#include <Keypad.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2);

const byte ROWS = 4; 
const byte COLS = 4; 
char hexaKeys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};
byte rowPins[ROWS] = {1, 2, 3, 4}; 
byte colPins[COLS] = {5, 6, 7, 8}; 
Keypad customKeypad = Keypad(makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS); 

char step;
char simbol;
enum {x, y, operasi, hitung};
String strx = "", stry="";
int intx, inty;
int hasil;

void setup() {
  Serial.begin(9600);
  //lcd.begin();  
  lcd.init();
  lcd.backlight();
  // lcd.setCursor(0,0);
  // lcd.print("Aritmatika");
}

void loop() {
  char customKey = customKeypad.getKey();
  switch(step){
  	case x:
      if(customKey){
        if(customKey == 'A' || customKey == 'B' || customKey == 'C' ||customKey == 'D'){
          step = operasi;
        }
        else{
          strx+=customKey;
          lcd.setCursor(0,0);
          lcd.print(strx);
        }
      }break;

    case operasi:
      if(customKey){
        if(customKey == 'A'){
          	lcd.print('+');
          	simbol = '+';
          	step = y;
        }
        else if(customKey == 'B'){
          	lcd.print('-');
          	simbol = '-';
          	step = y;
        }
        else if(customKey == 'C'){
          	lcd.print('x');
          	simbol = 'x';
          	step = y;
        }
        else if(customKey == 'D'){
          	lcd.print(':');
          	simbol = ':';
          	step = y;
        }
        else{
            strx+= customKey;
            lcd.setCursor(0,0);
            lcd.print(x);
        }
      }break;
    
    case y:
      if(customKey){
        if(customKey == '#'){
          step = hitung;
        }
        else{
          stry+=customKey;
          lcd.print(stry);
        }
      }break;

    case hitung:
      intx = strx.toInt();  //ubah ke integer dari float
      inty = stry.toInt();
      if (simbol == '+'){
        hasil = intx + inty;
      }
      else if (simbol == '-'){
        hasil = intx - inty;
      }
      else if(simbol == 'x'){
        hasil = intx * inty;
      }
      else if (simbol == ':'){
        hasil = intx / inty;
      }
    	lcd.setCursor(0, 1);
      lcd.println("=");
    	lcd.print(hasil);

    if(customKey){
      if(customKey == '*'){
        strx = "";
        stry = "";
        lcd.clear();
        step = x;
      }
    }
    break;
  }
}