from sqlalchemy.ext.asyncio import (
    create_async_engine,
    async_sessionmaker,
    AsyncSession,
)
from sqlalchemy.orm import declarative_base
from app.core.config import settings

# =========================
# Async Engine
# =========================
engine = create_async_engine(
    settings.database_url,      # ⚠️ 必须是 async URL
    echo=settings.debug,
    pool_pre_ping=True,
    pool_recycle=1800,
)

# =========================
# Async Session 工厂
# =========================
AsyncSessionLocal = async_sessionmaker(
    bind=engine,
    class_=AsyncSession,
    autoflush=False,
    expire_on_commit=False,
)

# ORM 基类
Base = declarative_base()


# =========================
# FastAPI 依赖
# =========================
async def get_db() -> AsyncSession:
    async with AsyncSessionLocal() as session:
        try:
            yield session
        except Exception:
            # --- 核心改进：全局兜底回滚 ---
            await session.rollback()
            raise
        finally:
            await session.close()