#!/usr/bin/env python3
# Copyright 2019 vg
# SPDX-License-Identifier: MIT

'''\
Takes json in stdin to modify a challenge in a zone txt record.

Usage: update-acme-challenge --zones=ZONES

Options:
 --zones  comma separated list of authorized zones to be changed

Json format:
{
    "action": "add|delete",
    "zone": "zone_name_to_modify",
    "challenge": "mandatory only with add action: challenge",
}
'''


import sys
import json
import subprocess
import docopt


def nsupdate(zone, challenge):
    content = f'''
        server ::1
        del {zone} TXT
        add {zone} TXT "{challenge}"
        send
    '''
    subprocess.run(['nsupdate'], check=True, input=content)


def main():
    args = docopt.docopt(__doc__)

    jsonmap = json.load(sys.stdin.read())

    zones = [x.strip() for x in args['--zones'].split(',')]
    zone = jsonmap.get('zone', '')
    if zone not in zones:
        raise ValueError(f'not permitted to modify zone {zone}')

    action = jsonmap.get('action', '')
    if action not in ('add', 'delete'):
        raise ValueError(f'bad value for action content: {action}')

    challenge = jsonmap.get('challenge', '')
    if not all(x.isalnum() or x in ('+', '/') for x in challenge):
        raise ValueError('bad format for challenge content')

    nsupdate(zone, challenge if action == 'add' else '')


main()