# Copyright (c) 2013 Hewlett-Packard Development Company, L.P.
# Copyright (c) 2012 VMware, Inc.
# Copyright (c) 2011 Citrix Systems, Inc.
# Copyright 2011 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.

"""
A connection to the VMware vCenter platform.
"""

import re

from oslo.config import cfg
from oslo.serialization import jsonutils
from oslo.vmware import api
from oslo.vmware import exceptions as vexc
from oslo.vmware import pbm
from oslo.vmware import vim
from oslo.vmware import vim_util
import suds

from nova import exception
from nova.i18n import _, _LW
from nova.openstack.common import log as logging
from nova.openstack.common import uuidutils
from nova.virt import driver
from nova.virt.vmwareapi import constants
from nova.virt.vmwareapi import error_util
from nova.virt.vmwareapi import host
from nova.virt.vmwareapi import vm_util
from nova.virt.vmwareapi import vmops
from nova.virt.vmwareapi import volumeops

LOG = logging.getLogger(__name__)

vmwareapi_opts = [
    cfg.StrOpt('host_ip',
               help='Hostname or IP address for connection to VMware VC '
                    'host.'),
    cfg.IntOpt('host_port',
               default=443,
               help='Port for connection to VMware VC host.'),
    cfg.StrOpt('host_username',
               help='Username for connection to VMware VC host.'),
    cfg.StrOpt('host_password',
               help='Password for connection to VMware VC host.',
               secret=True),
    cfg.MultiStrOpt('cluster_name',
                    help='Name of a VMware Cluster ComputeResource.'),
    cfg.StrOpt('datastore_regex',
               help='Regex to match the name of a datastore.'),
    cfg.FloatOpt('task_poll_interval',
                 default=0.5,
                 help='The interval used for polling of remote tasks.'),
    cfg.IntOpt('api_retry_count',
               default=10,
               help='The number of times we retry on failures, e.g., '
                    'socket error, etc.'),
    cfg.IntOpt('vnc_port',
               default=5900,
               help='VNC starting port'),
    cfg.IntOpt('vnc_port_total',
               default=10000,
               help='Total number of VNC ports'),
    cfg.BoolOpt('use_linked_clone',
                default=True,
                help='Whether to use linked clone'),
    cfg.StrOpt('wsdl_location',
               help='Optional VIM Service WSDL Location '
                    'e.g http://<server>/vimService.wsdl. '
                    'Optional over-ride to default location for bug '
                    'work-arounds')
    ]

spbm_opts = [
    cfg.BoolOpt('pbm_enabled',
                default=False,
                help='The PBM status.'),
    cfg.StrOpt('pbm_wsdl_location',
               help='PBM service WSDL file location URL. '
                    'e.g. file:///opt/SDK/spbm/wsdl/pbmService.wsdl '
                    'Not setting this will disable storage policy based '
                    'placement of instances.'),
    cfg.StrOpt('pbm_default_policy',
               help='The PBM default policy. If pbm_wsdl_location is set and '
                    'there is no defined storage policy for the specific '
                    'request then this policy will be used.'),
    ]

CONF = cfg.CONF
CONF.register_opts(vmwareapi_opts, 'vmware')
CONF.register_opts(spbm_opts, 'vmware')

TIME_BETWEEN_API_CALL_RETRIES = 1.0


class VMwareVCDriver(driver.ComputeDriver):
    """The VC host connection object."""

    capabilities = {
        "has_imagecache": True,
        "supports_recreate": False,
        }

    # The vCenter driver includes API that acts on ESX hosts or groups
    # of ESX hosts in clusters or non-cluster logical-groupings.
    #
    # vCenter is not a hypervisor itself, it works with multiple
    # hypervisor host machines and their guests. This fact can
    # subtly alter how vSphere and OpenStack interoperate.

