#   Copyright 2013 OpenStack Foundation
#
#   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.utils import strutils
from webob import exc

from nova.api.openstack import common
from nova.api.openstack import extensions
from nova.api.openstack import wsgi
from nova import compute
from nova import exception
from nova.i18n import _
from nova import utils

authorize = extensions.extension_authorizer('compute', 'evacuate')


class Controller(wsgi.Controller):
    def __init__(self, ext_mgr, *args, **kwargs):
        super(Controller, self).__init__(*args, **kwargs)
        self.compute_api = compute.API()
        self.host_api = compute.HostAPI()
        self.ext_mgr = ext_mgr

    @wsgi.action('evacuate')
    def _evacuate(self, req, id, body):
        """Permit admins to evacuate a server from a failed host
        to a new one.
        If host is empty, the scheduler will select one.
        """
        context = req.environ["nova.context"]
        authorize(context)

        if not self.is_valid_body(body, "evacuate"):
            raise exc.HTTPBadRequest(_("Malformed request body"))
        evacuate_body = body["evacuate"]

        host = evacuate_body.get("host")

        if (not host and
                not self.ext_mgr.is_loaded('os-extended-evacuate-find-host')):
            msg = _("host must be specified.")
            raise exc.HTTPBadRequest(explanation=msg)

        try:
            on_shared_storage = strutils.bool_from_string(
                                            evacuate_body["onSharedStorage"])
        except (TypeError, KeyError):
            msg = _("onSharedStorage must be specified.")
            raise exc.HTTPBadRequest(explanation=msg)

        password = None
        if 'adminPass' in evacuate_body:
            # check that if requested to evacuate server on shared storage
            # password not specified
            if on_shared_storage:
                msg = _("admin password can't be changed on existing disk")
                raise exc.HTTPBadRequest(explanation=msg)

            password = evacuate_body['adminPass']
        elif not on_shared_storage:
            password = utils.generate_password()

        if host is not None:
            try:
                self.host_api.service_get_by_compute_host(context, host)
            except exception.NotFound:
                msg = _("Compute host %s not found.") % host
                raise exc.HTTPNotFound(explanation=msg)

        instance = common.get_instance(self.compute_api, context, id,
                                       want_objects=True)
        try:
            if instance.host == host:
                msg = _("The target host can't be the same one.")
                raise exc.HTTPBadRequest(explanation=msg)
            self.compute_api.evacuate(context, instance, host,
                                      on_shared_storage, password)
        except exception.InstanceInvalidState as state_error:
            common.raise_http_conflict_for_instance_invalid_state(state_error,
                    'evacuate', id)
        except exception.InstanceNotFound as e:
            raise exc.HTTPNotFound(explanation=e.format_message())
        except exception.ComputeServiceInUse as e:
            raise exc.HTTPBadRequest(explanation=e.format_message())

        if password:
            return {'adminPass': password}


class Evacuate(extensions.ExtensionDescriptor):
    """Enables server evacuation."""

    name = "Evacuate"
    alias = "os-evacuate"
    namespace = "http://docs.openstack.org/compute/ext/evacuate/api/v2"
    updated = "2013-01-06T00:00:00Z"

    def get_controller_extensions(self):
        controller = Controller(self.ext_mgr)
        extension = extensions.ControllerExtension(self, 'servers', controller)
        return [extension]
