// Number of LEDs
#define NR_LED 4
// Number of Switches
#define NR_SWITCHES 5

// Array of Pins on which the LEDs are connected
const int ledPinArray[NR_LED] = {2, 3, 4, 5};
// Array of Pins on which the Switches are connected
const int switchArray[NR_SWITCHES] = {8, 9, 10, 11, 12};

// Number of active switches
int countInput;

/**
Calculates the Range with the given countInput

Returns the calculated range
**/
int calcRange(unsigned int countInput) {
  return 20 * countInput;
}

/**
 Changes the LED state
 **/
void changeLEDStates(int rangeSection) {
  int i = 0;
  
  // Turns the LEDs on which are in the range section
  for(i = 0; i < rangeSection; i++) {
    digitalWrite(ledPinArray[i], HIGH);
  }

  // Turns all other LEDs out
  // for(; i < NR_LED; i++) => Here we take the current counter variable without assigning a new value
  for(; i < NR_LED; i++) {
    digitalWrite(ledPinArray[i], LOW);
  }
}

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

  // Counter variable
  int i = 0;

  // Initialize variable
  countInput = 0;

  // Initialize output pins
  for(i = 0; i < NR_LED; i++) {
    pinMode(ledPinArray[i], OUTPUT);
  }

  // Initialize input pins
  for(i = 0; i < NR_SWITCHES; i++) {
    pinMode(switchArray[i], INPUT);
  }

  Serial.println("Please operate any switch to start.");

  // Endless loop until one switch is operated
  while(!(digitalRead(8) || digitalRead(9) || digitalRead(10) || digitalRead(11) || digitalRead(12))) {
    // Do nothing
  }

  Serial.println("Started.");
}

void loop() {
  int i = 0;
  int countInput = 0;

  // Count the number of active switches
  for(i = 0; i < NR_SWITCHES; i++) {
    if(digitalRead(switchArray[i])) {
      countInput++;
    }
  }

  // Calculate the range
  unsigned int range = calcRange(countInput);

  // Range section number 1
  if(range <= 25) {
    changeLEDStates(1);
  }

  // Range section number 2
  else if(range <= 50) {
    changeLEDStates(2);
  }

  // Range section number 3
  else if (range <= 75) {
    changeLEDStates(3);
  }

  // Range section number 4
  else {
    changeLEDStates(4);
  }
}