# Copyright 2010 OpenStack Foundation
# 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.

import calendar
import time

import eventlet
from glance_store import exceptions as store_exceptions
from oslo_config import cfg
from oslo_log import log as logging
from oslo_utils import encodeutils

from glance.common import crypt
from glance.common import exception
from glance.common import timeutils
from glance import context
import glance.db as db_api
from glance.i18n import _, _LC, _LE, _LI, _LW

LOG = logging.getLogger(__name__)

scrubber_opts = [
    cfg.IntOpt('scrub_time', default=0, min=0,
               help=_("""
The amount of time, in seconds, to delay image scrubbing.

When delayed delete is turned on, an image is put into ``pending_delete``
state upon deletion until the scrubber deletes its image data. Typically, soon
after the image is put into ``pending_delete`` state, it is available for
scrubbing. However, scrubbing can be delayed until a later point using this
configuration option. This option denotes the time period an image spends in
``pending_delete`` state before it is available for scrubbing.

It is important to realize that this has storage implications. The larger the
``scrub_time``, the longer the time to reclaim backend storage from deleted
images.

Possible values:
    * Any non-negative integer

Related options:
    * ``delayed_delete``

""")),
    cfg.IntOpt('scrub_pool_size', default=1, min=1,
               help=_("""
The size of thread pool to be used for scrubbing images.

When there are a large number of images to scrub, it is beneficial to scrub
images in parallel so that the scrub queue stays in control and the backend
storage is reclaimed in a timely fashion. This configuration option denotes
the maximum number of images to be scrubbed in parallel. The default value is
one, which signifies serial scrubbing. Any value above one indicates parallel
scrubbing.

Possible values:
    * Any non-zero positive integer

Related options:
    * ``delayed_delete``

""")),
    cfg.BoolOpt('delayed_delete', default=False,
                help=_("""
Turn on/off delayed delete.

Typically when an image is deleted, the ``glance-api`` service puts the image
into ``deleted`` state and deletes its data at the same time. Delayed delete
is a feature in Glance that delays the actual deletion of image data until a
later point in time (as determined by the configuration option ``scrub_time``).
When delayed delete is turned on, the ``glance-api`` service puts the image
into ``pending_delete`` state upon deletion and leaves the image data in the
storage backend for the image scrubber to delete at a later time. The image
scrubber will move the image into ``deleted`` state upon successful deletion
of image data.

NOTE: When delayed delete is turned on, image scrubber MUST be running as a
periodic task to prevent the backend storage from filling up with undesired
usage.

Possible values:
    * True
    * False

Related options:
    * ``scrub_time``
    * ``wakeup_time``
    * ``scrub_pool_size``

""")),
]

scrubber_cmd_opts = [
    cfg.IntOpt('wakeup_time', default=300, min=0,
               help=_("""
Time interval, in seconds, between scrubber runs in daemon mode.

Scrubber can be run either as a cron job or daemon. When run as a daemon, this
configuration time specifies the time period between two runs. When the
scrubber wakes up, it fetches and scrubs all ``pending_delete`` images that
are available for scrubbing after taking ``scrub_time`` into consideration.

If the wakeup time is set to a large number, there may be a large number of
images to be scrubbed for each run. Also, this impacts how quickly the backend
storage is reclaimed.

Possible values:
    * Any non-negative integer

Related options:
    * ``daemon``
    * ``delayed_delete``

"""))
]

scrubber_cmd_cli_opts = [
    cfg.BoolOpt('daemon',
                short='D',
                default=False,
                help=_("""
Run scrubber as a daemon.

This boolean configuration option indicates whether scrubber should
run as a long-running process that wakes up at regular intervals to
scrub images. The wake up interval can be specified using the
configuration option ``wakeup_time``.

If this configuration option is set to ``False``, which is the
default value, scrubber runs once to scrub images and exits. In this
case, if the operator wishes to implement continuous scrubbing of
images, scrubber needs to be scheduled as a cron job.

Possible values:
    * True
    * False

Related options:
    * ``wakeup_time``

""")),
    cfg.StrOpt('restore',
               metavar='<IMAGE_ID>',
               help=_("""
Restore the image status from 'pending_delete' to 'active'.

