"""
MySQL connector
===============
"""

from contextlib import contextmanager

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session
from sqlalchemy.orm import sessionmaker

from ytownership import config

BaseModel = declarative_base()

_db_engine = create_engine(
    config.DB_CONNECTION_STRING, poolclass=config.DB_POOLCLASS)
_db_session_factory = sessionmaker(bind=_db_engine, expire_on_commit=False)


@contextmanager
def session_scope():
    """Provide a transactional scope around a series of operations.
    """

    session = scoped_session(_db_session_factory)
    try:
        yield session
        session.commit()
    except: # noqa
        session.rollback()
        raise
    finally:
        session.remove()