#define LED1 11 // Which I/O pins are we using
#define LED2 10
#define DEBUG

void setup() {
  Serial.begin(9600); // Serial object set with "No Line Ending"
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
}

void loop() {
  int goodBadFlag; // Was the input good or bad?
  int LEDValue;

  #ifdef DEBUG // NOTE
  Serial.println(" ");
  #endif // ...end

  goodBadFlag = GetInput(&LEDValue);

  #ifdef DEBUG // NOTE
  Serial.print("flag = ");
  Serial.print(goodBadFlag);
  Serial.print(" LEDValue = ");
  Serial.print(LEDValue);
  #endif // ...end

  LightLEDs(LEDValue);
}

/*
void loop() {
  int goodBadFlag; // Was the input good or bad?
  int LEDValue;

  Serial.println();
  goodBadFlag = GetInput(&LEDValue);

  Serial.print("flag = ");
  Serial.print(goodBadFlag);
  Serial.print(" LEDValue = ");
  Serial.print(LEDValue);

  LightLEDs(LEDValue);
} 
*/

/*****
This function is used to get a numeric value from the user via the
Serial monitor. Valid input are the values 0 - 3.
Argument list:
int *which: the value entered by the user
Return value:
int: 0 if the value is bad, 1 if good
*****/
int GetInput(int *which) {
  char c;
  int temp = -1;
  *which = temp;

  while (true) {
    if (Serial.available() > 0) {
      c = Serial.read();
      if (isdigit(c)) { // If they entered a digit character
        temp = c - '0'; // Subtract ASCII zero from the digit character
        if (temp >= 0 && temp < 4) { // Is the value within range?
          *which = temp;
          return 1; // Yep, it's good
        }
      }
      return 0; // If we get here, it's bad input
    }
  }
}

/*****
This function is used to illuminate the correct combinations of LEDs
according to the value of which
Argument list:
int combo: key for lighting LEDs: 0=none, 1=LED1, 2=LED2, 3=both
Return value:
void
*****/
void LightLEDs(int combo) {
  switch(combo) {
    case 0: // both off
      digitalWrite(LED1, LOW);
      digitalWrite(LED2, LOW);
      break;
    case 1: // 1 on, 2 off
      digitalWrite(LED1, HIGH);
      digitalWrite(LED2, LOW);
      break;
    case 2: // 1 off, 2 on
      digitalWrite(LED1, LOW);
      digitalWrite(LED2, HIGH);
      break;
    case 3: // both on
      digitalWrite(LED1, HIGH);
      digitalWrite(LED2, HIGH);
      break;
    default:
      Serial.println("Control should never get here");
      break;
  }
}