LMS.java

//Import required libraries
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.io.*;
import java.time.LocalDate;
import java.time.temporal.ChronoUnit;
public class LMS {

    static Scanner input=new Scanner(System.in); // Create universal input object
    static String[][] books=new String[10000][6]; // Create books array to store books data
    //0 index for title
    //1 index for author
    //2 index for genre
    //3 index for Book Number
    //4 index for borrowed_by
    //5 index for due_date

    static String[][] members=new String[10000][6]; // Create members array to store members data
    //0 index for Member ID
    //1 index for Name
    //2 index for CNIC
    //3 index for Phone
    //4 index for encryptedPassword
    //5 index for late fees

    static String[][] admin=new String[20][5]; // Create admin array to store admins data
    //0 index for Admin ID
    //1 index for Name
    //2 index for CNIC
    //3 index for Phone
    //4 index for encryptedPassword

    static String[][] systemAdmin=new String[2][5]; // Create systemAdmin array to store System Admin data
    //0 index for Admin ID
    //1 index for Name
    //2 index for CNIC
    //3 index for Phone
    //4 index for encryptedPassword

    // global variables to store values for current logged in Member, Admin and System Admin
    static String loggedInMemberID;
    static String loggedInMemberPassword;
    static int memberExistanceIndex;
    static String loggedInAdminID;
    static String loggedInAdminPassword;
    static int adminExistanceIndex;
    static String loggedInSysAdminID;
    static String loggedInSysAdminPassword;
    static int sysAdminExistanceIndex = 0;

    // Create a default System Admin and save it's details in arrays and file
    static{
        systemAdmin[0][0]="1";
        systemAdmin[0][1]="Jeff";
        systemAdmin[0][2]="61101-8574331-0";
        systemAdmin[0][3]="0335-1234576";
        systemAdmin[0][4]=EncryptPassword("sysAdmin","library101","1");
        saveSysAdmins();
    }

    // load everything at startup
    static {
        MemberLateFeesInitialization();
        try {
            loadMembers();
            loadAdmins();
            loadSysAdmins();
            loadBooks();
        } catch (Exception e) {
            System.err.println("ERROR loading data files: " + e.getMessage());
        }
    }

    // Load members by creating a new file (members.txt)
    public static void loadMembers() {
        File file = new File("members.txt");
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                System.out.println("ERROR creating members.txt file.");
                return;
            }
        }

        // Read its data and store in arrays
        try (Scanner reader = new Scanner(file)) {
            int i = 0;
            while (reader.hasNextLine() && i < members.length) {
                String line = reader.nextLine().trim();
                if (line.isEmpty()) continue; // Skip line if it's empty
                String[] data = line.split(" ");
                for (int j = 0; j < data.length && j < members[0].length; j++) {
                    members[i][j] = data[j];
                    if(j == 1){
                        // Change space between each name of user with "_" for better readability
                        members[i][j] = members[i][j].replace("_", " ") ;
                    }
                }
                i++;
            }
        } catch (IOException e) {
            System.out.println("ERROR reading members.txt file.");
        }
        saveMembers();
    }

    // Save the updated array's data in members.txt
    public static void saveMembers() {
        try (PrintWriter pw = new PrintWriter(new FileOutputStream("members.txt", false))) {
            int n = NotEmpty(members);
            for (int i = 0; i < n; i++) {
                members[i][1] = members[i][1].replace(" ", "_") ;
                pw.printf("%s %s %s %s %s %s%n",
                        members[i][0], members[i][1], members[i][2],
                        members[i][3], members[i][4], members[i][5]
                );
            }
        } catch (IOException e) {
            System.err.println("ERROR saving members: " + e.getMessage());
        }
    }

    public static void loadAdmins() {
        File file = new File("admins.txt");
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                System.out.println("ERROR creating admins.txt file.");
                return;
            }
        }

        try (Scanner reader = new Scanner(file)) {
            int i = 0;
            while (reader.hasNextLine() && i < admin.length) {
                String line = reader.nextLine().trim();
                if (line.isEmpty()) continue;
                String[] data = line.split(" ");
                for (int j = 0; j < data.length && j < admin[0].length; j++) {
                    admin[i][j] = data[j];
                    if(j == 1){
                        admin[i][j] = admin[i][j].replace("_", " ") ;
                    }
                }
                i++;
            }
        } catch (FileNotFoundException e) {
            System.out.println("ERROR loading admin data: " + e.getMessage());
        }
        saveAdmins();
    }
    public static void saveAdmins(){
        try (PrintWriter pw = new PrintWriter(new FileOutputStream("admins.txt", false))) {
            int n = NotEmpty(admin);
            for (int i = 0; i < n; i++) {
                admin[i][1] = admin[i][1].replace(" ", "_") ;

                pw.printf("%s %s %s %s %s%n",
                        admin[i][0], admin[i][1], admin[i][2],
                        admin[i][3], admin[i][4]
                );
            }
        } catch (IOException e) {
            System.err.println("ERROR saving admins: " + e.getMessage());
        }
    }


    public static void loadSysAdmins() {
        File file = new File("sysAdmins.txt");
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                System.out.println("ERROR creating sysAdmins.txt file.");
                return;
            }
        }

        try (Scanner reader = new Scanner(file)) {
            int i = 0;
            while (reader.hasNextLine() && i < systemAdmin.length) {
                String line = reader.nextLine().trim();
                if (line.isEmpty()) continue;
                String[] data = line.split(" ");
                for (int j = 0; j < data.length && j < systemAdmin[0].length; j++) {
                    systemAdmin[i][j] = data[j];
                    if(j == 1){
                        systemAdmin[i][j] = systemAdmin[i][j].replace("_", " ") ;
                    }
                }
                i++;
            }
        } catch (FileNotFoundException e) {
            System.out.println("ERROR loading system system admin data: " + e.getMessage());
        }
    }

    public static void saveSysAdmins() {
        try (PrintWriter pw = new PrintWriter(new FileOutputStream("sysAdmins.txt", false))) {
            int n = NotEmpty(systemAdmin);
            for (int i = 0; i < n; i++) {
                systemAdmin[i][1] = systemAdmin[i][1].replace(" ", "_") ;

                pw.printf("%s %s %s %s %s%n",
                        systemAdmin[i][0], systemAdmin[i][1], systemAdmin[i][2],
                        systemAdmin[i][3], systemAdmin[i][4]
                );
            }
        } catch (IOException e) {
            System.err.println("ERROR saving sysAdmins: " + e.getMessage());
        }
    }


    public static void loadBooks() {
        File file = new File("books.txt");
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                System.out.println("ERROR creating books.txt file.");
                return;
            }
        }

        try (Scanner reader = new Scanner(file)) {
            int i = 0;
            while (reader.hasNextLine() && i < books.length) {
                String line = reader.nextLine().trim();
                if (line.isEmpty()) continue;
                String[] data = line.split(" ");
                for (int j = 0; j < data.length && j < books[0].length; j++) {
                    books[i][j] = data[j];
                    if(j == 0){
                        books[i][j] = books[i][j].replace("_", " ") ;
                    }
                    if (j == 1){
                        books[i][j] = books[i][j].replace("_", " ") ;
                    }
                }
                i++;
            }
        } catch (IOException e) {
            System.out.println("ERROR reading books.txt file.");
        }
    }

    public static void saveBooks() {
        try (PrintWriter pw = new PrintWriter(new FileOutputStream("books.txt", false))) {
            int n = NotEmpty(books);
            for (int i = 0; i < n; i++) {
                books[i][0] = books[i][0].replace(" ", "_");
                books[i][1] = books[i][1].replace(" ", "_");
                pw.printf("%s %s %s %s %s %s%n",
                        books[i][0], books[i][1], books[i][2],
                        books[i][3], books[i][4], books[i][5]
                );
            }
        } catch (IOException e) {
            System.err.println("ERROR saving books: " + e.getMessage());
        }
    }

    // main() function to run everything (main console/first menu)
    public static void main(String[] args) {

        // Run the management system until user wants to terminate the program
        while(true) {
            System.out.println("\n-------------------------------------------------------------");
            System.out.println("                 Library Management System                   ");
            System.out.println("-------------------------------------------------------------");
            System.out.println("1. Member Login");
            System.out.println("2. Admin Login");
            System.out.println("3. System Administrator Login");
            System.out.println("4. Exit Program");

            // Run the loop until user enters correct "choice" integer
            while (true) {
                System.out.print("\nEnter Your Choice(1-4): ");
                // Handle exception due to Miss Match Input by the user
                try {
                    int choice = input.nextInt();
                    input.nextLine();
                    switch (choice) {
                        case 1:

                            if (!(Confirmation())) {
                                break;
                            }

                            if (MemberLogin()) {
                                System.out.println("\nLogged In Successfully");
                                System.out.println("Redirecting to the console......");
                                delay(1500);
                                StudentConsole();
                            } else {
                                System.out.println("Invalid Credentials!");
                                delay(1500);
                            }

                            break;
                        case 2:

                            if (!(Confirmation())) {
                                break;
                            }

                            if (AdminLogin()) {
                                System.out.println("\nLogged In Successfully");
                                System.out.println("Redirecting to the console......");
                                delay(1500);
                                AdminConsole();
                            } else {
                                System.out.println("Invalid Credentials!");
                                delay(1500);
                            }

                            break;
                        case 3:

                            if (!(Confirmation())) {
                                break;
                            }

