import binascii
import struct

import pytest

from .helpers import Suite

@pytest.mark.integration_test
def test_crc32():
    # FIXME: Stub
    # crc = 0xFFFFFFFF
    # byt = 0x61
    # => (crc >> 8) ^ _CRC32_Table[(crc & 0xFF) ^ byt]
    # (crc >> 8) = 0x00FFFFFF
    # => 0x00FFFFFF ^ _CRC32_Table[(crc & 0xFF) ^ byt]
    # (crc & 0xFF) = 0xFF
    # => 0x00FFFFFF ^ _CRC32_Table[0xFF ^ byt]
    # 0xFF ^ 0x61 = 0x9E
    # => 0x00FFFFFF ^ _CRC32_Table[0x9E]
    # _CRC32_Table[0x9E] = 0x17b7be43
    # => 0x00FFFFFF ^ 0x17b7be43

    code_py = """
def _crc32_f(crc: u32, byt: u8) -> u32:
    return 16777215 ^ 397917763

def testEntry(data: bytes) -> u32:
    return 4294967295 ^ _crc32_f(4294967295, data[0])
"""
    exp_result = binascii.crc32(b'a')

    result = Suite(code_py).run_code(b'a')

    # exp_result returns a unsigned integer, as is proper
    exp_data = struct.pack('I', exp_result)
    # ints extracted from WebAssembly are always signed
    data = struct.pack('i', result.returned_value)

    assert exp_data == data