from collections.abc import AsyncGenerator

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

from app.core.config import settings

# SQLite (used by the smoke tests) has no connection pool to size.
_pool_options = (
    {}
    if settings.database_url.startswith("sqlite")
    else {
        "pool_size": settings.db_pool_size,
        "max_overflow": settings.db_max_overflow,
        "pool_pre_ping": True,
    }
)

engine = create_async_engine(settings.database_url, echo=settings.debug, **_pool_options)

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


async def get_session() -> AsyncGenerator[AsyncSession, None]:
    """FastAPI dependency yielding one database session per request."""
    async with SessionFactory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise