#!/usr/bin/env python3
"""Build BullTron/Daly-style BLE frames observed in the Android app."""

from __future__ import annotations

import argparse


def crc16_modbus_swapped(hex_data: str) -> str:
    data = bytes.fromhex(hex_data)
    crc = 0xFFFF
    for byte in data:
        crc ^= byte
        for _ in range(8):
            if crc & 1:
                crc = (crc >> 1) ^ 0xA001
            else:
                crc >>= 1
    swapped = ((crc & 0xFF00) >> 8) | ((crc & 0x00FF) << 8)
    return f"{swapped:04X}"


def read_frame(start: int, count: int) -> str:
    body = f"D203{start:04X}{count:04X}"
    return body + crc16_modbus_swapped(body)


def write_single_frame(register: int, value: int) -> str:
    body = f"D206{register:04X}{value:04X}"
    return body + crc16_modbus_swapped(body)


def write_multi_frame(start: int, count: int, payload_hex: str) -> str:
    payload = payload_hex.replace(" ", "").upper()
    body = f"D210{start:04X}{count:04X}{payload}"
    return body + crc16_modbus_swapped(body)


def main() -> None:
    parser = argparse.ArgumentParser()
    sub = parser.add_subparsers(dest="cmd", required=True)

    p_read = sub.add_parser("read")
    p_read.add_argument("start", type=lambda x: int(x, 0))
    p_read.add_argument("count", type=lambda x: int(x, 0))

    p_write = sub.add_parser("write")
    p_write.add_argument("register", type=lambda x: int(x, 0))
    p_write.add_argument("value", type=lambda x: int(x, 0))

    p_multi = sub.add_parser("write-multi")
    p_multi.add_argument("start", type=lambda x: int(x, 0))
    p_multi.add_argument("count", type=lambda x: int(x, 0))
    p_multi.add_argument("payload_hex")

    args = parser.parse_args()
    if args.cmd == "read":
        print(read_frame(args.start, args.count))
    elif args.cmd == "write":
        print(write_single_frame(args.register, args.value))
    elif args.cmd == "write-multi":
        print(write_multi_frame(args.start, args.count, args.payload_hex))


if __name__ == "__main__":
    main()