#!/usr/bin/env python3

import argparse
import base64
import dns.resolver
import ipaddress
import logging
import logging.handlers
import requests
import socket
import sys
import urllib


HE_DNS_API_HOST = "dyn.dns.he.net"

def build_ip(ip_string):
	try:
		ip = ipaddress.ip_address(ip_string)
	except ValueError:
		log.error("manually specified address is invalid format: %s" % ip_string)
		sys.exit(1)
	except:
		log.error(str(e))
		sys.exit(1)

	return ip

def haveIPv6():
	log.debug("inside haveIPv6()")
	haveIPv6 = True
	try:
		s = socket.socket(socket.AF_INET6)
		s.connect((HE_DNS_API_HOST,80))
	except socket.gaierror as e:
		log.debug("Exception {}".format(e.__class__))
		log.error("Testing IPv6 connection: " + str(e))
		sys.exit(1)
	except OSError as e:
		log.debug("Exception {}".format(e.__class__))
		log.debug(str(e))
		haveIPv6 = False
	except TimeoutError as e:
		log.error("Testing IPv6 connection: " + str(e))
		sys.exit(1)
	except Exception as e:
		log.debug("Exception {}".format(e.__class__))
		log.error(str(e))
		haveIPv6 = False
	return haveIPv6

def main():
	ap = argparse.ArgumentParser(description="Update Hurricane Electric DNS dynamic record")
	ap.add_argument("record", help="DNS record to update")
	ap.add_argument("--v4", help="Update IPv4 A record (default)", action="store_true", default=True)
	ap.add_argument("--v6", help="Update IPv6 AAAA record", action="store_true", default=False)
	ap.add_argument("--addr4", help="Update A record with provided IP rather than detected IP")
	ap.add_argument("--addr6", help="Update AAAA record with provided IP rather than detected IP")
	ap.add_argument("--key", help="HE DDNS key for record (by default read from /etc/he-dns-secret)")
	ap.add_argument("--debug", help="Enable debug logging", action="store_true", default=False)
	args = ap.parse_args()

	if args.debug:
		log.setLevel(logging.DEBUG)
	else:
		log.setLevel(logging.ERROR)

	# Handle manual addressing
	if args.addr4:
		ip = build_ip(args.addr4)	

	if args.addr6:
		ip = build_ip(args.addr6)

	if args.v6:
		if not haveIPv6  and not args.addr6:
			log.error("no IPv6 detected and --v6 specified without --addr6 (try --debug?)")
			sys.exit(1)			
	try:
		
		if args.v6:
			ans = dns.resolver.resolve(HE_DNS_API_HOST, "AAAA")[0]
			log.debug("DNS resolved: {}".format(ans.to_text()))
			apihost = "[{}]".format(ans.to_text())
		else:
			ans = dns.resolver.resolve(HE_DNS_API_HOST, "A")[0]
			log.debug("DNS resolved: {}".format(ans.to_text()))
			apihost = ans.to_text()

		# build the API URL to be called
		url = "http://{}/nic/update?hostname={}".format(apihost, args.record)
		if args.addr4 or args.addr6:
			url += "&myip={}".format(ip)
		log.debug("API request URL: " + url)

		# make the HTTP request
		authstr = base64.b64encode(bytes("%s:%s" % ( args.record, "yEuFfO74TskIX2NG0Yod" ), "ascii"))
		log.debug("auth string: %s" % authstr.decode("utf-8"))
		req = urllib.request.Request(url)
		req.add_header("Host", HE_DNS_API_HOST)
		req.add_header("Authorization", "Basic %s" % authstr.decode("utf-8"))
		with urllib.request.urlopen(req) as response:
			this_page = response.read()
		log.debug("HE response: " + this_page.decode("utf-8"))
		res = this_page.decode("utf-8").split()[0]

		if res == "good":
			return True
		elif res == "badauth":
			raise Exception("HE badauth: wrong key or record not configured for dynamic updates")
		elif res == "nochg":
			return True
		else:
			raise Exception("HE returned {}: unknown response code".format(res))

	except dns.resolver.NXDOMAIN as e:
		log.debug("Exception class: {}".format(e.__class__))
		log.error(str(e))
		sys.exit(1)

	except Exception as e:
		log.debug("Exception class: {}".format(e.__class__))
		log.error(str(e))    
		sys.exit(1)

if __name__ == "__main__":
	log = logging.getLogger("he-dyndns")
	lh = logging.StreamHandler()
	lf = logging.Formatter(fmt='%(name)s: %(levelname)s: %(message)s')
	lh.setFormatter(lf)
	log.addHandler(lh)
	main()
	sys.exit(0)