"""
MySQL Connector.

Manages interactions with MySQL
for art_relations and direct_delivery databse.
"""

from contextlib import contextmanager
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from assets import config


ar_db_engine = create_engine(config.AR_DB_URL, poolclass=config.POOL_CLASS)
ar_database_session = sessionmaker(bind=ar_db_engine)

dd_db_engine = create_engine(config.DD_DB_URL, poolclass=config.POOL_CLASS)
dd_database_session = sessionmaker(bind=dd_db_engine)

au_db_engine = create_engine(config.RDS_DB_URL, poolclass=config.POOL_CLASS)
au_database_session = sessionmaker(bind=au_db_engine)


baseModel = declarative_base()

DdModel = declarative_base()
ArModel = declarative_base()

AuModel = declarative_base()


@contextmanager
def ar_db_session():
    """
    Provide transactional scope around series of operations for art_relations.

    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 ar_database_session() as session:
            session.execute(query)
    """
    session = ar_database_session()
    try:
        yield session
        session.commit()
    except:
        session.rollback()
        raise
    finally:
        session.close()


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

    for direct_delivery database
    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 dd_database_session() as session:
            session.execute(query)
    """
    session = dd_database_session()
    try:
        yield session
        session.commit()
    except:
        session.rollback()
        raise
    finally:
        session.close()


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

    for asset_upload database
    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 au_database_session() as session:
            session.execute(query)
    """
    session = au_database_session()
    try:
        yield session
        session.commit()
    except:
        session.rollback()
        raise
    finally:
        session.close()