# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import pytest

from cryptography.exceptions import UnsupportedAlgorithm
from cryptography.hazmat.backends.multibackend import PrioritizedMultiBackend
from cryptography.hazmat.primitives import hashes, hmac
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC


class DummyCipherBackend(object):
    def __init__(self, supported_ciphers):
        self._ciphers = supported_ciphers

    def cipher_supported(self, algorithm, mode):
        return (type(algorithm), type(mode)) in self._ciphers

    def create_symmetric_encryption_ctx(self, algorithm, mode):
        if not self.cipher_supported(algorithm, mode):
            raise UnsupportedAlgorithm

    def create_symmetric_decryption_ctx(self, algorithm, mode):
        if not self.cipher_supported(algorithm, mode):
            raise UnsupportedAlgorithm


class DummyHashBackend(object):
    def __init__(self, supported_algorithms):
        self._algorithms = supported_algorithms

    def hash_supported(self, algorithm):
        return type(algorithm) in self._algorithms

    def create_hash_ctx(self, algorithm):
        if not self.hash_supported(algorithm):
            raise UnsupportedAlgorithm


class DummyHMACBackend(object):
    def __init__(self, supported_algorithms):
        self._algorithms = supported_algorithms

    def hmac_supported(self, algorithm):
        return type(algorithm) in self._algorithms

    def create_hmac_ctx(self, key, algorithm):
        if not self.hmac_supported(algorithm):
            raise UnsupportedAlgorithm


class DummyPBKDF2HMAC(object):
    def __init__(self, supported_algorithms):
        self._algorithms = supported_algorithms

    def pbkdf2_hmac_supported(self, algorithm):
        return type(algorithm) in self._algorithms

    def derive_pbkdf2_hmac(self, algorithm, length, salt, iterations,
                           key_material):
        if not self.pbkdf2_hmac_supported(algorithm):
            raise UnsupportedAlgorithm



class TestPrioritizedMultiBackend(object):
    def test_ciphers(self):
        backend = PrioritizedMultiBackend([
            DummyCipherBackend([
                (algorithms.AES, modes.CBC),
            ])
        ])
        assert backend.cipher_supported(
            algorithms.AES(b"\x00" * 16), modes.CBC(b"\x00" * 16)
        )

        cipher = Cipher(
            algorithms.AES(b"\x00" * 16),
            modes.CBC(b"\x00" * 16),
            backend=backend
        )
        cipher.encryptor()
        cipher.decryptor()

        cipher = Cipher(
            algorithms.Camellia(b"\x00" * 16),
            modes.CBC(b"\x00" * 16),
            backend=backend
        )
        with pytest.raises(UnsupportedAlgorithm):
            cipher.encryptor()
        with pytest.raises(UnsupportedAlgorithm):
            cipher.decryptor()

    def test_hashes(self):
        backend = PrioritizedMultiBackend([
            DummyHashBackend([hashes.MD5])
        ])
        assert backend.hash_supported(hashes.MD5())

        hashes.Hash(hashes.MD5(), backend=backend)

        with pytest.raises(UnsupportedAlgorithm):
            hashes.Hash(hashes.SHA1(), backend=backend)

    def test_hmac(self):
        backend = PrioritizedMultiBackend([
            DummyHMACBackend([hashes.MD5])
        ])
        assert backend.hmac_supported(hashes.MD5())

        hmac.HMAC(b"", hashes.MD5(), backend=backend)

        with pytest.raises(UnsupportedAlgorithm):
            hmac.HMAC(b"", hashes.SHA1(), backend=backend)

    def test_pbkdf2(self):
        backend = PrioritizedMultiBackend([
            DummyPBKDF2HMAC([hashes.MD5])
        ])
        assert backend.pbkdf2_hmac_supported(hashes.MD5())

        backend.derive_pbkdf2_hmac(hashes.MD5(), 10, b"", 10, b"")

        with pytest.raises(UnsupportedAlgorithm):
            backend.derive_pbkdf2_hmac(hashes.SHA1(), 10, b"", 10, b"")