from protocan.periph28335 import (
    bits_lsb_first, build_command, build_read_registers,
    build_write_register, crc16_modbus, word_from_bits,
)


def test_read_request_matches_delphi_byte_order():
    request = build_read_registers(16, 24, 64)
    assert request[:6] == bytes.fromhex("10 03 00 18 00 40")
    assert int.from_bytes(request[-2:], "little") == crc16_modbus(request[:-2])


def test_write_and_command_use_register_127():
    request = build_write_register(16, 7, 0x1234)
    assert request[:6] == bytes.fromhex("10 06 00 07 12 34")
    command = build_command(16, 15)
    assert command[:6] == bytes.fromhex("10 06 00 7F 80 00")


def test_bits_keep_original_lsb_first_order():
    bits = bits_lsb_first(0x8005)
    assert bits[0] and bits[2] and bits[15]
    assert word_from_bits(bits) == 0x8005