This option is used by administrator to reset the image's status from
'pending_delete' to 'active' when the image is deleted by mistake and
'pending delete' feature is enabled in Glance. Please make sure the
glance-scrubber daemon is stopped before restoring the image to avoid image
data inconsistency.

Possible values:
    * image's uuid

"""))
]

CONF = cfg.CONF
CONF.register_opts(scrubber_opts)
CONF.import_opt('metadata_encryption_key', 'glance.common.config')
REASONABLE_DB_PAGE_SIZE = 1000


class ScrubDBQueue(object):
    """Database-based image scrub queue class."""
    def __init__(self):
        self.scrub_time = CONF.scrub_time
        self.metadata_encryption_key = CONF.metadata_encryption_key
        self.admin_context = context.get_admin_context(show_deleted=True)

    def add_location(self, image_id, location):
        """Adding image location to scrub queue.

        :param image_id: The opaque image identifier
        :param location: The opaque image location

        :returns: A boolean value to indicate success or not
        """
        loc_id = location.get('id')
        if loc_id:
            db_api.get_api().image_location_delete(self.admin_context,
                                                   image_id, loc_id,
                                                   'pending_delete')
            return True
        else:
            return False

    def _get_images_page(self, marker):
        filters = {'deleted': True,
                   'status': 'pending_delete'}

        return db_api.get_api().image_get_all(self.admin_context,
                                              filters=filters,
                                              marker=marker,
                                              limit=REASONABLE_DB_PAGE_SIZE)

    def _get_all_images(self):
        """Generator to fetch all appropriate images, paging as needed."""

        marker = None
        while True:
            images = self._get_images_page(marker)
            if len(images) == 0:
                break
            marker = images[-1]['id']

            for image in images:
                yield image

    def get_all_locations(self):
        """Returns a list of image id and location tuple from scrub queue.

        :returns: a list of image id, location id and uri tuple from
            scrub queue

        """
        ret = []

        for image in self._get_all_images():
            deleted_at = image.get('deleted_at')
            if not deleted_at:
                continue
            # NOTE: Strip off microseconds which may occur after the last '.,'
            # Example: 2012-07-07T19:14:34.974216
            deleted_at = timeutils.isotime(deleted_at)
            date_str = deleted_at.rsplit('.', 1)[0].rsplit(',', 1)[0]
            delete_time = calendar.timegm(time.strptime(date_str,
                                                        "%Y-%m-%dT%H:%M:%SZ"))

            if delete_time + self.scrub_time > time.time():
                continue

            for loc in image['locations']:
                if loc['status'] != 'pending_delete':
                    continue

                if self.metadata_encryption_key:
                    uri = crypt.urlsafe_decrypt(self.metadata_encryption_key,
                                                loc['url'])
                else:
                    uri = loc['url']

                # if multi-store is enabled then we need to pass backend
                # to delete the image.
                backend = loc['metadata'].get('store')
                if CONF.enabled_backends:
                    ret.append((image['id'], loc['id'], uri, backend))
                else:
                    ret.append((image['id'], loc['id'], uri))
        return ret

    def has_image(self, image_id):
        """Returns whether the queue contains an image or not.

        :param image_id: The opaque image identifier

        :returns: a boolean value to inform including or not
        """
        try:
            image = db_api.get_api().image_get(self.admin_context, image_id)
            return image['status'] == 'pending_delete'
        except exception.NotFound:
            return False


_db_queue = None


def get_scrub_queue():
    global _db_queue
    if not _db_queue:
        _db_queue = ScrubDBQueue()
    return _db_queue


class Daemon(object):
    def __init__(self, wakeup_time=300, threads=100):
        LOG.info(_LI("Starting Daemon: wakeup_time=%(wakeup_time)s "
                     "threads=%(threads)s"),
                 {'wakeup_time': wakeup_time, 'threads': threads})
        self.wakeup_time = wakeup_time
        self.event = eventlet.event.Event()
        # This pool is used for periodic instantiation of scrubber
        self.daemon_pool = eventlet.greenpool.GreenPool(threads)

    def start(self, application):
        self._run(application)

    def wait(self):
        try:
            self.event.wait()
        except KeyboardInterrupt:
            msg = _LI("Daemon Shutdown on KeyboardInterrupt")
            LOG.info(msg)