                            if (SysAdminLogin()) {
                                System.out.println("\nLogged In Successfully");
                                System.out.println("Redirecting to the console......");
                                delay(1500);
                                SysAdminConsole();
                            } else {
                                System.out.println("Invalid Credentials!");
                                delay(1500);
                            }

                            break;
                        case 4:
                            System.out.println("Terminating the Program!");
                            delay(1500);
                            return;
                        default:
                            System.out.println("ERROR! Enter correct choice");
                            delay(1500);
                            break;
                    }
                    break;
                } catch (InputMismatchException ex) { // Catch the exception
                    System.out.println("\nERROR! Enter correct choice");
                    input.nextLine(); // Refresh the buffer
                }
            }
        }

    }

    // A method to add a new System Admin
    public static void AddSystemAdmin() {
        loadSysAdmins(); //Load current System Admin data
        line();
        // If System Admin array limit reached, then increase the limit
        if (NotEmpty(systemAdmin) == systemAdmin.length) {
            System.out.println("System Admin Limit Reached: Increase Limit In Source Code!");
            return;
        }

        // NotEmpty() will return length of "systemAdmin" array and store it as an index
        int index = NotEmpty(systemAdmin);

        // Run Loop until user enters correct information for new System Admin
        while(true) {
            // Handle exception
            try {
                // Enter new Admin details
                System.out.print("Enter First Name: ");
                String firstName = input.nextLine();
                System.out.print("Enter Last Name: ");
                String lastName = input.nextLine();
                System.out.print("Enter Mobile Phone Number (Format: 03xx-xxxxxxx): ");
                String num = input.nextLine();
                System.out.print("Enter CNIC (Format: xxxxx-xxxxxxx-x): ");
                String cnic = input.nextLine();

                // Trim any whitespaces (if exist)
                firstName = firstName.trim();
                lastName = lastName.trim();
                num = num.trim();
                cnic = cnic.trim();

                // If any data is empty, return to the main menu
                if (firstName.isEmpty() || lastName.isEmpty() || num.isEmpty() || cnic.isEmpty()) {
                    System.out.println("All fields (Name, Mobile Phone Number, CNIC) are Required!");
                    return;
                }

                if (!ValidateCNIC(cnic)) {
                    System.out.println("ERROR! Invalid CNIC!");
                    return;
                }

                if (!ValidatePhone(num)) {
                    System.out.println("ERROR! Invalid Mobile Number!");
                    return;
                }

                // The index is -1 from id
                String id = Integer.toString(index + 1);
                // Default Password
                String defaultPassword = "Sys123admin123";
                // Encrypt Password
                String encryptedPassword = EncryptPassword("sysAdmin", defaultPassword, id);

                // Add new System Admin data in "systemAdmin" array
                systemAdmin[index][0] = id;
                systemAdmin[index][1] = lastName + "," + firstName;
                systemAdmin[index][2] = cnic;
                systemAdmin[index][3] = num;
                systemAdmin[index][4] = encryptedPassword;

                // Print new System Admin data
                System.out.println("\nSystem Admin ID: " + id);
                System.out.println("Password: " + defaultPassword);

                System.out.println("\nSystem Admin Has Been Added!");

                // Update sysAdmins.txt file with new System Admins data
                UpdateFile("sysAdmin", "yes", id);

                line();
                break; // Break the loop if all the data is successfully saved

            } catch (InputMismatchException ex) { // Handle exception
                System.out.println("\nError! Enter correct information");
                input.nextLine(); // Refresh the buffer
            }
        }
    }

    // Create a function to add a new Admin
    public static void AddAdmin(){
        loadAdmins(); //Load current Admin data
        line();

        // If Admin array limit reached, then increase the limit
        if(NotEmpty(admin) == admin.length){
            System.out.println("Admin Limit Reached: Increase Limit In Source Code!");
            return;
        }

        // NotEmpty() will return length of "admin" array and store it as an index
        int index = NotEmpty(admin);

        // Run Loop until user enters correct information for new Admin
        while(true) {

            try { // Handle exception

                // Enter new Admin details
                System.out.print("Enter First Name: ");
                String firstName = input.nextLine();
                System.out.print("Enter Last Name: ");
                String lastName = input.nextLine();
                System.out.print("Enter Mobile Phone Number (Format: 03xx-xxxxxxx): ");
                String num = input.nextLine();
                System.out.print("Enter CNIC (Format: xxxxx-xxxxxxx-x): ");

                // Trim any whitespaces (if exist)
                String cnic = input.nextLine();
                firstName = firstName.trim();
                lastName = lastName.trim();
                num = num.trim();
                cnic = cnic.trim();

                // If any data is empty, return to the main menu
                if (firstName.isEmpty() || lastName.isEmpty() || num.isEmpty() || cnic.isEmpty()) {
                    System.out.println("All fields (Name,Mobile Phone Number,CNIC) are Required!");
                    return;
                }

                if (!ValidateCNIC(cnic)) {
                    System.out.println("ERROR! Invalid CNIC!");
                    return;
                }

                if (!ValidatePhone(num)) {
                    System.out.println("ERROR! Invalid Mobile Number!");
                    return;
                }

                // Create a unique random id for a new admin
                String id;
                while (true) {
                    int check = 0;
                    id = Integer.toString((int) (1 + Math.random() * 20));
                    for (int i = 0; i < index; i++) {
                        if (admin[i][0].equalsIgnoreCase(id)) {
                            check = 1;
                            break;
                        }
                    }
                    if (check == 0) {
                        break;
                    }
                }

                //Create a default password for a new admin
                String defaultPassword = "admin123";
                String encryptedPassword = EncryptPassword("admin", defaultPassword, id);

                // Add new Admin data in "Admin" array
                admin[index][0] = id;
                admin[index][1] = lastName + "," + firstName;
                admin[index][2] = cnic;
                admin[index][3] = num;
                admin[index][4] = encryptedPassword;

                // Print new Admin data
                System.out.println("\nAdmin ID: " + id);
                System.out.println("Password: " + defaultPassword);

                System.out.println("\nAdmin Has Been Added!");

                // Update admins.txt file with new admin data
                UpdateFile("admin", "yes", id);

                line();
                break; // Break the loop if all the data is successfully saved

            } catch (InputMismatchException ex) { // Catch the exception
                System.out.println("\nERROR! Enter correct information");
                input.nextLine(); // Refresh the buffer
            }
        }
    }

    // Create a function to remove an Admin
    public static void RemoveAdmin() {
        line();
        // Check Admin array if its empty
        if(NotEmpty(admin) == 0){
            System.out.println("The Database is Already Empty");
            return;
        }

        // Run Loop until user enters correct information for an Admin
        while(true) {

            try { // Handle the exception
                System.out.print("Enter Admin ID: ");
                String id = input.nextLine();
                id = id.trim(); // Remove any whitespaces

                try {
                    int idNum = Integer.parseInt(id);
                    if (idNum <= 0 || idNum > admin.length) {
                        System.out.println("ERROR! Invalid ID!");
                    }
                } catch (NumberFormatException e) {
                    System.out.println("ERROR! Invalid ID format!");
                }

                int check = 0; // Check if id exists
                int index = 0; // Find the index of ID

                for (int i = 0; i < NotEmpty(admin); i++) {
                    if (admin[i][0].equals(id)) {
                        check = 1;
                        index = i;
                        break;
                    }
                }

                // Print message if id does not exist
                if (check == 0) {
                    System.out.println("\nAdmin ID " + id + " Does Not Exist In The Database");
                    return;
                }

                // Print removed admin data
                System.out.printf("\n%-15s %-25s %-20s %-20s", "ADMIN ID", "NAME", "CNIC", "PHONE");

                line(); // Call a function to print some lines for formatting

                System.out.printf("%-15s %-25s %-20s %-20s\n", admin[index][0], admin[index][1], admin[index][2], admin[index][3]);

                //Ask for confirmation
                if (!Confirmation()) {
                    System.out.println("\nAdmin Removal Operation Cancelled!");
                    return;
                }

                NullifyRow(index, admin); // Put null values in removed admin indexes
                Normalize(index, admin); // Normalize the data for removed admin indexes

                System.out.println("\nAdmin Removal Operation Successful!");

                // Update the admins.txt file by removing admins data
                UpdateFile("admin", null, id);

                line();
                break; // Break the loop if all the data is successfully saved

            } catch (InputMismatchException ex) { //Catch the exception
                System.out.println("\nERROR! Enter correct details");
                input.nextLine(); // Refresh the buffer
            }
        }
    }

    // Create a function to edit Admin Information
    public static void EditAdminInfo(){
        loadAdmins(); // Load Data
        line();

        // Check if admin array is empty or not
        if(NotEmpty(admin)==0){
            System.out.println("The Database is Empty.");
            return;
        }

        // Run Loop until user enters correct information for Admin
        while(true) {

            try {
                System.out.print("Enter Admin ID: ");
                String id = input.nextLine();
                id = id.trim();

                // Check if ID exist
                boolean found = false;
                for (int i = 0; i < NotEmpty(admin); i++) {
                    if (admin[i][0].equals(id)) {
                        found = true;
                        break;
                    }
                }
                if (!found) {
                    System.out.println("ERRRO! ID not found!");
                    return;
                }

                // Print data
                System.out.printf("\n%-15s %-25s %-20s %-20s", "ADMIN ID", "NAME", "CNIC", "PHONE");

                line(); // For formatting

                int adminIndex = 0;
                int check = 0;

                for (int i = 0; i < NotEmpty(admin); i++) {
                    if ((admin[i][0]).equalsIgnoreCase(id)) {
                        check = 1;
                        adminIndex = i;
                        System.out.printf("%-15s %-25s %-20s %-20s\n", admin[i][0], admin[i][1], admin[i][2], admin[i][3]);
                    }
                }

                if (check == 0) {
                    System.out.println("Admin ID \"" + id + "\" Does Not Exist In The Database");
                    return;
                }

