#!/usr/bin/env python3
"""Listen on RX while sending candidate RCP-TX7 host-response frames.

Windows usually allows only one process to open a COM port, so this script
combines capture and transmit in one pyserial session.
"""

from __future__ import annotations

import argparse
import datetime as dt
import sys
import time

try:
    import serial
except ImportError:
    print(
        "Missing dependency: pyserial\n"
        "Install it with: python -m pip install pyserial",
        file=sys.stderr,
    )
    raise SystemExit(2)


def parse_hex_bytes(text: str) -> bytes:
    normalized = text.replace(",", " ").replace("0x", "").replace("0X", "")
    parts = normalized.split()
    try:
        values = [int(part, 16) for part in parts]
    except ValueError as exc:
        raise argparse.ArgumentTypeError(f"invalid hex byte list: {text}") from exc
    if not values:
        raise argparse.ArgumentTypeError("hex frame cannot be empty")
    if any(value < 0 or value > 0xFF for value in values):
        raise argparse.ArgumentTypeError("hex values must be bytes")
    return bytes(values)


def hex_preview(data: bytes) -> str:
    return " ".join(f"{byte:02X}" for byte in data)


def ascii_preview(data: bytes) -> str:
    return "".join(chr(byte) if 32 <= byte <= 126 else "." for byte in data)


def make_logger(path: str | None):
    log_file = open(path, "a", encoding="utf-8") if path else None

    def emit(line: str) -> None:
        print(line)
        if log_file:
            log_file.write(line + "\n")
            log_file.flush()

    return emit, log_file


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description="Capture RX frames while sending candidate TX responses."
    )
    parser.add_argument("--port", required=True, help="serial port, for example COM3")
    parser.add_argument("--baud", type=int, default=38400)
    parser.add_argument(
        "--tx-frame",
        type=parse_hex_bytes,
        default=parse_hex_bytes("00 00 00 00 80 DA"),
        help="hex frame to send on TXD",
    )
    parser.add_argument("--repeat", type=int, default=5)
    parser.add_argument("--interval", type=float, default=0.2)
    parser.add_argument(
        "--delay",
        type=float,
        default=3.0,
        help="seconds to listen before first transmit",
    )
    parser.add_argument(
        "--after",
        type=float,
        default=5.0,
        help="seconds to keep listening after the last transmit",
    )
    parser.add_argument("--frame-size", type=int, default=6)
    parser.add_argument("--chunk-size", type=int, default=64)
    parser.add_argument("--timeout", type=float, default=0.05)
    parser.add_argument("--ascii", action="store_true")
    parser.add_argument("--log", help="append capture/transmit log to this file")
    return parser.parse_args()


def main() -> int:
    args = parse_args()
    emit, log_file = make_logger(args.log)
    frame_buffer = bytearray()

    try:
        with serial.Serial(
            port=args.port,
            baudrate=args.baud,
            bytesize=serial.EIGHTBITS,
            parity=serial.PARITY_NONE,
            stopbits=serial.STOPBITS_ONE,
            timeout=args.timeout,
            write_timeout=1.0,
            rtscts=False,
            dsrdtr=False,
            xonxoff=False,
        ) as ser:
            ser.reset_input_buffer()
            start = time.monotonic()
            next_tx = start + args.delay
            sent = 0
            stop_at = None

            emit(
                f"Listening on {ser.port} at {ser.baudrate} 8N1; "
                f"will send {hex_preview(args.tx_frame)} after {args.delay:.1f}s"
            )

            while True:
                now = time.monotonic()

                if sent < args.repeat and now >= next_tx:
                    ser.write(args.tx_frame)
                    ser.flush()
                    stamp = dt.datetime.now().strftime("%H:%M:%S.%f")[:-3]
                    emit(f"{stamp}  TX frame {len(args.tx_frame):03d}  {hex_preview(args.tx_frame)}")
                    sent += 1
                    next_tx = now + args.interval
                    if sent == args.repeat:
                        stop_at = now + args.after

                data = ser.read(args.chunk_size)
                if data:
                    if args.frame_size:
                        frame_buffer.extend(data)
                        while len(frame_buffer) >= args.frame_size:
                            frame = bytes(frame_buffer[: args.frame_size])
                            del frame_buffer[: args.frame_size]
                            stamp = dt.datetime.now().strftime("%H:%M:%S.%f")[:-3]
                            emit(f"{stamp}  RX frame {args.frame_size:03d}  {hex_preview(frame)}")
                            if args.ascii:
                                emit(f"{'':14} ASCII      {ascii_preview(frame)}")
                    else:
                        stamp = dt.datetime.now().strftime("%H:%M:%S.%f")[:-3]
                        emit(f"{stamp}  RX {len(data):03d} bytes  {hex_preview(data)}")

                if stop_at is not None and now >= stop_at:
                    break

    except KeyboardInterrupt:
        emit("Stopped.")
        return 0
    except serial.SerialException as exc:
        print(f"Serial error: {exc}", file=sys.stderr)
        return 1
    finally:
        if log_file:
            log_file.close()

    return 0


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