"""Obtain four real DNS failure/absence results, including a silent UDP endpoint."""
import socket
import subprocess


def query(server, name, kind="A", port=53):
    command = ["dig", "@" + server, "-p", str(port), name, kind,
               "+tries=1", "+time=2", "+noall", "+comments", "+answer", "+authority"]
    print("\n$ " + " ".join(command), flush=True)
    result = subprocess.run(command, capture_output=True, text=True)
    print(result.stdout, end="", flush=True)
    return result


def main():
    nx = query("resolver", "missing.lab.test")
    nodata = query("resolver", "orders.lab.test", "AAAA")
    failed = query("resolver", "name.broken.test")
    # A bound UDP socket receives packets but sends nothing back: no ICMP port-unreachable.
    with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as silent:
        silent.bind(("127.0.0.1", 0))
        timeout = query("127.0.0.1", "orders.lab.test", port=silent.getsockname()[1])
    assert "status: NXDOMAIN" in nx.stdout
    assert "status: NOERROR" in nodata.stdout and "ANSWER: 0" in nodata.stdout
    assert "status: SERVFAIL" in failed.stdout
    assert timeout.returncode == 9 and "timed out" in timeout.stdout
    print("PASS: NXDOMAIN / NODATA / SERVFAIL / timeout")


if __name__ == "__main__":
    main()