import socket
import struct
from typing import Optional
from urllib.parse import urlparse


def is_loopback(address):
    host: Optional[str] = None

    try:
        parsed_url = urlparse(address)
        host = parsed_url.hostname
    except ValueError:
        return False  # url is not even a url

    loopback_checker = {
        socket.AF_INET: lambda x: struct.unpack("!I", socket.inet_aton(x))[0]
        >> (32 - 8)
        == 127,
        socket.AF_INET6: lambda x: x == "::1",
    }
    for family in (socket.AF_INET, socket.AF_INET6):
        try:
            r = socket.getaddrinfo(host, None, family, socket.SOCK_STREAM)
        except socket.gaierror:
            continue
        for family, _, _, _, sockaddr in r:
            if loopback_checker[family](sockaddr[0]):
                return True

    if host in ("localhost",):
        return True

    return False