#include <LiquidCrystal.h>
#include<Keypad.h>
 LiquidCrystal lcd(12,11,10,9,8,7);
 const byte KEYPAD_ROWS=4;
 const byte KEYPAD_COLS=4;
 byte rowPins[KEYPAD_ROWS]={5,4,3,2};
 byte colPins[KEYPAD_COLS]={A3,A2,A1,A0};
 char keys[KEYPAD_ROWS][KEYPAD_COLS]={
  {'1','2','3','+'},
  {'4','5','6','-'},
  {'7','8','9','*'},
  {'.','0','=','/'}
 };
 const int RESET_BUTTON_PIN = 6;
 const int pushbuttonRESET=false;
 bool resetButtonState = false;
 bool lastResetButtonState = false;

 Keypad keypad =Keypad(makeKeymap(keys),rowPins,colPins,KEYPAD_ROWS,KEYPAD_COLS);
 uint64_t value=0;
 String inputBuffer = "";
 void CALC_DISPLAY(){
  lcd.print("HCL TECH");
  lcd.setCursor(0,1);
  String message="Calculator";
  for(byte i=0;i<message.length();i++){
    lcd.print(message[i]);
    delay(50);
  }
  delay(500);
 }
 void updateCursor(){
  if(millis() /250 % 2==0){
    lcd.cursor();
    
  }
  else{
    lcd.noCursor();
  }
 }

void setup() {

 Serial.begin(115200);
 lcd.begin(16,2);
 pinMode(pushbuttonRESET, INPUT_PULLUP);
 CALC_DISPLAY();
 lcd.clear();
 lcd.cursor();
 lcd.setCursor(1,0);
}



void processInput(String input)
{
    int result = 0;
    char operation;
    int numIndex = 0;

    for (int i = 0; i < input.length(); i++)
    {
        if (isdigit(input[i]))
        {
            numIndex++;
        }
        else
        {
            operation = input[i];
            break;
        }
    }

    int num1 = input.substring(0, numIndex).toInt();
    int num2 = input.substring(numIndex + 1).toInt();

    switch (operation)
    {
    case '+':
        result = num1 + num2;
        break;
    case '-':
        result = num1 - num2;
        break;
    case '*':
        result = num1 * num2;
        break;
    case '/':
        if (num2 != 0)
        {
            result = num1 / num2;
        }
        else
        {
            lcd.print("Error: Divide by zero");
            return;
        }
        break;
    default:
        lcd.print("Error: Invalid operation");
        return;
    }
    lcd.setCursor(0, 1);
    lcd.print(result);
}
void checkResetButton()
{
    resetButtonState = digitalRead(RESET_BUTTON_PIN);
    if (resetButtonState != lastResetButtonState && resetButtonState == LOW)
    {
        // Reset button is pressed
        lcd.clear();
        inputBuffer = "";
    }
    lastResetButtonState = resetButtonState;
}


void loop()
{
    char key = keypad.getKey();
    if (key != NO_KEY)
    {
        if (key == '=')
        {
            processInput(inputBuffer);
            inputBuffer = "";
        }
        else
        {
            inputBuffer += key;
            lcd.print(key);
        }
    }
    checkResetButton();
}