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import secrets

from cryptography import __version__
from cryptography.exceptions import UnsupportedAlgorithm
from cryptography.hazmat.primitives.ciphers.algorithms import AES
from cryptography.hazmat.primitives.ciphers.base import Cipher
from cryptography.hazmat.primitives.ciphers.modes import CBC, ECB
from cryptography.hazmat.primitives.padding import PKCS7

from pypdf._crypt_providers._base import CryptBase
from pypdf._utils import logger_warning
from pypdf.errors import PdfStreamError

try:
    # 43.0.0: https://cryptography.io/en/latest/changelog/#v43-0-0
    from cryptography.hazmat.decrepit.ciphers.algorithms import ARC4
except ImportError:
    from cryptography.hazmat.primitives.ciphers.algorithms import ARC4

crypt_provider = ("cryptography", __version__)


class CryptRC4(CryptBase):
    # Assume OpenSSL provides RC4; flipped to False the first time it rejects
    # the cipher (e.g. legacy provider disabled), so the failing attempt is
    # paid once.
    _is_rc4_supported = True

    def __init__(self, key: bytes) -> None:
        self._key = key
        self._fallback = None
        if CryptRC4._is_rc4_supported:
            self.cipher = Cipher(ARC4(key), mode=None)
        else:
            self._fallback = self._pure_python_rc4(key)

    @staticmethod
    def _pure_python_rc4(key: bytes) -> CryptBase:
        from pypdf._crypt_providers import _fallback  # noqa: PLC0415

        return _fallback.CryptRC4(key)

    @classmethod
    def _disable_rc4(cls, key: bytes) -> CryptBase:
        if cls._is_rc4_supported:
            logger_warning(
                (
                    "RC4 is not supported by the current OpenSSL build; "
                    "falling back to the pure-Python RC4 implementation."
                ),
                source=__name__,
            )
            cls._is_rc4_supported = False
        return cls._pure_python_rc4(key)

    def encrypt(self, data: bytes) -> bytes:
        if self._fallback is not None:
            return self._fallback.encrypt(data)
        try:
            encryptor = self.cipher.encryptor()
            return encryptor.update(data) + encryptor.finalize()
        except UnsupportedAlgorithm:
            self._fallback = self._disable_rc4(self._key)
            return self._fallback.encrypt(data)

    def decrypt(self, data: bytes, *, strict: bool = True) -> bytes:
        if self._fallback is not None:
            return self._fallback.decrypt(data, strict=strict)
        try:
            decryptor = self.cipher.decryptor()
            return decryptor.update(data) + decryptor.finalize()
        except UnsupportedAlgorithm:
            self._fallback = self._disable_rc4(self._key)
            return self._fallback.decrypt(data, strict=strict)


class CryptAES(CryptBase):
    def __init__(self, key: bytes) -> None:
        self.alg = AES(key)

    def encrypt(self, data: bytes) -> bytes:
        iv = secrets.token_bytes(16)
        padder = PKCS7(128).padder()
        padded_data = padder.update(data) + padder.finalize()

        cipher = Cipher(self.alg, CBC(iv))
        encryptor = cipher.encryptor()
        return iv + encryptor.update(padded_data) + encryptor.finalize()

    def decrypt(self, data: bytes, *, strict: bool = True) -> bytes:
        iv = data[:16]
        data = data[16:]
        # for empty encrypted data
        if not data:
            return data

        if not strict and len(data) % 16 != 0:
            logger_warning("Adding missing padding.", source=__name__)
            padder = PKCS7(128).padder()
            data = padder.update(data) + padder.finalize()

        cipher = Cipher(self.alg, CBC(iv))
        decryptor = cipher.decryptor()
        try:
            padded_data = decryptor.update(data) + decryptor.finalize()
        except ValueError as exception:
            # Only raised in strict mode. Non-strict mode fixes padding.
            raise PdfStreamError(exception)

        unpadder = PKCS7(128).unpadder()
        try:
            return unpadder.update(padded_data) + unpadder.finalize()
        except ValueError as exception:
            if strict:
                raise PdfStreamError(exception)
            logger_warning("Ignoring padding error: %(exception)s", source=__name__, exception=exception)
            return padded_data[: -padded_data[-1]]


def rc4_encrypt(key: bytes, data: bytes) -> bytes:
    if CryptRC4._is_rc4_supported:
        try:
            encryptor = Cipher(ARC4(key), mode=None).encryptor()
            return encryptor.update(data) + encryptor.finalize()
        except UnsupportedAlgorithm:
            return CryptRC4._disable_rc4(key).encrypt(data)
    return CryptRC4._pure_python_rc4(key).encrypt(data)


def rc4_decrypt(key: bytes, data: bytes) -> bytes:
    if CryptRC4._is_rc4_supported:
        try:
            decryptor = Cipher(ARC4(key), mode=None).decryptor()
            return decryptor.update(data) + decryptor.finalize()
        except UnsupportedAlgorithm:
            return CryptRC4._disable_rc4(key).decrypt(data)
    return CryptRC4._pure_python_rc4(key).decrypt(data)


def aes_ecb_encrypt(key: bytes, data: bytes) -> bytes:
    encryptor = Cipher(AES(key), mode=ECB()).encryptor()
    return encryptor.update(data) + encryptor.finalize()


def aes_ecb_decrypt(key: bytes, data: bytes) -> bytes:
    decryptor = Cipher(AES(key), mode=ECB()).decryptor()
    return decryptor.update(data) + decryptor.finalize()


def aes_cbc_encrypt(key: bytes, iv: bytes, data: bytes) -> bytes:
    encryptor = Cipher(AES(key), mode=CBC(iv)).encryptor()
    return encryptor.update(data) + encryptor.finalize()


def aes_cbc_decrypt(key: bytes, iv: bytes, data: bytes) -> bytes:
    decryptor = Cipher(AES(key), mode=CBC(iv)).decryptor()
    return decryptor.update(data) + decryptor.finalize()