# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2011 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 datetime
import urlparse

from webob import exc

from nova.api.openstack import extensions
from nova.api.openstack import wsgi
from nova.api.openstack import xmlutil
from nova.compute import api
from nova.compute import flavors
from nova import exception
from nova.openstack.common.gettextutils import _
from nova.openstack.common import timeutils

ALIAS = 'os-simple-tenant-usage'
authorize_show = extensions.extension_authorizer('compute',
                                                 'v3:' + ALIAS + ':show')
authorize_list = extensions.extension_authorizer('compute',
                                                 'v3:' + ALIAS + ':list')
VALID_DATETIME_FORMAT = ["%Y-%m-%dT%H:%M:%S", "%Y-%m-%dT%H:%M:%S.%f",
                         "%Y-%m-%d %H:%M:%S.%f"]


def make_usage(elem):
    for subelem_tag in ('tenant_id', 'total_local_gb_usage',
                        'total_vcpus_usage', 'total_memory_mb_usage',
                        'total_hours', 'start', 'stop'):
        subelem = xmlutil.SubTemplateElement(elem, subelem_tag)
        subelem.text = subelem_tag

    server_usages = xmlutil.SubTemplateElement(elem, 'server_usages')
    server_usage = xmlutil.SubTemplateElement(server_usages, 'server_usage',
                                              selector='server_usages')
    for subelem_tag in ('instance_id', 'name', 'hours', 'memory_mb',
                        'local_gb', 'vcpus', 'tenant_id', 'flavor',
                        'started_at', 'ended_at', 'state', 'uptime'):
        subelem = xmlutil.SubTemplateElement(server_usage, subelem_tag)
        subelem.text = subelem_tag


class SimpleTenantUsageTemplate(xmlutil.TemplateBuilder):
    def construct(self):
        root = xmlutil.TemplateElement('tenant_usage', selector='tenant_usage')
        make_usage(root)
        return xmlutil.MasterTemplate(root, 1)


class SimpleTenantUsagesTemplate(xmlutil.TemplateBuilder):
    def construct(self):
        root = xmlutil.TemplateElement('tenant_usages')
        elem = xmlutil.SubTemplateElement(root, 'tenant_usage',
                                          selector='tenant_usages')
        make_usage(elem)
        return xmlutil.MasterTemplate(root, 1)


class SimpleTenantUsageController(object):
    def _hours_for(self, instance, period_start, period_stop):
        launched_at = instance['launched_at']
        terminated_at = instance['terminated_at']
        if terminated_at is not None:
            if not isinstance(terminated_at, datetime.datetime):
                terminated_at = timeutils.parse_strtime(terminated_at,
                                                        "%Y-%m-%d %H:%M:%S.%f")

        if launched_at is not None:
            if not isinstance(launched_at, datetime.datetime):
                launched_at = timeutils.parse_strtime(launched_at,
                                                      "%Y-%m-%d %H:%M:%S.%f")

        if terminated_at and terminated_at < period_start:
            return 0
        # nothing if it started after the usage report ended
        if launched_at and launched_at > period_stop:
            return 0
        if launched_at:
            # if instance launched after period_started, don't charge for first
            start = max(launched_at, period_start)
            if terminated_at:
                # if instance stopped before period_stop, don't charge after
                stop = min(period_stop, terminated_at)
            else:
                # instance is still running, so charge them up to current time
                stop = period_stop
            dt = stop - start
            seconds = (dt.days * 3600 * 24 + dt.seconds +
                       dt.microseconds / 100000.0)

            return seconds / 3600.0
        else:
            # instance hasn't launched, so no charge
            return 0

    def _get_flavor(self, context, compute_api, instance, flavors_cache):
        """Get flavor information from the instance's system_metadata,
        allowing a fallback to lookup by-id for deleted instances only.
        """
        try:
            return flavors.extract_flavor(instance)
        except KeyError:
            if not instance['deleted']:
                # Only support the fallback mechanism for deleted instances
                # that would have been skipped by migration #153
                raise

        flavor_type = instance['instance_type_id']
        if flavor_type in flavors_cache:
            return flavors_cache[flavor_type]

        try:
            it_ref = compute_api.get_instance_type(context, flavor_type)
            flavors_cache[flavor_type] = it_ref
        except exception.FlavorNotFound:
            # can't bill if there is no instance type
            it_ref = None

        return it_ref

    def _tenant_usages_for_period(self, context, period_start,
                                  period_stop, tenant_id=None, detailed=True):

        compute_api = api.API()
        instances = compute_api.get_active_by_window(context,
                                                     period_start,
                                                     period_stop,
                                                     tenant_id)
        rval = {}
        flavors = {}

        for instance in instances:
            info = {}
            info['hours'] = self._hours_for(instance,
                                            period_start,
                                            period_stop)
            flavor = self._get_flavor(context, compute_api, instance, flavors)
            if not flavor:
                continue

