# 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.

"""Quotas for volumes."""

from collections import deque
import datetime

from oslo_config import cfg
from oslo_log import log as logging
from oslo_log import versionutils
from oslo_utils import importutils
from oslo_utils import timeutils
import six

from cinder import context
from cinder import db
from cinder import exception
from cinder.i18n import _, _LE
from cinder import quota_utils


LOG = logging.getLogger(__name__)

quota_opts = [
    cfg.IntOpt('quota_volumes',
               default=10,
               help='Number of volumes allowed per project'),
    cfg.IntOpt('quota_snapshots',
               default=10,
               help='Number of volume snapshots allowed per project'),
    cfg.IntOpt('quota_consistencygroups',
               default=10,
               help='Number of consistencygroups allowed per project'),
    cfg.IntOpt('quota_groups',
               default=10,
               help='Number of groups allowed per project'),
    cfg.IntOpt('quota_gigabytes',
               default=1000,
               help='Total amount of storage, in gigabytes, allowed '
                    'for volumes and snapshots per project'),
    cfg.IntOpt('quota_backups',
               default=10,
               help='Number of volume backups allowed per project'),
    cfg.IntOpt('quota_backup_gigabytes',
               default=1000,
               help='Total amount of storage, in gigabytes, allowed '
                    'for backups per project'),
    cfg.IntOpt('reservation_expire',
               default=86400,
               help='Number of seconds until a reservation expires'),
    cfg.IntOpt('until_refresh',
               default=0,
               help='Count of reservations until usage is refreshed'),
    cfg.IntOpt('max_age',
               default=0,
               help='Number of seconds between subsequent usage refreshes'),
    cfg.StrOpt('quota_driver',
               default="cinder.quota.DbQuotaDriver",
               help='Default driver to use for quota checks'),
    cfg.BoolOpt('use_default_quota_class',
                default=True,
                help='Enables or disables use of default quota class '
                     'with default quota.'),
    cfg.IntOpt('per_volume_size_limit',
               default=-1,
               help='Max size allowed per volume, in gigabytes'), ]

CONF = cfg.CONF
CONF.register_opts(quota_opts)


class DbQuotaDriver(object):

    """Driver to perform check to enforcement of quotas.

    Also allows to obtain quota information.
    The default driver utilizes the local database.
    """

    def get_by_project(self, context, project_id, resource_name):
        """Get a specific quota by project."""

        return db.quota_get(context, project_id, resource_name)

    def get_by_class(self, context, quota_class, resource_name):
        """Get a specific quota by quota class."""

        return db.quota_class_get(context, quota_class, resource_name)

    def get_default(self, context, resource, project_id):
        """Get a specific default quota for a resource."""
        default_quotas = db.quota_class_get_default(context)
        return default_quotas.get(resource.name, resource.default)

    def get_defaults(self, context, resources, project_id=None):
        """Given a list of resources, retrieve the default quotas.

        Use the class quotas named `_DEFAULT_QUOTA_NAME` as default quotas,
        if it exists.

        :param context: The request context, for access checks.
        :param resources: A dictionary of the registered resources.
        :param project_id: The id of the current project
        """

        quotas = {}
        default_quotas = {}
        if CONF.use_default_quota_class:
            default_quotas = db.quota_class_get_default(context)

        for resource in resources.values():
            if default_quotas:
                if resource.name not in default_quotas:
                    versionutils.report_deprecated_feature(LOG, _(
                        "Default quota for resource: %(res)s is set "
                        "by the default quota flag: quota_%(res)s, "
                        "it is now deprecated. Please use the "
                        "default quota class for default "
                        "quota.") % {'res': resource.name})
            quotas[resource.name] = default_quotas.get(resource.name,
                                                       resource.default)
        return quotas

    def get_class_quotas(self, context, resources, quota_class,
                         defaults=True):
        """Given list of resources, retrieve the quotas for given quota class.

        :param context: The request context, for access checks.
        :param resources: A dictionary of the registered resources.
        :param quota_class: The name of the quota class to return
                            quotas for.
        :param defaults: If True, the default value will be reported
                         if there is no specific value for the
                         resource.
        """

        quotas = {}
        default_quotas = {}
        class_quotas = db.quota_class_get_all_by_name(context, quota_class)
        if defaults:
            default_quotas = db.quota_class_get_default(context)
        for resource in resources.values():
            if resource.name in class_quotas:
                quotas[resource.name] = class_quotas[resource.name]
                continue

            if defaults:
                quotas[resource.name] = default_quotas.get(resource.name,
                                                           resource.default)

        return quotas

    def get_project_quotas(self, context, resources, project_id,
                           quota_class=None, defaults=True,
                           usages=True):
        """Retrieve quotas for a project.

        Given a list of resources, retrieve the quotas for the given
        project.

