# 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.

from __future__ import absolute_import, division, print_function

import warnings

import six

from cryptography import utils
from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
from cryptography.hazmat.backends.interfaces import RSABackend


def generate_private_key(public_exponent, key_size, backend):
    if not isinstance(backend, RSABackend):
        raise UnsupportedAlgorithm(
            "Backend object does not implement RSABackend.",
            _Reasons.BACKEND_MISSING_INTERFACE
        )

    _verify_rsa_parameters(public_exponent, key_size)
    return backend.generate_rsa_private_key(public_exponent, key_size)


def _verify_rsa_parameters(public_exponent, key_size):
    if public_exponent < 3:
        raise ValueError("public_exponent must be >= 3.")

    if public_exponent & 1 == 0:
        raise ValueError("public_exponent must be odd.")

    if key_size < 512:
        raise ValueError("key_size must be at least 512-bits.")


def _check_private_key_components(p, q, private_exponent, dmp1, dmq1, iqmp,
                                  public_exponent, modulus):
    if modulus < 3:
        raise ValueError("modulus must be >= 3.")

    if p >= modulus:
        raise ValueError("p must be < modulus.")

    if q >= modulus:
        raise ValueError("q must be < modulus.")

    if dmp1 >= modulus:
        raise ValueError("dmp1 must be < modulus.")

    if dmq1 >= modulus:
        raise ValueError("dmq1 must be < modulus.")

    if iqmp >= modulus:
        raise ValueError("iqmp must be < modulus.")

    if private_exponent >= modulus:
        raise ValueError("private_exponent must be < modulus.")

    if public_exponent < 3 or public_exponent >= modulus:
        raise ValueError("public_exponent must be >= 3 and < modulus.")

    if public_exponent & 1 == 0:
        raise ValueError("public_exponent must be odd.")

    if dmp1 & 1 == 0:
        raise ValueError("dmp1 must be odd.")

    if dmq1 & 1 == 0:
        raise ValueError("dmq1 must be odd.")

    if p * q != modulus:
        raise ValueError("p*q must equal modulus.")


def _check_public_key_components(e, n):
    if n < 3:
        raise ValueError("n must be >= 3.")

    if e < 3 or e >= n:
        raise ValueError("e must be >= 3 and < n.")

    if e & 1 == 0:
        raise ValueError("e must be odd.")


class RSAPublicKey(object):
    def __init__(self, public_exponent, modulus):
        warnings.warn(
            "The RSAPublicKey class is deprecated and will be removed in a "
            "future version.",
            utils.DeprecatedIn05,
            stacklevel=2
        )
        if (
            not isinstance(public_exponent, six.integer_types) or
            not isinstance(modulus, six.integer_types)
        ):
            raise TypeError("RSAPublicKey arguments must be integers.")

        _check_public_key_components(public_exponent, modulus)

        self._public_exponent = public_exponent
        self._modulus = modulus

    def verifier(self, signature, padding, algorithm, backend):
        if not isinstance(backend, RSABackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement RSABackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        return backend.create_rsa_verification_ctx(self, signature, padding,
                                                   algorithm)

    def encrypt(self, plaintext, padding, backend):
        if not isinstance(backend, RSABackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement RSABackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        return backend.encrypt_rsa(self, plaintext, padding)

    @property
    def key_size(self):
        return utils.bit_length(self.modulus)

    @property
    def public_exponent(self):
        return self._public_exponent

    @property
    def modulus(self):
        return self._modulus

    @property
    def e(self):
        return self.public_exponent

    @property
    def n(self):
        return self.modulus


def _modinv(e, m):
    """
    Modular Multiplicative Inverse. Returns x such that: (x*e) mod m == 1
    """
    x1, y1, x2, y2 = 1, 0, 0, 1
    a, b = e, m
    while b > 0:
        q, r = divmod(a, b)
        xn, yn = x1 - q * x2, y1 - q * y2
        a, b, x1, y1, x2, y2 = b, r, x2, y2, xn, yn
    return x1 % m


def rsa_crt_iqmp(p, q):
    """
    Compute the CRT (q ** -1) % p value from RSA primes p and q.
    """
    return _modinv(q, p)


def rsa_crt_dmp1(private_exponent, p):
    """
    Compute the CRT private_exponent % (p - 1) value from the RSA
    private_exponent and p.
    """
    return private_exponent % (p - 1)


def rsa_crt_dmq1(private_exponent, q):
    """
    Compute the CRT private_exponent % (q - 1) value from the RSA
    private_exponent and q.
    """
    return private_exponent % (q - 1)


class RSAPrivateKey(object):
    def __init__(self, p, q, private_exponent, dmp1, dmq1, iqmp,
                 public_exponent, modulus):
        warnings.warn(
            "The RSAPrivateKey class is deprecated and will be removed in a "
            "future version.",
            utils.DeprecatedIn05,
            stacklevel=2
        )
        if (
            not isinstance(p, six.integer_types) or
            not isinstance(q, six.integer_types) or
            not isinstance(dmp1, six.integer_types) or
            not isinstance(dmq1, six.integer_types) or
            not isinstance(iqmp, six.integer_types) or
            not isinstance(private_exponent, six.integer_types) or
            not isinstance(public_exponent, six.integer_types) or
            not isinstance(modulus, six.integer_types)
        ):
            raise TypeError("RSAPrivateKey arguments must be integers.")

