#    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_log import log as logging
from sqlalchemy import MetaData, Table, Index

from nova.i18n import _LI

LOG = logging.getLogger(__name__)

INDEX_COLUMNS = ['uuid']
INDEX_NAME = 'virtual_interfaces_uuid_idx'


def _get_table_index(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine
    table = Table('virtual_interfaces', meta, autoload=True)
    for idx in table.indexes:
        if idx.columns.keys() == INDEX_COLUMNS:
            break
    else:
        idx = None
    return meta, table, idx


def upgrade(migrate_engine):
    meta, table, index = _get_table_index(migrate_engine)
    if index:
        LOG.info(_LI('Skipped adding %s because an equivalent index'
                     ' already exists.'), INDEX_NAME)
        return
    columns = [getattr(table.c, col_name) for col_name in INDEX_COLUMNS]
    index = Index(INDEX_NAME, *columns)
    index.create(migrate_engine)
