#include <Arduino.h>

#define LED_1_PIN 19 // most left
#define LED_2_PIN 18
#define LED_3_PIN 5
#define LED_4_PIN 17
#define LED_5_PIN 16 // most right

#define BTN_LEFT_PIN 22
#define BTN_RIGHT_PIN 23

#define LED_MODE_OFF 0
#define LED_MODE_LEFT_TO_RIGHT 1
#define LED_MODE_RIGHT_TO_LEFT 2
#define DELAY_TIME 100

// Globale Variablen
int led_array[5] = {LED_1_PIN, LED_2_PIN, LED_3_PIN, LED_4_PIN, LED_5_PIN};
int led_index = 0;
int direction = LED_MODE_OFF;
unsigned long last_led_update_time = 0;

// Funktionsprototyp
void run_led_chaser(int direction);

void setup()
{
  // put your setup code here, to run once:
  pinMode(BTN_LEFT_PIN, INPUT_PULLDOWN);
  pinMode(BTN_RIGHT_PIN, INPUT_PULLDOWN);
  // LEDS
  for (int i = 0; i < 5; i++)
  {
    pinMode(led_array[i], OUTPUT);
  }
}

void loop()
{
  // put your main code here, to run repeatedly

  if (HIGH == digitalRead(BTN_LEFT_PIN))
  {
    direction = LED_MODE_RIGHT_TO_LEFT;
  }
  else
  {
    direction = LED_MODE_LEFT_TO_RIGHT;
  }

  run_led_chaser(direction);
}

void run_led_chaser(int direction)
{
  auto current_millis = millis();
  if (current_millis - last_led_update_time > DELAY_TIME)
  {
    last_led_update_time = current_millis;
    // time to do something.
    digitalWrite(led_array[led_index], LOW);
    switch (direction)
    {
    case LED_MODE_LEFT_TO_RIGHT:
      led_index++;
      if (led_index > 4)
      {
        led_index = 0;
      }
      break;
    case LED_MODE_RIGHT_TO_LEFT:
      led_index--;
      if (led_index < 0)
      {
        led_index = 4;
      }
      break;
    default:
      //LED_MODE_OFF -> return early.
      return;
      break;
    }
    digitalWrite(led_array[led_index], HIGH);
  }
}