        :param context: The request context, for access checks.
        :param resources: A dictionary of the registered resources.
        :param project_id: The ID of the project to return quotas for.
        :param quota_class: If project_id != context.project_id, the
                            quota class cannot be determined.  This
                            parameter allows it to be specified.  It
                            will be ignored if project_id ==
                            context.project_id.
        :param defaults: If True, the quota class value (or the
                         default value, if there is no value from the
                         quota class) will be reported if there is no
                         specific value for the resource.
        :param usages: If True, the current in_use, reserved and allocated
                       counts will also be returned.
        """

        quotas = {}
        project_quotas = db.quota_get_all_by_project(context, project_id)
        allocated_quotas = None
        default_quotas = None
        if usages:
            project_usages = db.quota_usage_get_all_by_project(context,
                                                               project_id)
            allocated_quotas = db.quota_allocated_get_all_by_project(
                context, project_id)
            allocated_quotas.pop('project_id')

        # Get the quotas for the appropriate class.  If the project ID
        # matches the one in the context, we use the quota_class from
        # the context, otherwise, we use the provided quota_class (if
        # any)
        if project_id == context.project_id:
            quota_class = context.quota_class
        if quota_class:
            class_quotas = db.quota_class_get_all_by_name(context, quota_class)
        else:
            class_quotas = {}

        for resource in resources.values():
            # Omit default/quota class values
            if not defaults and resource.name not in project_quotas:
                continue

            quota_val = project_quotas.get(resource.name)
            if quota_val is None:
                quota_val = class_quotas.get(resource.name)
                if quota_val is None:
                    # Lazy load the default quotas
                    if default_quotas is None:
                        default_quotas = self.get_defaults(
                            context, resources, project_id)
                    quota_val = default_quotas[resource.name]

            quotas[resource.name] = {'limit': quota_val}

            # Include usages if desired.  This is optional because one
            # internal consumer of this interface wants to access the
            # usages directly from inside a transaction.
            if usages:
                usage = project_usages.get(resource.name, {})
                quotas[resource.name].update(
                    in_use=usage.get('in_use', 0),
                    reserved=usage.get('reserved', 0), )
            if allocated_quotas:
                quotas[resource.name].update(
                    allocated=allocated_quotas.get(resource.name, 0), )
        return quotas

    def _get_quotas(self, context, resources, keys, has_sync, project_id=None):
        """A helper method which retrieves the quotas for specific resources.

        This specific resource is identified by keys, and which apply to the
        current context.

        :param context: The request context, for access checks.
        :param resources: A dictionary of the registered resources.
        :param keys: A list of the desired quotas to retrieve.
        :param has_sync: If True, indicates that the resource must
                         have a sync attribute; if False, indicates
                         that the resource must NOT have a sync
                         attribute.
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """

        # Filter resources
        if has_sync:
            sync_filt = lambda x: hasattr(x, 'sync')
        else:
            sync_filt = lambda x: not hasattr(x, 'sync')
        desired = set(keys)
        sub_resources = {k: v for k, v in resources.items()
                         if k in desired and sync_filt(v)}

        # Make sure we accounted for all of them...
        if len(keys) != len(sub_resources):
            unknown = desired - set(sub_resources.keys())
            raise exception.QuotaResourceUnknown(unknown=sorted(unknown))

        # Grab and return the quotas (without usages)
        quotas = self.get_project_quotas(context, sub_resources,
                                         project_id,
                                         context.quota_class, usages=False)

        return {k: v['limit'] for k, v in quotas.items()}

    def limit_check(self, context, resources, values, project_id=None):
        """Check simple quota limits.

        For limits--those quotas for which there is no usage
        synchronization function--this method checks that a set of
        proposed values are permitted by the limit restriction.

        This method will raise a QuotaResourceUnknown exception if a
        given resource is unknown or if it is not a simple limit
        resource.

        If any of the proposed values is over the defined quota, an
        OverQuota exception will be raised with the sorted list of the
        resources which are too high.  Otherwise, the method returns
        nothing.

        :param context: The request context, for access checks.
        :param resources: A dictionary of the registered resources.
        :param values: A dictionary of the values to check against the
                       quota.
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """

        # Ensure no value is less than zero
        unders = [key for key, val in values.items() if val < 0]
        if unders:
            raise exception.InvalidQuotaValue(unders=sorted(unders))

        # If project_id is None, then we use the project_id in context
        if project_id is None:
            project_id = context.project_id

        # Get the applicable quotas
        quotas = self._get_quotas(context, resources, values.keys(),
                                  has_sync=False, project_id=project_id)
        # Check the quotas and construct a list of the resources that
        # would be put over limit by the desired values
        overs = [key for key, val in values.items()
                 if quotas[key] >= 0 and quotas[key] < val]
        if overs:
            raise exception.OverQuota(overs=sorted(overs), quotas=quotas,
                                      usages={})

    def reserve(self, context, resources, deltas, expire=None,
                project_id=None):
        """Check quotas and reserve resources.

