#!/usr/bin/env python
# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright (c) 2011 Openstack, LLC.
# 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.

"""Cron script to generate usage notifications for instances neither created
   nor destroyed in a given time period.

   Together with the notifications generated by compute on instance
   create/delete/resize, over that ime period, this allows an external
   system consuming usage notification feeds to calculate instance usage
   for each tenant.

   Time periods are specified like so:
   <number>[mdy]

   1m = previous month. If the script is run April 1, it will generate usages
        for March 1 thry March 31.
   3m = 3 previous months.
   90d = previous 90 days.
   1y = previous year. If run on Jan 1, it generates usages for
        Jan 1 thru Dec 31 of the previous year.
"""

import datetime
import gettext
import os
import sys
import time

# If ../nova/__init__.py exists, add ../ to Python search path, so that
# it will override what happens to be installed in /usr/(local/)lib/python...
POSSIBLE_TOPDIR = os.path.normpath(os.path.join(os.path.abspath(sys.argv[0]),
                                   os.pardir,
                                   os.pardir))
if os.path.exists(os.path.join(POSSIBLE_TOPDIR, 'nova', '__init__.py')):
    sys.path.insert(0, POSSIBLE_TOPDIR)

gettext.install('nova', unicode=1)


from nova import context
from nova import db
from nova import exception
from nova import flags
from nova import log as logging
from nova import utils

from nova.notifier import api as notifier_api

FLAGS = flags.FLAGS
flags.DEFINE_string('instance_usage_audit_period', '1m',
                    'time period to generate instance usages for.')


def time_period(period):
    today = datetime.date.today()
    unit = period[-1]
    if unit not in 'mdy':
        raise ValueError('Time period must be m, d, or y')
    n = int(period[:-1])
    if unit == 'm':
        year = today.year - (n // 12)
        n = n % 12
        if n >= today.month:
            year -= 1
            month = 12 + (today.month - n)
        else:
            month = today.month - n
        begin = datetime.datetime(day=1, month=month, year=year)
        end = datetime.datetime(day=1, month=today.month, year=today.year)

    elif unit == 'y':
        begin = datetime.datetime(day=1, month=1, year=today.year - n)
        end = datetime.datetime(day=1, month=1, year=today.year)

    elif unit == 'd':
        b = today - datetime.timedelta(days=n)
        begin = datetime.datetime(day=b.day, month=b.month, year=b.year)
        end = datetime.datetime(day=today.day,
                               month=today.month,
                               year=today.year)

    return (begin, end)

if __name__ == '__main__':
    utils.default_flagfile()
    flags.FLAGS(sys.argv)
    logging.setup()
    begin, end = time_period(FLAGS.instance_usage_audit_period)
    print "Creating usages for %s until %s" % (str(begin), str(end))
    instances = db.instance_get_active_by_window(context.get_admin_context(),
                                                 begin,
                                                 end)
    print "%s instances" % len(instances)
    for instance_ref in instances:
        usage_info = utils.usage_from_instance(instance_ref,
                              audit_period_begining=str(begin),
                              audit_period_ending=str(end))
        notifier_api.notify('compute.%s' % FLAGS.host,
                            'compute.instance.exists',
                            notifier_api.INFO,
                            usage_info)