    def __init__(self, virtapi, scheme="https"):
        super(VMwareVCDriver, self).__init__(virtapi)

        if (CONF.vmware.host_ip is None or
            CONF.vmware.host_username is None or
            CONF.vmware.host_password is None):
            raise Exception(_("Must specify host_ip, host_username and "
                              "host_password to use vmwareapi.VMwareVCDriver"))

        self._datastore_regex = None
        if CONF.vmware.datastore_regex:
            try:
                self._datastore_regex = re.compile(CONF.vmware.datastore_regex)
            except re.error:
                raise exception.InvalidInput(reason=
                    _("Invalid Regular Expression %s")
                    % CONF.vmware.datastore_regex)

        self._session = VMwareAPISession(scheme=scheme)

        # Update the PBM location if necessary
        if CONF.vmware.pbm_enabled:
            self._update_pbm_location()

        self._validate_configuration()

        # Get the list of clusters to be used
        self._cluster_names = CONF.vmware.cluster_name
        self.dict_mors = vm_util.get_all_cluster_refs_by_name(self._session,
                                          self._cluster_names)
        if not self.dict_mors:
            raise exception.NotFound(_("All clusters specified %s were not"
                                       " found in the vCenter")
                                     % self._cluster_names)

        # Check if there are any clusters that were specified in the nova.conf
        # but are not in the vCenter, for missing clusters log a warning.
        clusters_found = [v.get('name') for k, v in self.dict_mors.iteritems()]
        missing_clusters = set(self._cluster_names) - set(clusters_found)
        if missing_clusters:
            LOG.warn(_LW("The following clusters could not be found in the "
                         "vCenter %s") % list(missing_clusters))

        # The _resources is used to maintain the vmops, volumeops and vcstate
        # objects per cluster
        self._resources = {}
        self._resource_keys = set()
        self._virtapi = virtapi
        self._update_resources()

        # The following initialization is necessary since the base class does
        # not use VC state.
        first_cluster = self._resources.keys()[0]
        self._vmops = self._resources.get(first_cluster).get('vmops')
        self._volumeops = self._resources.get(first_cluster).get('volumeops')
        self._vc_state = self._resources.get(first_cluster).get('vcstate')

        # Register the OpenStack extension
        self._register_openstack_extension()

    def _update_pbm_location(self):
        if CONF.vmware.pbm_wsdl_location:
            pbm_wsdl_loc = CONF.vmware.pbm_wsdl_location
        else:
            version = vim_util.get_vc_version(self._session)
            pbm_wsdl_loc = pbm.get_pbm_wsdl_location(version)
        # TODO(garyk): Update this with oslo.vmware method. The session.pbm
        # is lazy loaded so this enables us to update this entry on the fly
        self._session._pbm_wsdl_loc = pbm_wsdl_loc
        self._session._pbm = None

    def _validate_configuration(self):
        if CONF.vmware.use_linked_clone is None:
            raise vexc.UseLinkedCloneConfigurationFault()

        if CONF.vmware.pbm_enabled:
            if not CONF.vmware.pbm_default_policy:
                raise error_util.PbmDefaultPolicyUnspecified()
            if not pbm.get_profile_id_by_name(
                            self._session,
                            CONF.vmware.pbm_default_policy):
                raise error_util.PbmDefaultPolicyDoesNotExist()
            if CONF.vmware.datastore_regex:
                LOG.warning(_LW(
                    "datastore_regex is ignored when PBM is enabled"))
                self._datastore_regex = None

    def init_host(self, host):
        vim = self._session.vim
        if vim is None:
            self._session._create_session()

    def cleanup_host(self, host):
        # NOTE(hartsocks): we lean on the init_host to force the vim object
        # to not be None.
        vim = self._session.vim
        service_content = vim.service_content
        session_manager = service_content.sessionManager
        try:
            vim.client.service.Logout(session_manager)
        except suds.WebFault:
            LOG.debug("No vSphere session was open during cleanup_host.")

