from typing import Optional
import subprocess

def query_txt(domain: str, fallback_ns:str='8.8.8.8') -> Optional[str]:
    # get the authoritative nameserver first
    # just the top domain
    top_domain = '.'.join(domain.split('.')[-2:])
    ns_response = subprocess.run(['dig', top_domain, 'ns', '+short'], capture_output=True)
    # get the first one
    ns_response = ns_response.stdout.decode('utf-8')
    if ns_response == '':
        ns = fallback_ns
    else:
        ns = ns_response.split('\n')[0]

    # now actually query for the txt record
    output = subprocess.run(['dig', f'@{ns}', domain, 'txt', '+short'], capture_output=True)
    record = output.stdout.decode('utf-8').strip()
    if record == '':
        return None
    else:
        return record

def find_last_int(domain: str, max=50) -> int:
    post_int = 1

    while post_int < max:
        test_domain = f'{post_int}.{domain}'
        txt = query_txt(test_domain)
        if txt is None:
            break
        post_int += 1

    return post_int