            info['instance_id'] = instance['uuid']
            info['name'] = instance['display_name']

            info['memory_mb'] = flavor['memory_mb']
            info['local_gb'] = flavor['root_gb'] + flavor['ephemeral_gb']
            info['vcpus'] = flavor['vcpus']

            info['tenant_id'] = instance['project_id']

            info['flavor'] = flavor['name']

            info['started_at'] = instance['launched_at']

            info['ended_at'] = instance['terminated_at']

            if info['ended_at']:
                info['state'] = 'terminated'
            else:
                info['state'] = instance['vm_state']

            now = timeutils.utcnow()

            if info['state'] == 'terminated':
                delta = info['ended_at'] - info['started_at']
            else:
                delta = now - info['started_at']

            info['uptime'] = delta.days * 24 * 3600 + delta.seconds

            if info['tenant_id'] not in rval:
                summary = {}
                summary['tenant_id'] = info['tenant_id']
                if detailed:
                    summary['server_usages'] = []
                summary['total_local_gb_usage'] = 0
                summary['total_vcpus_usage'] = 0
                summary['total_memory_mb_usage'] = 0
                summary['total_hours'] = 0
                summary['start'] = period_start
                summary['stop'] = period_stop
                rval[info['tenant_id']] = summary

            summary = rval[info['tenant_id']]
            summary['total_local_gb_usage'] += info['local_gb'] * info['hours']
            summary['total_vcpus_usage'] += info['vcpus'] * info['hours']
            summary['total_memory_mb_usage'] += (info['memory_mb'] *
                                                 info['hours'])

            summary['total_hours'] += info['hours']
            if detailed:
                summary['server_usages'].append(info)

        return rval.values()

    def _parse_datetime(self, dtstr):
        if not dtstr:
            return timeutils.utcnow()
        elif isinstance(dtstr, datetime.datetime):
            return dtstr
        for format in VALID_DATETIME_FORMAT:
            try:
                return timeutils.parse_strtime(dtstr, format)
            except ValueError:
                continue
        return None

    def _get_datetime_range(self, req):
        qs = req.environ.get('QUERY_STRING', '')
        env = urlparse.parse_qs(qs)
        # NOTE(lzyeval): env.get() always returns a list
        period_start = self._parse_datetime(env.get('start', [None])[0])
        if not period_start:
            msg = _("Start time is invalid format, valid "
                    "formats are %s") % VALID_DATETIME_FORMAT
            raise exc.HTTPBadRequest(explanation=msg)
        period_stop = self._parse_datetime(env.get('end', [None])[0])
        if not period_stop:
            msg = _("Stop time is invalid format, valid "
                    "formats are %s") % VALID_DATETIME_FORMAT
            raise exc.HTTPBadRequest(explanation=msg)
        if not period_start < period_stop:
            msg = _("Invalid start time. The start time cannot occur after "
                    "the end time.")
            raise exc.HTTPBadRequest(explanation=msg)

        detailed = env.get('detailed', ['0'])[0] == '1'
        return (period_start, period_stop, detailed)

    @extensions.expected_errors(400)
    @wsgi.serializers(xml=SimpleTenantUsagesTemplate)
    def index(self, req):
        """Retrieve tenant_usage for all tenants."""
        context = req.environ['nova.context']

        authorize_list(context)

        (period_start, period_stop, detailed) = self._get_datetime_range(req)
        now = timeutils.utcnow()
        if period_stop > now:
            period_stop = now
        usages = self._tenant_usages_for_period(context,
                                                period_start,
                                                period_stop,
                                                detailed=detailed)
        return {'tenant_usages': usages}

    @extensions.expected_errors(400)
    @wsgi.serializers(xml=SimpleTenantUsageTemplate)
    def show(self, req, id):
        """Retrieve tenant_usage for a specified tenant."""
        tenant_id = id
        context = req.environ['nova.context']

        authorize_show(context, {'project_id': tenant_id})

        (period_start, period_stop, ignore) = self._get_datetime_range(req)
        now = timeutils.utcnow()
        if period_stop > now:
            period_stop = now
        usage = self._tenant_usages_for_period(context,
                                               period_start,
                                               period_stop,
                                               tenant_id=tenant_id,
                                               detailed=True)
        if len(usage):
            usage = usage[0]
        else:
            usage = {}
        return {'tenant_usage': usage}


class SimpleTenantUsage(extensions.V3APIExtensionBase):
    """Simple tenant usage extension."""

    name = "SimpleTenantUsage"
    alias = ALIAS
    namespace = ("http://docs.openstack.org/compute/ext/"
                 "os-simple-tenant-usage/api/v3")
    version = 1

    def get_resources(self):
        res = [extensions.ResourceExtension('os-simple-tenant-usage',
                                           SimpleTenantUsageController())]
        return res

    def get_controller_extensions(self):
        """It's an abstract function V3APIExtensionBase and the extension
        will not be loaded without it.
        """
        return []