        For counting quotas--those quotas for which there is a usage
        synchronization function--this method checks quotas against
        current usage and the desired deltas.

        This method will raise a QuotaResourceUnknown exception if a
        given resource is unknown or if it does not have a usage
        synchronization function.

        If any of the proposed values is over the defined quota, an
        OverQuota exception will be raised with the sorted list of the
        resources which are too high.  Otherwise, the method returns a
        list of reservation UUIDs which were created.

        :param context: The request context, for access checks.
        :param resources: A dictionary of the registered resources.
        :param deltas: A dictionary of the proposed delta changes.
        :param expire: An optional parameter specifying an expiration
                       time for the reservations.  If it is a simple
                       number, it is interpreted as a number of
                       seconds and added to the current time; if it is
                       a datetime.timedelta object, it will also be
                       added to the current time.  A datetime.datetime
                       object will be interpreted as the absolute
                       expiration time.  If None is specified, the
                       default expiration time set by
                       --default-reservation-expire will be used (this
                       value will be treated as a number of seconds).
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """

        # Set up the reservation expiration
        if expire is None:
            expire = CONF.reservation_expire
        if isinstance(expire, six.integer_types):
            expire = datetime.timedelta(seconds=expire)
        if isinstance(expire, datetime.timedelta):
            expire = timeutils.utcnow() + expire
        if not isinstance(expire, datetime.datetime):
            raise exception.InvalidReservationExpiration(expire=expire)

        # If project_id is None, then we use the project_id in context
        if project_id is None:
            project_id = context.project_id

        # Get the applicable quotas.
        # NOTE(Vek): We're not worried about races at this point.
        #            Yes, the admin may be in the process of reducing
        #            quotas, but that's a pretty rare thing.
        quotas = self._get_quotas(context, resources, deltas.keys(),
                                  has_sync=True, project_id=project_id)
        return self._reserve(context, resources, quotas, deltas, expire,
                             project_id)

    def _reserve(self, context, resources, quotas, deltas, expire, project_id):
        # NOTE(Vek): Most of the work here has to be done in the DB
        #            API, because we have to do it in a transaction,
        #            which means access to the session.  Since the
        #            session isn't available outside the DBAPI, we
        #            have to do the work there.
        return db.quota_reserve(context, resources, quotas, deltas, expire,
                                CONF.until_refresh, CONF.max_age,
                                project_id=project_id)

    def commit(self, context, reservations, project_id=None):
        """Commit reservations.

        :param context: The request context, for access checks.
        :param reservations: A list of the reservation UUIDs, as
                             returned by the reserve() method.
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """
        # If project_id is None, then we use the project_id in context
        if project_id is None:
            project_id = context.project_id

        db.reservation_commit(context, reservations, project_id=project_id)

    def rollback(self, context, reservations, project_id=None):
        """Roll back reservations.

        :param context: The request context, for access checks.
        :param reservations: A list of the reservation UUIDs, as
                             returned by the reserve() method.
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """
        # If project_id is None, then we use the project_id in context
        if project_id is None:
            project_id = context.project_id

        db.reservation_rollback(context, reservations, project_id=project_id)

    def destroy_by_project(self, context, project_id):
        """Destroy all limit quotas associated with a project.

        Leave usage and reservation quotas intact.

        :param context: The request context, for access checks.
        :param project_id: The ID of the project being deleted.
        """
        db.quota_destroy_by_project(context, project_id)

    def expire(self, context):
        """Expire reservations.

        Explores all currently existing reservations and rolls back
        any that have expired.

        :param context: The request context, for access checks.
        """

        db.reservation_expire(context)


class NestedDbQuotaDriver(DbQuotaDriver):
    def validate_nested_setup(self, ctxt, resources, project_tree,
                              fix_allocated_quotas=False):
        """Ensures project_tree has quotas that make sense as nested quotas.

        Validates the following:
          * No parent project has child_projects who have more combined quota
            than the parent's quota limit
          * No child quota has a larger in-use value than it's current limit
            (could happen before because child default values weren't enforced)
          * All parent projects' "allocated" quotas match the sum of the limits
            of its children projects

        TODO(mc_nair): need a better way to "flip the switch" to use nested
                       quotas to make this less race-ee
        """
        self._allocated = {}
        project_queue = deque(project_tree.items())
        borked_allocated_quotas = {}

        while project_queue:
            # Tuple of (current root node, subtree)
            cur_proj_id, project_subtree = project_queue.popleft()

            # If we're on a leaf node, no need to do validation on it, and in
            # order to avoid complication trying to get its children, skip it.
            if not project_subtree:
                continue

            cur_project_quotas = self.get_project_quotas(
                ctxt, resources, cur_proj_id)

