#    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.

import functools

import os_traits
from oslo_log import log as logging
from oslo_utils import timeutils

import nova.conf
from nova import exception
from nova.i18n import _
from nova import objects
from nova.scheduler import utils


CONF = nova.conf.CONF
LOG = logging.getLogger(__name__)
TENANT_METADATA_KEY = 'filter_tenant_id'


def trace_request_filter(fn):
    @functools.wraps(fn)
    def wrapper(ctxt, request_spec):
        timer = timeutils.StopWatch()
        ran = False
        with timer:
            try:
                ran = fn(ctxt, request_spec)
            finally:
                if ran:
                    # Only log info if the filter was enabled and not
                    # excluded for some reason
                    LOG.debug('Request filter %r took %.1f seconds',
                        fn.__name__, timer.elapsed())
        return ran
    return wrapper


@trace_request_filter
def isolate_aggregates(ctxt, request_spec):
    """Prepare list of aggregates that should be isolated.

    This filter will prepare the list of aggregates that should be
    ignored by the placement service. It checks if aggregates has metadata
    'trait:<trait_name>='required' and if <trait_name> is not present in
    either of flavor extra specs or image properties, then those aggregates
    will be included in the list of isolated aggregates.

    Precisely this filter gets the trait request form the image and
    flavor and unions them. Then it accumulates the set of aggregates that
    request traits are "non_matching_by_metadata_keys" and uses that to
    produce the list of isolated aggregates.
    """

    if not CONF.scheduler.enable_isolated_aggregate_filtering:
        return False

    # Get required traits set in flavor and image
    res_req = utils.ResourceRequest(request_spec)
    required_traits = res_req.all_required_traits

    keys = ['trait:%s' % trait for trait in required_traits]

    isolated_aggregates = (
        objects.aggregate.AggregateList.get_non_matching_by_metadata_keys(
            ctxt, keys, 'trait:', value='required'))

    # Set list of isolated aggregates to destination object of request_spec
    if isolated_aggregates:
        if ('requested_destination' not in request_spec or
                request_spec.requested_destination is None):
            request_spec.requested_destination = objects.Destination()

        destination = request_spec.requested_destination
        destination.append_forbidden_aggregates(
            agg.uuid for agg in isolated_aggregates)

    return True


@trace_request_filter
def require_tenant_aggregate(ctxt, request_spec):
    """Require hosts in an aggregate based on tenant id.

    This will modify request_spec to request hosts in an aggregate
    defined specifically for the tenant making the request. We do that
    by looking for a nova host aggregate with metadata indicating which
    tenant it is for, and passing that aggregate uuid to placement to
    limit results accordingly.
    """

    enabled = CONF.scheduler.limit_tenants_to_placement_aggregate
    agg_required = CONF.scheduler.placement_aggregate_required_for_tenants
    if not enabled:
        return False

    aggregates = objects.AggregateList.get_by_metadata(
        ctxt, value=request_spec.project_id)
    aggregate_uuids_for_tenant = set([])
    for agg in aggregates:
        for key, value in agg.metadata.items():
            if key.startswith(TENANT_METADATA_KEY):
                aggregate_uuids_for_tenant.add(agg.uuid)
                break

    if aggregate_uuids_for_tenant:
        if ('requested_destination' not in request_spec or
                request_spec.requested_destination is None):
            request_spec.requested_destination = objects.Destination()
        destination = request_spec.requested_destination
        destination.require_aggregates(aggregate_uuids_for_tenant)
        LOG.debug('require_tenant_aggregate request filter added '
                  'aggregates %s for tenant %r',
                  ','.join(aggregate_uuids_for_tenant),
                  request_spec.project_id)
    elif agg_required:
        LOG.warning('Tenant %(tenant)s has no available aggregates',
                    {'tenant': request_spec.project_id})
        raise exception.RequestFilterFailed(
            reason=_('No hosts available for tenant'))

    return True


@trace_request_filter
def map_az_to_placement_aggregate(ctxt, request_spec):
    """Map requested nova availability zones to placement aggregates.

