"""
异步数据库引擎 & Session 工厂
"""

from collections.abc import AsyncGenerator

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

from app.core.config import settings

engine = create_async_engine(
    settings.DATABASE_URL,
    echo=settings.DEBUG,
    pool_size=20,
    max_overflow=10,
    pool_pre_ping=True,
    pool_recycle=3600,
)

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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """FastAPI Dependency —— 每个请求一个 Session，自动关闭"""
    async with async_session_factory() as session:
        try:
            yield session
        finally:
            await session.close()