//AE CODE USE THIS CODE

#include <Keypad.h>
#include <Wire.h> 
#include <LiquidCrystal.h>

LiquidCrystal lcd(13, 12, 11, 10, 9, 8);

long first = 0; 
long second = 0;
double total = 0;

char customKey;
const byte ROWS = 4;
const byte COLS = 4;

char keys [ROWS] [COLS] = {

{'1', '2','3','+'},
{'4','5', '6', '-'},
{'7', '8', '9', '*'},
{'C', '0', '=', '/'}
};
byte rowPins [ROWS] = {7,6,5,4};
byte colPins[COLS] =  {3,2,1,0};

Keypad customKeypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup() {

lcd.begin(16, 2);  // start
for(int i=0;i<=3;i++); 
lcd.setCursor(0,0);
lcd.print ("Ahmad Aprilian");
lcd.setCursor(0,1);
lcd.print ("SPE XI TEI 2");
delay(4000);
lcd.clear();
lcd.setCursor(0, 0);
}

void loop() {

customKey = customKeypad.getKey();
switch(customKey)
{
case '0'... '9':
lcd.setCursor(0,0);
first = first * 10 + (customKey - '0');
lcd.print(first);
break;

case '+':

first = (total != 0 ? total : first);
lcd.setCursor(0,1);
lcd.print("+");
second = SecondNumber();
total = first + second;
lcd.setCursor(0,3);
lcd.print(total);
first = second = 0;
break;

case '-':

first = (total != 0 ? total : first);
lcd.setCursor(0,1);
lcd.print("-");
second = SecondNumber();
total = first - second;
lcd.setCursor(0,3); 
lcd.print(total);
first = second = 0;
break;

case'=':

first = (total != 0 ? total : first);
lcd.setCursor(0,1);
lcd.print("*");
second = SecondNumber();
total = first * second;
lcd.setCursor(0,3);
lcd.print(total);
first = 0, second = 0;
break;

case '/':
first = (total != 0 ? total : first);
lcd.setCursor(0,1); 
lcd.print("/");
second = SecondNumber();
lcd.setCursor(0,3);

second == 0 ? lcd.print("Invalid") : total = (float)first / (float) second;

lcd.print(total);
first = 0, second = 0;
break;

case 'C':
total = 0;
lcd.clear();
break;
}
}
long SecondNumber()
{
  while(1)
  {
    customKey = customKeypad.getKey();
    if(customKey >= '0' && customKey <= '9')
    {
      second = second *10 + (customKey - '0');
      lcd.setCursor(0,2);
      lcd.print(second );
    }
    if(customKey == '=')break;
  }
  return second ;
}