# Copyright 2014 Hewlett-Packard Development Company, L.P.
#
# Author: Kiall Mac Innes <kiall@hp.com>
#
# 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 copy
import threading

from oslo_config import cfg
from oslo_db import options
from oslo_log import log as logging
from oslo_utils import excutils
from sqlalchemy.sql import select

from designate import exceptions
from designate.i18n import _LC
from designate.backend import base
from designate.backend.impl_powerdns import tables
from designate.sqlalchemy import session

LOG = logging.getLogger(__name__)


def _map_col(keys, col):
    return dict([(keys[i], col[i]) for i in range(len(keys))])


class PowerDNSBackend(base.Backend):
    __plugin_name__ = 'powerdns'

    __backend_status__ = 'integrated'

    @classmethod
    def get_cfg_opts(cls):
        group = cfg.OptGroup('backend:powerdns')
        opts = copy.deepcopy(options.database_opts)

        # Strip connection options
        discard_opts = ('sqlite_db', 'connection', 'slave_connection')
        opts = [opt for opt in opts if opt.name not in discard_opts]

        return [(group, opts,)]

    def __init__(self, target):
        super(PowerDNSBackend, self).__init__(target)

        self.local_store = threading.local()

        default_connection = 'sqlite:///%(state_path)s/powerdns.sqlite' % {
            'state_path': cfg.CONF.state_path
        }

        self.connection = self.options.get('connection', default_connection)

    @property
    def session(self):
        # NOTE: This uses a thread local store, allowing each greenthread to
        #       have it's own session stored correctly. Without this, each
        #       greenthread may end up using a single global session, which
        #       leads to bad things happening.
        if not hasattr(self.local_store, 'session'):
            self.local_store.session = session.get_session(
                self.name, self.connection, self.target.id)

        return self.local_store.session

    def _create(self, table, values):
        query = table.insert()

        resultproxy = self.session.execute(query, values)

        # Refetch the row, for generated columns etc
        query = select([table])\
            .where(table.c.id == resultproxy.inserted_primary_key[0])
        resultproxy = self.session.execute(query)

        return _map_col(query.columns.keys(), resultproxy.fetchone())

    def _get(self, table, id_, exc_notfound, id_col=None):
        if id_col is None:
            id_col = table.c.id

        query = select([table])\
            .where(id_col == id_)

        resultproxy = self.session.execute(query)

        results = resultproxy.fetchall()

        if len(results) != 1:
            raise exc_notfound()

        # Map col keys to values in result
        return _map_col(query.columns.keys(), results[0])

    def _delete(self, table, id_, exc_notfound, id_col=None):
        if id_col is None:
            id_col = table.c.id

        query = table.delete()\
            .where(id_col == id_)

        resultproxy = self.session.execute(query)

        if resultproxy.rowcount != 1:
            raise exc_notfound()

    # Domain Methods
    def create_domain(self, context, domain):
        try:
            self.session.begin()

            def _parse_master(master):
                return '%s:%d' % (master.host, master.port)
            masters = map(_parse_master, self.masters)

            domain_values = {
                'designate_id': domain['id'],
                'name': domain['name'].rstrip('.'),
                'master': ','.join(masters),
                'type': 'SLAVE',
                'account': context.tenant
            }

            self._create(tables.domains, domain_values)
        except Exception:
            with excutils.save_and_reraise_exception():
                self.session.rollback()
        else:
            self.session.commit()

    def delete_domain(self, context, domain):
        # TODO(kiall): We should make this match create_domain with regard to
        #              transactions.
        try:
            self._get(tables.domains, domain['id'], exceptions.DomainNotFound,
                      id_col=tables.domains.c.designate_id)
        except exceptions.DomainNotFound:
            # If the Domain is already gone, that's ok. We're deleting it
            # anyway, so just log and continue.
            LOG.critical(_LC('Attempted to delete a domain which is '
                             'not present in the backend. ID: %s') %
                         domain['id'])
            return

        self._delete(tables.domains, domain['id'],
                     exceptions.DomainNotFound,
                     id_col=tables.domains.c.designate_id)