    def _register_openstack_extension(self):
        # Register an 'OpenStack' extension in vCenter
        LOG.debug('Registering extension %s with vCenter',
                  constants.EXTENSION_KEY)
        os_extension = self._session._call_method(vim_util, 'find_extension',
                                                  constants.EXTENSION_KEY)
        if os_extension is None:
            LOG.debug('Extension does not exist. Registering type %s.',
                      constants.EXTENSION_TYPE_INSTANCE)
            self._session._call_method(vim_util, 'register_extension',
                                       constants.EXTENSION_KEY,
                                       constants.EXTENSION_TYPE_INSTANCE)

    def cleanup(self, context, instance, network_info, block_device_info=None,
                destroy_disks=True, migrate_data=None, destroy_vifs=True):
        """Cleanup after instance being destroyed by Hypervisor."""
        pass

    def resume_state_on_host_boot(self, context, instance, network_info,
                                  block_device_info=None):
        """resume guest state when a host is booted."""
        # Check if the instance is running already and avoid doing
        # anything if it is.
        instances = self.list_instances()
        if instance['uuid'] not in instances:
            LOG.warn(_LW('Instance cannot be found in host, or in an unknown'
                         'state.'), instance=instance)
        else:
            state = vm_util.get_vm_state_from_name(self._session,
                                                   instance['uuid'])
            ignored_states = ['poweredon', 'suspended']

            if state.lower() in ignored_states:
                return
        # Instance is not up and could be in an unknown state.
        # Be as absolute as possible about getting it back into
        # a known and running state.
        self.reboot(context, instance, network_info, 'hard',
                    block_device_info)

    def list_instance_uuids(self):
        """List VM instance UUIDs."""
        uuids = self._vmops.list_instances()
        return [uuid for uuid in uuids if uuidutils.is_uuid_like(uuid)]

    def list_instances(self):
        """List VM instances from all nodes."""
        instances = []
        nodes = self.get_available_nodes()
        for node in nodes:
            vmops = self._get_vmops_for_compute_node(node)
            instances.extend(vmops.list_instances())
        return instances

    def migrate_disk_and_power_off(self, context, instance, dest,
                                   flavor, network_info,
                                   block_device_info=None,
                                   timeout=0, retry_interval=0):
        """Transfers the disk of a running instance in multiple phases, turning
        off the instance before the end.
        """
        # TODO(PhilDay): Add support for timeout (clean shutdown)
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        return _vmops.migrate_disk_and_power_off(context, instance,
                                                 dest, flavor)

    def confirm_migration(self, migration, instance, network_info):
        """Confirms a resize, destroying the source VM."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.confirm_migration(migration, instance, network_info)

    def finish_revert_migration(self, context, instance, network_info,
                                block_device_info=None, power_on=True):
        """Finish reverting a resize, powering back on the instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.finish_revert_migration(context, instance, network_info,
                                       block_device_info, power_on)

    def finish_migration(self, context, migration, instance, disk_info,
                         network_info, image_meta, resize_instance,
                         block_device_info=None, power_on=True):
        """Completes a resize, turning on the migrated instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.finish_migration(context, migration, instance, disk_info,
                                network_info, image_meta, resize_instance,
                                block_device_info, power_on)

    def live_migration(self, context, instance, dest,
                       post_method, recover_method, block_migration=False,
                       migrate_data=None):
        """Live migration of an instance to another host."""
        self._vmops.live_migration(context, instance, dest,
                                   post_method, recover_method,
                                   block_migration)

    def rollback_live_migration_at_destination(self, context, instance,
                                               network_info,
                                               block_device_info,
                                               destroy_disks=True,
                                               migrate_data=None):
        """Clean up destination node after a failed live migration."""
        self.destroy(context, instance, network_info, block_device_info)

    def get_instance_disk_info(self, instance_name, block_device_info=None):
        pass

    def get_vnc_console(self, context, instance):
        """Return link to instance's VNC console using vCenter logic."""
        # vCenter does not actually run the VNC service
        # itself. You must talk to the VNC host underneath vCenter.
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        return _vmops.get_vnc_console(instance)

    def _update_resources(self):
        """This method creates a dictionary of VMOps, VolumeOps and VCState.

