from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from backend.config import DB_URL

engine = create_engine(DB_URL, connect_args={"check_same_thread": False})
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)


def get_db():
    """
    Dependency for FastAPI routes: yields a SQLAlchemy session.
    Usage: add as a dependency in route functions.
    """
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


from contextlib import contextmanager


@contextmanager
def session_scope():
    """
    Context manager for non-FastAPI scripts:
    with session_scope() as db:
        ...
    Commits on success, rolls back on exception.
    """
    db = SessionLocal()
    try:
        yield db
        db.commit()
    except Exception:
        db.rollback()
        raise
    finally:
        db.close()