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


class NsupdateError(Exception):
	def __init__(self, returncode):
		self.returncode = returncode


class BlockipError(Exception):
	def __init__(self, returncode):
		self.returncode = returncode


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


def nsupdate_add(fqdn, ttl, ip):
	"""
	:param fqdn: Fully qualified domain name
	:param ip_family: A or AAAA
	:raises an NsupdateError in case of errors."""
	command = "update add {fqdn} {ttl} IN {ip_family} {ip}\n\n".format(fqdn=fqdn, ttl=ttl, ip_family=ipfamily_by_ip(ip), ip=ip)
	p = Popen(['nsupdate', '-l'], stdin=PIPE)
	p.communicate(command)
	if p.returncode != 0:
		raise NsupdateError(p.returncode)

def nsupdate_delete(fqdn, ip_family):
	"""
	:param fqdn: Fully qualified domain name
	:param ip_family: A or AAAA
	:raises an NsupdateError in case of errors."""
	command = "update delete {fqdn} {ip_family}\n\n".format(fqdn=fqdn, ip_family=ip_family)
	p = Popen(['nsupdate', '-l'], stdin=PIPE)
	p.communicate(command)
	if p.returncode != 0:
		raise NsupdateError(p.returncode)


def blockip_whitelist_add(ip):
	"""
	:param ip: ipv4 address
	:raises a BlockipError in case of errors."""
	command = "-I blockip -s {ip} -j ACCEPT\n\n".format(ip=ip)
	p = Popen(['iptables'], stdin=PIPE)
	p.communicate(command)
	if p.returncode != 0:
		raise NsupdateError(p.returncode)


def blockip_whitelist_delete(ip):
	"""
	:param ip: ipv4 address
	:raises a BlockipError in case of errors."""
	command = "-D blockip -s {ip} -j ACCEPT\n\n".format(ip=ip)
	p = Popen(['iptables'], stdin=PIPE)
	p.communicate(command)
	if p.returncode != 0:
		raise NsupdateError(p.returncode)


def main(args):
	try:
		if args.delete:
			if args.ip is None:
				nsupdate_delete(args.fqdn, 'A')
				nsupdate_delete(args.fqdn, 'AAAA')
			else:
				nsupdate_delete(args.fqdn, ipfamily_by_ip(args.ip))
				if ipfamily_by_ip(args.ip) == 'A':
					blockip_whitelist_delete(args.ip)
		else:
			nsupdate_delete(args.fqdn, ipfamily_by_ip(args.ip))
			nsupdate_add(args.fqdn, args.ttl, args.ip)
			if ipfamily_by_ip(args.ip) == 'A':
				blockip_whitelist_add(args.ip)
	except NsupdateError as e:
		sys.exit(e.returncode)



if __name__ == '__main__':
	parser = argparse.ArgumentParser(description='Add or delete a domain name 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('fqdn', help='fully qualified domain name to add or delete, e.g. myserver.dyn.example.com')
	args = parser.parse_args()

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

	main(args)