# 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.

import binascii
import copy
import dataclasses
import os

import pytest

from cryptography.exceptions import _Reasons
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric.mlkem import (
    MLKEM768PrivateKey,
    MLKEM768PublicKey,
    MLKEM1024PrivateKey,
    MLKEM1024PublicKey,
)

from ...doubles import DummyKeySerializationEncryption
from ...utils import (
    load_nist_vectors,
    load_vectors_from_file,
    raises_unsupported_algorithm,
)


@dataclasses.dataclass
class MLKEMVariant:
    private_key_class: type
    public_key_class: type
    pub_key_size: int
    ciphertext_size: int
    shared_secret_size: int
    seed_size: int


ML_KEM_VARIANTS = [
    pytest.param(
        MLKEMVariant(
            private_key_class=MLKEM768PrivateKey,
            public_key_class=MLKEM768PublicKey,
            pub_key_size=1184,
            ciphertext_size=1088,
            shared_secret_size=32,
            seed_size=64,
        ),
        id="ML-KEM-768",
    ),
    pytest.param(
        MLKEMVariant(
            private_key_class=MLKEM1024PrivateKey,
            public_key_class=MLKEM1024PublicKey,
            pub_key_size=1568,
            ciphertext_size=1568,
            shared_secret_size=32,
            seed_size=64,
        ),
        id="ML-KEM-1024",
    ),
]


@pytest.mark.supported(
    only_if=lambda backend: not backend.mlkem_supported(),
    skip_message="Requires a backend without ML-KEM support",
)
def test_mlkem_unsupported():
    with raises_unsupported_algorithm(
        _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM
    ):
        MLKEM768PrivateKey.from_seed_bytes(b"0" * 64)

    with raises_unsupported_algorithm(
        _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM
    ):
        MLKEM768PrivateKey.generate()

    with raises_unsupported_algorithm(
        _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM
    ):
        MLKEM768PublicKey.from_public_bytes(b"0" * 1184)

    with raises_unsupported_algorithm(
        _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM
    ):
        MLKEM1024PrivateKey.from_seed_bytes(b"0" * 64)

    with raises_unsupported_algorithm(
        _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM
    ):
        MLKEM1024PrivateKey.generate()

    with raises_unsupported_algorithm(
        _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM
    ):
        MLKEM1024PublicKey.from_public_bytes(b"0" * 1568)


@pytest.mark.supported(
    only_if=lambda backend: backend.mlkem_supported(),
    skip_message="Requires a backend with ML-KEM support",
)
class TestMLKEM:
    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_encapsulate_decapsulate(self, variant):
        key = variant.private_key_class.generate()
        pub = key.public_key()
        shared_secret, ciphertext = pub.encapsulate()
        decapped = key.decapsulate(ciphertext)
        assert shared_secret == decapped
        assert len(shared_secret) == variant.shared_secret_size
        assert len(ciphertext) == variant.ciphertext_size

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_private_bytes_raw(self, variant):
        key = variant.private_key_class.generate()
        raw = key.private_bytes_raw()
        assert len(raw) == variant.seed_size
        assert raw == key.private_bytes(
            serialization.Encoding.Raw,
            serialization.PrivateFormat.Raw,
            serialization.NoEncryption(),
        )

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    @pytest.mark.parametrize(
        ("encoding", "fmt", "encryption", "passwd", "load_func"),
        [
            (
                serialization.Encoding.PEM,
                serialization.PrivateFormat.PKCS8,
                serialization.NoEncryption(),
                None,
                serialization.load_pem_private_key,
            ),
            (
                serialization.Encoding.DER,
                serialization.PrivateFormat.PKCS8,
                serialization.NoEncryption(),
                None,
                serialization.load_der_private_key,
            ),
            (
                serialization.Encoding.PEM,
                serialization.PrivateFormat.PKCS8,
                serialization.BestAvailableEncryption(b"password"),
                b"password",
                serialization.load_pem_private_key,
            ),
            (
                serialization.Encoding.DER,
                serialization.PrivateFormat.PKCS8,
                serialization.BestAvailableEncryption(b"password"),
                b"password",
                serialization.load_der_private_key,
            ),
        ],
    )
    def test_round_trip_private_serialization(
        self, variant, encoding, fmt, encryption, passwd, load_func
    ):
        key = variant.private_key_class.generate()
        serialized = key.private_bytes(encoding, fmt, encryption)
        loaded_key = load_func(serialized, passwd)
        assert isinstance(loaded_key, variant.private_key_class)
        # Verify round-trip by checking seed matches
        assert loaded_key.private_bytes_raw() == key.private_bytes_raw()

