# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.

from __future__ import absolute_import, division, print_function

import binascii
import os

import pytest

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.backends.interfaces import HashBackend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.x963kdf import X963KDF

from ...doubles import DummyHashAlgorithm
from ...utils import load_vectors_from_file, load_x963_vectors


def _skip_hashfn_unsupported(backend, hashfn):
    if not backend.hash_supported(hashfn):
        pytest.skip(
            "Hash {} is not supported by this backend {}".format(
                hashfn.name, backend
            )
        )


@pytest.mark.requires_backend_interface(interface=HashBackend)
class TestX963(object):
    _algorithms_dict = {
        'SHA-1': hashes.SHA1,
        'SHA-224': hashes.SHA224,
        'SHA-256': hashes.SHA256,
        'SHA-384': hashes.SHA384,
        'SHA-512': hashes.SHA512
    }

    @pytest.mark.parametrize(
        ("vector"),
        load_vectors_from_file(
            os.path.join("KDF", "ansx963_2001.txt"),
            load_x963_vectors
        )
    )
    def test_x963(self, backend, vector):
        hashfn = self._algorithms_dict[vector["hash"]]
        _skip_hashfn_unsupported(backend, hashfn())

        key = binascii.unhexlify(vector["Z"])
        sharedinfo = None
        if vector["sharedinfo_length"] != 0:
            sharedinfo = binascii.unhexlify(vector["sharedinfo"])
        key_data_len = vector["key_data_length"] // 8
        key_data = binascii.unhexlify(vector["key_data"])

        xkdf = X963KDF(algorithm=hashfn(),
                       length=key_data_len,
                       sharedinfo=sharedinfo,
                       backend=default_backend())
        xkdf.verify(key, key_data)

    def test_unsupported_hash(self, backend):
        with pytest.raises(pytest.skip.Exception):
            _skip_hashfn_unsupported(backend, DummyHashAlgorithm())