#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

#define nextButton 3
#define selectButton 8

int PresentState = 0; // can't go over 3
int previousState = -1; // to track changes in state

bool isShowTitle = true;
volatile bool nextButtonPressed = false;

unsigned long previousMillis = 0;

void setup()
{
  lcd.init();
  lcd.backlight();
  pinMode(nextButton, INPUT_PULLUP);
  pinMode(selectButton, INPUT_PULLUP);

  attachInterrupt(digitalPinToInterrupt(nextButton), goNext, FALLING);

  
}

void loop()
{

  if (isShowTitle == true)
  {
    lcd.setCursor(4, 0);
    lcd.print("Select");
   lcd.setCursor(3, 1);
   lcd.print("an option");
  }
  else if (isShowTitle == false && (previousState != PresentState))
  {
    updateLCD();
    previousState = PresentState;
  }

  int selectButtonState = digitalRead(selectButton);

  if (selectButtonState == LOW)
  {
    lcd.clear();
    lcd.setCursor(4, 0);
    lcd.print("Selected");
    lcd.setCursor(4, 1);

    switch (PresentState)
    {
    case 1:
      lcd.print("Option A");
      break;

    case 2:
      lcd.print("Option B");
      break;

    case 3:
      lcd.print("Option C");
      break;

    default:
      break;
    }

    // Wait for the select button to be released
    while (digitalRead(selectButton) == LOW)
    {
    }
  }

  nextButtonPressed = false;

}


void handleNextButton()
{
    nextButtonPressed = true;
}


void goNext()
{

  if (millis() - previousMillis >= 400){  
    handleNextButton();  
    if (nextButtonPressed == true){
      PresentState = (PresentState % 3) + 1;
      isShowTitle = false;
    }
    previousMillis = millis();
  }
}


void updateLCD()
{
  lcd.clear();
  lcd.setCursor(2, 0);

  switch (PresentState)
  {
  case 1:
    lcd.print("Option A");
    break;

  case 2:
    lcd.print("Option B");
    break;

  case 3:
    lcd.print("Option C");
    break;

  default:
    break;
  }
}