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    @pytest.mark.parametrize(
        ("encoding", "fmt", "load_func"),
        [
            (
                serialization.Encoding.PEM,
                serialization.PublicFormat.SubjectPublicKeyInfo,
                serialization.load_pem_public_key,
            ),
            (
                serialization.Encoding.DER,
                serialization.PublicFormat.SubjectPublicKeyInfo,
                serialization.load_der_public_key,
            ),
        ],
    )
    def test_round_trip_public_serialization(
        self, variant, encoding, fmt, load_func
    ):
        key = variant.private_key_class.generate()
        pub = key.public_key()
        serialized = pub.public_bytes(encoding, fmt)
        loaded_pub = load_func(serialized)
        assert isinstance(loaded_pub, variant.public_key_class)
        assert loaded_pub == pub

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_invalid_seed_length(self, variant):
        with pytest.raises(ValueError):
            variant.private_key_class.from_seed_bytes(b"a" * 10)

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_invalid_type_seed(self, variant):
        with pytest.raises(TypeError):
            variant.private_key_class.from_seed_bytes(object())

    def test_kat_vectors_768(self, subtests):
        vectors = load_vectors_from_file(
            os.path.join("asymmetric", "MLKEM", "kat_MLKEM_768.rsp"),
            load_nist_vectors,
        )
        for vector in vectors:
            with subtests.test():
                d = binascii.unhexlify(vector["d"])
                z = binascii.unhexlify(vector["z"])

                seed = d + z
                key = MLKEM768PrivateKey.from_seed_bytes(seed)
                assert key.private_bytes_raw() == seed

                # Verify public key matches
                pub = key.public_key()
                assert pub.public_bytes_raw() == binascii.unhexlify(
                    vector["pk"]
                )

                # Verify decapsulation produces the expected shared secret
                ss = key.decapsulate(binascii.unhexlify(vector["ct"]))
                assert ss == binascii.unhexlify(vector["ss"])

                # Decapsulating an invalid ciphertext should use
                # implicit rejection, producing a deterministic but
                # different shared secret.
                ss_n = key.decapsulate(binascii.unhexlify(vector["ct_n"]))
                assert ss_n == binascii.unhexlify(vector["ss_n"])

    def test_kat_vectors_1024(self, subtests):
        vectors = load_vectors_from_file(
            os.path.join("asymmetric", "MLKEM", "kat_MLKEM_1024.rsp"),
            load_nist_vectors,
        )
        for vector in vectors:
            with subtests.test():
                d = binascii.unhexlify(vector["d"])
                z = binascii.unhexlify(vector["z"])

                seed = d + z
                key = MLKEM1024PrivateKey.from_seed_bytes(seed)
                assert key.private_bytes_raw() == seed

                # Verify public key matches
                pub = key.public_key()
                assert pub.public_bytes_raw() == binascii.unhexlify(
                    vector["pk"]
                )

                # Verify decapsulation produces the expected shared secret
                ss = key.decapsulate(binascii.unhexlify(vector["ct"]))
                assert ss == binascii.unhexlify(vector["ss"])

                # Decapsulating an invalid ciphertext should use
                # implicit rejection, producing a deterministic but
                # different shared secret.
                ss_n = key.decapsulate(binascii.unhexlify(vector["ct_n"]))
                assert ss_n == binascii.unhexlify(vector["ss_n"])

