# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright (c) 2010 Openstack, LLC.
# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# 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.

"""
Scheduler Service
"""

import functools

from nova import db
from nova import flags
from nova import log as logging
from nova import manager
from nova import rpc
from nova import utils
from nova.scheduler import zone_manager

LOG = logging.getLogger('nova.scheduler.manager')
FLAGS = flags.FLAGS
flags.DEFINE_string('scheduler_driver',
                    'nova.scheduler.chance.ChanceScheduler',
                    'Driver to use for the scheduler')


class SchedulerManager(manager.Manager):
    """Chooses a host to run instances on."""
    def __init__(self, scheduler_driver=None, *args, **kwargs):
        self.zone_manager = zone_manager.ZoneManager()
        if not scheduler_driver:
            scheduler_driver = FLAGS.scheduler_driver
        self.driver = utils.import_object(scheduler_driver)
        self.driver.set_zone_manager(self.zone_manager)
        super(SchedulerManager, self).__init__(*args, **kwargs)

    def __getattr__(self, key):
        """Converts all method calls to use the schedule method"""
        return functools.partial(self._schedule, key)

    def periodic_tasks(self, context=None):
        """Poll child zones periodically to get status."""
        self.zone_manager.ping(context)

    def get_zone_list(self, context=None):
        """Get a list of zones from the ZoneManager."""
        return self.zone_manager.get_zone_list()

    def get_zone_capabilities(self, context=None):
        """Get the normalized set of capabilites for this zone."""
        return self.zone_manager.get_zone_capabilities(context)

    def update_service_capabilities(self, context=None, service_name=None,
                                                host=None, capabilities={}):
        """Process a capability update from a service node."""
        self.zone_manager.update_service_capabilities(service_name,
                            host, capabilities)

    def select(self, context=None, *args, **kwargs):
        """Select a list of hosts best matching the provided specs."""
        return self.driver.select(context, *args, **kwargs)

    def get_scheduler_rules(self, context=None, *args, **kwargs):
        """Ask the driver how requests should be made of it."""
        return self.driver.get_scheduler_rules(context, *args, **kwargs)

    def _schedule(self, method, context, topic, *args, **kwargs):
        """Tries to call schedule_* method on the driver to retrieve host.

        Falls back to schedule(context, topic) if method doesn't exist.
        """
        driver_method = 'schedule_%s' % method
        elevated = context.elevated()
        try:
            host = getattr(self.driver, driver_method)(elevated, *args,
                                                       **kwargs)
        except AttributeError, e:
            LOG.warning(_("Driver Method %(driver_method)s missing: %(e)s."
                            "Reverting to schedule()") % locals())
            host = self.driver.schedule(elevated, topic, *args, **kwargs)

        if not host:
            LOG.debug(_("%(topic)s %(method)s handled in Scheduler")
                        % locals())
            return

        rpc.cast(context,
                 db.queue_get_for(context, topic, host),
                 {"method": method,
                  "args": kwargs})
        LOG.debug(_("Casted to %(topic)s %(host)s for %(method)s") % locals())

    # NOTE (masumotok) : This method should be moved to nova.api.ec2.admin.
    #                    Based on bexar design summit discussion,
    #                    just put this here for bexar release.
    def show_host_resources(self, context, host, *args):
        """Shows the physical/usage resource given by hosts.

        :param context: security context
        :param host: hostname
        :returns:
            example format is below.
            {'resource':D, 'usage':{proj_id1:D, proj_id2:D}}
            D: {'vcpus':3, 'memory_mb':2048, 'local_gb':2048}

        """

        compute_ref = db.service_get_all_compute_by_host(context, host)
        compute_ref = compute_ref[0]

        # Getting physical resource information
        compute_node_ref = compute_ref['compute_node'][0]
        resource = {'vcpus': compute_node_ref['vcpus'],
                    'memory_mb': compute_node_ref['memory_mb'],
                    'local_gb': compute_node_ref['local_gb'],
                    'vcpus_used': compute_node_ref['vcpus_used'],
                    'memory_mb_used': compute_node_ref['memory_mb_used'],
                    'local_gb_used': compute_node_ref['local_gb_used']}

        # Getting usage resource information
        usage = {}
        instance_refs = db.instance_get_all_by_host(context,
                                                    compute_ref['host'])
        if not instance_refs:
            return {'resource': resource, 'usage': usage}

        project_ids = [i['project_id'] for i in instance_refs]
        project_ids = list(set(project_ids))
        for project_id in project_ids:
            vcpus = db.instance_get_vcpu_sum_by_host_and_project(context,
                                                                 host,
                                                                 project_id)
            mem = db.instance_get_memory_sum_by_host_and_project(context,
                                                                 host,
                                                                 project_id)
            hdd = db.instance_get_disk_sum_by_host_and_project(context,
                                                               host,
                                                               project_id)
            usage[project_id] = {'vcpus': int(vcpus),
                                 'memory_mb': int(mem),
                                 'local_gb': int(hdd)}

        return {'resource': resource, 'usage': usage}