#!/usr/bin/python3

# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
#
# SPDX-License-Identifier: MPL-2.0
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0.  If a copy of the MPL was not distributed with this
# file, you can obtain one at https://mozilla.org/MPL/2.0/.
#
# See the COPYRIGHT file distributed with this work for additional
# information regarding copyright ownership.

"""
Example property-based test for wildcard synthesis.
Verifies that otherwise-empty zone with single wildcard record * A 192.0.2.1
produces synthesized answers for <random_label>.test. A, and returns NODATA for
<random_label>.test. when rdtype is not A.

Limitations - untested properties:
    - expansion works with multiple labels
    - asterisk in qname does not cause expansion
    - empty non-terminals prevent expansion
    - or more generally any existing node prevents expansion
    - DNSSEC record inclusion
    - possibly others, see RFC 4592 and company
    - content of authority & additional sections
    - flags beyond RCODE
    - special behavior of rdtypes like CNAME
"""
import pytest

pytest.importorskip("dns")
import dns.message
import dns.name
import dns.query
import dns.rcode
import dns.rdatatype

pytest.importorskip("hypothesis")
from hypothesis import given
from hypothesis.strategies import binary, integers


# labels of a zone with * A 192.0.2.1 wildcard
WILDCARD_ZONE = ('allwild', 'test', '')
WILDCARD_RDTYPE = dns.rdatatype.A
WILDCARD_RDATA = '192.0.2.1'
IPADDR = '10.53.0.1'
TIMEOUT = 5  # seconds, just a sanity check


# Helpers
def is_nonexpanding_rdtype(rdtype):
    """skip meta types to avoid weird rcodes caused by AXFR etc.; RFC 6895"""
    return not(rdtype == WILDCARD_RDTYPE
               or dns.rdatatype.is_metatype(rdtype)  # known metatypes: OPT ...
               or 128 <= rdtype <= 255)  # unknown meta types


def tcp_query(where, port, qname, qtype):
    querymsg = dns.message.make_query(qname, qtype)
    assert len(querymsg.question) == 1
    return querymsg, dns.query.tcp(querymsg, where, port=port, timeout=TIMEOUT)


def query(where, port, label, rdtype):
    labels = (label, ) + WILDCARD_ZONE
    qname = dns.name.Name(labels)
    return tcp_query(where, port, qname, rdtype)


# Tests
@given(label=binary(min_size=1, max_size=63),
       rdtype=integers(min_value=0, max_value=65535).filter(
           is_nonexpanding_rdtype))
def test_wildcard_rdtype_mismatch(label, rdtype, named_port):
    """any label non-matching rdtype must result in to NODATA"""
    check_answer_nodata(*query(IPADDR, named_port, label, rdtype))


def check_answer_nodata(querymsg, answer):
    assert querymsg.is_response(answer), str(answer)
    assert answer.rcode() == dns.rcode.NOERROR, str(answer)
    assert answer.answer == [], str(answer)


@given(label=binary(min_size=1, max_size=63))
def test_wildcard_match(label, named_port):
    """any label with maching rdtype must result in wildcard data in answer"""
    check_answer_noerror(*query(IPADDR, named_port, label, WILDCARD_RDTYPE))


def check_answer_noerror(querymsg, answer):
    assert querymsg.is_response(answer), str(answer)
    assert answer.rcode() == dns.rcode.NOERROR, str(answer)
    assert len(querymsg.question) == 1, str(answer)
    expected_answer = [dns.rrset.from_text(
                            querymsg.question[0].name,
                            300,  # TTL, ignored by dnspython comparison
                            dns.rdataclass.IN,
                            WILDCARD_RDTYPE,
                            WILDCARD_RDATA)]
    assert answer.answer == expected_answer, str(answer)