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                System.out.println("\nWrite Updated Info For Concerned Admin.");
                System.out.println("\nPress Enter To Leave Info For That Field As Is, Anything Entered will be Stored In that Field If Appropriate.\n");

                System.out.print("Enter Updated Admin First Name (Enter Current First Name If Last Name Is To Be Updated): ");
                String firstName = input.nextLine();
                firstName = firstName.trim();

                System.out.print("Enter Updated Admin Last Name (Enter Current Last Name If First Name Is Being Updated): ");
                String lastName = input.nextLine();
                lastName = lastName.trim();

                if (!(firstName.isEmpty()) || !(lastName.isEmpty())) {
                    admin[adminIndex][1] = lastName + "," + firstName;
                    System.out.println("Admin Name Updated!");
                } else {
                    System.out.println("Admin Name Retained!");
                }

                System.out.print("Enter Updated CNIC (Format: xxxxx-xxxxxxx-x): ");
                String cnic = input.nextLine();
                cnic = cnic.trim();

                if (!(cnic.isEmpty())) {

                    if (!(ValidateCNIC(cnic))) {
                        System.out.println("ERROR! Invalid CNIC!");
                        return;
                    }

                    admin[adminIndex][2] = cnic;
                    System.out.println("Admin CNIC Updated!");
                } else {
                    System.out.println("Admin CNIC Retained!");
                }

                System.out.print("Enter Updated Mobile Phone Number (Format: 03xx-xxxxxxx): ");
                String num = input.nextLine();
                num = num.trim();

                if (!(num.isEmpty())) {

                    if (!(ValidatePhone(num))) {
                        System.out.println("ERROR! Invalid Phone Number!");
                        return;
                    }

                    admin[adminIndex][3] = num;
                    System.out.println("Admin Phone Number Updated!");
                } else {
                    System.out.println("Admin Phone Number Retained!");
                }

                System.out.println("\nInformation Updated!\n");

                // Update the admins.txt file by removing admins data
                UpdateFile("admin", "yes", id);

                line();
                break; // Break the loop if all the data is successfully saved

            } catch (InputMismatchException ex) { // Catch exception
                System.out.println("\nERROR! Enter correct details");
                input.nextLine(); // Refresh Buffer
            }
        }
    }

    // Create method to edit System Admin Info
    public static void EditSysAdminInfo(){
        loadSysAdmins(); // Load Data
        line();

        if(NotEmpty(systemAdmin)==0){
            System.out.println("The Database is Empty.");
            return;
        }
        while (true) {
            try {
                System.out.print("Enter System Administrator ID: ");
                String id = input.nextLine();
                id = id.trim();

                boolean found = false;
                for (int i = 0; i < NotEmpty(systemAdmin); i++) {
                    if (systemAdmin[i][0].equals(id)) {
                        found = true;
                        break;
                    }
                }
                if (!found) {
                    System.out.println("ERROR! ID not found!");
                    return;
                }


                System.out.print("Enter Password: ");
                String pass = input.nextLine();
                pass = pass.trim();

                int sysAdminIndex = 0;
                int check = 0;

                // Check if ID exists
                for (int i = 0; i < NotEmpty(systemAdmin); i++) {
                    if (systemAdmin[i][0].equals(id)) {
                        if (!(pass.equals(DecryptPassword("systemAdmin", systemAdmin[i][4], id)))) {
                            System.out.println("Invalid Credentials!");
                            return;
                        }
                        sysAdminIndex = i;
                        check = 1;

                    }
                }

                if (check == 0) {
                    System.out.println("System Administrator ID \"" + id + "\" Does Not Exist In The Database");
                    return;
                }

                System.out.printf("\n%-20s %-25s %-20s %-20s", "SYSTEM ADMIN ID", "NAME", "CNIC", "PHONE");

                line(); // For Formatting

                //Print System Admin data
                System.out.printf("%-20s %-25s %-20s %-20s\n", systemAdmin[sysAdminIndex][0], systemAdmin[sysAdminIndex][1], systemAdmin[sysAdminIndex][2], systemAdmin[sysAdminIndex][3]);

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                System.out.println("\nWrite Updated Info For Concerned System Administrator.");
                System.out.println("\nPress Enter To Leave Info For That Field As Is, Anything Entered will be Stored In that Field If Appropriate.\n");

                // Get required inputs
                System.out.print("Enter Updated System Admin First Name (Enter Current First Name If Last Name Is To Be Updated): ");
                String firstName = input.nextLine();
                firstName = firstName.trim();

                System.out.print("Enter Updated System Admin Last Name (Enter Current Last Name If First Name Is Being Updated): ");
                String lastName = input.nextLine();
                lastName = lastName.trim();

                if (!(firstName.isEmpty()) || !(lastName.isEmpty())) {
                    systemAdmin[sysAdminIndex][1] = lastName + "," + firstName;
                    System.out.println("System Admin Name Updated!");
                } else {
                    System.out.println("System Admin Name Retained!");
                }

                System.out.print("Enter Updated CNIC (Format: xxxxx-xxxxxxx-x): ");
                String cnic = input.nextLine();
                cnic = cnic.trim();

                if (!(cnic.isEmpty())) {

                    if (!(ValidateCNIC(cnic))) {
                        System.out.println("Invalid CNIC!");
                        return;
                    }

                    systemAdmin[sysAdminIndex][2] = cnic;
                    System.out.println("System Administrator CNIC Updated!");
                } else {
                    System.out.println("System Administrator CNIC Retained!");
                }

                System.out.print("Enter Updated Mobile Phone Number (Format: 03xx-xxxxxxx): ");
                String num = input.nextLine();
                num = num.trim();

                if (!(num.isEmpty())) {

                    if (!(ValidatePhone(num))) {
                        System.out.println("ERROR! Invalid Phone Number!");
                        return;
                    }

                    systemAdmin[sysAdminIndex][3] = num;
                    System.out.println("System Administrator Phone Number Updated!");
                } else {
                    System.out.println("System Administrator Phone Number Retained!");
                }

                System.out.println("\nInformation Updated!\n");

                // Update the sysAdmins.txt file by changing system admins data
                UpdateFile("sysAdmin", "yes", id);

                line();
                break; // Break the loop if all the data is successfully saved

            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine(); // Refresh buffer
            }
        }

    }

    // Create a function to edit member Info
    public static void EditMemberInfo(){
        loadMembers(); // Load data
        line();

        if(NotEmpty(members)==0){
            System.out.println("The Database is Empty.");
            return;
        }

        // Run Loop until use enters correct data
        while (true) {
            try {
                System.out.print("Enter Member ID: ");
                String id = input.nextLine();
                id = id.trim();

                boolean found = false;
                for (int i = 0; i < NotEmpty(members); i++) {
                    if (members[i][0].equals(id)) {
                        found = true;
                        break;
                    }
                }
                if (!found) {
                    System.out.println("ERROR! ID not found!");
                    return;
                }


                System.out.printf("\n%-15s %-25s %-20s %-20s %-20s", "MemberID", "NAME", "CNIC", "PHONE", "LATEFEES");

                line();

                int memberIndex = 0;
                int check = 0;

                for (int i = 0; i < NotEmpty(members); i++) {
                    if ((members[i][0]).equalsIgnoreCase(id)) {
                        check = 1;
                        memberIndex = i;
                        System.out.printf("%-15s %-25s %-20s %-20s %-20s\n", members[i][0], members[i][1], members[i][2], members[i][3], members[i][5]);
                    }
                }

                if (check == 0) {
                    System.out.println("Member ID \"" + id + "\" Does Not Exist In The Database");
                    return;
                }

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                System.out.println("\nWrite Updated Info For Concerned Member.");
                System.out.println("\nPress Enter To Leave Info For That Field As Is, Anything Entered will be Stored In that Field If Appropriate.\n");

                System.out.print("Enter Updated Member First Name (Enter Current First Name If Last Name Is To Be Updated): ");
                String firstName = input.nextLine();
                firstName = firstName.trim();

                System.out.print("Enter Updated Member Last Name (Enter Current Last Name If First Name Is Being Updated): ");
                String lastName = input.nextLine();
                lastName = lastName.trim();

                if (!(firstName.isEmpty()) || !(lastName.isEmpty())) {
                    members[memberIndex][1] = lastName + "," + firstName;
                    System.out.println("Member Name Updated!");
                } else {
                    System.out.println("Member Name Retained!");
                }

                System.out.print("Enter Updated CNIC (Format: xxxxx-xxxxxxx-x): ");
                String cnic = input.nextLine();
                cnic = cnic.trim();

                if (!(cnic.isEmpty())) {

                    if (!(ValidateCNIC(cnic))) {
                        System.out.println("ERROR! Invalid CNIC!");
                        return;
                    }

                    members[memberIndex][2] = cnic;
                    System.out.println("Member CNIC Updated!");
                } else {
                    System.out.println("Member CNIC Retained!");
                }

                System.out.print("Enter Updated Mobile Phone Number (Format: 03xx-xxxxxxx): ");
                String num = input.nextLine();
                num = num.trim();

                if (!(num.isEmpty())) {

                    if (!(ValidatePhone(num))) {
                        System.out.println("ERROR! Invalid Phone Number!");
                        return;
                    }

                    members[memberIndex][3] = num;
                    System.out.println("Member Phone Number Updated!");
                } else {
                    System.out.println("Member Phone Number Retained!");
                }