        The VMwareVMOps, VMwareVolumeOps and VCState object is for each
        cluster/rp. The dictionary is of the form
        {
            domain-1000 : {'vmops': vmops_obj,
                          'volumeops': volumeops_obj,
                          'vcstate': vcstate_obj,
                          'name': MyCluster},
            resgroup-1000 : {'vmops': vmops_obj,
                              'volumeops': volumeops_obj,
                              'vcstate': vcstate_obj,
                              'name': MyRP},
        }
        """
        added_nodes = set(self.dict_mors.keys()) - set(self._resource_keys)
        for node in added_nodes:
            _volumeops = volumeops.VMwareVolumeOps(self._session,
                                        self.dict_mors[node]['cluster_mor'])
            _vmops = vmops.VMwareVMOps(self._session, self._virtapi,
                                       _volumeops,
                                       self.dict_mors[node]['cluster_mor'],
                                       datastore_regex=self._datastore_regex)
            name = self.dict_mors.get(node)['name']
            nodename = self._create_nodename(node, name)
            _vc_state = host.VCState(self._session, nodename,
                                     self.dict_mors.get(node)['cluster_mor'])
            self._resources[nodename] = {'vmops': _vmops,
                                         'volumeops': _volumeops,
                                         'vcstate': _vc_state,
                                         'name': name,
                                     }
            self._resource_keys.add(node)

        deleted_nodes = (set(self._resource_keys) -
                            set(self.dict_mors.keys()))
        for node in deleted_nodes:
            name = self.dict_mors.get(node)['name']
            nodename = self._create_nodename(node, name)
            del self._resources[nodename]
            self._resource_keys.discard(node)

    def _create_nodename(self, mo_id, display_name):
        """Creates the name that is stored in hypervisor_hostname column.

        The name will be of the form similar to
        domain-1000(MyCluster)
        resgroup-1000(MyResourcePool)
        """
        return mo_id + '(' + display_name + ')'

    def _get_resource_for_node(self, nodename):
        """Gets the resource information for the specific node."""
        resource = self._resources.get(nodename)
        if not resource:
            msg = _("The resource %s does not exist") % nodename
            raise exception.NotFound(msg)
        return resource

    def _get_vmops_for_compute_node(self, nodename):
        """Retrieve vmops object from mo_id stored in the node name.

        Node name is of the form domain-1000(MyCluster)
        """
        resource = self._get_resource_for_node(nodename)
        return resource['vmops']

    def _get_volumeops_for_compute_node(self, nodename):
        """Retrieve vmops object from mo_id stored in the node name.

        Node name is of the form domain-1000(MyCluster)
        """
        resource = self._get_resource_for_node(nodename)
        return resource['volumeops']

    def _get_vc_state_for_compute_node(self, nodename):
        """Retrieve VCState object from mo_id stored in the node name.

        Node name is of the form domain-1000(MyCluster)
        """
        resource = self._get_resource_for_node(nodename)
        return resource['vcstate']

    def _get_available_resources(self, host_stats):
        return {'vcpus': host_stats['vcpus'],
               'memory_mb': host_stats['host_memory_total'],
               'local_gb': host_stats['disk_total'],
               'vcpus_used': 0,
               'memory_mb_used': host_stats['host_memory_total'] -
                                 host_stats['host_memory_free'],
               'local_gb_used': host_stats['disk_used'],
               'hypervisor_type': host_stats['hypervisor_type'],
               'hypervisor_version': host_stats['hypervisor_version'],
               'hypervisor_hostname': host_stats['hypervisor_hostname'],
               'cpu_info': jsonutils.dumps(host_stats['cpu_info']),
               'supported_instances': jsonutils.dumps(
                   host_stats['supported_instances']),
               'numa_topology': None,
               }

    def get_available_resource(self, nodename):
        """Retrieve resource info.

        This method is called when nova-compute launches, and
        as part of a periodic task.

