import sys
import os
import struct
import ctypes

ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if ROOT not in sys.path:
    sys.path.insert(0, ROOT)

from pymsc.lib1553.structures import Udp1553Header, Udp1553Message, CommandWord
from pymsc.lib1553.constants import Marker
from pymsc.lib1553.messages.a3_graphic_setting import MsgA3Payload
from pymsc.lib1553.message_base import BaseMessage


def test_base_message_pack_inverted_cw():
    # Create BaseMessage for A3
    # is_transmit=True -> include payload in packed bytes
    msg = BaseMessage('A3', MsgA3Payload, sub_addr=3, frequency=0, is_transmit=True)
    packed = msg.pack()
    # Find CTRL_BEGIN marker somewhere in the packed bytes (may be without Udp1553Header)
    ctrl_begin = struct.pack('<H', Marker.CTRL_BEGIN)
    pos = packed.find(ctrl_begin)
    assert pos != -1, 'CTRL_BEGIN not found in packed bytes'

    wrapper = Udp1553Message.from_buffer_copy(packed[pos:pos+ctypes.sizeof(Udp1553Message)])
    cw_raw = int(wrapper.cw.raw)
    # payload length after wrapper
    payload_start = pos + ctypes.sizeof(Udp1553Message)
    payload_len = ctypes.sizeof(MsgA3Payload)
    inv_in_packet = struct.unpack_from('<H', packed, payload_start + payload_len)[0]
    assert inv_in_packet == ((~cw_raw) & 0xFFFF)