/*
 * LedBasics.ino  —  Part 1: the minimal round trip.
 *
 * Godot sends "L1" / "L0" over USB serial (via the Python bridge) and this
 * sketch toggles an LED. No sensors yet — Part 2 (JoystickBridge.ino) adds the
 * joystick telemetry going the other way.
 *
 * PROTOCOL
 *   IN (host -> Uno):  "L1" = LED on, "L0" = LED off  (newline-terminated)
 *
 * WIRING
 *   D13 -> 220 ohm resistor -> LED anode (+, long leg)
 *   LED cathode (-, short leg) -> GND
 *   (D13 is also the Uno's onboard LED, so it flashes during every upload —
 *    a free "is this pin alive" check before you've wired anything.)
 */

const uint8_t PIN_LED = 13;   // LED via 220 ohm resistor (also the onboard LED)

char cmdBuf[8];
uint8_t cmdLen = 0;

void setup() {
  Serial.begin(115200);
  pinMode(PIN_LED, OUTPUT);
  digitalWrite(PIN_LED, LOW);
}

void loop() {
  // Commands in from Godot: "L1" / "L0", one per line.
  while (Serial.available() > 0) {
    char c = Serial.read();
    if (c == '\n' || c == '\r') {
      if (cmdLen >= 2 && cmdBuf[0] == 'L') {
        digitalWrite(PIN_LED, cmdBuf[1] == '1' ? HIGH : LOW);
      }
      cmdLen = 0;
    } else if (cmdLen < sizeof(cmdBuf) - 1) {
      cmdBuf[cmdLen++] = c;
    } else {
      cmdLen = 0;  // overflow guard: drop the runt line
    }
  }
}