"""Подключение к БД и базовый класс моделей (SQLAlchemy 2.0, sync)."""

from collections.abc import Generator

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

from app.config import get_settings


class Base(DeclarativeBase):
    pass


_engine: Engine | None = None
_session_factory: sessionmaker[Session] | None = None


def get_engine() -> Engine:
    global _engine
    if _engine is None:
        _engine = create_engine(get_settings().database_url, pool_pre_ping=True)
    return _engine


def get_session_factory() -> sessionmaker[Session]:
    global _session_factory
    if _session_factory is None:
        _session_factory = sessionmaker(bind=get_engine(), expire_on_commit=False)
    return _session_factory


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