"""数据库引擎与会话。"""

from collections.abc import Generator
from contextlib import contextmanager

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

from config.settings import database_url

_engine = None
_SessionLocal = None


def get_engine():
    global _engine, _SessionLocal
    if _engine is None:
        _engine = create_engine(
            database_url(),
            pool_pre_ping=True,
            pool_recycle=3600,
            echo=False,
        )
        _SessionLocal = sessionmaker(bind=_engine, autoflush=False, autocommit=False)
    return _engine


def get_session_factory() -> sessionmaker[Session]:
    get_engine()
    assert _SessionLocal is not None
    return _SessionLocal


@contextmanager
def session_scope() -> Generator[Session, None, None]:
    factory = get_session_factory()
    session = factory()
    try:
        yield session
        session.commit()
    except Exception:
        session.rollback()
        raise
    finally:
        session.close()