#!/usr/bin/python3
#
# Maximilian Wilhelm <max@sdn.clinic>
#  --  Fri 28 Apr 2023 08:41:13 PM CEST
#

import re
import sys

if len (sys.argv) != 2:
    print("Usage: get-bridge-vids IFACE", file=sys.stderr)
    sys.exit(1)

ifname = sys.argv[1]

ifstanza_re = re.compile(rf"^iface {ifname}")
bridge_vid_re = re.compile(r"bridge-vids (.*)$")

interfaces_fh = open("/etc/network/interfaces", "r")
iface_found = False

for line in interfaces_fh.readlines():
    line = line.strip()

    if line.startswith('#'):
        continue

    if iface_found:
        match = bridge_vid_re.search(line)
        if match:
            print (match.group(1))

        continue

    match = ifstanza_re.search(line)
    if match:
        iface_found = True