# Copyright 2016 - Brocade Communications Systems, Inc.
#
#    Licensed under the Apache License, Version 2.0 (the "License");
#    you may not use this file except in compliance with the License.
#    You may obtain a copy of the License at
#
#        http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS,
#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#    See the License for the specific language governing permissions and
#    limitations under the License.

import abc

from oslo_config import cfg
import six
from stevedore import driver

from mistral import exceptions as exc


_IMPL_AUTH_HANDLER = None


def get_auth_handler():
    auth_type = cfg.CONF.auth_type

    global _IMPL_AUTH_HANDLER

    if not _IMPL_AUTH_HANDLER:
        mgr = driver.DriverManager(
            'mistral.auth',
            auth_type,
            invoke_on_load=True
        )

        _IMPL_AUTH_HANDLER = mgr.driver

    return _IMPL_AUTH_HANDLER


@six.add_metaclass(abc.ABCMeta)
class AuthHandler(object):
    """Abstract base class for an authentication plugin."""

    @abc.abstractmethod
    def authenticate(self, req):
        raise exc.UnauthorizedException()
