#!/usr/bin/python
import re
import argparse
from subprocess import Popen, PIPE
import ipaddr


def ipfamily_by_ip(ip):
	if isinstance(ip, ipaddr.IPv4Address):
		return 'A'
	elif isinstance(ip, ipaddr.IPv6Address):
		return 'AAAA'
	assert False


def nsupdate_add(hostname, domain, ttl, ip):
	"""ip_family: A or AAAA"""
	command = "update add {hostname}.{domain} {ttl} IN {ip_family} {ip}\n\n".format(hostname=hostname, domain=domain, ttl=ttl, ip_family=ipfamily_by_ip(ip), ip=ip)
	p = Popen(['nsupdate', '-l'], stdin=PIPE)
	p.communicate(command)


def nsupdate_delete(hostname, domain, ip_family):
	"""ip_family: A or AAAA"""
	command = "update delete {hostname}.{domain} {ip_family}\n\n".format(hostname=hostname, domain=domain, ip_family=ip_family)
	p = Popen(['nsupdate', '-l'], stdin=PIPE)
	p.communicate(command)


def main(args):
	if args.delete:
		if args.ip is None:
			nsupdate_delete(args.hostname, args.domain, 'A')
			nsupdate_delete(args.hostname, args.domain, 'AAAA')
		else:
			nsupdate_delete(args.hostname, args.domain, ipfamily_by_ip(args.ip))
	else:
		nsupdate_delete(args.hostname, args.domain, ipfamily_by_ip(args.ip))
		nsupdate_add(args.hostname, args.domain, args.ttl, args.ip)


if __name__ == '__main__':
	parser = argparse.ArgumentParser(description='Add or delete a hostname from dyndns (simplifies call to nsupdate).')
	parser.add_argument('-d', '--delete', action='store_true', help='delete instead of add')
	parser.add_argument('-i', '--ip', help='IP address (either IPv4 or IPv6)')
	# parser.add_argument('-t', '--ttl', type=int, default=600, help='TTL (default: 600)')
	parser.add_argument('hostname', help='hostname to add or delete, e.g. myserver')
	args = parser.parse_args()

	args.domain = 'dyn.colgarra.priv.at' # <---- TODO
	args.ttl = 600 # <---- TODO

	# check ip
	if not args.delete and not args.ip:
		parser.error('The IP address is mandatory')
	if args.ip:
		try:
			args.ip = ipaddr.IPAddress(args.ip) # throws an exception if the IP address is not valid
		except ValueError:
			parser.error('The IP address is not valid')

	# check hostname
	if re.match(r'[-0-9a-z]+(\.[-0-9a-z]+)*$', args.hostname) is None:
		parser.error('The hostname has an invalid format.')

	main(args)