        :returns: dictionary describing resources

        """
        stats_dict = {}
        vc_state = self._get_vc_state_for_compute_node(nodename)
        if vc_state:
            host_stats = vc_state.get_host_stats(refresh=True)

            # Updating host information
            stats_dict = self._get_available_resources(host_stats)

        else:
            LOG.info(_("Invalid cluster or resource pool"
                       " name : %s") % nodename)

        return stats_dict

    def get_available_nodes(self, refresh=False):
        """Returns nodenames of all nodes managed by the compute service.

        This method is for multi compute-nodes support. If a driver supports
        multi compute-nodes, this method returns a list of nodenames managed
        by the service. Otherwise, this method should return
        [hypervisor_hostname].
        """
        self.dict_mors = vm_util.get_all_cluster_refs_by_name(
                                self._session,
                                CONF.vmware.cluster_name)
        node_list = []
        self._update_resources()
        for node in self.dict_mors.keys():
            nodename = self._create_nodename(node,
                                          self.dict_mors.get(node)['name'])
            node_list.append(nodename)
        LOG.debug("The available nodes are: %s", node_list)
        return node_list

    def spawn(self, context, instance, image_meta, injected_files,
              admin_password, network_info=None, block_device_info=None,
              instance_type=None):
        """Create VM instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.spawn(context, instance, image_meta, injected_files,
              admin_password, network_info, block_device_info)

    def attach_volume(self, context, connection_info, instance, mountpoint,
                      disk_bus=None, device_type=None, encryption=None):
        """Attach volume storage to VM instance."""
        _volumeops = self._get_volumeops_for_compute_node(instance['node'])
        return _volumeops.attach_volume(connection_info,
                                             instance,
                                             mountpoint)

    def detach_volume(self, connection_info, instance, mountpoint,
                      encryption=None):
        """Detach volume storage to VM instance."""
        _volumeops = self._get_volumeops_for_compute_node(instance['node'])
        return _volumeops.detach_volume(connection_info,
                                             instance,
                                             mountpoint)

    def get_volume_connector(self, instance):
        """Return volume connector information."""
        _volumeops = self._get_volumeops_for_compute_node(instance['node'])
        return _volumeops.get_volume_connector(instance)

    def get_host_ip_addr(self):
        """Returns the IP address of the vCenter host."""
        return CONF.vmware.host_ip

    def snapshot(self, context, instance, image_id, update_task_state):
        """Create snapshot from a running VM instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.snapshot(context, instance, image_id, update_task_state)

    def reboot(self, context, instance, network_info, reboot_type,
               block_device_info=None, bad_volumes_callback=None):
        """Reboot VM instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.reboot(instance, network_info)

    def destroy(self, context, instance, network_info, block_device_info=None,
                destroy_disks=True, migrate_data=None):
        """Destroy VM instance."""

        # Destroy gets triggered when Resource Claim in resource_tracker
        # is not successful. When resource claim is not successful,
        # node is not set in instance. Perform destroy only if node is set
        if not instance['node']:
            return

        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.destroy(instance, destroy_disks)

    def pause(self, instance):
        """Pause VM instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.pause(instance)

    def unpause(self, instance):
        """Unpause paused VM instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.unpause(instance)

    def suspend(self, instance):
        """Suspend the specified instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.suspend(instance)

    def resume(self, context, instance, network_info, block_device_info=None):
        """Resume the suspended VM instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.resume(instance)

    def rescue(self, context, instance, network_info, image_meta,
               rescue_password):
        """Rescue the specified instance."""
        _vmops = self._get_vmops_for_compute_node(instance.node)
        _vmops.rescue(context, instance, network_info, image_meta)

    def unrescue(self, instance, network_info):
        """Unrescue the specified instance."""
        _vmops = self._get_vmops_for_compute_node(instance.node)
        _vmops.unrescue(instance)

    def power_off(self, instance, timeout=0, retry_interval=0):
        """Power off the specified instance."""
        # TODO(PhilDay): Add support for timeout (clean shutdown)
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.power_off(instance)

    def power_on(self, context, instance, network_info,
                 block_device_info=None):
        """Power on the specified instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.power_on(instance)

