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"""
Objects relating to sourcing connections from metastore database
"""

from typing import List

from airflow.models.connection import Connection
from airflow.secrets import BaseSecretsBackend
from airflow.utils.db import provide_session


class MetastoreBackend(BaseSecretsBackend):
    """
    Retrieves Connection object from airflow metastore database.
    """

    # pylint: disable=missing-docstring
    @provide_session
    def get_connections(self, conn_id, session=None):
        # type: (...) -> List[Connection]
        conn_list = session.query(Connection).filter(Connection.conn_id == conn_id).all()
        session.expunge_all()
        return conn_list

    @provide_session
    def get_variable(self, key, session=None):
        """
        Get Airflow Variable from Metadata DB

        :param key: Variable Key
        :type key: str
        :param session: Sqlalchemy ORM Session
        :return: Variable Value
        """
        from airflow.models.variable import Variable
        var_value = session.query(Variable).filter(Variable.key == key).first()
        session.expunge_all()
        if var_value:
            return var_value.val
        return None