            # Validate each resource when compared to it's child quotas
            for resource in cur_project_quotas.keys():
                parent_quota = cur_project_quotas[resource]
                parent_limit = parent_quota['limit']
                parent_usage = (parent_quota['in_use'] +
                                parent_quota['reserved'])

                cur_parent_allocated = parent_quota.get('allocated', 0)
                calc_parent_allocated = self._get_cur_project_allocated(
                    ctxt, resources[resource], {cur_proj_id: project_subtree})

                if parent_limit > 0:
                    parent_free_quota = parent_limit - parent_usage
                    if parent_free_quota < calc_parent_allocated:
                        msg = _("Sum of child usage '%(sum)s' is greater "
                                "than free quota of '%(free)s' for project "
                                "'%(proj)s' for resource '%(res)s'. Please "
                                "lower the limit or usage for one or more of "
                                "the following projects: '%(child_ids)s'") % {
                            'sum': calc_parent_allocated,
                            'free': parent_free_quota,
                            'proj': cur_proj_id, 'res': resource,
                            'child_ids': ', '.join(project_subtree.keys())
                        }
                        raise exception.InvalidNestedQuotaSetup(reason=msg)

                # If "allocated" value wasn't right either err or fix DB
                if calc_parent_allocated != cur_parent_allocated:
                    if fix_allocated_quotas:
                        try:
                            db.quota_allocated_update(ctxt, cur_proj_id,
                                                      resource,
                                                      calc_parent_allocated)
                        except exception.ProjectQuotaNotFound:
                            # If it was default quota create DB entry for it
                            db.quota_create(
                                ctxt, cur_proj_id, resource,
                                parent_limit, allocated=calc_parent_allocated)
                    else:
                        if cur_proj_id not in borked_allocated_quotas:
                            borked_allocated_quotas[cur_proj_id] = {}

                        borked_allocated_quotas[cur_proj_id][resource] = {
                            'db_allocated_quota': cur_parent_allocated,
                            'expected_allocated_quota': calc_parent_allocated}

            project_queue.extend(project_subtree.items())

        if borked_allocated_quotas:
            msg = _("Invalid allocated quotas defined for the following "
                    "project quotas: %s") % borked_allocated_quotas
            raise exception.InvalidNestedQuotaSetup(message=msg)

    def _get_cur_project_allocated(self, ctxt, resource, project_tree):
        """Recursively calculates the allocated value of a project

        :param ctxt: context used to retrieve DB values
        :param resource: the resource to calculate allocated value for
        :param project_tree: the project tree used to calculate allocated
                e.g. {'A': {'B': {'D': None}, 'C': None}}

        A project's "allocated" value depends on:
            1) the quota limits which have been "given" to it's children, in
               the case those limits are not unlimited (-1)
            2) the current quota being used by a child plus whatever the child
               has given to it's children, in the case of unlimited (-1) limits

        Scenario #2 requires recursively calculating allocated, and in order
        to efficiently calculate things we will save off any previously
        calculated allocated values.

        NOTE: this currently leaves a race condition when a project's allocated
        value has been calculated (with a -1 limit), but then a child project
        gets a volume created, thus changing the in-use value and messing up
        the child's allocated value. We should look into updating the allocated
        values as we're going along and switching to NestedQuotaDriver with
        flip of a switch.
        """
        # Grab the current node
        cur_project_id = list(project_tree)[0]
        project_subtree = project_tree[cur_project_id]
        res_name = resource.name

        if cur_project_id not in self._allocated:
            self._allocated[cur_project_id] = {}

        if res_name not in self._allocated[cur_project_id]:
            # Calculate the allocated value for this resource since haven't yet
            cur_project_allocated = 0
            child_proj_ids = project_subtree.keys() if project_subtree else {}
            res_dict = {res_name: resource}
            child_project_quotas = {child_id: self.get_project_quotas(
                ctxt, res_dict, child_id) for child_id in child_proj_ids}

            for child_id, child_quota in child_project_quotas.items():
                child_limit = child_quota[res_name]['limit']
                # Non-unlimited quota is easy, anything explicitly given to a
                # child project gets added into allocated value
                if child_limit != -1:
                    if child_quota[res_name].get('in_use', 0) > child_limit:
                        msg = _("Quota limit invalid for project '%(proj)s' "
                                "for resource '%(res)s': limit of %(limit)d "
                                "is less than in-use value of %(used)d") % {
                            'proj': child_id, 'res': res_name,
                            'limit': child_limit,
                            'used': child_quota[res_name]['in_use']
                        }
                        raise exception.InvalidNestedQuotaSetup(reason=msg)

