from collections.abc import Generator

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

from app.core.config import get_settings


class Base(DeclarativeBase):
    pass


_engine: Engine | None = None


def get_engine() -> Engine:
    global _engine
    url = get_settings().database_url.strip()
    if not url:
        raise RuntimeError("数据库连接未配置")
    if _engine is None:
        _engine = create_engine(url, pool_pre_ping=True)
        SessionLocal.configure(bind=_engine)
    return _engine


SessionLocal = sessionmaker(autocommit=False, autoflush=False, expire_on_commit=False)


def get_db() -> Generator[Session, None, None]:
    SessionLocal.configure(bind=get_engine())
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()