"""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 salessheets import config


BaseModel = declarative_base()

_db_engine = create_engine(
    config.AR_DB_CONNECTION_STRING, poolclass=config.DB_POOLCLASS,
    connect_args=config.DB_CONNECT_ARGS)

_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:
        session.rollback()
        raise
    finally:
        session.remove()


_salessheets_history_engine = create_engine(
    config.SS_DB_CONNECTION_STRING, poolclass=config.DB_POOLCLASS,
    connect_args=config.DB_CONNECT_ARGS)

_salessheets_history_factory = sessionmaker(
    bind=_salessheets_history_engine, expire_on_commit=False)


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

    Taken from http://docs.sqlalchemy.org/en/latest/orm/session_basics.html.
    This handles rollback and closing of session, so there is no need
    to do that throughout the code. Usage:
    with bulk_statuses_session_scope() as session:
        session.execute(query)
    """
    session = scoped_session(_salessheets_history_factory)
    try:
        yield session
        session.commit()
    except:
        session.rollback()
        raise
    finally:
        session.close()