#
# Copyright 2012 New Dream Network, LLC (DreamHost)
# Copyright 2014 Hewlett-Packard Company
#
# 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.

"""Access Control Lists (ACL's) control access the API server."""

from oslo_config import cfg
from oslo_policy import opts
from oslo_policy import policy
import pecan

from panko import policies

_ENFORCER = None

# TODO(gmann): Remove setting the default value of config policy_file
# once oslo_policy change the default value to 'policy.yaml'.
# https://github.com/openstack/oslo.policy/blob/a626ad12fe5a3abd49d70e3e5b95589d279ab578/oslo_policy/opts.py#L49
DEFAULT_POLICY_FILE = 'policy.yaml'
opts.set_defaults(cfg.CONF, DEFAULT_POLICY_FILE)


def init():
    global _ENFORCER
    if not _ENFORCER:
        _ENFORCER = policy.Enforcer(pecan.request.cfg)
        _ENFORCER.load_rules()
        _ENFORCER.register_defaults(policies.list_policies())


def reset():
    global _ENFORCER
    if _ENFORCER:
        _ENFORCER.clear()
        _ENFORCER = None


def _has_rule(name):
    return name in _ENFORCER.rules.keys()


def enforce(policy_name, request):
    """Return the user and project the request should be limited to.

    :param request: HTTP request
    :param policy_name: the policy name to validate authz against.


    """
    init()

    rule_method = "telemetry:" + policy_name
    headers = request.headers

    policy_dict = dict()
    policy_dict['roles'] = headers.get('X-Roles', "").split(",")
    policy_dict['user_id'] = (headers.get('X-User-Id'))
    policy_dict['project_id'] = (headers.get('X-Project-Id'))

    # maintain backward compat with Juno and previous by allowing the action if
    # there is no rule defined for it
    if ((_has_rule('default') or _has_rule(rule_method)) and
            not _ENFORCER.enforce(rule_method, {}, policy_dict)):
        pecan.core.abort(status_code=403, detail='RBAC Authorization Failed')


# TODO(fabiog): these methods are still used because the scoping part is really
# convoluted and difficult to separate out.

def get_limited_to(headers):
    """Return the user and project the request should be limited to.

    :param headers: HTTP headers dictionary
    :return: A tuple of (user, project), set to None if there's no limit on
             one of these.
    """

    init()

    policy_dict = dict()
    policy_dict['roles'] = headers.get('X-Roles', "").split(",")
    policy_dict['user_id'] = (headers.get('X-User-Id'))
    policy_dict['project_id'] = (headers.get('X-Project-Id'))

    # maintain backward compat with Juno and previous by using context_is_admin
    # rule if the segregation rule (added in Kilo) is not defined
    rule_name = 'segregation' if _has_rule(
        'segregation') else 'context_is_admin'
    if not _ENFORCER.enforce(rule_name,
                             {},
                             policy_dict):
        return headers.get('X-User-Id'), headers.get('X-Project-Id')

    return None, None


def get_limited_to_project(headers):
    """Return the project the request should be limited to.

    :param headers: HTTP headers dictionary
    :return: A project, or None if there's no limit on it.

    """
    return get_limited_to(headers)[1]