                System.out.println("\nInformation Updated!\n");

                // Update the members.txt file by removing members data
                UpdateFile("member", "yes", id);

                line();
                break; // Break the loop if all the data is successfully saved

            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine(); // Refresh Buffer
            }
        }

    }

    // Create a method to show Member login console
    public static boolean MemberLogin(){
        loadMembers();
        line();
        //Run Loop until use enters correct data
        while (true) {
            try {
                System.out.print("\nEnter Membership ID: ");
                String id = input.nextLine();
                System.out.print("Enter Password: ");
                String password = input.nextLine();
                id = id.trim();
                password = password.trim();

                // Check If ID exisit
                boolean idExists = false;
                for (int i = 0; i < NotEmpty(members); i++) {
                    if (members[i][0].equals(id)) {
                        idExists = true;
                        break;
                    }
                }
                if (!idExists) {
                    System.out.println("ERROR! Invalid Member ID!");
                    return false;
                }

                int index = 0;
                int check = 0;

                for (int i = 0; i < NotEmpty(members); i++) {
                    if ((members[i][0]).equals(id)) {
                        index = i;
                        memberExistanceIndex = i;
                        check = 1;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.println("Record With Provided ID Not Found!");
                    return false;
                }

                String decryptedPassword = DecryptPassword("member", members[index][4], id);

                // Save data of that member who just Logged In
                if (password.equals(decryptedPassword)) {
                    loggedInMemberID = id;
                    loggedInMemberPassword = members[index][4];
                    line();
                    return true;
                }
                line();
                return false;
            } catch (InputMismatchException ex){
                System.out.println("ERROR! Enter correct information");
            }
        }
    }

    public static boolean AdminLogin(){
        loadAdmins(); // Load data
        line();
        // Run Loop until user enter correct data
        while (true) {
            try {
                System.out.print("\nEnter Admin ID: ");
                String id = input.nextLine();
                System.out.print("Enter Password: ");
                String password = input.nextLine();
                id = id.trim();
                password = password.trim();

                boolean idExists = false;
                for (int i = 0; i < NotEmpty(admin); i++) {
                    if (admin[i][0].equals(id)) {
                        idExists = true;
                        break;
                    }
                }
                if (!idExists) {
                    System.out.println("ERROR! Invalid Admin ID!");
                    return false;
                }

                // Validate ID and Password
                for (int i = 0; i < NotEmpty(admin); i++) {
                    if ((admin[i][0]).equals(id)) {
                        String decryptedPassword = DecryptPassword("admin", admin[i][4], admin[i][0]);
                        if (decryptedPassword.equals(password)) {
                            int index = i;

                            // Save Logged In admin data
                            adminExistanceIndex = i;
                            loggedInAdminID = id;
                            loggedInAdminPassword = admin[i][4];
                            return true;
                        } else {
                            System.out.println("ERROR! Invalid password.");
                            return false;
                        }
                    }
                }
                System.out.println("ERROR! Record With Provided ID Not Found!");
                line();
                return false;
            } catch (InputMismatchException ex){
                System.out.println("ERROR! Enter correct information");
            }
        }

    }

    public static boolean SysAdminLogin(){
        loadSysAdmins(); // Load data
        line();

        // Run Loop until user enter correct data
        while (true) {
            try {
                System.out.print("\nEnter System Administrator ID: ");
                String id = input.nextLine();
                System.out.print("Enter Password: ");
                String password = input.nextLine();
                id = id.trim();
                password = password.trim();

                // Handle Exception
                try {
                    boolean idExists = false;
                    for (int i = 0; i < NotEmpty(systemAdmin); i++) {
                        if (systemAdmin[i][0].equals(id)) {
                            idExists = true;
                            break;
                        }
                    }
                    if (!idExists) {
                        System.out.println("Invalid System Administrator ID!");
                        return false;
                    }
                } catch (NumberFormatException e) {
                    System.out.println("Invalid System Administrator ID format.");
                    return false;
                }

                // Validate ID
                int index = 0;
                int check = 0;

                for (int i = 0; i < NotEmpty(systemAdmin); i++) {
                    if ((systemAdmin[i][0]).equals(id)) {
                        index = i;
                        sysAdminExistanceIndex = i;
                        check = 1;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.println("Record With Provided ID Not Found!");
                    return false;
                }

                // Decrypt Password and then validate it
                // Also save logged In System Admin data
                String decryptedPassword = DecryptPassword("systemAdmin", systemAdmin[index][4], id);

                if (password.equals(decryptedPassword)) {
                    loggedInSysAdminID = id;
                    loggedInSysAdminPassword = systemAdmin[index][4];
                    line();
                    return true;
                }
                line();
                return false;

            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }

    }

    // Display Admin Console
    public static void DisplayAdminConsole() {
        System.out.println("\n1. Book Functions");
        System.out.println("2. Member Functions");
        System.out.println("3. Change Password");
        System.out.println("4. Log Out");
    }

    // Display Student Console
    public static void DisplayStudentConsole() {
        System.out.println("\n1. View all books");
        System.out.println("2. Borrow a book");
        System.out.println("3. Return a book");
        System.out.println("4. Search for books");
        System.out.println("5. Change Password");
        System.out.println("6. Log Out");
    }

    // Display available Book Functions
    public static void DisplayBookFunctions() {
        System.out.println("\nBook Functions");
        System.out.println("1. Add a book");
        System.out.println("2. Remove a book");
        System.out.println("3. View all books");
        System.out.println("4. Borrow a book");
        System.out.println("5. Return a book");
        System.out.println("6. Search for books");
        System.out.println("7. Edit book details");
        System.out.println("8. View Overdue Books");
        System.out.println("9. Exit to Main Console");
    }

    // Display available Member Functions
    public static void DisplayMemberFunctions() {
        System.out.println("\nMember Functions");
        System.out.println("1. Add a member");
        System.out.println("2. Remove a member");
        System.out.println("3. View members");
        System.out.println("4. Search for members");
        System.out.println("5. Edit Member Info");
        System.out.println("6. Change Member Password");
        System.out.println("7. Exit to Main Console");
    }

    // Display System Admin Console
    public static void DisplaySystemAdminConsole(){
        System.out.println("\n1. Book Functions");
        System.out.println("2. Add Admin");
        System.out.println("3. Remove Admin");
        System.out.println("4. Admin Password Change");
        System.out.println("5. Edit Admin Info");
        System.out.println("6. View Admins");
        System.out.println("7. Edit System Administrator Info");
        System.out.println("8. Edit System Administrator Password");
        System.out.println("9. Add System Admin");
        System.out.println("10. Log Out");
    }


    public static void SysAdminConsole(){
        System.out.println("\n-------------------------------------------------------------");
        System.out.println("                    System Admin Console                     ");
        System.out.println("-------------------------------------------------------------");
        while (true) {
            DisplaySystemAdminConsole();
            System.out.print("Enter Choice(1-10): ");
            try {
                int choice = input.nextInt();
                input.nextLine();
                switch (choice) {
                    case 1:
                        delay(1500);
                        BookMenu();
                        break;
                    case 2:
                        delay(1500);
                        AddAdmin();
                        break;
                    case 3:
                        delay(1500);
                        RemoveAdmin();
                        break;
                    case 4:
                        delay(1500);
                        AdminPasswordChangeSysAdmin();
                        break;
                    case 5:
                        delay(1500);
                        EditAdminInfo();
                        break;
                    case 6:
                        delay(1500);
                        ViewAdmin();
                        break;
                    case 7:
                        delay(1500);
                        EditSysAdminInfo();
                        break;
                    case 8:
                        delay(1500);
                        SysAdminPasswordChange();
                        break;
                    case 9:
                        delay(1500);
                        AddSystemAdmin();
                        break;
                    case 10:
                        System.out.println("Logging Out!");
                        delay(1500);
                        return;
                    default:
                        System.out.println("ERROR: Invalid Input!");
                        delay(1500);
                        break;
                }
            } catch (InputMismatchException ex){
                System.out.println("\nError! Enter correct choice");
                input.nextLine();
            }
        }

    }

    public static void AdminConsole() {
        System.out.println("\n-------------------------------------------------------------");
        System.out.println("                       Admin Console                         ");
        System.out.println("-------------------------------------------------------------");
        while (true) {
            DisplayAdminConsole();
            System.out.print("Enter Choice(1-4): ");
            try {
                int choice = input.nextInt();
                input.nextLine();
                switch (choice) {
                    case 1:
                        delay(1500);
                        BookMenu();
                        break;
                    case 2:
                        delay(1500);
                        MemberMenu();
                        break;
                    case 3:
                        delay(1500);
                        AdminPasswordChangeSelf();
                        break;
                    case 4:
                        System.out.println("Logging Out!");
                        delay(1500);
                        return;
                    default:
                        System.out.println("ERROR: Invalid Input!");
                        delay(1500);
                        break;
                }
            } catch (InputMismatchException ex){
                System.out.println("\nError! Enter correct choice");
                input.nextLine();
            }
        }
    }

    public static void BookMenu() {
        line();

        while (true) {
            DisplayBookFunctions();
            System.out.print("Enter Your Choice(1-9): ");
            try {
                int choice = input.nextInt();
                input.nextLine();
                switch (choice) {
                    case 1:
                        delay(1500);
                        AddBook();
                        break;
                    case 2:
                        delay(1500);
                        RemoveBook();
                        break;
                    case 3:
                        delay(1500);
                        ViewBooks();
                        break;
                    case 4:
                        delay(1500);
                        BorrowBook();
                        break;
                    case 5:
                        delay(1500);
                        ReturnBook();
                        break;
                    case 6:
                        delay(1500);
                        SearchBooks();
                        break;
                    case 7:
                        delay(1500);
                        EditBook();
                        break;
                    case 8:
                        delay(1500);
                        OverdueBooks();
                        break;
                    case 9:
                        delay(1500);
                        return;
                    default:
                        System.out.println("ERROR: Invalid Input!");
                        delay(1500);
                        break;
                }
                line();

