#!/usr/bin/env python
"""
ddns.py
Simple wrapper class for the nsupdate commmand

3 methods:
domainExists(domain): returns true if domain exists
addDomain(domain, *args): add string in nsupdate format
delDomain(domain, *args): delete domain in nsupdate format

examples:
ddns.py add host.domain A 192.168.1.1
ddns.py del host.domain A 192.168.1.1

Basically, just the same format as nsupdate except
you don't have to specify the timeout on the command
line and you can shorten delete to del.

"""

"""
config variables
"""
server = '127.0.0.1'
nscmd = "/usr/bin/nsupdate"
keyfile = "/path/to/key"
timeout = 36000

"""
imports
"""
import os, sys, dns.resolver

"""
code
"""

class nsupdate:
	def __init__(self, config):
		self.config = config
		self.command = "%s -v -k %s" % (self.config['nscmd'], self.config['keyfile'])
		self.batch = []
		self.batch.append("server %s" % self.config['server'])

	def domainExists(self, domain):
		try:
			answer = dns.resolver.query(domain, 'a')
		except dns.resolver.NXDOMAIN:
			return 0
		else:
			return 1

	def addDomain(self, domain, *args):
		parts = domain.split('.')
		zone = '.'.join(parts[1:])
		self.batch.append("zone %s" % zone)
		self.batch.append("update add %s %s IN %s" % (domain, self.config['timeout'], args[0]))
		self.batch.append("send")
		self.commit()

	def delDomain(self, domain, *args):
		parts = domain.split('.')
		zone = '.'.join(parts[1:])
		self.batch.append("zone %s" % zone)
		self.batch.append("update delete %s %s IN %s" % (domain, self.config['timeout'], args[0]))
		self.batch.append("send")
		self.commit()
	
	def commit(self):
		opipe = os.popen(self.command, 'w')
		for b in self.batch:
			print b
			opipe.write("%s\n" % b)
		opipe.close()

if __name__ == "__main__":
	if len(sys.argv) < 5:
		print "\nSyntax: ddns.py [add|del] nsupdate string\n"
	else:
		config = {} 
		config['nscmd'] = nscmd
		config['server'] = server
		config['keyfile'] = keyfile
		config['timeout'] = timeout

		NS = nsupdate(config)

		if sys.argv[1] == 'add':
			if not NS.domainExists(sys.argv[2]):
				NS.addDomain(sys.argv[2], ' '.join(sys.argv[3:]))
		elif sys.argv[1] == 'del':
			if NS.domainExists(sys.argv[2]):
				NS.delDomain(sys.argv[2], ' '.join(sys.argv[3:]))
		else:
			print "\nSyntax: ddns.py [add|del] nsupdate string\n"