    def poll_rebooting_instances(self, timeout, instances):
        """Poll for rebooting instances."""
        for instance in instances:
            _vmops = self._get_vmops_for_compute_node(instance['node'])
            _vmops.poll_rebooting_instances(timeout, [instance])

    def get_info(self, instance):
        """Return info about the VM instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        return _vmops.get_info(instance)

    def get_diagnostics(self, instance):
        """Return data about VM diagnostics."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        data = _vmops.get_diagnostics(instance)
        return data

    def get_instance_diagnostics(self, instance):
        """Return data about VM diagnostics."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        data = _vmops.get_instance_diagnostics(instance)
        return data

    def host_power_action(self, action):
        """Host operations not supported by VC driver.

        This needs to override the ESX driver implementation.
        """
        raise NotImplementedError()

    def host_maintenance_mode(self, host, mode):
        """Host operations not supported by VC driver.

        This needs to override the ESX driver implementation.
        """
        raise NotImplementedError()

    def set_host_enabled(self, enabled):
        """Host operations not supported by VC driver.

        This needs to override the ESX driver implementation.
        """
        raise NotImplementedError()

    def get_host_uptime(self, host):
        """Host uptime operation not supported by VC driver."""

        msg = _("Multiple hosts may be managed by the VMWare "
                "vCenter driver; therefore we do not return "
                "uptime for just one host.")
        raise NotImplementedError(msg)

    def inject_network_info(self, instance, nw_info):
        """inject network info for specified instance."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        _vmops.inject_network_info(instance, nw_info)

    def manage_image_cache(self, context, all_instances):
        """Manage the local cache of images."""

        # Running instances per cluster
        cluster_instances = {}
        for instance in all_instances:
            instances = cluster_instances.get(instance['node'])
            if instances:
                instances.append(instance)
            else:
                instances = [instance]
            cluster_instances[instance['node']] = instances

        # Invoke the image aging per cluster
        for resource in self._resources.keys():
            instances = cluster_instances.get(resource, [])
            _vmops = self._get_vmops_for_compute_node(resource)
            _vmops.manage_image_cache(context, instances)

    def instance_exists(self, instance):
        """Efficient override of base instance_exists method."""
        _vmops = self._get_vmops_for_compute_node(instance['node'])
        return _vmops.instance_exists(instance)

    def attach_interface(self, instance, image_meta, vif):
        """Attach an interface to the instance."""
        _vmops = self._get_vmops_for_compute_node(instance.node)
        _vmops.attach_interface(instance, image_meta, vif)

    def detach_interface(self, instance, vif):
        """Detach an interface from the instance."""
        _vmops = self._get_vmops_for_compute_node(instance.node)
        _vmops.detach_interface(instance, vif)


class VMwareAPISession(api.VMwareAPISession):
    """Sets up a session with the VC/ESX host and handles all
    the calls made to the host.
    """
    def __init__(self, host_ip=CONF.vmware.host_ip,
                 host_port=CONF.vmware.host_port,
                 username=CONF.vmware.host_username,
                 password=CONF.vmware.host_password,
                 retry_count=CONF.vmware.api_retry_count,
                 scheme="https"):
        super(VMwareAPISession, self).__init__(
                host=host_ip,
                port=host_port,
                server_username=username,
                server_password=password,
                api_retry_count=retry_count,
                task_poll_interval=CONF.vmware.task_poll_interval,
                scheme=scheme,
                create_session=True,
                wsdl_loc=CONF.vmware.wsdl_location
                )

    def _is_vim_object(self, module):
        """Check if the module is a VIM Object instance."""
        return isinstance(module, vim.Vim)

    def _call_method(self, module, method, *args, **kwargs):
        """Calls a method within the module specified with
        args provided.
        """
        if not self._is_vim_object(module):
            return self.invoke_api(module, method, self.vim, *args, **kwargs)
        else:
            return self.invoke_api(module, method, *args, **kwargs)

    def _wait_for_task(self, task_ref):
        """Return a Deferred that will give the result of the given task.
        The task is polled until it completes.
        """
        return self.wait_for_task(task_ref)
