from collections.abc import Iterator
from contextlib import contextmanager

from sqlalchemy import Engine, create_engine
from sqlalchemy.orm import Session, sessionmaker

from backend.config import get_settings


def get_engine(url: str | None = None) -> Engine:
    settings = get_settings()
    database_url = url or settings.database_url
    connect_args: dict[str, object] = {}
    if database_url.startswith("sqlite"):
        connect_args = {"check_same_thread": False}
    return create_engine(database_url, connect_args=connect_args)


@contextmanager
def get_session(engine: Engine) -> Iterator[Session]:
    factory = sessionmaker(autocommit=False, autoflush=False, bind=engine)
    session = factory()
    try:
        yield session
        session.commit()
    except Exception:
        session.rollback()
        raise
    finally:
        session.close()