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

// Define the LCD address and dimensions (change if needed)
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Define the keypad layout
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] = {2, 3, 4, 5};
byte colPins[COLS] = {6, 7, 8, 9};

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

const int resetButtonPin = 10; // Pin for the reset button
String inputString = "";
char operatorChar;
float num1, num2, result;
bool resetFlag = false;

void setup() {
  pinMode(resetButtonPin, INPUT_PULLUP); // Set the reset button pin as input with internal pull-up
  lcd.init(); // Initialize the LCD
  lcd.backlight(); // Turn on the backlight
  lcd.setCursor(0, 0);
  lcd.print("Calculator");
  delay(2000);
  lcd.clear();
}

void loop() {
  char key = keypad.getKey();
  
  // Check if the reset button is pressed
  if (digitalRead(resetButtonPin) == LOW) {
    resetCalculator();
  }

  if (key) {
    if (key >= '0' && key <= '9') {
      inputString += key;
      lcd.print(key);
    } else if (key == '+' || key == '-' || key == '*' || key == '/') {
      num1 = inputString.toFloat();
      operatorChar = key;
      inputString = "";
      lcd.print(key);
    } else if (key == '=') {
      num2 = inputString.toFloat();
      inputString = "";
      switch (operatorChar) {
        case '+':
          result = num2 + num1;
          break;
        case '-':
          result = num1 - num2;
          break;
        case '*':
          result = num1 * num2;
          break;
        case '/':
          if (num2 != 0) {
            result = num1 / num2;
          } else {
            lcd.clear();
            lcd.print("Error: Div0");
            return;
          }
          break;
      }
      lcd.clear();
      lcd.print(result);
    } else if (key == 'C') {
      inputString = "";
      lcd.clear();
    }
  }
}

void resetCalculator() {
  inputString = "";
  num1 = num2 = result = 0;
  operatorChar = '\0';
  lcd.clear();
  lcd.print("Calculator");
  delay(1000);
  lcd.clear();
}