                    cur_project_allocated += child_limit
                # For -1, take any quota being eaten up by child, as well as
                # what the child itself has given up to its children
                else:
                    child_in_use = child_quota[res_name].get('in_use', 0)
                    # Recursively calculate child's allocated
                    child_alloc = self._get_cur_project_allocated(
                        ctxt, resource, {child_id: project_subtree[child_id]})
                    cur_project_allocated += child_in_use + child_alloc

            self._allocated[cur_project_id][res_name] = cur_project_allocated

        return self._allocated[cur_project_id][res_name]

    def get_default(self, context, resource, project_id):
        """Get a specific default quota for a resource."""
        resource = super(NestedDbQuotaDriver, self).get_default(
            context, resource, project_id)

        return 0 if quota_utils.get_parent_project_id(
            context, project_id) else resource.default

    def get_defaults(self, context, resources, project_id=None):
        defaults = super(NestedDbQuotaDriver, self).get_defaults(
            context, resources, project_id)
        # All defaults are 0 for child project
        if quota_utils.get_parent_project_id(context, project_id):
            for key in defaults.keys():
                defaults[key] = 0
        return defaults

    def _reserve(self, context, resources, quotas, deltas, expire, project_id):
        reserved = []
        # As to not change the exception behavior, flag every res that would
        # be over instead of failing on first OverQuota
        resources_failed_to_update = []
        failed_usages = {}
        for res in deltas.keys():
            try:
                reserved += db.quota_reserve(
                    context, resources, quotas, {res: deltas[res]},
                    expire, CONF.until_refresh, CONF.max_age, project_id)
                if quotas[res] == -1:
                    reserved += quota_utils.update_alloc_to_next_hard_limit(
                        context, resources, deltas, res, expire, project_id)
            except exception.OverQuota as e:
                resources_failed_to_update.append(res)
                failed_usages.update(e.kwargs['usages'])

        if resources_failed_to_update:
            db.reservation_rollback(context, reserved, project_id)
            # We change OverQuota to OverVolumeLimit in other places and expect
            # to find all of the OverQuota kwargs
            raise exception.OverQuota(overs=sorted(resources_failed_to_update),
                                      quotas=quotas, usages=failed_usages)

        return reserved


class BaseResource(object):
    """Describe a single resource for quota checking."""

    def __init__(self, name, flag=None, parent_project_id=None):
        """Initializes a Resource.

        :param name: The name of the resource, i.e., "volumes".
        :param flag: The name of the flag or configuration option
                     which specifies the default value of the quota
                     for this resource.
        :param parent_project_id: The id of the current project's parent,
                                  if any.
        """

        self.name = name
        self.flag = flag
        self.parent_project_id = parent_project_id

    def quota(self, driver, context, **kwargs):
        """Given a driver and context, obtain the quota for this resource.

        :param driver: A quota driver.
        :param context: The request context.
        :param project_id: The project to obtain the quota value for.
                           If not provided, it is taken from the
                           context.  If it is given as None, no
                           project-specific quota will be searched
                           for.
        :param quota_class: The quota class corresponding to the
                            project, or for which the quota is to be
                            looked up.  If not provided, it is taken
                            from the context.  If it is given as None,
                            no quota class-specific quota will be
                            searched for.  Note that the quota class
                            defaults to the value in the context,
                            which may not correspond to the project if
                            project_id is not the same as the one in
                            the context.
        """

        # Get the project ID
        project_id = kwargs.get('project_id', context.project_id)

        # Ditto for the quota class
        quota_class = kwargs.get('quota_class', context.quota_class)

        # Look up the quota for the project
        if project_id:
            try:
                return driver.get_by_project(context, project_id, self.name)
            except exception.ProjectQuotaNotFound:
                pass

        # Try for the quota class
        if quota_class:
            try:
                return driver.get_by_class(context, quota_class, self.name)
            except exception.QuotaClassNotFound:
                pass

        # OK, return the default
        return driver.get_default(context, self,
                                  parent_project_id=self.parent_project_id)

    @property
    def default(self):
        """Return the default value of the quota."""

        if self.parent_project_id:
            return 0

        return CONF[self.flag] if self.flag else -1


class ReservableResource(BaseResource):
    """Describe a reservable resource."""

    def __init__(self, name, sync, flag=None):
        """Initializes a ReservableResource.

        Reservable resources are those resources which directly
        correspond to objects in the database, i.e., volumes, gigabytes,
        etc.  A ReservableResource must be constructed with a usage
        synchronization function, which will be called to determine the
        current counts of one or more resources.

        The usage synchronization function will be passed three
        arguments: an admin context, the project ID, and an opaque
        session object, which should in turn be passed to the
        underlying database function.  Synchronization functions
        should return a dictionary mapping resource names to the
        current in_use count for those resources; more than one
        resource and resource count may be returned.  Note that
        synchronization functions may be associated with more than one
        ReservableResource.

