//cpp  With the support of ChatGPT


const int ledPins[] = {2, 3, 4, 5};
const int ledCount = 4;

void setup() {
  Serial.begin(9600);


  // Setup LED pins
  for (int i = 0; i < ledCount; i++) {
    pinMode(ledPins[i], OUTPUT);
    digitalWrite(ledPins[i], LOW);
  }

  Serial.println("Receiver ready.");
}

void loop() {
  if (Serial.available()) {
    String cmd = Serial.readStringUntil('\n');
    Serial.println("Received: " + cmd);

    processCommand(cmd);
  }
}

void processCommand(String cmd) {
  cmd.trim(); 

  // Expected format:   LED <num> <ON/OFF>
  // Example:            LED 3 ON

  // Split into 3 parts
  int firstSpace  = cmd.indexOf(' ');
  int secondSpace = cmd.indexOf(' ', firstSpace + 1);

  if (firstSpace == -1 || secondSpace == -1) return;

  String token1 = cmd.substring(0, firstSpace);          // "LED"
  String token2 = cmd.substring(firstSpace + 1, secondSpace); // number
  String token3 = cmd.substring(secondSpace + 1);        // ON or OFF

  if (token1 != "LED") return;

  int ledNum = token2.toInt();
  bool state = (token3 == "ON");

  Operate_Pin(ledNum, state);
}

void Operate_Pin(int ledNum, bool state) {
  if (ledNum < 2 || ledNum > 5) {
    Serial.println("Invalid LED Number!");
    return;
  }

  digitalWrite(ledNum, state ? HIGH : LOW);

  Serial.print("LED ");
  Serial.print(ledNum);
  Serial.print(" turned ");
  Serial.println(state ? "ON" : "OFF");
}