# Copyright (c) 2014-2023 by Ron Frederick <ronf@timeheart.net> and others.
#
# This program and the accompanying materials are made available under
# the terms of the Eclipse Public License v2.0 which accompanies this
# distribution and is available at:
#
#     http://www.eclipse.org/legal/epl-2.0/
#
# This program may also be made available under the following secondary
# licenses when the conditions for such availability set forth in the
# Eclipse Public License v2.0 are satisfied:
#
#    GNU General Public License, Version 2.0, or any later versions of
#    that license
#
# SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
#
# Contributors:
#     Ron Frederick - initial implementation, API, and documentation

"""A shim around PyCA for RSA public and private keys"""

from typing import Optional, cast

from cryptography.exceptions import InvalidSignature
from cryptography.hazmat.primitives.asymmetric.padding import MGF1, OAEP
from cryptography.hazmat.primitives.asymmetric.padding import PKCS1v15
from cryptography.hazmat.primitives.asymmetric import rsa

from .misc import CryptoKey, PyCAKey, hashes


# Short variable names are used here, matching names in the spec
# pylint: disable=invalid-name


class _RSAKey(CryptoKey):
    """Base class for shim around PyCA for RSA keys"""

    def __init__(self, pyca_key: PyCAKey, pub: rsa.RSAPublicNumbers,
                 priv: Optional[rsa.RSAPrivateNumbers] = None):
        super().__init__(pyca_key)

        self._pub = pub
        self._priv = priv

    @property
    def n(self) -> int:
        """Return the RSA public modulus"""

        return self._pub.n

    @property
    def e(self) -> int:
        """Return the RSA public exponent"""

        return self._pub.e

    @property
    def d(self) -> Optional[int]:
        """Return the RSA private exponent"""

        return self._priv.d if self._priv else None

    @property
    def p(self) -> Optional[int]:
        """Return the RSA first private prime"""

        return self._priv.p if self._priv else None

    @property
    def q(self) -> Optional[int]:
        """Return the RSA second private prime"""

        return self._priv.q if self._priv else None

    @property
    def dmp1(self) -> Optional[int]:
        """Return d modulo p-1"""

        return self._priv.dmp1 if self._priv else None

    @property
    def dmq1(self) -> Optional[int]:
        """Return q modulo p-1"""

        return self._priv.dmq1 if self._priv else None

    @property
    def iqmp(self) -> Optional[int]:
        """Return the inverse of q modulo p"""

        return self._priv.iqmp if self._priv else None


class RSAPrivateKey(_RSAKey):
    """A shim around PyCA for RSA private keys"""

    @classmethod
    def construct(cls, n: int, e: int, d: int, p: int, q: int,
                  dmp1: int, dmq1: int, iqmp: int,
                  skip_validation: bool) -> 'RSAPrivateKey':
        """Construct an RSA private key"""

        pub = rsa.RSAPublicNumbers(e, n)
        priv = rsa.RSAPrivateNumbers(p, q, d, dmp1, dmq1, iqmp, pub)
        priv_key = priv.private_key(
            unsafe_skip_rsa_key_validation=skip_validation)

        return cls(priv_key, pub, priv)

    @classmethod
    def generate(cls, key_size: int, exponent: int) -> 'RSAPrivateKey':
        """Generate a new RSA private key"""

        priv_key = rsa.generate_private_key(exponent, key_size)
        priv = priv_key.private_numbers()
        pub = priv.public_numbers

        return cls(priv_key, pub, priv)

    def decrypt(self, data: bytes, hash_name: str) -> Optional[bytes]:
        """Decrypt a block of data"""

        try:
            hash_alg = hashes[hash_name]()
            priv_key = cast('rsa.RSAPrivateKey', self.pyca_key)
            return priv_key.decrypt(data, OAEP(MGF1(hash_alg), hash_alg, None))
        except ValueError:
            return None

    def sign(self, data: bytes, hash_name: str = '') -> bytes:
        """Sign a block of data"""

        priv_key = cast('rsa.RSAPrivateKey', self.pyca_key)
        return priv_key.sign(data, PKCS1v15(), hashes[hash_name]())


class RSAPublicKey(_RSAKey):
    """A shim around PyCA for RSA public keys"""

    @classmethod
    def construct(cls, n: int, e: int) -> 'RSAPublicKey':
        """Construct an RSA public key"""

        pub = rsa.RSAPublicNumbers(e, n)
        pub_key = pub.public_key()

        return cls(pub_key, pub)

    def encrypt(self, data: bytes, hash_name: str) -> Optional[bytes]:
        """Encrypt a block of data"""

        try:
            hash_alg = hashes[hash_name]()
            pub_key = cast('rsa.RSAPublicKey', self.pyca_key)
            return pub_key.encrypt(data, OAEP(MGF1(hash_alg), hash_alg, None))
        except ValueError:
            return None

    def verify(self, data: bytes, sig: bytes, hash_name: str = '') -> bool:
        """Verify the signature on a block of data"""

        try:
            pub_key = cast('rsa.RSAPublicKey', self.pyca_key)
            pub_key.verify(sig, data, PKCS1v15(), hashes[hash_name]())
            return True
        except InvalidSignature:
            return False