            } catch (InputMismatchException ex){
                System.out.println("\nError! Enter correct choice");
                input.nextLine();
            }
        }
    }

    public static void MemberMenu() {
        line();

        while (true) {
            DisplayMemberFunctions();
            System.out.print("Enter Your Choice(1-7): ");
            try {
                int choice = input.nextInt();
                input.nextLine();
                switch (choice) {
                    case 1:
                        delay(1500);
                        AddMember();
                        break;
                    case 2:
                        delay(1500);
                        RemoveMember();
                        break;
                    case 3:
                        delay(1500);
                        ViewMembers();
                        break;
                    case 4:
                        delay(1500);
                        SearchMembers();
                        break;
                    case 5:
                        delay(1500);
                        EditMemberInfo();
                        break;
                    case 6:
                        delay(1500);
                        MemberPasswordChangeAdmin();
                        break;
                    case 7:
                        delay(1500);
                        return;
                    default:
                        System.out.println("ERROR: Invalid Input!");
                        delay(1500);
                        break;
                }
                line();

            } catch (InputMismatchException ex){
                System.out.println("\nError! Enter correct choice");
                input.nextLine();
            }
        }
    }

    public static void StudentConsole(){
        System.out.println("\n-------------------------------------------------------------");
        System.out.println("                      Member Console                        ");
        System.out.println("-------------------------------------------------------------");
        while(true) {
            DisplayStudentConsole();
            System.out.print("Enter Your Choice(1-6): ");
            try {
                int choice = input.nextInt();
                input.nextLine();
                switch (choice) {
                    case 1:
                        delay(1500);
                        ViewBooks();
                        break;
                    case 2:
                        delay(1500);
                        BorrowBook(loggedInMemberID, memberExistanceIndex);
                        break;
                    case 3:
                        delay(1500);
                        ReturnBook();
                        break;
                    case 4:
                        delay(1500);
                        SearchBooks();
                        break;
                    case 5:
                        delay(1500);
                        MemberPasswordChangeSelf();
                        break;
                    case 6:
                        System.out.println("Logging Out!");
                        delay(1500);
                        return;
                    default:
                        System.out.println("ERROR: Invalid Input!");
                        delay(1500);
                        break;
                }
            } catch (InputMismatchException ex){
                System.out.println("\nError! Enter correct choice");
                input.nextLine();
            }
        }
    }


    public static void ViewAdmin(){
        line();

        // Check if admin data exist
        if(NotEmpty(admin)==0){
            System.out.printf("%52s\n","No Records Found!");
            return;
        }

        // Display Data
        System.out.printf("\n%-15s %-25s %-20s %-20s","ADMIN ID","NAME","CNIC","PHONE");

        line();

        for(int i=0;i<NotEmpty(admin);i++){
            System.out.printf("%-15s %-25s %-20s %-20s\n",admin[i][0],admin[i][1],admin[i][2],admin[i][3]);
        }

        line();

    }

    // Create a function to Delay the execution
    public static void delay(int ms) {
        try {
            Thread.sleep(ms);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }


    public static String ToString(LocalDate date) {
        return date.format(DateTimeFormatter.ofPattern("dd-MM-yyyy"));
    }

    public static LocalDate ToDate(String dateString) {
        return LocalDate.parse(dateString, DateTimeFormatter.ofPattern("dd-MM-yyyy"));
    }


    // Return length of the array
    public static int NotEmpty(String[][] arr){
        int length = 0;
        for(int i = 0; i < arr.length; i++){
            if (arr[i][0] != null && !arr[i][0].isEmpty()){
                length++;
            }
        }
        return length;
    }


    public static void AddBook() {
        line();
        //Check if books data exists
        if (NotEmpty(books) == books.length) {
            System.out.println("Book Limit Reached!");
            return;
        }
        while (true) {
            try {
                System.out.print("Enter Book Title: ");
                String title = input.nextLine().trim();
                System.out.print("Enter Book Author: ");
                String author = input.nextLine().trim();
                System.out.print("Enter Book Genre: ");
                String genre = input.nextLine().trim();
                System.out.print("Enter Book ID (First Character should be a Letter and 5 Digits): ");
                String id = input.nextLine().trim();

                if (title.isEmpty() || author.isEmpty() || genre.isEmpty() || id.isEmpty()) {
                    System.out.println("All fields (Title, Author, Genre, Book ID) are required!");
                    return;
                }

                if (!FirstBookIdCheck(id)) {
                    System.out.println("ERROR! Invalid Book ID!");
                    return;
                }
                int count = NotEmpty(books);
                for (int i = 0; i < count; i++) {
                    if (books[i][0].equalsIgnoreCase(title) && books[i][1].equalsIgnoreCase(author)) {
                        System.out.println("The book \"" + title + "\" by " + author + " already exists in the library.");
                        return;
                    }
                    if (books[i][3].equalsIgnoreCase(id)) {
                        System.out.println("The Book ID \"" + id + "\" already exists in the database.");
                        return;
                    }
                }

                title = title.replace(" ", "_");
                author = author.replace(" ", "_");

                int index = NotEmpty(books);
                books[index][0] = title;
                books[index][1] = author;
                books[index][2] = genre;
                books[index][3] = id;
                books[index][4] = "None";
                books[index][5] = "None";

                // Save and print data
                saveBooks();
                System.out.println("Book \"" + title.replace("_", " ") + "\" by " + author.replace("_", " ") + " added successfully!");
                line();
                break;
            } catch (InputMismatchException ex){
                System.out.println("ERROR! Enter correct information");
            }
        }
    }

    public static boolean BookIdCheck(String id) {
        line();
        // Check if ID is equal to 6
        if (!(id.length() == 6)) {
            System.out.println("The ID is not 6 Characters!");
            return false;
        }

        int letter = 0;

        for (int i = 0; i < 6; i++) {
            if (Character.isLetterOrDigit(id.charAt(i))) {
                if (Character.isLetter(id.charAt(i))) {
                    letter++;
                }
            } else {
                System.out.println("ERROR! Invalid Book ID!");
                return false;
            }
        }

        if (letter != 1 && !(Character.isLetter(id.charAt(0)))) {
            System.out.print("ERROR! Invalid Book ID!");
            return false;
        }
        return true;
    }


    public static boolean FirstBookIdCheck(String id) {
        line();
        // Check if ID is equal to 6
        if (!(id.length() == 6)) {
            System.out.println("The ID is not 6 Characters!");
            return false;
        }

        int letter = 0;

        for (int i = 0; i < 6; i++) {
            if (Character.isLetterOrDigit(id.charAt(i))) {
                if (Character.isLetter(id.charAt(i))) {
                    letter++;
                }
            } else {
                System.out.println("ERROR! Invalid Book ID!");
                return false;
            }
        }

        if (letter != 1 && !(Character.isLetter(id.charAt(0)))) {
            System.out.print("ERROR! Invalid Book ID!");
            return false;
        }

        // File handling part: check if ID already exists in the file
        try (Scanner fileScanner = new Scanner(new FileInputStream("books.txt"))) {
            while (fileScanner.hasNextLine()) {
                String line = fileScanner.nextLine();
                String[] parts = line.split(" ");
                if (parts.length >= 4 && parts[3].equalsIgnoreCase(id)) {
                    System.out.println("Book ID already exists in file!");
                    return false;
                }
            }
            line();
        } catch (FileNotFoundException e) {
            System.out.println("Book file not found during ID check!");
            line();
            return false;
        }

        return true;
    }


    public static void RemoveBook() {
        line();
        if (NotEmpty(books) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        while (true) {
            try {
                System.out.print("Enter Book ID: ");
                String id = input.nextLine();
                id = id.trim();

                if (!(BookIdCheck(id))) {
                    System.out.println("Invalid format for Book ID!");
                    return;
                }

                int count = NotEmpty(books);
                for (int i = 0; i < count; i++) {
                    if ((books[i][3]).equalsIgnoreCase(id)) {
                        if ((books[i][4].equalsIgnoreCase("None"))) {

                            System.out.printf("\n%-15s %-45s %-30s %-20s", "Book ID", "Title", "Author", "Genre");

                            line();

                            System.out.printf("%-15s %-45s %-30s %-20s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2]);

                            if (!(Confirmation())) {
                                System.out.println("\nRemoval Cancelled!");
                                return;
                            }
                            NullifyRow(i, books);
                            Normalize(i, books);
                            saveBooks();  // Save updated book list to file
                            System.out.println("\nBook ID:" + id + " Has Been Removed From The Database.");
                            return;
                        } else {
                            System.out.println("Cannot Remove Book. Borrowed By " + books[i][4]);
                            return;
                        }
                    }
                }
                System.out.println("The Book Does Not Exist In the Database.");
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }
    }

