#! /usr/bin/env python3
# vim:set noet sw=8 ts=8 sts=8:

import sys, socket
import dns.query
import dns.name
import dns.rdatatype
import dns.zone

def resolve(hostname):
	try:
		addrs = socket.getaddrinfo(
				hostname, 53, proto=socket.IPPROTO_UDP)
		return list(dict.fromkeys([addr[4][0] for addr in addrs]))
	except Exception as e:
		raise (Exception(f"resolving {hostname}: {e}"))

def axfr(zonename, hostname):
	addrs = resolve(hostname)
	last_exc = None

	for addr in addrs:
		try:
			name = dns.name.from_unicode(zonename)
			zone = dns.zone.Zone(origin=name)
			dns.query.inbound_xfr(addr, zone)
			return zone
		except Exception as e:
			last_exc = e
	raise (last_exc)

def print_catalog(zone):
	def origin(node):
		try:
			return [
				''.join(s.decode('utf-8') for s in rdata.strings)
				for rdata in
					zone.find_node(f"origin.ext.{node}")
						.find_rdataset(dns.rdataclass.IN,
							       dns.rdatatype.TXT)
			]
		except KeyError:
			return []

	nodes = [node
		 for (name, node) in zone.nodes.items()
		 if len(name) == 2 and name[1] == b"zones"]

	ptrs = [str(ptr.target).rstrip('.')
		for node in nodes
		for rdataset in node.rdatasets
			if rdataset.rdtype == dns.rdatatype.PTR
		for ptr in rdataset]

	print("\n".join(ptrs))

def main():
	if len(sys.argv) != 3:
		print(f"Usage: {sys.argv[0]} <zone> <server>", file=sys.stderr)
		return 1

	zone_name = sys.argv[1]
	server = sys.argv[2]

	try:
		zone = axfr(zone_name, server)
		print_catalog(zone)
	except Exception as e:
		print(f"Failed to load catalog: {e}", file=sys.stderr)
		return 1

	return 0

if __name__ == "__main__":
	sys.exit(main())