"""SQLAlchemy async engine and session factory."""
from collections.abc import AsyncGenerator

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

from app.config import settings

engine = create_async_engine(
    settings.database_url,
    echo=settings.debug,
    pool_size=20,
    max_overflow=10,
    pool_pre_ping=True,
)

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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """Yield an async database session."""
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