    // Enter null in a row in an array
    public static void NullifyRow(int i, String[][] arr){
        for(int j=0;j<arr[i].length;j++){
            arr[i][j] = null;
        }
    }

    // Normalize the array
    public static void Normalize(int i, String[][] arr){
        for(int j=i;j<NotEmpty(arr);j++) {
            if (j == (NotEmpty(arr) - 1)) {
                for (int z = 0; z < arr[0].length; z++) {
                    arr[j][z] = null;
                }
            } else {
                for (int z = 0; z < arr[0].length; z++) {
                    arr[j][z] = arr[j + 1][z];
                }
            }
        }
    }

    // Enter some lines for formatting
    public static void line(){
        System.out.println();
        for (int i = 0; i < 120; i++) {
            System.out.print("=");
        }
        System.out.println();
    }

    public static void ViewBooks() {
        loadBooks(); // Load the latest data from file before displaying
        line();

        if (NotEmpty(books) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        System.out.printf("\n%-15s %-45s %-30s %-20s %-15s","Book ID","Title","Author","Genre","Status");

        line();

        String status;
        for (int i = 0; i < NotEmpty(books); i++) {
            if (books[i][4].equalsIgnoreCase("None")) {
                status = "Available";
            } else {
                status = "Borrowed by " + books[i][4];
            }

            System.out.printf("%-15s %-45s %-30s %-20s %-15s\n",books[i][3],books[i][0].replace("_"," "),books[i][1].replace("_"," "),books[i][2],status);
        }
        line();

    }

    public static void BorrowBook() {
        line();
        if (NotEmpty(books) == 0) {
            System.out.println("The Database Is Empty.");
            return;
        }

        if(NotEmpty(members)==0){
            System.out.println("The Member Database Is Empty!");
            return;
        }

        while (true) {
            try {
                System.out.print("Enter Membership ID: ");
                String id = input.nextLine();
                id = id.trim();

                boolean validMember = false;
                for (String[] member : members) {
                    if (member[0] != null && member[0].equals(id)) {
                        validMember = true;
                        break;
                    }
                }
                if (!validMember) {
                    System.out.println("ERROR! Invalid Member ID!");
                    return;
                }

                System.out.print("Enter Book ID: ");
                String bookID = input.nextLine();
                bookID = bookID.trim();

                if (!(BookIdCheck(bookID))) {
                    System.out.println("Invalid Book ID!");
                    return;
                }

                int counter = 4;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (books[i][4].equals(id)) {
                        counter--;
                    }
                }

                if (counter == 0) {
                    System.out.println("YOU CANNOT BORROW ANY MORE BOOKS! LIMIT HAS BEEN REACHED!");
                    return;
                }

                System.out.println("\nMember Information\n");

                int memberIndex = 0;
                int check = 0;
                System.out.printf("\n%-15s %-25s %-10s", "MemberID", "NAME", "BOOK LIMIT LEFT");
                line();

                for (int i = 0; i < NotEmpty(members); i++) {
                    if ((members[i][0]).equals(id)) {
                        memberIndex = i;
                        System.out.printf("%-15s %-25s %-10d\n", members[i][0], members[i][1], counter);
                        check = 1;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.printf("%52s\n", "Matching Member Record Not Found!");
                    return;
                }

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                System.out.println("\nBook Information\n");

                int bookIndex = 0;
                String status = "";
                check = 0;
                System.out.printf("\n%-15s %-25s %-25s %-15s %-15s", "BOOK ID", "BOOK NAME", "AUTHOR", "GENRE", "STATUS");
                line();

                for (int i = 0; i < NotEmpty(books); i++) {

                    if (bookID.equalsIgnoreCase(books[i][3])) {
                        bookIndex = i;
                        if (!(books[i][4].equalsIgnoreCase("None"))) {
                            status = "Book Not Available";
                        }
                        else{
                            status="Available";
                        }
                        System.out.printf("%-15s %-25s %-25s %-15s %-15s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2], status);
                        check = 1;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.printf("%52s\n", "Matching Book Record Not Found!");
                    return;
                }

                if (status.equals("Book Not Available")) {
                    System.out.println("The Book Is Not Available!");
                    return;
                }

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                LocalDate today = LocalDate.now();
                String date = ToString(today);

                books[bookIndex][4] = members[memberIndex][0];
                books[bookIndex][5] = date;

                saveBooks(); // File handling step added here
                System.out.println("Book Borrowed Successfully!");
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }
    }


    public static void BorrowBook(String id, int memberIndex) {
        loadBooks(); // Load books from file
        line();
        if (NotEmpty(books) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }
        while (true) {

            try {
                System.out.print("Enter Book ID: ");
                String bookID = input.nextLine();
                bookID = bookID.trim();

                if (!(BookIdCheck(bookID))) {
                    System.out.println("Invalid Book ID!");
                    return;
                }

                int counter = 4;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (books[i][4].equals(id)) {
                        counter--;
                    }
                }

                if (counter == 0) {
                    System.out.println("YOU CANNOT BORROW ANY MORE BOOKS! LIMIT HAS BEEN REACHED!");
                    return;
                }

                System.out.println("\nBook Information\n");
                String status = "";
                int bookIndex = 0;
                int check = 0;
                System.out.printf("\n%-15s %-25s %-25s %-15s %-15s", "BOOK ID", "BOOK NAME", "AUTHOR", "GENRE", "STATUS");
                line();

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (bookID.equalsIgnoreCase(books[i][3])) {
                        status = "";
                        bookIndex = i;
                        if (!(books[i][4].equalsIgnoreCase("None"))) {
                            status = "Book Not Available";
                        }
                        else{
                            status= "Available";
                        }
                        System.out.printf("%-15s %-25s %-25s %-15s %-15s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2], status);
                        check = 1;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.printf("%52s\n", "Matching Book Record Not Found!");
                    return;
                }

                if (status.equals("Book Not Available")) {
                    System.out.println("The Book Is Not Available!");
                    return;
                }

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                LocalDate today = LocalDate.now();
                LocalDate dueDate = today.plusDays(7);
                String date = ToString(dueDate);

                books[bookIndex][4] = members[memberIndex][0];
                books[bookIndex][5] = date;

                saveBooks(); // Save updated books to file
                System.out.println("Book successfully borrowed and recorded.");
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }
    }



    public static void ReturnBook() {
        loadBooks();     // Load latest book data from file
        line();
        if (NotEmpty(books) == 0) {
            System.out.println("The Database Is Empty.");
            return;
        }

        if(NotEmpty(members)==0) {
            System.out.println("The Member Database Is Empty!");
            return;
        }
        while (true) {

            try {
                System.out.print("Enter Membership ID: ");
                String id = input.nextLine();
                id = id.trim();

                if (!(Integer.parseInt(id) > 0 && Integer.parseInt(id) <= members.length)) {
                    System.out.println("ERROR! Invalid ID!");
                    return;
                }

                int check = 0;
                int memberIndex = 0;

                for (int i = 0; i < NotEmpty(members); i++) {
                    if ((members[i][0]).equals(id)) {
                        memberIndex = i;
                        check = 1;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.printf("%52s\n", "Member Record Not Found!");
                    return;
                }

                int counter = 0;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (books[i][4].equals(id)) {
                        counter++;
                    }
                }

                if (counter == 0) {
                    System.out.println("NO BOOKS HAVE BEEN BORROWED!");
                    return;
                }

                System.out.printf("\n%-15s %-25s %-10s", "MemberID", "NAME", "BOOKS BORROWED");

                line();

                System.out.printf("%-15s %-25s %-10d\n", members[memberIndex][0], members[memberIndex][1], counter);

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                System.out.print("Enter Book ID: ");
                String bookID = input.nextLine();
                bookID = bookID.trim();

                if (!(BookIdCheck(bookID))) {
                    System.out.println("ERROR! Invalid Book ID!");
                    return;
                }

                check = 0;
                int bookIndex = 0;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (bookID.equalsIgnoreCase(books[i][3])) {
                        check = 1;
                        if (!(books[i][4].equalsIgnoreCase(id))) {
                            System.out.println("YOU HAVEN'T BORROWED THIS BOOK!");
                            return;
                        }
                        bookIndex = i;
                    }
                }

                if (check == 0) {
                    System.out.println("NO SUCH BOOK IN THE DATABASE!");
                    return;
                }

                System.out.printf("\n%-15s %-25s %-25s %-15s", "MemberID", "BOOK NAME", "AUTHOR", "GENRE");

                line();

                System.out.printf("%-15s %-25s %-25s %-15s\n", books[bookIndex][3], books[bookIndex][0].replace("_", " "), books[bookIndex][1].replace("_", " "), books[bookIndex][2]);

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                LocalDate dueDate = ToDate(books[bookIndex][5]);
                int lateFees = LateFees(dueDate);
                LocalDate today = LocalDate.now();
                long daysLate = ChronoUnit.DAYS.between(dueDate, today);

                if (members[memberIndex][5].equalsIgnoreCase("None")) {
                    members[memberIndex][5] = Integer.toString(lateFees);
                } else {
                    int totalFees = lateFees + (Integer.parseInt(members[memberIndex][5]));
                    members[memberIndex][5] = Integer.toString(totalFees);
                }

                System.out.println(books[bookIndex][0] + " returned late by " + daysLate + " days. Late fee: " + lateFees + ". Total outstanding fees: " + members[memberIndex][5]);
                System.out.println("Late Fees Paid?");

                if (!(Confirmation())) {
                    System.out.println("PAY LATE FEES FIRST!");
                    return;
                }

                members[memberIndex][5] = Integer.toString((Integer.parseInt(members[memberIndex][5])) - lateFees);

                if (members[memberIndex][5].equals("0")) {
                    members[memberIndex][5] = "None";
                }

