#!/usr/bin/env python3
import argparse
import struct
from pymodbus.client import ModbusSerialClient


def regs_to_bytes(regs, mode):
    a = regs[0]
    b = regs[1]

    ab = a.to_bytes(2, "big")
    cd = b.to_bytes(2, "big")

    if mode == "ABCD":
        return ab + cd
    if mode == "CDAB":
        return cd + ab
    if mode == "BADC":
        return ab[::-1] + cd[::-1]
    if mode == "DCBA":
        return cd[::-1] + ab[::-1]

    raise ValueError(mode)


def decode_float_candidates(regs):
    out = {}
    for mode in ["ABCD", "CDAB", "BADC", "DCBA"]:
        try:
            raw = regs_to_bytes(regs, mode)
            out[mode] = struct.unpack(">f", raw)[0]
        except Exception as exc:
            out[mode] = f"ERR: {exc}"
    return out


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--port", default="/dev/ttyRS485")
    parser.add_argument("--slave", type=int, default=1)
    parser.add_argument("--baud", type=int, default=9600)
    parser.add_argument("--parity", default="N", choices=["N", "E", "O"])
    parser.add_argument("--stopbits", type=int, default=1)
    parser.add_argument("--bytesize", type=int, default=8)
    parser.add_argument("--address", type=int, default=0)
    parser.add_argument("--count", type=int, default=2)
    parser.add_argument("--timeout", type=float, default=1.5)
    args = parser.parse_args()

    print("--- MODBUS RTU PROBE ---")
    print(f"port={args.port}")
    print(f"slave={args.slave}")
    print(f"baud={args.baud}")
    print(f"parity={args.parity}")
    print(f"address={args.address}")
    print(f"count={args.count}")

    client = ModbusSerialClient(
        port=args.port,
        baudrate=args.baud,
        parity=args.parity,
        stopbits=args.stopbits,
        bytesize=args.bytesize,
        timeout=args.timeout,
    )

    if not client.connect():
        print("[ERROR] Cannot open serial port")
        return 2

    try:
        rr = client.read_input_registers(
            address=args.address,
            count=args.count,
            device_id=args.slave,
        )

        if rr.isError():
            print(f"[ERROR] Modbus error: {rr}")
            return 3

        regs = rr.registers
        print(f"registers={regs}")
        print("float_candidates:")
        for mode, value in decode_float_candidates(regs).items():
            print(f"  {mode}: {value}")

        return 0
    except Exception as exc:
        print(f"[ERROR] No Modbus response: {type(exc).__name__}: {exc}")
        return 3
    finally:
        client.close()


if __name__ == "__main__":
    raise SystemExit(main())