from Crypto.Cipher import AES as ccAES
from cryptography.exceptions import InvalidTag

# https://www.pycryptodome.org/src/cipher/modern#gcm-mode

class CipherEncryptor:
	def __init__(self, encor):
		self._encor = encor

		self.authenticate_additional_data = encor.update
		self.update = encor.encrypt

	@property
	def tag(self):
		return self._encor.digest()

	def finalize(self):
		return b''

class CipherDecryptor:
	def __init__(self, decor, tag=None):
		self._decor = decor
		self._tag = tag

		self.authenticate_additional_data = decor.update
		self.update = decor.decrypt

	def finalize(self):
		try:
			#print(repr(self._decor))
			self._decor.verify(self._tag)
		except ValueError:
			raise InvalidTag('tag mismatch')

		return b''

class Cipher:
	def __init__(self, algo, mode, backend=None):
		self._algo = algo
		self._mode = mode

	def _getmode(self):
		if isinstance(self._mode, GCM):
			return ccAES.MODE_GCM

	def _nonce(self):
		return self._mode._iv

	def encryptor(self):
		return CipherEncryptor(ccAES.new(self._algo._key,
		    self._getmode(), nonce=self._nonce()))

	def decryptor(self):
		return CipherDecryptor(ccAES.new(self._algo._key,
		    self._getmode(), nonce=self._nonce()), tag=self._mode._tag)

class AES:
	def __init__(self, key):
		self._key = key

class algorithms:
	AES = AES

class GCM:
	def __init__(self, iv, tag=None):
		self._iv = iv
		self._tag = tag

class modes:
	GCM = GCM