# Copyright (c) 2012 OpenStack, LLC.
# 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.

from nova import config
from nova import flags
from nova.openstack.common import cfg
from nova.openstack.common import log as logging
from nova.scheduler import filters

LOG = logging.getLogger(__name__)

disk_allocation_ratio_opt = cfg.FloatOpt("disk_allocation_ratio", default=1.0,
                         help="virtual disk to physical disk allocation ratio")

CONF = config.CONF
CONF.register_opt(disk_allocation_ratio_opt)


class DiskFilter(filters.BaseHostFilter):
    """Disk Filter with over subscription flag"""

    def host_passes(self, host_state, filter_properties):
        """Filter based on disk usage"""
        instance_type = filter_properties.get('instance_type')
        requested_disk = 1024 * (instance_type['root_gb'] +
                                 instance_type['ephemeral_gb'])

        free_disk_mb = host_state.free_disk_mb
        total_usable_disk_mb = host_state.total_usable_disk_gb * 1024

        disk_mb_limit = total_usable_disk_mb * CONF.disk_allocation_ratio
        used_disk_mb = total_usable_disk_mb - free_disk_mb
        usable_disk_mb = disk_mb_limit - used_disk_mb

        if not usable_disk_mb >= requested_disk:
            LOG.debug(_("%(host_state)s does not have %(requested_disk)s MB "
                    "usable disk, it only has %(usable_disk_mb)s MB usable "
                    "disk."), locals())
            return False

        disk_gb_limit = disk_mb_limit / 1024
        host_state.limits['disk_gb'] = disk_gb_limit
        return True