    def _run(self, application):
        LOG.debug("Running application")
        self.daemon_pool.spawn_n(application.run, self.event)
        eventlet.spawn_after(self.wakeup_time, self._run, application)
        LOG.debug("Next run scheduled in %s seconds", self.wakeup_time)


class Scrubber(object):
    def __init__(self, store_api):
        LOG.info(_LI("Initializing scrubber"))
        self.store_api = store_api
        self.admin_context = context.get_admin_context(show_deleted=True)
        self.db_queue = get_scrub_queue()
        self.pool = eventlet.greenpool.GreenPool(CONF.scrub_pool_size)

    def _get_delete_jobs(self):
        try:
            records = self.db_queue.get_all_locations()
        except Exception as err:
            # Note(dharinic): spawn_n, in Daemon mode will log the
            # exception raised. Otherwise, exit 1 will occur.
            msg = (_LC("Can not get scrub jobs from queue: %s") %
                   encodeutils.exception_to_unicode(err))
            LOG.critical(msg)
            raise exception.FailedToGetScrubberJobs()

        delete_jobs = {}
        if CONF.enabled_backends:
            for image_id, loc_id, loc_uri, backend in records:
                if image_id not in delete_jobs:
                    delete_jobs[image_id] = []
                delete_jobs[image_id].append((image_id, loc_id,
                                              loc_uri, backend))
        else:
            for image_id, loc_id, loc_uri in records:
                if image_id not in delete_jobs:
                    delete_jobs[image_id] = []
                delete_jobs[image_id].append((image_id, loc_id, loc_uri))

        return delete_jobs

    def run(self, event=None):
        delete_jobs = self._get_delete_jobs()

        if delete_jobs:
            list(self.pool.starmap(self._scrub_image, delete_jobs.items()))

    def _scrub_image(self, image_id, delete_jobs):
        if len(delete_jobs) == 0:
            return

        LOG.info(_LI("Scrubbing image %(id)s from %(count)d locations."),
                 {'id': image_id, 'count': len(delete_jobs)})

        success = True
        if CONF.enabled_backends:
            for img_id, loc_id, uri, backend in delete_jobs:
                try:
                    self._delete_image_location_from_backend(img_id, loc_id,
                                                             uri,
                                                             backend=backend)
                except Exception:
                    success = False
        else:
            for img_id, loc_id, uri in delete_jobs:
                try:
                    self._delete_image_location_from_backend(img_id, loc_id,
                                                             uri)
                except Exception:
                    success = False

        if success:
            image = db_api.get_api().image_get(self.admin_context, image_id)
            if image['status'] == 'pending_delete':
                db_api.get_api().image_update(self.admin_context, image_id,
                                              {'status': 'deleted'})
            LOG.info(_LI("Image %s has been scrubbed successfully"), image_id)
        else:
            LOG.warning(_LW("One or more image locations couldn't be scrubbed "
                            "from backend. Leaving image '%s' in "
                            "'pending_delete' status"), image_id)

    def _delete_image_location_from_backend(self, image_id, loc_id, uri,
                                            backend=None):
        try:
            LOG.debug("Scrubbing image %s from a location.", image_id)
            try:
                if CONF.enabled_backends:
                    self.store_api.delete(uri, backend, self.admin_context)
                else:
                    self.store_api.delete_from_backend(uri, self.admin_context)
            except store_exceptions.NotFound:
                LOG.info(_LI("Image location for image '%s' not found in "
                             "backend; Marking image location deleted in "
                             "db."), image_id)

            if loc_id != '-':
                db_api.get_api().image_location_delete(self.admin_context,
                                                       image_id,
                                                       int(loc_id),
                                                       'deleted')
            LOG.info(_LI("Image %s is scrubbed from a location."), image_id)
        except Exception as e:
            LOG.error(_LE("Unable to scrub image %(id)s from a location. "
                          "Reason: %(exc)s "),
                      {'id': image_id,
                       'exc': encodeutils.exception_to_unicode(e)})
            raise

    def revert_image_status(self, image_id):
        db_api.get_api().image_restore(self.admin_context, image_id)
