#define back A0
#define ok A3
#define up A1
#define down A2

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);

int layar, menu, absen = 0;

char *nama[] = {"1. HASAN","2. ALIFYA","3. ALVIN","4. ALYA","5. AMBAR",
                "6. ARDAN","7. ATINA","8. FIKA","9. EZRA","10. ROZI",
                "11. KRISNA","12. BARUNA","13. DZAKY","14. FACHRI","15. NAUFAL",
                "16. NURIS","17. RAKHA","18. RASZA","19. ZULFA","20. ULLY",
                "21. VANIA","22. DHANU","23. ZAENAL"};

void setup() {
  // put your setup code here, to run once:
  pinMode(back, INPUT_PULLUP);
  pinMode(ok, INPUT_PULLUP);
  pinMode(up, INPUT_PULLUP);
  pinMode(down, INPUT_PULLUP);
  lcd.init();
  lcd.setCursor(1,0);
  lcd.print("SELAMAT DATANG");
  delay(2000);
  lcd.clear();
}

void loop() {
  // put your main code here, to run repeatedly:
  bacatombol();
  if (layar == 0){ //MAIN MENU
    lcd.setCursor(0,0);
    lcd.print("GRUP A");
    lcd.setCursor(0,1);
    lcd.print("GRUP B");
    
    if(menu == 0){
      lcd.setCursor(14,0);
      lcd.print("<<");
      lcd.setCursor(14,1);
      lcd.print("  ");
    }
    else if(menu == 1){
      lcd.setCursor(14,0);
      lcd.print("  ");
      lcd.setCursor(14,1);
      lcd.print("<<");
    }
  }
  else if(layar == 1){ //GRUP A
    lcd.setCursor(0,0);
    lcd.print("Anggota Grup A");
    lcd.setCursor (0,1);
    lcd.print(nama[absen]);
  }
  else if(layar == 2){
    lcd.setCursor(0,0);
    lcd.print("Anggota Grup B");
    lcd.setCursor (0,1);
    lcd.print(nama[absen]);
  }
}

void bacatombol(){
  if (digitalRead(back)==0){
    if(layar > 0) {
      layar = 0;
      lcd.clear();
    }
  }
  else if (digitalRead(ok)==0){
    lcd.clear();
    if(menu == 0) {
      layar = 1;
      absen = 0;
    }
    else if (menu == 1) {
      layar = 2;
      absen = 12;
    }
  }
  if (digitalRead(up)==0){
    lcd.clear();
    if (layar == 0){
      menu = 0;
    }
    else if (layar == 1) {
      if (absen < 11) {
        absen++;
      }
    }
    else if (layar == 2){
      if (absen < 22) {
        absen++;
      }
    }
    while (digitalRead(up)==0){
      if (digitalRead(up)==1) break;
    }
  }
  else if (digitalRead(down)==0){
    lcd.clear();
    if (layar == 0){
      menu = 1;
    }
    else if (layar == 1) {
      if (absen > 0) {
        absen--;
      }
    }
    else if (layar == 2){
      if (absen > 12) {
        absen--;
      }
    }
    while (digitalRead(down)==0){
      if (digitalRead(down)==1) break;
    }
  }
}