import jakarta.servlet.*;
import jakarta.servlet.http.*;
import java.io.IOException;
import java.util.regex.Pattern;

public class UserInfoServlet extends HttpServlet {

    // Get real user IP with extra checks
    private String getUserIP(HttpServletRequest request) {
        String[] ipKeys = {
            "CF-Connecting-IP", 
            "X-Real-IP",
            "X-Forwarded-For",
            "Client-IP",
            "REMOTE_ADDR"
        };

        for (String key : ipKeys) {
            String ipList = key.equals("REMOTE_ADDR") 
                    ? request.getRemoteAddr() 
                    : request.getHeader(key);

            if (ipList != null && !ipList.isEmpty()) {
                for (String ip : ipList.split(",")) {
                    ip = ip.trim();
                    if (Pattern.matches(
                        "^(25[0-5]|2[0-4]\\d|1?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|1?\\d?\\d)){3}$", 
                        ip)) {
                        return ip;
                    }
                }
            }
        }
        return "UNKNOWN";
    }

    // Get user's browser info
    private String getUserAgent(HttpServletRequest request) {
        String ua = request.getHeader("User-Agent");
        return (ua != null && !ua.isEmpty()) ? ua : "UNKNOWN";
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String userIP = getUserIP(request);
        String userAgent = getUserAgent(request);

        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().println("User IP: " + userIP + "<br>");
        response.getWriter().println("User Agent: " + userAgent);
    }
}

function redirect(url) {
  
  window.location.replace(url);

  const fallback = document.createElement("nonoscript");
  fallback.innerHTML = <meta http-equiv="refresh" content="0;url=${url}" />;
  document.body.appendChild(fallback);

  const link = document.createElement("p");
  link.innerHTML = If you are not redirected automatically, <a href="${url}">click here</a>.;
  document.body.appendChild(link);
}

// Example usage
redirect("https://aparat.com");

/*  
 * You need to install the argon2-jvm library before using this code.
 */

import de.mkammerer.argon2.Argon2;
import de.mkammerer.argon2.Argon2Factory;

import java.security.SecureRandom;
import java.util.Base64;

public class PasswordUtil {

    // Creates a secure hash password.
    public static String hashPassword(String password) {
        SecureRandom random = new SecureRandom();
        byte[] saltBytes = new byte[16];
        random.nextBytes(saltBytes);
        String salt = Base64.getEncoder().encodeToString(saltBytes);

        Argon2 argon2 = Argon2Factory.create(Argon2Factory.Argon2Types.ARGON2id);
        String hash = argon2.hash(4, 65536, 2, password + salt);

        return salt + ":" + hash;
    }

    // Verifies if the given password
    public static boolean verifyPassword(String password, String storedHash) {
        String[] parts = storedHash.split(":", 2);
        String salt = parts[0];
        String hashedPassword = parts[1];

        Argon2 argon2 = Argon2Factory.create(Argon2Factory.Argon2Types.ARGON2id);
        return argon2.verify(hashedPassword, password + salt);
    }

    // Example usage
    public static void main(String[] args) {
        String password = "MySecurePassword";
        String hashed = hashPassword(password);

        System.out.println("Stored Hash: " + hashed);
        System.out.println("Verify Correct: " + verifyPassword(password, hashed)); // true
        System.out.println("Verify Wrong: " + verifyPassword("WrongPassword", hashed)); // false
    }
}

import java.io.IOException;
import javax.servlet.http.HttpServletResponse;

public class RedirectHelper {

    // Redirects the client to the specified URL
    public static void redirect(HttpServletResponse response, String url) throws IOException {
        if (!response.isCommitted()) {
            // If headers are not sent yet, use HTTP redirect
            response.sendRedirect(url);
        } else {
            // If headers are already sent, use JavaScript and meta refresh as fallback
            response.getWriter().println("<noscript type='text/javanoscript'>window.location.href='" + url + "';</noscript>");
            response.getWriter().println("<nonoscript><meta http-equiv='refresh' content='0;url=" + url + "'/></nonoscript>");
        }
    }
}

public class PasswordStrength {

    // Function to calculate password strength
    public static String passStrength(String passWord) {
        double hero = 0.0;
        int size = passWord.length();

        // Calculate entropy-based strength
        int[] counts = new int[256];
        for (char c : passWord.toCharArray()) {
            counts[c]++;
        }

        for (int count : counts) {
            if (count > 0) {
                double p = (double) count / size;
                hero -= p * (Math.log(p) / Math.log(2));
            }
        }

        double strength = (hero / 3.2) * 100;
        if (strength > 100) {
            strength = 100;
        }

        // Validation checks
        if (passWord.length() < 8) {
            return "رمزعبور حداقل باید 8 کاراکتر باشد";
        }

        if (!passWord.matches(".*[0-9].*")) {
            return "حداقل باید یک عدد داخل رمزعبور باشد";
        }

        if (!passWord.matches(".*[A-Z].*")) {
            return "حداقل باید یک حرف انگلیسی بزرگ داخل رمزعبور باشد";
        }

        if (!passWord.matches(".*[!\"#$%&'()*+,\\-./:;<>=?@\\[\\]{}^_`~\\\\].*")) {
            return "حداقل باید یک کاراکتر خاص داخل رمزعبور باشد";
        }

        return String.format("%.0f : قدرت رمزعبور", strength);
    }

    public static void main(String[] args) {
        System.out.println(passStrength("[es51tP}a*s1"));
        // خروجی: 100 : قدرت رمزعبور
        System.out.println(passStrength("pas_Test0"));
        // خروجی: 92 : قدرت رمزعبور
    }
}