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

// LCD configuration
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Variables to store the registered UID and flags
String registeredUID = "";
bool manualRegistration = false;
bool readingRFID = false;

void setup() {
  Serial.begin(9600); // Initialize serial communications with the PC
  lcd.init(); // Initialize the LCD
  lcd.backlight(); // Turn on the LCD backlight

  lcd.setCursor(0, 0);
  lcd.print("Scan or Input UID");

  Serial.println("Type 'R' to register manually, 'S' to start reading RFID or place your card to the reader...");
  Serial.println();
}

void loop() {
  // Check for manual input
  if (Serial.available()) {
    char command = Serial.read();
    if (command == 'R' || command == 'r') {
      manualRegistration = true;
      Serial.println("Enter the UID manually (e.g., 12345678):");
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Enter UID:");
    } else if (command == 'S' || command == 's') {
      readingRFID = true;
      Serial.println("Reading RFID UID...");
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Reading RFID...");
    }
  }

  // Manual Registration
  if (manualRegistration && Serial.available()) {
    registeredUID = Serial.readStringUntil('\n');
    registeredUID.trim(); // Remove any leading/trailing whitespace
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Registered UID:");
    lcd.setCursor(0, 1);
    lcd.print(registeredUID);
    Serial.println("UID registered manually.");
    manualRegistration = false;
    delay(3000);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Scan or Input UID");
  }

  // Simulated RFID Reading
  if (readingRFID && Serial.available()) {
    String content = Serial.readStringUntil('\n');
    content.trim();
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("UID Read:");
    lcd.setCursor(0, 1);
    lcd.print(content);
    Serial.print("UID Read: ");
    Serial.println(content);

    if (registeredUID == "") {
      registeredUID = content;
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Registered UID:");
      lcd.setCursor(0, 1);
      lcd.print(content);
      Serial.println("UID registered.");
    } else if (content == registeredUID) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("UID Matched!");
      lcd.setCursor(0, 1);
      lcd.print(content);
      Serial.println("Authorized access.");
    } else {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Access denied!");
      lcd.setCursor(0, 1);
      lcd.print(content);
      Serial.println("Access denied.");
    }

    delay(3000); // Delay for display
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Scan or Input UID");
    readingRFID = false;
  }
}