# Copyright (c) 2016 IBM
# All Rights Reserved.
#
#    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 netaddr

from designateclient import exceptions as d_exc
from designateclient.v2 import client as d_client
from keystoneauth1 import loading
from keystoneauth1 import token_endpoint
from neutron_lib import constants
from neutron_lib.exceptions import dns as dns_exc
from oslo_config import cfg
from oslo_log import log

from neutron.conf.services import extdns_designate_driver
from neutron.services.externaldns import driver

_SESSION = None

CONF = cfg.CONF
extdns_designate_driver.register_designate_opts()

LOG = log.getLogger(__name__)


def get_clients(context):
    global _SESSION

    if not _SESSION:
        _SESSION = loading.load_session_from_conf_options(
            CONF, 'designate')

    auth = token_endpoint.Token(CONF.designate.url, context.auth_token)
    client = d_client.Client(session=_SESSION, auth=auth)
    admin_auth = loading.load_auth_from_conf_options(CONF, 'designate')
    admin_client = d_client.Client(session=_SESSION, auth=admin_auth,
                                   endpoint_override=CONF.designate.url)
    return client, admin_client


def get_all_projects_client(context):
    auth = token_endpoint.Token(CONF.designate.url, context.auth_token)
    return d_client.Client(session=_SESSION, auth=auth, all_projects=True)


class Designate(driver.ExternalDNSService):
    """Driver for Designate."""

    def create_record_set(self, context, dns_domain, dns_name, records):
        designate, designate_admin = get_clients(context)
        v4, v6 = self._classify_records(records)
        try:
            if v4:
                designate.recordsets.create(dns_domain, dns_name, 'A', v4)
            if v6:
                designate.recordsets.create(dns_domain, dns_name, 'AAAA', v6)
        except d_exc.NotFound:
            raise dns_exc.DNSDomainNotFound(dns_domain=dns_domain)
        except d_exc.Conflict:
            raise dns_exc.DuplicateRecordSet(dns_name=dns_name)
        except d_exc.OverQuota:
            raise dns_exc.ExternalDNSOverQuota(resource="recordset")

        if not CONF.designate.allow_reverse_dns_lookup:
            return
        # Set up the PTR records
        recordset_name = '{}.{}'.format(dns_name, dns_domain)
        ptr_zone_email = 'admin@%s' % dns_domain[:-1]
        if CONF.designate.ptr_zone_email:
            ptr_zone_email = CONF.designate.ptr_zone_email
        for record in records:
            in_addr_name = netaddr.IPAddress(record).reverse_dns
            in_addr_zone_name = self._get_in_addr_zone_name(in_addr_name)
            in_addr_zone_description = (
                'An %s zone for reverse lookups set up by Neutron.' %
                '.'.join(in_addr_name.split('.')[-3:]))
            try:
                # Since we don't delete in-addr zones, assume it already
                # exists. If it doesn't, create it
                designate_admin.recordsets.create(in_addr_zone_name,
                                                  in_addr_name, 'PTR',
                                                  [recordset_name])
            except d_exc.NotFound:
                # Note(jh): If multiple PTRs get created at the same time,
                # the creation of the zone may fail with a conflict because
                # it has already been created by a parallel job. So we
                # ignore that error and try to create the recordset
                # anyway. That call will still fail in the end if something
                # is really broken. See bug 1891309.
                try:
                    designate_admin.zones.create(
                        in_addr_zone_name, email=ptr_zone_email,
                        description=in_addr_zone_description)
                except d_exc.Conflict:
                    LOG.debug('Conflict when trying to create PTR zone %s,'
                              ' assuming it exists.',
                              in_addr_zone_name)
                    pass
                except d_exc.OverQuota:
                    raise dns_exc.ExternalDNSOverQuota(resource='zone')
                designate_admin.recordsets.create(in_addr_zone_name,
                                                  in_addr_name, 'PTR',
                                                  [recordset_name])

    def _classify_records(self, records):
        v4 = []
        v6 = []
        for record in records:
            if netaddr.IPAddress(record).version == 4:
                v4.append(record)
            else:
                v6.append(record)
        return v4, v6

    def _get_in_addr_zone_name(self, in_addr_name):
        units = self._get_bytes_or_nybles_to_skip(in_addr_name)
        return '.'.join(in_addr_name.split('.')[units:])

    def _get_bytes_or_nybles_to_skip(self, in_addr_name):
        if 'in-addr.arpa' in in_addr_name:
            return int((constants.IPv4_BITS -
                        CONF.designate.ipv4_ptr_zone_prefix_size) / 8)
        return int((constants.IPv6_BITS -
                    CONF.designate.ipv6_ptr_zone_prefix_size) / 4)

    def delete_record_set(self, context, dns_domain, dns_name, records):
        client, admin_client = get_clients(context)
        try:
            ids_to_delete = self._get_ids_ips_to_delete(
                dns_domain, '{}.{}'.format(
                    dns_name, dns_domain), records, client)
        except dns_exc.DNSDomainNotFound:
            # Try whether we have admin powers and can see all projects
            client = get_all_projects_client(context)
            ids_to_delete = self._get_ids_ips_to_delete(
                dns_domain, '{}.{}'.format(
                    dns_name, dns_domain), records, client)

        for _id in ids_to_delete:
            client.recordsets.delete(dns_domain, _id)
        if not CONF.designate.allow_reverse_dns_lookup:
            return

        for record in records:
            in_addr_name = netaddr.IPAddress(record).reverse_dns
            in_addr_zone_name = self._get_in_addr_zone_name(in_addr_name)
            admin_client.recordsets.delete(in_addr_zone_name, in_addr_name)

    def _get_ids_ips_to_delete(self, dns_domain, name, records,
                               designate_client):
        try:
            recordsets = designate_client.recordsets.list(
                dns_domain, criterion={"name": "%s" % name})
        except (d_exc.NotFound, d_exc.Forbidden):
            raise dns_exc.DNSDomainNotFound(dns_domain=dns_domain)
        ids = [rec['id'] for rec in recordsets]
        ips = [str(ip) for rec in recordsets for ip in rec['records']]
        if set(ips) != set(records):
            raise dns_exc.DuplicateRecordSet(dns_name=name)
        return ids
