#!/usr/bin/python3

import os
import re
import socket

def main():
    """
        # ddns for phuslu.ddns.net
        /home/phuslu 1.1.1.1(rw,async,no_subtree_check,all_squash,anonuid=1000,anongid=1000)
    """
    with open('/etc/exports', 'rb') as file:
        lines = file.read().decode().splitlines()
    pos = next((i for i, x in enumerate(lines) if x.startswith('# ddns')), None)
    if pos is None or pos == len(lines)-1:
        return
    domain = re.search(r' for ([\w\.]+)', lines[pos]).group(1)
    ip = socket.gethostbyname(domain)
    newline = re.sub(r'\s+\d{1,3}\.\d{1,3}.\d{1,3}.\d{1,3}\(', ' '+ip+'(', lines[pos+1])
    if newline == lines[pos+1]:
        return
    lines[pos+1] = newline
    with open('/etc/exports', 'wb') as file:
        file.write('\n'.join(lines).encode())
    #os.system('exportfs -arv')
    os.system('/usr/sbin/exportfs -arv >/dev/null')


if __name__ == '__main__':
    main()