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    @pytest.mark.parametrize(
        ("encoding", "fmt", "encryption", "err"),
        [
            (
                serialization.Encoding.Raw,
                serialization.PrivateFormat.Raw,
                DummyKeySerializationEncryption(),
                ValueError,
            ),
            (
                serialization.Encoding.Raw,
                serialization.PrivateFormat.PKCS8,
                DummyKeySerializationEncryption(),
                ValueError,
            ),
            (
                serialization.Encoding.PEM,
                serialization.PrivateFormat.Raw,
                serialization.NoEncryption(),
                ValueError,
            ),
            (
                serialization.Encoding.PEM,
                serialization.PrivateFormat.OpenSSH,
                serialization.NoEncryption(),
                ValueError,
            ),
            (
                serialization.Encoding.PEM,
                serialization.PrivateFormat.PKCS8,
                DummyKeySerializationEncryption(),
                ValueError,
            ),
            (
                serialization.Encoding.PEM,
                serialization.PrivateFormat.PKCS8,
                serialization.BestAvailableEncryption(b"a" * 1024),
                ValueError,
            ),
            (
                serialization.Encoding.Raw,
                serialization.PrivateFormat.Raw,
                None,
                TypeError,
            ),
        ],
    )
    def test_invalid_private_bytes(
        self, variant, encoding, fmt, encryption, err
    ):
        key = variant.private_key_class.generate()
        with pytest.raises(err):
            key.private_bytes(encoding, fmt, encryption)

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_invalid_public_bytes(self, variant):
        key = variant.private_key_class.generate().public_key()
        with pytest.raises(ValueError):
            key.public_bytes(
                serialization.Encoding.Raw,
                serialization.PublicFormat.SubjectPublicKeyInfo,
            )
        with pytest.raises(ValueError):
            key.public_bytes(
                serialization.Encoding.PEM,
                serialization.PublicFormat.PKCS1,
            )
        with pytest.raises(ValueError):
            key.public_bytes(
                serialization.Encoding.PEM,
                serialization.PublicFormat.Raw,
            )

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_public_key_equality(self, variant):
        key = variant.private_key_class.generate()
        pub1 = key.public_key()
        pub2 = key.public_key()
        pub3 = variant.private_key_class.generate().public_key()
        assert pub1 == pub2
        assert pub1 != pub3
        assert pub1 != object()

        with pytest.raises(TypeError):
            pub1 < pub2

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_public_key_copy(self, variant):
        key = variant.private_key_class.generate()
        pub1 = key.public_key()
        pub2 = copy.copy(pub1)
        assert pub1 == pub2

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_public_key_deepcopy(self, variant):
        key = variant.private_key_class.generate()
        pub1 = key.public_key()
        pub2 = copy.deepcopy(pub1)
        assert pub1 == pub2

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_private_key_copy(self, variant):
        key1 = variant.private_key_class.generate()
        key2 = copy.copy(key1)
        assert key1.private_bytes_raw() == key2.private_bytes_raw()

    @pytest.mark.parametrize("variant", ML_KEM_VARIANTS)
    def test_private_key_deepcopy(self, variant):
        key1 = variant.private_key_class.generate()
        key2 = copy.deepcopy(key1)
        assert key1.private_bytes_raw() == key2.private_bytes_raw()


@pytest.mark.supported(
    only_if=lambda backend: backend.mlkem_supported(),
    skip_message="Requires a backend with ML-KEM support",
)
def test_mlkem768_kat_serialization():
    vectors = load_vectors_from_file(
        os.path.join("asymmetric", "MLKEM", "kat_MLKEM_768.rsp"),
        load_nist_vectors,
    )

    first_vector = next(iter(vectors))
    d = binascii.unhexlify(first_vector["d"])
    z = binascii.unhexlify(first_vector["z"])
    key = MLKEM768PrivateKey.from_seed_bytes(d + z)

    serialized_pem = key.private_bytes(
        serialization.Encoding.PEM,
        serialization.PrivateFormat.PKCS8,
        serialization.NoEncryption(),
    )
    kat_pem = load_vectors_from_file(
        os.path.join("asymmetric", "MLKEM", "mlkem768.pem"),
        lambda f: f.read(),
        mode="rb",
    )
    assert serialized_pem == kat_pem

    serialized_der = key.private_bytes(
        serialization.Encoding.DER,
        serialization.PrivateFormat.PKCS8,
        serialization.NoEncryption(),
    )
    kat_der = load_vectors_from_file(
        os.path.join("asymmetric", "MLKEM", "mlkem768.der"),
        lambda f: f.read(),
        mode="rb",
    )
    assert serialized_der == kat_der
