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

LiquidCrystal screen(12, 11, 10, 9, 8, 7);

const byte NUM_ROWS = 4;
const byte NUM_COLS = 4;
byte rowPins[NUM_ROWS] = {5, 4, 3, 2};
byte colPins[NUM_COLS] = {A3, A2, A1, A0};
char keypadKeys[NUM_ROWS][NUM_COLS] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'^', '0', '=', '/'}
};

Keypad myKeypad = Keypad(makeKeymap(keypadKeys), rowPins, colPins, NUM_ROWS, NUM_COLS);

uint64_t displayValue = 0;

void showWelcomeScreen() {
  screen.print("Welcome");
  screen.setCursor(3, 1);
  String welcomeMsg = "Calculator";
  for (byte i = 0; i < welcomeMsg.length(); i++) {
    screen.print(welcomeMsg[i]);
    delay(50);
  }
  delay(500);
}

void blinkCursor() {
  if (millis() / 250 % 2 == 0) {
    screen.cursor();
  } else {
    screen.noCursor();
  }
}

char currentOperation = 0;
String storedValue = "";
String inputValue = "";
uint64_t inputDecimal;
bool hasDecimal = false;

double performCalculation(char op, double left, double right) {
  switch (op) {
    case '+': return left + right;
    case '-': return left - right;
    case '*': return left * right;
    case '/': return left / right;
    case '^': return pow(left, right); // Add power calculation
  }
}

void handleInput(char key) {
  if ('-' == key && inputValue == "") {
    inputValue = "-";
    screen.print("-");
    return;
  }

  switch (key) {
    case '+':
    case '-':
    case '*':
    case '/':
    case '^': // Handle ^ operator
      if (!currentOperation) {
        storedValue = inputValue;
        inputValue = "";
      }
      currentOperation = key;
      screen.setCursor(0, 1);
      screen.print(key);
      screen.setCursor(inputValue.length() + 1, 1);
      return;

    case '=':
      float leftOperand = storedValue.toDouble();
      float rightOperand = inputValue.toDouble();
      storedValue = String(performCalculation(currentOperation, leftOperand, rightOperand));
      inputValue = "";
      // screen.clear();
      screen.setCursor(5, 5);
      screen.print(storedValue);
      // screen.setCursor(0, 1);
      // screen.print(currentOperation);
      return;
  }

  if ('.' == key && inputValue.indexOf('.') >= 0) {
    return;
  }

  if ('.' != key && inputValue == "0") {
    inputValue = String(key);
  } else if (key) {
    inputValue += String(key);
  }

  screen.print(key);
}

void setup() {
  Serial.begin(115200);
  screen.begin(16, 2);

  showWelcomeScreen();
  screen.clear();
  screen.cursor();

  screen.setCursor(1, 0);
}

void loop() {
  blinkCursor();

  char key = myKeypad.getKey();
  if (key) {
    handleInput(key);
  }
}