//Declare and assign led pins
const int LEDS[16] = {27, 26, 23, 22, 21, 19, 18, 5, 17, 16, 4, 0, 2, 15, 12, 14};
const int IN_LEDS[3][4] = {{23, 22, 21, 19}, {18, 5, 17, 16}, {27, 26, 26, 27}};
const int OUT_LEDS[6] = {4, 0, 2, 15, 12, 14};

//Variables for arithmetic operation
long input1, input2, result, op;

void setup() {
  Serial.begin(115200);

  //Mark all 16 Led Pins as OUTPUT
  for (int a = 0; a < 16; a++) {
    pinMode(LEDS[a], OUTPUT);
  }
}

//FOR INPUT 1 LEDs, INPUT 2 LEDs, and Operator LEDs
//Funtion for converting integer into byte array, byte array
//Match Led output pins into byte array, turn on Led when byte is 1
void outLeds(int num, int index) {
  String binaryStr = String( num, BIN);
  binaryStr = ("0000" + binaryStr).substring(binaryStr.length());

  for (int a  = 0; a < 4; a++) {
    digitalWrite(IN_LEDS[index][a], binaryStr.charAt(a) == '1' ? HIGH : LOW);
  }
}

//FOR OUTPUT LEDs
void resultLeds(int num) {
  String binaryStr = String( num, BIN);
  binaryStr = ("000000" + binaryStr).substring(binaryStr.length());

  for (int a  = 0; a < 6; a++) {
    digitalWrite(OUT_LEDS[a], binaryStr.charAt(a) == '1' ? HIGH : LOW);
  }
}

void loop() {
  Serial.println("Input any key to start... ");
  while (Serial.available() == 0)
  {
  }

  //Wait for any input in the terminal to start
  Serial.readString();

   //Turn OFF all LEDs
  for (int a = 0; a < 16; a++) {
    digitalWrite(LEDS[a], LOW);
  }

  Serial.print("Enter the first input (Red LED): ");
  while (Serial.available() == 0)
  {
  }

  //Wait for input 1
  input1 = Serial.readString().toInt();
  Serial.println(input1);

  //Call function to turn on LEDs for Input 1
  outLeds(input1, 0);

  Serial.print("Enter the second input (Green LED): ");
  while (Serial.available() == 0)
  {
  }

   //Wait for input 2
  input2 = Serial.readString().toInt();
  Serial.println(input2);

  //Call function to turn on LEDs for Input 2
  outLeds(input2, 1);

  Serial.println("\nOperation:");
  Serial.println("[1] Addition (Yellow LED)");
  Serial.println("[2] Subtraction (Blue LED)");
  Serial.print("Choose your operation: ");
  while (Serial.available() == 0) {
  }

  //Wait for operator input 
  op = Serial.readString().toInt();
  Serial.println(op);
  outLeds(op, 2);

  //Perform arithmetic operation
  switch (op) {
    case 1:
      result = input1 + input2;
      break;
    case 2:
      result = input1 - input2;
      break;
    default:
      Serial.println("Invalid input.");
  }

  //Display the result of the operation
  Serial.print("Result (Cyan LED): ");
  Serial.println(result);

  //Call funtion to turn on LEDs for Output
  resultLeds(result);
}