                System.out.println("Total Outstanding Fees After Late Fees Submission: " + members[memberIndex][5]);

                books[bookIndex][4] = "None";
                books[bookIndex][5] = "None";

                System.out.println("The Book Has Been Returned.");

                saveBooks();    // Save updated book data to file
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }
    }

    public static int LateFees(LocalDate dueDate){

        int ratePerDay=100;
        LocalDate today=LocalDate.now();
        if(today.isAfter(dueDate)){
            int daysLate = (int)ChronoUnit.DAYS.between(dueDate,today);
            return daysLate*ratePerDay;
        }
        else{
            return 0;
        }
    }

    public static void MemberLateFeesInitialization() {
        // Load data from files
        loadBooks();

        for (int i = 0; i < NotEmpty(members); i++) {
            String id = members[i][0];
            int memberLateFees = 0;

            for (int j = 0; j < NotEmpty(books); j++) {
                if (books[j][4].equalsIgnoreCase(id)) {
                    int lateFees = LateFees(ToDate(books[j][5]));
                    memberLateFees += lateFees;
                }
            }

            if (memberLateFees != 0) {
                members[i][5] = Integer.toString(memberLateFees);
            }
        }


    }


    public static void SearchBooks() {
        // Load latest book records from the file
        loadBooks();
        line();
        if (NotEmpty(books) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        while (true) {
            System.out.println("\n1. Search By Title");
            System.out.println("2. Search By Book ID");
            System.out.println("3. Search By Genre");
            System.out.println("4. Search By Author");
            System.out.println("5. Exit to Main Menu");
            System.out.print("Enter Choice(1-5): ");
            try{
                int choice = input.nextInt();
                input.nextLine();

                switch (choice) {
                    case 1:
                        delay(1500);
                        SearchByTitle();
                        break;
                    case 2:
                        delay(1500);
                        SearchByBookID();
                        break;
                    case 3:
                        delay(1500);
                        SearchByGenre();
                        break;
                    case 4:
                        delay(1500);
                        SearchByAuthor();
                        break;
                    case 5:
                        delay(1500);
                        return;
                    default:
                        System.out.println("Invalid Input");
                        delay(1500);
                        break;
                }
                line();

            } catch (InputMismatchException ex){
                System.out.println("\nERROR! Enter correct choice");
                input.nextLine();
            }
        }
    }

    public static void SearchByTitle() {
        line();
        if (NotEmpty(books) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }
        while (true) {

            try {
                System.out.print("Enter Book Title: ");
                String title = input.nextLine();
                title = title.trim();

                System.out.printf("\n%-15s %-45s %-30s %-20s %-15s", "Book ID", "Title", "Author", "Genre", "Status");

                line();

                int check = 0;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (((books[i][0].replace("_", " ")).toLowerCase()).contains(title.toLowerCase())) {
                        check = 1;
                        String status;
                        if (books[i][4].equalsIgnoreCase("None")) {
                            status = "Available";
                        } else {
                            status = "Not Available";
                        }
                        System.out.printf("%-15s %-45s %-30s %-20s %-15s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2], status);
                    }
                }

                if (check == 0) {
                    System.out.println("Title \"" + title + "\" Does Not Exist In The Database");
                }
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }
    }

    public static void SearchByBookID(){
        line();
        if(NotEmpty(books)==0){
            System.out.println("The Database is Empty.");
            return;
        }

        while (true) {
            try {
                System.out.print("Enter Book ID: ");
                String bookID = input.nextLine();
                bookID = bookID.trim();

                if (!(BookIdCheck(bookID))) {
                    System.out.println("Invalid Book ID!");
                    return;
                }

                System.out.printf("\n%-15s %-45s %-30s %-20s %-15s", "Book ID", "Title", "Author", "Genre", "Status");

                line();

                int check = 0;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if ((books[i][3]).equalsIgnoreCase(bookID)) {
                        check = 1;
                        String status;
                        if (books[i][4].equalsIgnoreCase("None")) {
                            status = "Available";
                        } else {
                            status = "Not Available";
                        }
                        System.out.printf("%-15s %-45s %-30s %-20s %-15s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2], status);
                    }
                }

                if (check == 0) {
                    System.out.println("Book ID \"" + bookID + "\" Does Not Exist In The Database");
                }
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }
    }

    public static void SearchByGenre(){
        line();
        if(NotEmpty(books)==0){
            System.out.println("The Database is Empty.");
            return;
        }

        while(true) {

            try {
                System.out.print("Enter Book Genre: ");
                String genre = input.nextLine();
                genre = genre.trim();

                System.out.printf("\n%-15s %-45s %-30s %-20s %-15s", "Book ID", "Title", "Author", "Genre", "Status");

                line();

                int check = 0;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if ((books[i][2]).equalsIgnoreCase(genre)) {
                        check = 1;
                        String status;
                        if (books[i][4].equalsIgnoreCase("None")) {
                            status = "Available";
                        } else {
                            status = "Not Available";
                        }
                        System.out.printf("%-15s %-45s %-30s %-20s %-15s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2], status);
                    }
                }

                if (check == 0) {
                    System.out.println("Books Of Genre \"" + genre + "\" Do Not Exist In The Database");
                }
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }

    }

    public static void SearchByAuthor(){
        line();
        if(NotEmpty(books)==0){
            System.out.println("The Database is Empty.");
            return;
        }
        while (true) {
            try {
                System.out.print("Enter Book Author: ");
                String author = input.nextLine();
                author = author.trim();

                System.out.printf("\n%-15s %-45s %-30s %-20s %-15s", "Book ID", "Title", "Author", "Genre", "Status");

                line();

                int check = 0;

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (((books[i][1].replace("_", " ")).toLowerCase()).contains(author.toLowerCase())) {
                        check = 1;
                        String status;
                        if (books[i][4].equalsIgnoreCase("None")) {
                            status = "Available";
                        } else {
                            status = "Not Available";
                        }
                        System.out.printf("%-15s %-45s %-30s %-20s %-15s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2], status);
                    }
                }

                if (check == 0) {
                    System.out.println("Books By Author \"" + author + "\" Do Not Exist In The Database");
                }
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }
    }

    public static void EditBook() {
        line();
        try {
            loadBooks(); // Load from file
        } catch (Exception e) {
            System.out.println("ERROR: Unable to load book data.");
            return;
        }

        if (NotEmpty(books) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        while(true) {

            try {
                System.out.print("Enter Book ID: ");
                String bookID = input.nextLine().trim();

                if (!(BookIdCheck(bookID))) {
                    System.out.println("ERROR! Invalid Book ID!");
                    return;
                }

                System.out.printf("\n%-15s %-45s %-30s %-20s %-15s", "Book ID", "Title", "Author", "Genre", "Status");

                line();

                String status;
                int bookIndex = -1;
                for (int i = 0; i < NotEmpty(books); i++) {
                    if ((books[i][3]).equalsIgnoreCase(bookID)) {
                        bookIndex = i;
                        status = books[i][4].equalsIgnoreCase("None") ? "Available" : "Not Available";
                        System.out.printf("%-15s %-45s %-30s %-20s %-15s\n", books[i][3], books[i][0].replace("_", " "), books[i][1].replace("_", " "), books[i][2], status);
                        break;
                    }
                }

                if (bookIndex == -1) {
                    System.out.println("Book ID \"" + bookID + "\" Does Not Exist In The Database");
                    return;
                }

                if(status.equalsIgnoreCase("Not Available")){
                    System.out.println("Book ID \"" + bookID + "\" Cannot be Edited at the Moment!");
                    return;
                }

                if (!(Confirmation())) {
                    System.out.println("Operation Cancelled!");
                    return;
                }

                System.out.println("\nWrite Updated Info For Concerned Book.");
                System.out.println("\nPress Enter To Leave Info For That Column As Is, Anything Entered will be Stored In that Column If Appropriate.\n");

                System.out.print("Enter Updated Book Title: ");
                String title = input.nextLine().trim();
                if (!title.isEmpty()) {
                    title = title.replace(" ", "_");
                    books[bookIndex][0] = title;
                    System.out.println("Book Title Updated!");
                } else {
                    System.out.println("Book Title Retained!");
                }

                System.out.print("Enter Updated Book Author: ");
                String author = input.nextLine().trim();
                if (!author.isEmpty()) {
                    author = author.replace(" ", "_");
                    books[bookIndex][1] = author;
                    System.out.println("Book Author Updated!");
                } else {
                    System.out.println("Book Author Retained!");
                }

                System.out.print("Enter Updated Book Genre: ");
                String genre = input.nextLine().trim();
                if (!genre.isEmpty()) {
                    books[bookIndex][2] = genre;
                    System.out.println("Book Genre Updated!");
                } else {
                    System.out.println("Book Genre Retained!");
                }

                System.out.print("Enter Updated Book ID: ");
                String id = input.nextLine().trim();
                if (!id.isEmpty()) {
                    if (!(FirstBookIdCheck(id))) {
                        System.out.println("ERROR! Invalid Book ID");
                        return;
                    }
                    for (int i = 0; i < NotEmpty(books); i++) {
                        if (i != bookIndex && books[i][3].equalsIgnoreCase(id)) {
                            System.out.println("Book ID Already In Use!");
                            return;
                        }
                    }
                    books[bookIndex][3] = id;
                    System.out.println("Book ID Updated!");
                } else {
                    System.out.println("Book ID Retained!");
                }

                try {
                    saveBooks(); // Save updated book data to file
                } catch (Exception e) {
                    System.out.println("Error saving updated book data.");
                    return;
                }

