import hashlib
import struct
import unittest
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes

from proxy.tg_ws_proxy import (
    PROTO_TAG_ABRIDGED,
    PROTO_TAG_INTERMEDIATE,
    _generate_relay_init,
    _try_handshake,
)


KEY = bytes(range(32))
IV = bytes(range(16))
SECRET = bytes.fromhex("0123456789abcdef0123456789abcdef")


def _xor(left: bytes, right: bytes) -> bytes:
    return bytes(a ^ b for a, b in zip(left, right))


def _build_client_handshake(dc_raw: int, proto_tag: bytes) -> bytes:
    packet = bytearray(64)
    packet[8:40] = KEY
    packet[40:56] = IV

    dec_key = hashlib.sha256(KEY + SECRET).digest()
    decryptor = Cipher(algorithms.AES(dec_key), modes.CTR(IV)).encryptor()
    keystream = decryptor.update(b"\x00" * 64)

    plain_tail = proto_tag + struct.pack("<h", dc_raw) + b"\x00\x00"
    packet[56:64] = _xor(plain_tail, keystream[56:64])
    return bytes(packet)


class MtProtoProtocolTests(unittest.TestCase):
    def test_try_handshake_accepts_abridged_proto(self):
        handshake = _build_client_handshake(2, PROTO_TAG_ABRIDGED)

        result = _try_handshake(handshake, SECRET)

        self.assertIsNotNone(result)
        self.assertEqual(result[:3], (2, False, PROTO_TAG_ABRIDGED))

    def test_try_handshake_accepts_intermediate_proto(self):
        handshake = _build_client_handshake(-4, PROTO_TAG_INTERMEDIATE)

        result = _try_handshake(handshake, SECRET)

        self.assertIsNotNone(result)
        self.assertEqual(result[:3], (4, True, PROTO_TAG_INTERMEDIATE))

    def test_generate_relay_init_produces_handshake_sized_packet(self):
        relay_init = _generate_relay_init(PROTO_TAG_ABRIDGED, -2)

        self.assertEqual(len(relay_init), 64)
        self.assertEqual(relay_init[0], relay_init[0] & 0xFF)


if __name__ == "__main__":
    unittest.main()