from ctypes import *

ECCref_MAX_BITS = 512
ECCref_MAX_LEN = int((ECCref_MAX_BITS + 7) / 8)


class EncodeMixin:
    def encode(self):
        raise NotImplementedError


class ECCrefPublicKey(Structure, EncodeMixin):
    _fields_ = [
        ('bits', c_uint),
        ('x', c_ubyte * ECCref_MAX_LEN),
        ('y', c_ubyte * ECCref_MAX_LEN),
    ]

    def encode(self):
        return bytes([0x04]) + bytes(self.x[32:]) + bytes(self.y[32:])


class ECCrefPrivateKey(Structure, EncodeMixin):
    _fields_ = [
        ('bits', c_uint,),
        ('K', c_ubyte * ECCref_MAX_LEN),
    ]

    def encode(self):
        return bytes(self.K[32:])


class ECCCipherEncode(EncodeMixin):

    def __init__(self):
        self.x = None
        self.y = None
        self.M = None
        self.C = None
        self.L = None

    def encode(self):
        c1 = bytes(self.x[32:]) + bytes(self.y[32:])
        c2 = bytes(self.C[:self.L])
        c3 = bytes(self.M)
        return bytes([0x04]) + c1 + c2 + c3


def new_ecc_cipher_cla(length):
    _cache = {}
    cla_name = "ECCCipher{}".format(length)
    if _cache.__contains__(cla_name):
        return _cache[cla_name]
    else:
        cla = type(cla_name, (Structure, ECCCipherEncode), {
            "_fields_": [
                ('x', c_ubyte * ECCref_MAX_LEN),
                ('y', c_ubyte * ECCref_MAX_LEN),
                ('M', c_ubyte * 32),
                ('L', c_uint),
                ('C', c_ubyte * length)
            ]
        })
        _cache[cla_name] = cla
        return cla


class ECCKeyPair:
    def __init__(self, public_key, private_key):
        self.public_key = public_key
        self.private_key = private_key