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

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int ledPin = 13;
const int buttonPin = 7; // Button connected to digital pin 7

int attemptCount = 0;
const int maxAttempts = 3;
bool unauthorizedAccess = false;

String correctFullName = "kushal sourav";
String correctRegisterNumber = "2347125";

String enteredFullName = "";
String enteredRegisterNumber = "";

void displayPattern() {
  String initials = String(correctFullName.charAt(0)) + "." + correctFullName.charAt(correctFullName.indexOf(' ') + 1) + ".";
  String lastFourDigits = correctRegisterNumber.substring(correctRegisterNumber.length() - 4);

  lcd.setCursor(0, 0);
  lcd.print(initials+ " " + lastFourDigits);

  String sequence = "";
  int minLength = min(correctFullName.length(), correctRegisterNumber.length());
  for (int i = 0; i < minLength; i++) {
    sequence += String(correctFullName.charAt(i), HEX) + " ";
    sequence += String(correctRegisterNumber.charAt(i), HEX) + " ";
  }

  lcd.setCursor(0, 1);
  lcd.print(sequence);
}

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

  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);

  Serial.begin(9600);
  Serial.println("Enter Full Name:");

  displayPattern();
}

void blinkLED() {
  digitalWrite(ledPin, HIGH);
  delay(500); // 500 ms ON
  digitalWrite(ledPin, LOW);
  delay(500); // 500 ms OFF
}

void loop() {
  if (Serial.available() > 0) {
    String input = Serial.readStringUntil('\n');
    input.trim();

    if (enteredFullName.length() == 0) {
      enteredFullName = input;
      Serial.println("Enter Register Number:");
    } else if (enteredRegisterNumber.length() == 0) {
      enteredRegisterNumber = input;

      if (enteredFullName == correctFullName && enteredRegisterNumber == correctRegisterNumber) {
        Serial.println("Access Granted");
        unauthorizedAccess = false;
        attemptCount = 0;
      } else {
        Serial.println("Access Denied");
        attemptCount++;
        if (attemptCount >= maxAttempts) {
          unauthorizedAccess = true;
        }
      }

      enteredFullName = "";
      enteredRegisterNumber = "";
    }
  }

  if (unauthorizedAccess || digitalRead(buttonPin) == HIGH) {
    blinkLED();
  } else {
    digitalWrite(ledPin, LOW);
  }

  delay(100); 
}