# coding=utf-8
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

try:
    from loguru import logger
except ImportError:
    import logging
    logger = logging.getLogger(__name__)

session = None


def get_db_session():
    """MySQL 会话（服务端/后台使用）。"""
    global session
    if session is not None:
        return session
    try:
        from dao.settings import CAIHUI_DATABASE
        from dao.dbutils import get_db_engine
        from sqlalchemy.orm import sessionmaker
        import models  # noqa: F401
        engine = get_db_engine(**CAIHUI_DATABASE)
        Session = sessionmaker(bind=engine)
        Base.metadata.create_all(engine)
        session = Session()
        return session
    except Exception as e:
        logger.error('Create Session Failed for %s' % e)
        return None