#!/usr/bin/python3
#
# Maximilian Wilhelm <max@rfc2324.org>
#  --  Sat, 15 Apr 2023 01:52:36 +0200
#

import argparse
import netifaces
import os
import os.path
import requests
import sys


def get_active_interface() -> str:
	try:
		# netifaces.gateway() will return a dict with multiple keys:
		# 'default'          -> dict with default route information (AF -> (ip, iface))
		# netifaces.AF_INET  -> list of IPv4 next-hop tuples (IP, iface, default yes/no)
		# netifaces.AF_INET6 -> list of IPv6 next-hop tuples (see above)
		def_gw = netifaces.gateways()['default']

		# The 'default' dict should contain an IPv6 default gw (we need IPv6 to reach NACL),
		# and if so we care about the interface name
		return def_gw[netifaces.AF_INET6][1]
	except KeyError:
		return None

def get_interface_mac(ifname: str) -> str:
	iface_addrs = netifaces.ifaddresses(ifname)
	try:
		# We care about the MAC of the 1st entry in the AF_LINK addresses (from right to left)
		return iface_addrs[netifaces.AF_LINK][0]['addr']
	except KeyError:
		return None
	except IndexError:
		return None

def get_fqdn(nacl_url: str, mac: str):
	params = {}

	if mac:
		params['mac'] = mac

	try:
		res = requests.get (f"{nacl_url}/node/whoami", params = params)
		if res.status_code == 200:
			return res.json()
		else:
			print(f"Failed to get FQDN: {res.text}", file=sys.stderr)
			sys.exit(3)
	except Exception as e:
		print(f"Failed to get FQDN: {str(e)}", file=sys.stderr)
		sys.exit(4)


parser = argparse.ArgumentParser(description = 'NACL SSH key registration tool')
parser.add_argument('--mac', '-m', help = 'Use MAC address from gateway interface rather than IP address to identify ourselves', action = 'store_true', default = False)
parser.add_argument('--url', help = "URL to reach NACL service, e.g http://nacl:2342", default = os.environ.get('NACL_URL', 'http://nacl'))
args = parser.parse_args()

mac = None
if args.mac:
	uplink_ifname = get_active_interface()
	if uplink_ifname is None:
		print("Failed to identify uplink interface!", file=sys.stderr)
		sys.exit(1)

	mac = get_interface_mac(uplink_ifname)
	if mac is None:
		print(f"Failed to get MAC address of uplink interface {uplink_ifname}!", file=sys.stderr)
		sys.exit(2)

print(get_fqdn(args.url, mac))