        :param name: The name of the resource, i.e., "volumes".
        :param sync: A dbapi methods name which returns a dictionary
                     to resynchronize the in_use count for one or more
                     resources, as described above.
        :param flag: The name of the flag or configuration option
                     which specifies the default value of the quota
                     for this resource.
        """

        super(ReservableResource, self).__init__(name, flag=flag)
        if sync:
            self.sync = sync


class AbsoluteResource(BaseResource):
    """Describe a non-reservable resource."""

    pass


class CountableResource(AbsoluteResource):
    """Describe a resource where counts aren't based only on the project ID."""

    def __init__(self, name, count, flag=None):
        """Initializes a CountableResource.

        Countable resources are those resources which directly
        correspond to objects in the database, i.e., volumes, gigabytes,
        etc., but for which a count by project ID is inappropriate.  A
        CountableResource must be constructed with a counting
        function, which will be called to determine the current counts
        of the resource.

        The counting function will be passed the context, along with
        the extra positional and keyword arguments that are passed to
        Quota.count().  It should return an integer specifying the
        count.

        Note that this counting is not performed in a transaction-safe
        manner.  This resource class is a temporary measure to provide
        required functionality, until a better approach to solving
        this problem can be evolved.

        :param name: The name of the resource, i.e., "volumes".
        :param count: A callable which returns the count of the
                      resource.  The arguments passed are as described
                      above.
        :param flag: The name of the flag or configuration option
                     which specifies the default value of the quota
                     for this resource.
        """

        super(CountableResource, self).__init__(name, flag=flag)
        self.count = count


class VolumeTypeResource(ReservableResource):
    """ReservableResource for a specific volume type."""

    def __init__(self, part_name, volume_type):
        """Initializes a VolumeTypeResource.

        :param part_name: The kind of resource, i.e., "volumes".
        :param volume_type: The volume type for this resource.
        """

        self.volume_type_name = volume_type['name']
        self.volume_type_id = volume_type['id']
        name = "%s_%s" % (part_name, self.volume_type_name)
        super(VolumeTypeResource, self).__init__(name, "_sync_%s" % part_name)


class QuotaEngine(object):
    """Represent the set of recognized quotas."""

    def __init__(self, quota_driver_class=None):
        """Initialize a Quota object."""

        self._resources = {}
        self._quota_driver_class = quota_driver_class
        self._driver_class = None

    @property
    def _driver(self):
        # Lazy load the driver so we give a chance for the config file to
        # be read before grabbing the config for which QuotaDriver to use
        if self._driver_class:
            return self._driver_class

        if not self._quota_driver_class:
            # Grab the current driver class from CONF
            self._quota_driver_class = CONF.quota_driver

        if isinstance(self._quota_driver_class, six.string_types):
            self._quota_driver_class = importutils.import_object(
                self._quota_driver_class)

        self._driver_class = self._quota_driver_class
        return self._driver_class

    def using_nested_quotas(self):
        """Returns true if nested quotas are being used"""
        return isinstance(self._driver, NestedDbQuotaDriver)

    def __contains__(self, resource):
        return resource in self.resources

    def register_resource(self, resource):
        """Register a resource."""

        self._resources[resource.name] = resource

    def register_resources(self, resources):
        """Register a list of resources."""

        for resource in resources:
            self.register_resource(resource)

    def get_by_project(self, context, project_id, resource_name):
        """Get a specific quota by project."""
        return self._driver.get_by_project(context, project_id, resource_name)

    def get_by_project_or_default(self, context, project_id, resource_name):
        """Get specific quota by project or default quota if doesn't exists."""
        try:
            val = self.get_by_project(
                context, project_id, resource_name).hard_limit
        except exception.ProjectQuotaNotFound:
            val = self.get_defaults(context, project_id)[resource_name]

        return val

    def get_by_class(self, context, quota_class, resource_name):
        """Get a specific quota by quota class."""

        return self._driver.get_by_class(context, quota_class, resource_name)

    def get_default(self, context, resource, parent_project_id=None):
        """Get a specific default quota for a resource.

        :param parent_project_id: The id of the current project's parent,
                                  if any.
        """

        return self._driver.get_default(context, resource,
                                        parent_project_id=parent_project_id)

    def get_defaults(self, context, project_id=None):
        """Retrieve the default quotas.

        :param context: The request context, for access checks.
        :param project_id: The id of the current project
        """

        return self._driver.get_defaults(context, self.resources,
                                         project_id)

    def get_class_quotas(self, context, quota_class, defaults=True):
        """Retrieve the quotas for the given quota class.

