# Copyright 2012 Managed I.T.
#
# Author: Kiall Mac Innes <kiall@managedit.ie>
#
# 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.
from oslo_config import cfg
from oslo_log import log as logging
from oslo_policy import policy
from oslo_policy import opts

from designate.i18n import _
from designate.i18n import _LI
from designate import utils
from designate import exceptions


CONF = cfg.CONF

# Add the default policy opts
opts.set_defaults(CONF)

LOG = logging.getLogger(__name__)


_ENFORCER = None


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


def set_rules(data, default_rule=None, overwrite=True):
    default_rule = default_rule or cfg.CONF.policy_default_rule
    if not _ENFORCER:
        LOG.debug("Enforcer not present, recreating at rules stage.")
        init()

    if default_rule:
        _ENFORCER.default_rule = default_rule

    msg = "Loading rules %s, default: %s, overwrite: %s"
    LOG.debug(msg, data, default_rule, overwrite)

    if isinstance(data, dict):
        rules = policy.Rules.from_dict(data, default_rule)
    else:
        rules = policy.Rules.load_json(data, default_rule)

    _ENFORCER.set_rules(rules, overwrite=overwrite)


def init(default_rule=None):
    policy_files = utils.find_config(CONF['oslo_policy'].policy_file)

    if len(policy_files) == 0:
        msg = 'Unable to determine appropriate policy json file'
        raise exceptions.ConfigurationError(msg)

    LOG.info(_LI('Using policy_file found at: %s'), policy_files[0])

    with open(policy_files[0]) as fh:
        policy_string = fh.read()
    rules = policy.Rules.load_json(policy_string, default_rule=default_rule)

    global _ENFORCER
    if not _ENFORCER:
        LOG.debug("Enforcer is not present, recreating.")
        _ENFORCER = policy.Enforcer(CONF)

    _ENFORCER.set_rules(rules)


def check(rule, ctxt, target=None, do_raise=True, exc=exceptions.Forbidden):
    creds = ctxt.to_dict()
    target = target or {}
    try:
        result = _ENFORCER.enforce(rule, target, creds, do_raise, exc)
    except Exception:
        result = False
        raise
    else:
        return result
    finally:
        extra = {'policy': {'rule': rule, 'target': target}}

        if result:
            LOG.info(_("Policy check succeeded for rule '%(rule)s' "
                       "on target %(target)s"),
                     {'rule': rule, 'target': repr(target)}, extra=extra)
        else:
            LOG.info(_("Policy check failed for rule '%(rule)s' "
                       "on target %(target)s"),
                     {'rule': rule, 'target': repr(target)}, extra=extra)
