"""MySQL connector."""
from contextlib import contextmanager

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


_engine, _session_factory, _session = None, None, None


def init_db(host: str, port: int, user: str, password: str, database_name: str):
    global _engine, _session_factory, _session
    if _session:
        return

    _engine = create_engine(
        "mysql+pymysql://{user}:{password}@{host}:{port}/{database_name}".format(
            user=user, password=password, host=host, port=port, database_name=database_name
        )
    )
    _session_factory = scoped_session(sessionmaker(bind=_engine))
    _session = _session_factory()


@contextmanager
def session_scope():
    try:
        yield _session
        _session.commit()
    except Exception:
        _session.rollback()
        raise
    finally:
        _session.close()