    This will modify request_spec to request hosts in an aggregate that
    matches the desired AZ of the user's request.
    """
    if not CONF.scheduler.query_placement_for_availability_zone:
        return False

    az_hint = request_spec.availability_zone
    if not az_hint:
        return False

    aggregates = objects.AggregateList.get_by_metadata(ctxt,
                                                       key='availability_zone',
                                                       value=az_hint)
    if aggregates:
        if ('requested_destination' not in request_spec or
                request_spec.requested_destination is None):
            request_spec.requested_destination = objects.Destination()
        agg_uuids = [agg.uuid for agg in aggregates]
        request_spec.requested_destination.require_aggregates(agg_uuids)
        LOG.debug('map_az_to_placement_aggregate request filter added '
                  'aggregates %s for az %r',
                  ','.join(agg_uuids),
                  az_hint)

    return True


@trace_request_filter
def require_image_type_support(ctxt, request_spec):
    """Request type-specific trait on candidates.

    This will modify the request_spec to request hosts that support the
    disk_format of the image provided.
    """
    if not CONF.scheduler.query_placement_for_image_type_support:
        return False

    if request_spec.is_bfv:
        # We are booting from volume, and thus compute node image
        # disk_format support does not matter.
        return False

    disk_format = request_spec.image.disk_format
    trait_name = 'COMPUTE_IMAGE_TYPE_%s' % disk_format.upper()
    if not hasattr(os_traits, trait_name):
        LOG.error(('Computed trait name %r is not valid; '
                   'is os-traits up to date?'), trait_name)
        return False

    request_spec.root_required.add(trait_name)

    LOG.debug('require_image_type_support request filter added required '
              'trait %s', trait_name)

    return True


@trace_request_filter
def transform_image_metadata(ctxt, request_spec):
    """Transform image metadata to required traits.

    This will modify the request_spec to request hosts that support
    virtualisation capabilities based on the image metadata properties.
    """
    if not CONF.scheduler.image_metadata_prefilter:
        return False

    prefix_map = {
        'hw_cdrom_bus': 'COMPUTE_STORAGE_BUS',
        'hw_disk_bus': 'COMPUTE_STORAGE_BUS',
        'hw_video_model': 'COMPUTE_GRAPHICS_MODEL',
        'hw_vif_model': 'COMPUTE_NET_VIF_MODEL',
    }

    trait_names = []

    for key, prefix in prefix_map.items():
        if key in request_spec.image.properties:
            value = request_spec.image.properties.get(key).replace(
                '-', '_').upper()
            trait_name = f'{prefix}_{value}'
            if not hasattr(os_traits, trait_name):
                LOG.error(('Computed trait name %r is not valid; '
                           'is os-traits up to date?'), trait_name)
                return False

            trait_names.append(trait_name)

    for trait_name in trait_names:
        LOG.debug(
            'transform_image_metadata request filter added required '
            'trait %s', trait_name
        )
        request_spec.root_required.add(trait_name)

    return True


@trace_request_filter
def compute_status_filter(ctxt, request_spec):
    """Pre-filter compute node resource providers using COMPUTE_STATUS_DISABLED

    The ComputeFilter filters out hosts for compute services that are
    disabled. Compute node resource providers managed by a disabled compute
    service should have the COMPUTE_STATUS_DISABLED trait set and be excluded
    by this mandatory pre-filter.
    """
    trait_name = os_traits.COMPUTE_STATUS_DISABLED
    request_spec.root_forbidden.add(trait_name)
    LOG.debug('compute_status_filter request filter added forbidden '
              'trait %s', trait_name)
    return True


@trace_request_filter
def accelerators_filter(ctxt, request_spec):
    """Allow only compute nodes with accelerator support.

    This filter retains only nodes whose compute manager published the
    COMPUTE_ACCELERATORS trait, thus indicating the version of n-cpu is
    sufficient to handle accelerator requests.
    """
    trait_name = os_traits.COMPUTE_ACCELERATORS
    if request_spec.flavor.extra_specs.get('accel:device_profile'):
        request_spec.root_required.add(trait_name)
        LOG.debug('accelerators_filter request filter added required '
                  'trait %s', trait_name)
    return True


ALL_REQUEST_FILTERS = [
    require_tenant_aggregate,
    map_az_to_placement_aggregate,
    require_image_type_support,
    compute_status_filter,
    isolate_aggregates,
    transform_image_metadata,
    accelerators_filter,
]


def process_reqspec(ctxt, request_spec):
    """Process an objects.ReqestSpec before calling placement.

    :param ctxt: A RequestContext
    :param request_spec: An objects.RequestSpec to be inspected/modified
    """
    for filter in ALL_REQUEST_FILTERS:
        filter(ctxt, request_spec)