# Copyright 2017 - 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 jwt
import memcache
from oslo_config import cfg
from oslo_log import log as logging
from oslo_middleware import base as base_middleware
import pprint
import requests
from six.moves import urllib
import webob.dec

from glare.common import exception
from glare.common import utils
from glare.i18n import _

LOG = logging.getLogger(__name__)

keycloak_oidc_opts = [
    cfg.StrOpt(
        'auth_url',
        default='http://127.0.0.1:8080/auth',
        help='Keycloak base url (e.g. https://my.keycloak:8443/auth)'
    ),
    cfg.StrOpt(
        'user_info_endpoint_url',
        default='/realms/%s/protocol/openid-connect/userinfo',
        help='Endpoint against which authorization will be performed'
    ),
    cfg.StrOpt(
        'certfile',
        help='Required if identity server requires client certificate'
    ),
    cfg.StrOpt(
        'keyfile',
        help='Required if identity server requires client certificate'
    ),
    cfg.StrOpt(
        'cafile',
        help='A PEM encoded Certificate Authority to use when verifying '
             'HTTPs connections. Defaults to system CAs.'
    ),
    cfg.BoolOpt(
        'insecure',
        default=False,
        help='If True, SSL/TLS certificate verification is disabled'
    ),
    cfg.StrOpt(
        'memcached_server',
        default=None,
        help='Url of memcached server to use for caching'
    ),
    cfg.IntOpt(
        'token_cache_time',
        default=60,
        min=0,
        help='In order to prevent excessive effort spent validating '
             'tokens, the middleware caches previously-seen tokens '
             'for a configurable duration (in seconds).'
    ),
]

CONF = cfg.CONF
CONF.register_opts(keycloak_oidc_opts, group="keycloak_oidc")


class KeycloakAuthMiddleware(base_middleware.Middleware):
    def __init__(self, app):
        super(KeycloakAuthMiddleware, self).__init__(application=app)
        mcserv_url = CONF.keycloak_oidc.memcached_server
        self.mcclient = memcache.Client(mcserv_url) if mcserv_url else None

        self.certfile = CONF.keycloak_oidc.certfile
        self.keyfile = CONF.keycloak_oidc.keyfile
        self.cafile = CONF.keycloak_oidc.cafile or utils.get_system_ca_file()
        self.insecure = CONF.keycloak_oidc.insecure

    def authenticate(self, access_token, realm_name):
        info = None
        if self.mcclient:
            info = self.mcclient.get(access_token)

        user_info_endpoint_url = CONF.keycloak_oidc.user_info_endpoint_url
        if info is None and user_info_endpoint_url:
            if user_info_endpoint_url.startswith(('http://', 'https://')):
                url = user_info_endpoint_url
            else:
                url_template = CONF.keycloak_oidc.auth_url + \
                    CONF.keycloak_oidc.user_info_endpoint_url
                url = url_template % realm_name

            verify = None
            if urllib.parse.urlparse(url).scheme == "https":
                verify = False if self.insecure else self.cafile

            cert = (self.certfile, self.keyfile) \
                if self.certfile and self.keyfile else None

            try:
                resp = requests.get(
                    url,
                    headers={"Authorization": "Bearer %s" % access_token},
                    verify=verify,
                    cert=cert
                )
            except requests.ConnectionError:
                msg = _("Can't connect to keycloak server with address '%s'."
                        ) % CONF.keycloak_oidc.auth_url
                LOG.error(msg)
                raise exception.GlareException(message=msg)

            if resp.status_code == 400:
                raise exception.BadRequest(message=resp.text)
            if resp.status_code == 401:
                LOG.warning("HTTP response from OIDC provider:"
                            " [%s] with WWW-Authenticate: [%s]",
                            pprint.pformat(resp.text),
                            resp.headers.get("WWW-Authenticate"))
                raise exception.Unauthorized(message=resp.text)
            if resp.status_code == 403:
                raise exception.Forbidden(message=resp.text)
            elif resp.status_code > 400:
                raise exception.GlareException(message=resp.text)

            if self.mcclient:
                self.mcclient.set(access_token, resp.json(),
                                  time=CONF.keycloak_oidc.token_cache_time)
            info = resp.json()

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

        return info

    @webob.dec.wsgify
    def __call__(self, request):
        if 'X-Auth-Token' not in request.headers:
            msg = _("Auth token must be provided in 'X-Auth-Token' header.")
            LOG.error(msg)
            raise exception.Unauthorized()
        access_token = request.headers.get('X-Auth-Token')
        try:
            decoded = jwt.decode(access_token, algorithms=['RS256'],
                                 verify=False)
        except Exception as e:
            msg = _("Token can't be decoded because of wrong format %s")\
                % str(e)
            LOG.error(msg)
            raise exception.Unauthorized()

        # Get user realm from parsed token
        # Format is "iss": "http://<host>:<port>/auth/realms/<realm_name>",
        __, __, realm_name = decoded['iss'].strip().rpartition('/realms/')

        # Get roles from from parsed token
        roles = ','.join(decoded['realm_access']['roles']) \
            if 'realm_access' in decoded else ''

        self.authenticate(access_token, realm_name)

        request.headers["X-Identity-Status"] = "Confirmed"
        request.headers["X-Project-Id"] = realm_name
        request.headers["X-Roles"] = roles
        return request.get_response(self.application)