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from optparse import make_option
from django.core.management.base import BaseCommand, CommandError
from django.utils import simplejson as json

from astakos.im.models import Resource
from astakos.im.resources import update_resource
from ._common import show_resource_value, style_options, check_style, units


class Command(BaseCommand):
    args = "<resource name>"
    help = ("Modify a resource (currently only change the default base quota)."
            "\nIf no resource is specified, all resources are considered.")

    option_list = BaseCommand.option_list + (
        make_option('--limit',
                    dest='limit',
                    help="Specify default base quota"),
        make_option('--interactive',
                    action='store_true',
                    dest='interactive',
                    default=None,
                    help="Prompt user to change default base quotas"),
        make_option('--from-file',
                    dest='from_file',
                    metavar='<limits_file.json>',
                    help="Read default base quotas from a json file"),
        make_option('--unit-style',
                    default='mb',
                    help=("Specify display unit for resource values "
                          "(one of %s); defaults to mb") % style_options),
    )

    def handle(self, *args, **options):
        resource_name = args[0] if len(args) > 0 else None

        actions = {
            'limit': self.change_limit,
            'interactive': self.change_interactive,
            'from_file': self.change_from_file,
        }

        opts = [(key, value)
                for (key, value) in options.items()
                if key in actions and value is not None]

        if len(opts) != 1:
            raise CommandError("Please provide exactly one of the options: %s."
                               % ", ".join(actions.keys()))

        self.unit_style = options['unit_style']
        check_style(self.unit_style)

        key, value = opts[0]
        action = actions[key]
        action(resource_name, value)

    def get_resource(self, resource_name):
        try:
            return Resource.objects.get_for_update(name=resource_name)
        except Resource.DoesNotExist:
            raise CommandError("Resource %s does not exist."
                               % resource_name)

    def change_limit(self, resource_name, limit):
        if resource_name is None:
            raise CommandError("Please provide a resource name.")

        resource = self.get_resource(resource_name)
        self.change_resource_limit(resource, limit)

    def change_from_file(self, resource_name, filename):
        with open(filename) as file_data:
            try:
                config = json.load(file_data)
            except json.JSONDecodeError:
                raise CommandError("Malformed JSON file.")
            if not isinstance(config, dict):
                raise CommandError("Malformed JSON file.")
            self.change_with_conf(resource_name, config)

    def change_with_conf(self, resource_name, config):
        if resource_name is None:
            resources = Resource.objects.all().select_for_update()
        else:
            resources = [self.get_resource(resource_name)]

        for resource in resources:
            limit = config.get(resource.name)
            if limit is not None:
                self.change_resource_limit(resource, limit)

    def change_interactive(self, resource_name, _placeholder):
        if resource_name is None:
            resources = Resource.objects.all().select_for_update()
        else:
            resources = [self.get_resource(resource_name)]

        for resource in resources:
            self.stdout.write("Resource '%s' (%s)\n" %
                              (resource.name, resource.desc))
            value = show_resource_value(resource.uplimit, resource.name,
                                        self.unit_style)
            self.stdout.write("Current limit: %s\n" % value)
            while True:
                self.stdout.write("New limit (leave blank to keep current): ")
                response = raw_input()
                if response == "":
                    break
                else:
                    try:
                        value = units.parse(response)
                    except units.ParseError:
                        continue
                    update_resource(resource, value)
                    break

    def change_resource_limit(self, resource, limit):
        if not isinstance(limit, (int, long)):
            try:
                limit = units.parse(limit)
            except units.ParseError:
                m = ("Limit should be an integer, optionally followed "
                     "by a unit.")
                raise CommandError(m)
            update_resource(resource, limit)