"""Database session management for the API gateway."""

from collections.abc import AsyncGenerator

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

from cartsnitch_api.config import settings


def _build_engine_kwargs() -> dict:
    url = settings.database_url
    kwargs: dict = {"echo": False}
    if not url.startswith("sqlite"):
        kwargs.update(
            pool_size=10,
            max_overflow=20,
            pool_timeout=30,
            pool_pre_ping=True,
            pool_recycle=3600,
        )
    return kwargs


engine = create_async_engine(settings.database_url, **_build_engine_kwargs())
async_session_factory = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """FastAPI dependency that yields an async DB session."""
    async with async_session_factory() as session:
        yield session


async def dispose_engine() -> None:
    """Dispose the database engine, closing all pooled connections."""
    await engine.dispose()