"""mysql connector for the legacy database."""

from pricing import config

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker


if config.ENVIRONMENT == config.TEST_ENVIRONMENT:
    # For the test environment the database used is an in-memory sqlite db.
    # This db gets dropped immediately after the execution of the tests.
    _db_engine = create_engine('sqlite://')
else:
    _db_engine = create_engine(config.AR_DB_URL, poolclass=config.POOL)


# A session() instance establishes all conversations with the database
# and represents a "staging zone" for all the objects loaded into the
# database session object. Any change made against the objects in the
# session won't be persisted into the database until you call
# session.commit(). If you're not happy about the changes, you can
# revert all of them back to the last commit by calling
# session.rollback()
#
# Description taken from:
# pythoncentral.io/introductory-tutorial-python-sqlalchemy/
_db_session = sessionmaker(bind=_db_engine)


def get_session():
    """Get a database session.

    Returns:
        callable: the encapsulated wrapper.
    """
    return _db_session()