#!/usr/bin/env python3
"""
bridge.py  —  serial <-> UDP relay between the Arduino Uno and Godot (Main.gd)

Godot never touches the serial port; it only speaks UDP:
  * it LISTENS  on 127.0.0.1:4242  for telemetry  ("x,y,btn")
  * it SENDS to 127.0.0.1:4243     for LED commands ("L1" / "L0")

This bridge sits in the middle:
  Arduino  --serial line "x,y,btn\\n"-->  bridge  --UDP-->  Godot :4242
  Godot :4243  --UDP "L1"/"L0"-->        bridge  --serial-->  Arduino

Double-click friendly: with no arguments it auto-detects the Arduino port and
keeps the window open on exit so you can read any error. Override if needed:
    python bridge.py --port COM3
    python bridge.py --port COM3 --baud 115200   # baud must match the .ino

Requires pyserial:  pip install pyserial
"""

import argparse
import socket
import sys
import time

try:
    import serial  # pyserial
    from serial.tools import list_ports
except ImportError:
    print("pyserial not installed. Run:  pip install pyserial")
    input("\nPress Enter to close...")
    sys.exit(1)

TELEMETRY_ADDR = ("127.0.0.1", 4242)  # Godot listens here
COMMAND_PORT = 4243                    # Godot sends LED commands here

# Substrings that identify a typical Uno / clone in the port description.
PORT_HINTS = ("arduino", "ch340", "usb-serial", "usb serial", "wchusb", "cp210")


def pick_port() -> str:
    """Return a serial port: the obvious Arduino one, else the only one, else ask."""
    ports = list(list_ports.comports())
    if not ports:
        raise SystemExit("No serial ports found. Is the Uno plugged in?")

    for p in ports:
        blob = f"{p.description} {p.manufacturer or ''}".lower()
        if any(h in blob for h in PORT_HINTS):
            print(f"auto-detected {p.device}  ({p.description})")
            return p.device

    if len(ports) == 1:
        print(f"using only port {ports[0].device}  ({ports[0].description})")
        return ports[0].device

    print("Multiple serial ports found:")
    for i, p in enumerate(ports):
        print(f"  [{i}] {p.device}  {p.description}")
    choice = input("Pick a number: ").strip()
    return ports[int(choice)].device


def run(port: str, baud: int) -> None:
    # UDP socket: sends telemetry to Godot AND receives LED commands from it.
    # Bind to all interfaces ("") not just 127.0.0.1 — on some Windows setups a
    # loopback-only bind won't see packets whose source the sender picked freely.
    udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    udp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    udp.bind(("", COMMAND_PORT))
    udp.setblocking(False)

    # Open the serial port. A short timeout keeps readline() from blocking forever.
    ser = serial.Serial(port, baud, timeout=0.05)
    time.sleep(2.0)  # Uno auto-resets when the port opens; wait for the sketch to boot
    ser.reset_input_buffer()
    print(f"bridge up: {port}@{baud}  ->  UDP {TELEMETRY_ADDR}, <- UDP :{COMMAND_PORT}")
    print("leave this window open. Ctrl+C to quit.")

    try:
        while True:
            # 1) Arduino -> Godot: forward each complete telemetry line.
            line = ser.readline()  # b"x,y,btn\r\n" or b"" on timeout
            if line:
                text = line.strip()
                if text:
                    udp.sendto(text, TELEMETRY_ADDR)

            # 2) Godot -> Arduino: drain any pending LED commands, newest applied last.
            while True:
                try:
                    data, src = udp.recvfrom(64)
                except BlockingIOError:
                    break
                except ConnectionResetError:
                    # Windows: a prior sendto hit a closed port; ICMP resets recv. Ignore.
                    break
                cmd = data.strip()
                if cmd in (b"L1", b"L0"):
                    ser.write(cmd + b"\n")
                    ser.flush()
                    print(f"cmd {cmd.decode()} from {src} -> serial")
                else:
                    print(f"ignored UDP {data!r} from {src}")
    except KeyboardInterrupt:
        pass
    finally:
        ser.close()
        udp.close()
        print("\nbridge closed.")


def main() -> None:
    ap = argparse.ArgumentParser(description="Arduino <-> Godot serial/UDP bridge")
    ap.add_argument("--port", help="serial port, e.g. COM3 (auto-detected if omitted)")
    ap.add_argument("--baud", type=int, default=115200, help="must match JoystickBridge.ino")
    args = ap.parse_args()

    try:
        port = args.port or pick_port()
        run(port, args.baud)
    except Exception as e:
        # Keep the window open so double-click users can actually read the error.
        print(f"\nERROR: {e}")
    input("\nPress Enter to close...")


if __name__ == "__main__":
    main()