# Copyright 2016 - Nokia Networks
#
#    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 logging
import os
import pprint
import urllib

import requests

from mistralclient import auth


LOG = logging.getLogger(__name__)


class KeycloakAuthHandler(auth.AuthHandler):

    def authenticate(self, req, session=None):
        """Performs authentication using Keycloak OpenID Protocol.

        :param req: Request dict containing list of parameters required
            for Keycloak authentication.

            * auth_url: Base authentication url of KeyCloak server (e.g.
                "https://my.keycloak:8443/auth"
            * client_id: Client ID (according to OpenID Connect protocol).
            * client_secret: Client secret (according to OpenID Connect
                protocol).
            * project_name: KeyCloak realm name.
            * username: User name (Optional, if None then access_token must be
                provided).
            * api_key: Password (Optional).
            * access_token: Access token. If passed, username and password are
                not used and this method just validates the token and refreshes
                it if needed (Optional, if None then username must be
                provided).
            * cacert: SSL certificate file (Optional).
            * insecure: If True, SSL certificate is not verified (Optional).

        :param session: Keystone session object. Not used by this plugin.

        """

        if not isinstance(req, dict):
            raise TypeError('The input "req" is not typeof dict.')

        auth_url = req.get('auth_url')
        client_id = req.get('client_id')
        client_secret = req.get('client_secret')
        realm_name = req.get('project_name')
        username = req.get('username')
        password = req.get('api_key')
        access_token = req.get('access_token')
        cacert = req.get('cacert')
        insecure = req.get('insecure', False)

        if not auth_url:
            raise ValueError('Base authentication url is not provided.')

        if not client_id:
            raise ValueError('Client ID is not provided.')

        if not realm_name:
            raise ValueError('Project(realm) name is not provided.')

        if username and access_token:
            raise ValueError(
                "User name and access token can't be "
                "provided at the same time."
            )

        if not username and not access_token:
            raise ValueError(
                'Either user name or access token must be provided.'
            )

        if access_token:
            response = self._authenticate_with_token(
                auth_url,
                client_id,
                client_secret,
                access_token,
                cacert,
                insecure
            )
        else:
            response = self._authenticate_with_password(
                auth_url,
                client_id,
                client_secret,
                realm_name,
                username,
                password,
                cacert,
                insecure
            )

        return {'auth_token': response, 'project_id': realm_name}

    @staticmethod
    def _authenticate_with_token(auth_url, client_id, client_secret,
                                 auth_token, cacert=None, insecure=None):
        # TODO(rakhmerov): Implement.
        raise NotImplementedError

    @staticmethod
    def _authenticate_with_password(auth_url, client_id, client_secret,
                                    realm_name, username, password,
                                    cacert=None, insecure=None):
        access_token_endpoint = (
            "%s/realms/%s/protocol/openid-connect/token" %
            (auth_url, realm_name)
        )

        verify = None
        if urllib.parse.urlparse(access_token_endpoint).scheme == "https":
            verify = False if insecure else cacert if cacert else True

        body = {
            'grant_type': 'password',
            'username': username,
            'password': password,
            'client_id': client_id,
            'scope': 'profile'
        }

        if client_secret:
            body['client_secret'] = client_secret,

        resp = requests.post(
            access_token_endpoint,
            data=body,
            verify=verify
        )

        try:
            resp.raise_for_status()
        except Exception as e:
            raise Exception("Failed to get access token:\n %s" % str(e))

        LOG.debug("HTTP response from OIDC provider: %s",
                  pprint.pformat(resp.json()))

        return resp.json()['access_token']


def get_system_ca_file():
    """Return path to system default CA file."""
    # Standard CA file locations for Debian/Ubuntu, RedHat/Fedora,
    # Suse, FreeBSD/OpenBSD, MacOSX, and the bundled ca
    ca_path = ['/etc/ssl/certs/ca-certificates.crt',
               '/etc/pki/tls/certs/ca-bundle.crt',
               '/etc/ssl/ca-bundle.pem',
               '/etc/ssl/cert.pem',
               '/System/Library/OpenSSL/certs/cacert.pem',
               requests.certs.where()]
    for ca in ca_path:
        LOG.debug("Looking for ca file %s", ca)
        if os.path.exists(ca):
            LOG.debug("Using ca file %s", ca)
            return ca
    LOG.warning("System ca file could not be found.")


# An example of working curl request to keycloak
# curl -d "client_id=admin-cli" -d "client_secret=secret"
# -d "username=admin" -d "password=qwerty" -d "grant_type=password"
# "http://localhost:8080/auth/realms/master/protocol/openid-connect/token"

# An example of using KeyCloak OpenID authentication.
if __name__ == '__main__':
    print("Using username/password to get access token from KeyCloak...")

    auth_handler = KeycloakAuthHandler()

    a_token = auth_handler.authenticate(
        dict(
            "https://my.keycloak:8443/auth",
            client_id="mistral_client",
            client_secret="secret",
            project_name="mistral",
            username="user",
            api_key="secret",
            insecure=True
        )
    )['auth_token']

    print("Auth token: %s" % a_token)