"""Async SQLAlchemy engine, session factory, and request transaction boundary."""

from collections.abc import AsyncGenerator

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

from app.core.config import Settings, get_settings


def create_database_engine(settings: Settings | None = None) -> AsyncEngine:
    resolved_settings = settings or get_settings()
    return create_async_engine(resolved_settings.database_url, pool_pre_ping=True)


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


async def get_db_session() -> AsyncGenerator[AsyncSession, None]:
    async with SessionFactory() as session:
        try:
            yield session
        except Exception:
            await session.rollback()
            raise
        else:
            await session.commit()