQLAlchemy 直接建表（生产环境请使用 SQL 迁移文件）"""
    from app.models.domain import Base
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)