"""비동기 DB 엔진 + 세션 팩토리"""

from sqlalchemy.ext.asyncio import (
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)
from sqlalchemy.orm import DeclarativeBase
from app.config import get_settings

settings = get_settings()

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

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


class Base(DeclarativeBase):
    pass


async def get_db():
    """FastAPI Depends용 DB 세션 제너레이터"""
    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():
    """테이블 생성 (개발용 — 프로덕션에서는 Alembic 사용)"""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)