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

// Keypad configuration
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] = {13, 12, 11, 10};
byte colPins[COLS] = {7, 6, 5, 4};

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

// I2C LCD configuration
LiquidCrystal_I2C lcd(0x27, 16, 2); // Adjust the I2C address if necessary

String inputString = "";
String operatorChar = "";
int firstNum = 0;
int secondNum = 0;

void setup() {
  lcd.begin(16, 2);

  delay(2000);
  lcd.clear();
  lcd.backlight();
}

void loop() {
  char key = keypad.getKey();

  if (key) {
    // Handle number keys
    if (key >= '0' && key <= '9') {
      inputString += key;
      lcd.print(key);
    }
    // Handle clear key
    else if (key == 'C') {
      inputString = "";
      operatorChar = "";
      firstNum = 0;
      secondNum = 0;
      lcd.clear();
    }
    // Handle operator keys
    else if (key == '+' || key == '-' || key == '*' || key == '/') {
      firstNum = inputString.toInt();
      operatorChar = key;
      inputString = "";
      lcd.print(key);
    }
    // Handle equals key
    else if (key == '=') {
      secondNum = inputString.toInt();
      int result = 0;

      // Perform the calculation based on the operator
      if (operatorChar == "+") {
        result = firstNum + secondNum;
      } else if (operatorChar == "-") {
        result = firstNum - secondNum;
      } else if (operatorChar == "*") {
        result = firstNum * secondNum;
      } else if (operatorChar == "/") {
        result = firstNum / secondNum;
      }


      lcd.setCursor(0,1);
      lcd.print(result);

      // Reset variables for new calculations
      inputString = "";
      operatorChar = "";
      firstNum = 0;
      secondNum = 0;
    }
  }
}