/*
  Forum: https://forum.arduino.cc/t/variable-types-used-in-state-machine/1405843
  Wokwi: https://wokwi.com/projects/441646568487244801

*/

constexpr uint8_t analogPins[] = {A3, A4, A5};   // analog pin names for the LEDs
constexpr uint8_t ledNumber = sizeof(analogPins) / sizeof(analogPins[0]);

unsigned long base_time_increment = 150;                   // increment of time between LEDs
unsigned long base_time_offset  = 200;                      // time added to all of the time_limits
int directionState;
int lastDirection;
int step  = 0;
unsigned long previousMillis;

void setup() {
  Serial.begin(115200);
  pinMode(A0, INPUT_PULLUP);
  directionState = digitalRead(A0);
  lastDirection = directionState;
  allLedsOn();
}

void loop() {
  directionState = digitalRead(A0);        // get current status of button
  if (directionState != lastDirection) {
    lastDirection = directionState;
    delay(50);  // Simple debouncing!
    allLedsOn();

  }
  handleTiming();
}

void handleTiming() {
  constexpr int addedSteps {10};
  if (millis() - previousMillis > base_time_offset + base_time_increment * (step + 1)) {
    if (step >= ledNumber + addedSteps) {
      allLedsOn();
    } else {
      if (step < ledNumber && step >= 0) {
        byte no = (lastDirection) ? step : ledNumber - step - 1;
        digitalWrite(analogPins[no], LOW);
      }
      step++;
    }
  }
}

void allLedsOn() {
  for (int i = 0; i < ledNumber; i++) {
    pinMode(analogPins[i], OUTPUT);
    digitalWrite(analogPins[i], HIGH);  // initialize the state of the LEDs
  }
  previousMillis = millis();
  step = 0;
}