        _check_private_key_components(p, q, private_exponent, dmp1, dmq1, iqmp,
                                      public_exponent, modulus)

        self._p = p
        self._q = q
        self._dmp1 = dmp1
        self._dmq1 = dmq1
        self._iqmp = iqmp
        self._private_exponent = private_exponent
        self._public_exponent = public_exponent
        self._modulus = modulus

    @classmethod
    def generate(cls, public_exponent, key_size, backend):
        warnings.warn(
            "generate is deprecated and will be removed in a future version.",
            utils.DeprecatedIn05,
            stacklevel=2
        )
        if not isinstance(backend, RSABackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement RSABackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        _verify_rsa_parameters(public_exponent, key_size)
        key = backend.generate_rsa_private_key(public_exponent, key_size)
        private_numbers = key.private_numbers()
        return RSAPrivateKey(
            p=private_numbers.p,
            q=private_numbers.q,
            dmp1=private_numbers.dmp1,
            dmq1=private_numbers.dmq1,
            iqmp=private_numbers.iqmp,
            private_exponent=private_numbers.d,
            public_exponent=private_numbers.public_numbers.e,
            modulus=private_numbers.public_numbers.n
        )

    def signer(self, padding, algorithm, backend):
        if not isinstance(backend, RSABackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement RSABackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        return backend.create_rsa_signature_ctx(self, padding, algorithm)

    def decrypt(self, ciphertext, padding, backend):
        if not isinstance(backend, RSABackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement RSABackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        return backend.decrypt_rsa(self, ciphertext, padding)

    @property
    def key_size(self):
        return utils.bit_length(self.modulus)

    def public_key(self):
        return RSAPublicKey(self.public_exponent, self.modulus)

    @property
    def p(self):
        return self._p

    @property
    def q(self):
        return self._q

    @property
    def private_exponent(self):
        return self._private_exponent

    @property
    def public_exponent(self):
        return self._public_exponent

    @property
    def modulus(self):
        return self._modulus

    @property
    def d(self):
        return self.private_exponent

    @property
    def dmp1(self):
        return self._dmp1

    @property
    def dmq1(self):
        return self._dmq1

    @property
    def iqmp(self):
        return self._iqmp

    @property
    def e(self):
        return self.public_exponent

    @property
    def n(self):
        return self.modulus


class RSAPrivateNumbers(object):
    def __init__(self, p, q, d, dmp1, dmq1, iqmp,
                 public_numbers):
        if (
            not isinstance(p, six.integer_types) or
            not isinstance(q, six.integer_types) or
            not isinstance(d, six.integer_types) or
            not isinstance(dmp1, six.integer_types) or
            not isinstance(dmq1, six.integer_types) or
            not isinstance(iqmp, six.integer_types)
        ):
            raise TypeError(
                "RSAPrivateNumbers p, q, d, dmp1, dmq1, iqmp arguments must"
                " all be an integers."
            )

        if not isinstance(public_numbers, RSAPublicNumbers):
            raise TypeError(
                "RSAPrivateNumbers public_numbers must be an RSAPublicNumbers"
                " instance."
            )

        self._p = p
        self._q = q
        self._d = d
        self._dmp1 = dmp1
        self._dmq1 = dmq1
        self._iqmp = iqmp
        self._public_numbers = public_numbers

    @property
    def p(self):
        return self._p

    @property
    def q(self):
        return self._q

    @property
    def d(self):
        return self._d

    @property
    def dmp1(self):
        return self._dmp1

    @property
    def dmq1(self):
        return self._dmq1

    @property
    def iqmp(self):
        return self._iqmp

    @property
    def public_numbers(self):
        return self._public_numbers

    def private_key(self, backend):
        return backend.load_rsa_private_numbers(self)


class RSAPublicNumbers(object):
    def __init__(self, e, n):
        if (
            not isinstance(e, six.integer_types) or
            not isinstance(n, six.integer_types)
        ):
            raise TypeError("RSAPublicNumbers arguments must be integers.")

        self._e = e
        self._n = n

    @property
    def e(self):
        return self._e

    @property
    def n(self):
        return self._n

    def public_key(self, backend):
        return backend.load_rsa_public_numbers(self)

    def __repr__(self):
        return "<RSAPublicNumbers(e={0}, n={1})>".format(self._e, self._n)