#include <Keypad.h>

const byte ROWS = 4; // Four rows
const byte COLS = 4; // Four columns

// Define the keymap
char keys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

// Connect to the keypad rows and columns
byte rowPins[ROWS] = {32, 33, 25, 26}; // Connect to the row pins
byte colPins[COLS] = {16, 4, 0, 2}; // Connect to the column pins

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

int result = 0;
int currentNumber = 0;
char lastOp = '\0';

void setup() {
  Serial.begin(115200);
}

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

  if (key) {
    if (key >= '0' && key <= '9') {
      int digit = key - '0';
      currentNumber = currentNumber * 10 + digit;
      Serial.print("Current Number: ");
      Serial.println(currentNumber);
    } else if (key == 'A' || key == 'B' || key == 'C' || key == 'D') {
      if (lastOp != '\0') {
        calculate();
      } else {
        result = currentNumber;
      }
      lastOp = key;
      currentNumber = 0;
      Serial.print("Operator: ");
      Serial.println(lastOp);
    } else if (key == '#') {
      if (lastOp != '\0') {
        calculate();
        lastOp = '\0';
      }
      Serial.print("Final Result: ");
      Serial.println(result);

      // Reset for next calculation
      result = 0;
      currentNumber = 0;
      lastOp = '\0';
    } else if (key == '*') {
      // Reset all variables
      result = 0;
      currentNumber = 0;
      lastOp = '\0';
      Serial.println("Resetting calculator...");
    }
  }
}

void calculate() {
  switch (lastOp) {
    case 'A': result += currentNumber; break;
    case 'B': result -= currentNumber; break;
    case 'C': result *= currentNumber; break;
    case 'D': result /= currentNumber; break;
  }
  Serial.print("Result after operation: ");
  Serial.println(result);
}