# Copyright (c) 2010-2012 OpenStack, LLC.
#
# 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 urllib
from random import random
from time import time
from os.path import join
import hashlib

from eventlet import sleep, Timeout
from eventlet.greenpool import GreenPool

from swift.common.daemon import Daemon
from swift.common.internal_client import InternalClient
from swift.common.utils import get_logger, dump_recon_cache
from swift.common.http import HTTP_NOT_FOUND, HTTP_CONFLICT, \
    HTTP_PRECONDITION_FAILED


class ObjectExpirer(Daemon):
    """
    Daemon that queries the internal hidden expiring_objects_account to
    discover objects that need to be deleted.

    :param conf: The daemon configuration.
    """

    def __init__(self, conf):
        self.conf = conf
        self.logger = get_logger(conf, log_route='object-expirer')
        self.interval = int(conf.get('interval') or 300)
        self.expiring_objects_account = \
            (conf.get('auto_create_account_prefix') or '.') + \
            'expiring_objects'
        conf_path = conf.get('__file__') or '/usr/local/etc/swift/object-expirer.conf'
        request_tries = int(conf.get('request_tries') or 3)
        self.swift = InternalClient(conf_path,
                                    'Swift Object Expirer',
                                    request_tries)
        self.report_interval = int(conf.get('report_interval') or 300)
        self.report_first_time = self.report_last_time = time()
        self.report_objects = 0
        self.recon_cache_path = conf.get('recon_cache_path',
                                         '/var/cache/swift')
        self.rcache = join(self.recon_cache_path, 'object.recon')
        self.concurrency = int(conf.get('concurrency', 1))
        if self.concurrency < 1:
            raise ValueError("concurrency must be set to at least 1")
        self.processes = int(self.conf.get('processes', 0))
        self.process = int(self.conf.get('process', 0))

    def report(self, final=False):
        """
        Emits a log line report of the progress so far, or the final progress
        is final=True.

        :param final: Set to True for the last report once the expiration pass
                      has completed.
        """
        if final:
            elapsed = time() - self.report_first_time
            self.logger.info(_('Pass completed in %ds; %d objects expired') %
                             (elapsed, self.report_objects))
            dump_recon_cache({'object_expiration_pass': elapsed,
                              'expired_last_pass': self.report_objects},
                             self.rcache, self.logger)
        elif time() - self.report_last_time >= self.report_interval:
            elapsed = time() - self.report_first_time
            self.logger.info(_('Pass so far %ds; %d objects expired') %
                             (elapsed, self.report_objects))
            self.report_last_time = time()

    def run_once(self, *args, **kwargs):
        """
        Executes a single pass, looking for objects to expire.

        :param args: Extra args to fulfill the Daemon interface; this daemon
                     has no additional args.
        :param kwargs: Extra keyword args to fulfill the Daemon interface; this
                       daemon accepts processes and process keyword args.
                       These will override the values from the config file if
                       provided.
        """
        processes, process = self.get_process_values(kwargs)
        pool = GreenPool(self.concurrency)
        containers_to_delete = []
        self.report_first_time = self.report_last_time = time()
        self.report_objects = 0
        try:
            self.logger.debug(_('Run begin'))
            containers, objects = \
                self.swift.get_account_info(self.expiring_objects_account)
            self.logger.info(_('Pass beginning; %s possible containers; %s '
                               'possible objects') % (containers, objects))
            for c in self.swift.iter_containers(self.expiring_objects_account):
                container = c['name']
                timestamp = int(container)
                if timestamp > int(time()):
                    break
                containers_to_delete.append(container)
                for o in self.swift.iter_objects(self.expiring_objects_account,
                                                 container):
                    obj = o['name'].encode('utf8')
                    if processes > 0:
                        obj_process = int(
                            hashlib.md5('%s/%s' % (container, obj)).
                            hexdigest(), 16)
                        if obj_process % processes != process:
                            continue
                    timestamp, actual_obj = obj.split('-', 1)
                    timestamp = int(timestamp)
                    if timestamp > int(time()):
                        break
                    pool.spawn_n(
                        self.delete_object, actual_obj, timestamp,
                        container, obj)
            pool.waitall()
            for container in containers_to_delete:
                try:
                    self.swift.delete_container(
                        self.expiring_objects_account,
                        container,
                        acceptable_statuses=(2, HTTP_NOT_FOUND, HTTP_CONFLICT))
                except (Exception, Timeout), err:
                    self.logger.exception(
                        _('Exception while deleting container %s %s') %
                        (container, str(err)))
            self.logger.debug(_('Run end'))
            self.report(final=True)
        except (Exception, Timeout):
            self.logger.exception(_('Unhandled exception'))

    def run_forever(self, *args, **kwargs):
        """
        Executes passes forever, looking for objects to expire.

        :param args: Extra args to fulfill the Daemon interface; this daemon
                     has no additional args.
        :param kwargs: Extra keyword args to fulfill the Daemon interface; this
                       daemon has no additional keyword args.
        """
        sleep(random() * self.interval)
        while True:
            begin = time()
            try:
                self.run_once(*args, **kwargs)
            except (Exception, Timeout):
                self.logger.exception(_('Unhandled exception'))
            elapsed = time() - begin
            if elapsed < self.interval:
                sleep(random() * (self.interval - elapsed))

    def get_process_values(self, kwargs):
        """
        Gets the processes, process from the kwargs if those values exist.

        Otherwise, return processes, process set in the config file.

        :param kwargs: Keyword args passed into the run_forever(), run_once()
                       methods.  They have values specified on the command
                       line when the daemon is run.
        """
        if kwargs.get('processes') is not None:
            processes = int(kwargs['processes'])
        else:
            processes = self.processes

        if kwargs.get('process') is not None:
            process = int(kwargs['process'])
        else:
            process = self.process

        if process < 0:
            raise ValueError(
                'process must be an integer greater than or equal to 0')

        if processes < 0:
            raise ValueError(
                'processes must be an integer greater than or equal to 0')

        if processes and process >= processes:
            raise ValueError(
                'process must be less than or equal to processes')

        return processes, process

    def delete_object(self, actual_obj, timestamp, container, obj):
        start_time = time()
        try:
            self.delete_actual_object(actual_obj, timestamp)
            self.swift.delete_object(self.expiring_objects_account,
                                     container, obj)
            self.report_objects += 1
            self.logger.increment('objects')
        except (Exception, Timeout), err:
            self.logger.increment('errors')
            self.logger.exception(
                _('Exception while deleting object %s %s %s') %
                (container, obj, str(err)))
        self.logger.timing_since('timing', start_time)
        self.report()

    def delete_actual_object(self, actual_obj, timestamp):
        """
        Deletes the end-user object indicated by the actual object name given
        '<account>/<container>/<object>' if and only if the X-Delete-At value
        of the object is exactly the timestamp given.

        :param actual_obj: The name of the end-user object to delete:
                           '<account>/<container>/<object>'
        :param timestamp: The timestamp the X-Delete-At value must match to
                          perform the actual delete.
        """
        path = '/v1/' + urllib.quote(actual_obj.lstrip('/'))
        self.swift.make_request('DELETE', path,
                                {'X-If-Delete-At': str(timestamp)},
                                (2, HTTP_NOT_FOUND, HTTP_PRECONDITION_FAILED))