        :param context: The request context, for access checks.
        :param quota_class: The name of the quota class to return
                            quotas for.
        :param defaults: If True, the default value will be reported
                         if there is no specific value for the
                         resource.
        """

        return self._driver.get_class_quotas(context, self.resources,
                                             quota_class, defaults=defaults)

    def get_project_quotas(self, context, project_id, quota_class=None,
                           defaults=True, usages=True):
        """Retrieve the quotas for the given project.

        :param context: The request context, for access checks.
        :param project_id: The ID of the project to return quotas for.
        :param quota_class: If project_id != context.project_id, the
                            quota class cannot be determined.  This
                            parameter allows it to be specified.
        :param defaults: If True, the quota class value (or the
                         default value, if there is no value from the
                         quota class) will be reported if there is no
                         specific value for the resource.
        :param usages: If True, the current in_use, reserved and
                       allocated counts will also be returned.
        """
        return self._driver.get_project_quotas(context, self.resources,
                                               project_id,
                                               quota_class=quota_class,
                                               defaults=defaults,
                                               usages=usages)

    def count(self, context, resource, *args, **kwargs):
        """Count a resource.

        For countable resources, invokes the count() function and
        returns its result.  Arguments following the context and
        resource are passed directly to the count function declared by
        the resource.

        :param context: The request context, for access checks.
        :param resource: The name of the resource, as a string.
        """

        # Get the resource
        res = self.resources.get(resource)
        if not res or not hasattr(res, 'count'):
            raise exception.QuotaResourceUnknown(unknown=[resource])

        return res.count(context, *args, **kwargs)

    def limit_check(self, context, project_id=None, **values):
        """Check simple quota limits.

        For limits--those quotas for which there is no usage
        synchronization function--this method checks that a set of
        proposed values are permitted by the limit restriction.  The
        values to check are given as keyword arguments, where the key
        identifies the specific quota limit to check, and the value is
        the proposed value.

        This method will raise a QuotaResourceUnknown exception if a
        given resource is unknown or if it is not a simple limit
        resource.

        If any of the proposed values is over the defined quota, an
        OverQuota exception will be raised with the sorted list of the
        resources which are too high.  Otherwise, the method returns
        nothing.

        :param context: The request context, for access checks.
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """

        return self._driver.limit_check(context, self.resources, values,
                                        project_id=project_id)

    def reserve(self, context, expire=None, project_id=None, **deltas):
        """Check quotas and reserve resources.

        For counting quotas--those quotas for which there is a usage
        synchronization function--this method checks quotas against
        current usage and the desired deltas.  The deltas are given as
        keyword arguments, and current usage and other reservations
        are factored into the quota check.

        This method will raise a QuotaResourceUnknown exception if a
        given resource is unknown or if it does not have a usage
        synchronization function.

        If any of the proposed values is over the defined quota, an
        OverQuota exception will be raised with the sorted list of the
        resources which are too high.  Otherwise, the method returns a
        list of reservation UUIDs which were created.

        :param context: The request context, for access checks.
        :param expire: An optional parameter specifying an expiration
                       time for the reservations.  If it is a simple
                       number, it is interpreted as a number of
                       seconds and added to the current time; if it is
                       a datetime.timedelta object, it will also be
                       added to the current time.  A datetime.datetime
                       object will be interpreted as the absolute
                       expiration time.  If None is specified, the
                       default expiration time set by
                       --default-reservation-expire will be used (this
                       value will be treated as a number of seconds).
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """

        reservations = self._driver.reserve(context, self.resources, deltas,
                                            expire=expire,
                                            project_id=project_id)

        LOG.debug("Created reservations %s", reservations)

        return reservations

    def commit(self, context, reservations, project_id=None):
        """Commit reservations.

        :param context: The request context, for access checks.
        :param reservations: A list of the reservation UUIDs, as
                             returned by the reserve() method.
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """

        try:
            self._driver.commit(context, reservations, project_id=project_id)
        except Exception:
            # NOTE(Vek): Ignoring exceptions here is safe, because the
            # usage resynchronization and the reservation expiration
            # mechanisms will resolve the issue.  The exception is
            # logged, however, because this is less than optimal.
            LOG.exception(_LE("Failed to commit "
                              "reservations %s"), reservations)

    def rollback(self, context, reservations, project_id=None):
        """Roll back reservations.

        :param context: The request context, for access checks.
        :param reservations: A list of the reservation UUIDs, as
                             returned by the reserve() method.
        :param project_id: Specify the project_id if current context
                           is admin and admin wants to impact on
                           common user's tenant.
        """

        try:
            self._driver.rollback(context, reservations, project_id=project_id)
        except Exception:
            # NOTE(Vek): Ignoring exceptions here is safe, because the
            # usage resynchronization and the reservation expiration
            # mechanisms will resolve the issue.  The exception is
            # logged, however, because this is less than optimal.
            LOG.exception(_LE("Failed to roll back reservations "
                              "%s"), reservations)

    def destroy_by_project(self, context, project_id):
        """Destroy all quota limits associated with a project.

        :param context: The request context, for access checks.
        :param project_id: The ID of the project being deleted.
        """

        self._driver.destroy_by_project(context, project_id)

    def expire(self, context):
        """Expire reservations.

        Explores all currently existing reservations and rolls back
        any that have expired.

        :param context: The request context, for access checks.
        """

        self._driver.expire(context)

    def add_volume_type_opts(self, context, opts, volume_type_id):
        """Add volume type resource options.

        Adds elements to the opts hash for volume type quotas.
        If a resource is being reserved ('gigabytes', etc) and the volume
        type is set up for its own quotas, these reservations are copied
        into keys for 'gigabytes_<volume type name>', etc.

        :param context: The request context, for access checks.
        :param opts: The reservations options hash.
        :param volume_type_id: The volume type id for this reservation.
        """
        if not volume_type_id:
            return

        # NOTE(jdg): set inactive to True in volume_type_get, as we
        # may be operating on a volume that was created with a type
        # that has since been deleted.
        volume_type = db.volume_type_get(context, volume_type_id, True)

        for quota in ('volumes', 'gigabytes', 'snapshots'):
            if quota in opts:
                vtype_quota = "%s_%s" % (quota, volume_type['name'])
                opts[vtype_quota] = opts[quota]

    @property
    def resource_names(self):
        return sorted(self.resources.keys())

    @property
    def resources(self):
        return self._resources


class VolumeTypeQuotaEngine(QuotaEngine):
    """Represent the set of all quotas."""

    @property
    def resources(self):
        """Fetches all possible quota resources."""

        result = {}
        # Global quotas.
        argses = [('volumes', '_sync_volumes', 'quota_volumes'),
                  ('per_volume_gigabytes', None, 'per_volume_size_limit'),
                  ('snapshots', '_sync_snapshots', 'quota_snapshots'),
                  ('gigabytes', '_sync_gigabytes', 'quota_gigabytes'),
                  ('backups', '_sync_backups', 'quota_backups'),
                  ('backup_gigabytes', '_sync_backup_gigabytes',
                   'quota_backup_gigabytes')]
        for args in argses:
            resource = ReservableResource(*args)
            result[resource.name] = resource

        # Volume type quotas.
        volume_types = db.volume_type_get_all(context.get_admin_context(),
                                              False)
        for volume_type in volume_types.values():
            for part_name in ('volumes', 'gigabytes', 'snapshots'):
                resource = VolumeTypeResource(part_name, volume_type)
                result[resource.name] = resource
        return result

    def register_resource(self, resource):
        raise NotImplementedError(_("Cannot register resource"))

    def register_resources(self, resources):
        raise NotImplementedError(_("Cannot register resources"))

    def update_quota_resource(self, context, old_type_name, new_type_name):
        """Update resource in quota.

        This is to update resource in quotas, quota_classes, and
        quota_usages once the name of a volume type is changed.

        :param context: The request context, for access checks.
        :param old_type_name: old name of volume type.
        :param new_type_name: new name of volume type.
        """

        for quota in ('volumes', 'gigabytes', 'snapshots'):
            old_res = "%s_%s" % (quota, old_type_name)
            new_res = "%s_%s" % (quota, new_type_name)
            db.quota_usage_update_resource(context,
                                           old_res,
                                           new_res)
            db.quota_class_update_resource(context,
                                           old_res,
                                           new_res)
            db.quota_update_resource(context,
                                     old_res,
                                     new_res)


class CGQuotaEngine(QuotaEngine):
    """Represent the consistencygroup quotas."""

    @property
    def resources(self):
        """Fetches all possible quota resources."""

        result = {}
        # Global quotas.
        argses = [('consistencygroups', '_sync_consistencygroups',
                   'quota_consistencygroups'), ]
        for args in argses:
            resource = ReservableResource(*args)
            result[resource.name] = resource

        return result

    def register_resource(self, resource):
        raise NotImplementedError(_("Cannot register resource"))

    def register_resources(self, resources):
        raise NotImplementedError(_("Cannot register resources"))


class GroupQuotaEngine(QuotaEngine):
    """Represent the group quotas."""

    @property
    def resources(self):
        """Fetches all possible quota resources."""

        result = {}
        # Global quotas.
        argses = [('groups', '_sync_groups',
                   'quota_groups'), ]
        for args in argses:
            resource = ReservableResource(*args)
            result[resource.name] = resource

        return result

    def register_resource(self, resource):
        raise NotImplementedError(_("Cannot register resource"))

    def register_resources(self, resources):
        raise NotImplementedError(_("Cannot register resources"))

QUOTAS = VolumeTypeQuotaEngine()
CGQUOTAS = CGQuotaEngine()
GROUP_QUOTAS = GroupQuotaEngine()