                System.out.println("\nInformation Updated!\n");
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("\nERROR! Enter correct information");
                input.nextLine();
            }
        }
    }


    public static void OverdueBooks() {
        line();
        try {
            loadBooks(); // Load the books array from the file
        } catch (Exception e) {
            System.out.println("Error: Could not load books data.");
            return;
        }

        if (NotEmpty(books) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        System.out.printf("\n%-15s %-45s %-30s %-20s %-15s %-20s","Book ID","Title","Author","Genre","Borrowed By","Due Date");

        line();

        LocalDate today = LocalDate.now();
        int check = 0;

        for (int i = 0; i < NotEmpty(books); i++) {
            String date = books[i][5];
            if (!(date.equalsIgnoreCase("None"))) {
                LocalDate dueDate = ToDate(date);

                if (dueDate.isBefore(today)) {
                    check = 1;
                    System.out.printf("%-15s %-45s %-30s %-20s %-15s %-20s\n", books[i][3], books[i][0].replace("_"," "), books[i][1].replace("_"," "), books[i][2], books[i][4], books[i][5]);
                }
            }
        }

        if (check == 0) {
            System.out.println("No Overdue Books!");
        }
        line();

    }

    // Function to encrypt password and save its encryption and decryption key
    public static String EncryptPassword(String type, String password, String memberID){
        // Folder name to create a folder where every memebers, admins and system Admins keys will be stored
        String folderName;
        if (type.equalsIgnoreCase("admin")) {
            folderName = "admins";
        } else if (type.equalsIgnoreCase("member")) {
            folderName = "members";
        } else {
            folderName = "systemAdmins";
        }

        // Create a directory/folder if it does not exixts
        File directory = new File(folderName);
        if (!directory.exists()) {
            directory.mkdirs();
        }

        // Encrypt Password
        String encryptedPassword = ""; // String to store encryoted password
        File memberEncryptionKey = new File(directory, memberID + ".txt"); // File where the key will be stored

        // Make a writer to write in the key file
        try(PrintWriter writer = new PrintWriter(memberEncryptionKey)){

            // Find random number which will be length of key of each character of the password
            int encryptionKeyLength = 6 + (int) (Math.random() * 7);

            // Loop to create a key for each character of password
            for (int i = 0; i < password.length(); i++) {
                writer.print(password.charAt(i));
                writer.print(":");

                // Variable to store encrypted key for each character
                String encryptionKey = "";

                // Loop to find actual key of each character
                for (int j = 0; j < encryptionKeyLength; j++) {

                    // Find random value from 33 to 123
                    int randomValueForKey = 33 + (int) (Math.random() * 91);

                    // Convert the number to a character
                    char characterForKey = (char)(randomValueForKey);

                    // Append that character to the encrypted key variable
                    encryptionKey += characterForKey;
                }
                // Write encryption Key in file after :
                writer.print(encryptionKey);

                // Append that key to the last of encryptedPassword variable along with "}" to make it easy for decryption
                encryptedPassword += (encryptionKey + "}");

                // Go to next line
                writer.println();
            }
        }catch (IOException ex){
            System.out.println("ERROR! An error occurred.");
        }

        // Return encrypted password
        return encryptedPassword;
    }


    //Function to decrypt password
    public static String DecryptPassword(String type, String encryptedPassword, String memberID){
        // Find folder where key is stored
        String folderName = "";
        if (type.equalsIgnoreCase("admin")) {
            folderName = "admins";
        } else if (type.equalsIgnoreCase("member")) {
            folderName = "members";
        } else {
            folderName = "systemAdmins";
        }

        // Open directory and then file
        File directory = new File(folderName);
        File memberFile = new File(directory, memberID + ".txt");

        // Create an object of String Builder to store decrypted password
        StringBuilder decryptedPassword = new StringBuilder();

        try {

            // Create an object of String Builder to each line of the file
            StringBuilder fileContent = new StringBuilder();

            // Open key file as a reader
            try (BufferedReader reader = new BufferedReader(new FileReader(memberFile))) {
                String line; // To save line

                // If content stored in line is not equal to null, then store that data in fileContent with new line
                while ((line = reader.readLine()) != null) {
                    fileContent.append(line).append("\n");
                }
            }

            // Split Encrypted Password with "}"
            String[] encryptedParts = encryptedPassword.split("}");

            // Split each line of the file (after converting it to string) with "\n" (new Line)
            String[] fileLines = fileContent.toString().split("\n");

            // Loop to check each part of the encrypted password with all the lines of the file content
            for (String part : encryptedParts) {

                if (part.isEmpty()) continue; // If the line is empty, skip it

                // Check if there is any part of encrypted password which is not matching with user entered password
                boolean found = false;

                // Loop to check above selected part of encrypted password with each line
                for (String line : fileLines) {
                    if (line.isEmpty()) continue;

                    // The key was stored as "character:key". So, find ":" index to telly characters till it
                    int colonIndex = line.indexOf(':');

                    // Start validating only if the index exists
                    if (colonIndex > 0) {

                        // Find substring from 0 to that ":" index ans store it
                        String storedKey = line.substring(colonIndex + 1);

                        // IF that part is equal to the encerypted password part (from last loop), then append that key
                        if (storedKey.equals(part)) {
                            decryptedPassword.append(line.substring(0, colonIndex));
                            found = true;
                            break;
                        }
                    }
                }

                // If there is any key missing then return it
                if (!found) {
                    System.out.println("Warning: No key found for: " + part);
                }
            }
        } catch (IOException ex) {
            System.out.println("Error reading key file: " + ex.getMessage());
            return ""; // Because the method is returning string
        }

        // Return that decrypted password generated. We used .toString becaus we were appending keys in String Builder not string
        return decryptedPassword.toString();

    }

    public static boolean ValidateCNIC(String cnic){
        int digit=0;
        int hash=0;
        if(cnic.length()!=15){
            return false;
        }

        for(int i=0;i<cnic.length();i++){
            if(Character.isDigit(cnic.charAt(i))){
                digit++;
            }
            else if(cnic.charAt(i)=='-'){
                hash++;
            }
            else{
                return false;
            }
        }

        if(digit!=13 || hash!=2){
            return false;
        }

        if(cnic.charAt(5)!='-' || cnic.charAt(13)!='-'){
            return false;
        }

        return true;

    }

    public static boolean ValidatePhone(String num){
        int digit=0;
        int hash=0;
        if(num.length()!=12){
            return false;
        }

        for(int i=0;i<num.length();i++){
            if(Character.isDigit(num.charAt(i))){
                digit++;
            }
            else if(num.charAt(i)=='-'){
                hash++;
            }
            else{
                return false;
            }
        }

        if(digit!=11){
            return false;
        }

        if(num.charAt(4)!='-'){
            return false;
        }

        if(!(num.charAt(0)=='0' && num.charAt(1)=='3')){
            return false;
        }

        return true;

    }

    public static void AddMember() {
        loadMembers();
        line();
        if(NotEmpty(members)==members.length){
            System.out.println("Member Limit Has Been Reached!");
            return;
        }

        int count=NotEmpty(members);

        while (true) {
            try {
                System.out.print("Enter First Name: ");
                String firstName = input.nextLine();
                System.out.print("Enter Last Name: ");
                String lastName = input.nextLine();
                System.out.print("Enter Mobile Phone Number (Format: 03xx-xxxxxxx): ");
                String num = input.nextLine();
                System.out.print("Enter CNIC (Format: xxxxx-xxxxxxx-x): ");
                String cnic = input.nextLine();
                firstName = firstName.trim();
                lastName = lastName.trim();
                num = num.trim();
                cnic = cnic.trim();

                if (firstName.isEmpty() || lastName.isEmpty() || num.isEmpty() || cnic.isEmpty()) {
                    System.out.println("All fields (First Name, Last Name, Mobile Phone Number, CNIC) are Required!");
                    return;
                }

                if (!(ValidateCNIC(cnic))) {
                    System.out.println("ERROR! Invalid CNIC!");
                    return;
                }

                if (!(ValidatePhone(num))) {
                    System.out.println("ERROR! Invalid Mobile Number!");
                    return;
                }

                String id;
                while (true) {
                    int check = 0;
                    id = Integer.toString((int) (1 + Math.random() * 10000));
                    for (int i = 0; i < count; i++) {
                        if (members[i][0].equalsIgnoreCase(id)) {
                            check = 1;
                            break;
                        }
                    }
                    if (check == 0) {
                        break;
                    }
                }

                String defaultPassword = "abc123";
                String encryptedPassword = EncryptPassword("member", defaultPassword, id); // corrected folder

                members[count][0] = id;
                members[count][1] = lastName + "," + firstName;
                members[count][2] = cnic;
                members[count][3] = num;
                members[count][4] = encryptedPassword;
                members[count][5] = "None";

                System.out.println("\nMembership ID: " + id);
                System.out.println("Password: " + defaultPassword);

                System.out.println("Member Has Been Added!");

                // Update the members.txt file by adding memeber data
                UpdateFile("member", "yes", id);
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }
    }


    public static boolean Confirmation(){

        while (true) {
            System.out.print("\nEnter \"Y\" to Confirm Or Anything Else to Cancel Operation: ");
            try{
                String choice = input.nextLine().trim();
                if (choice.equalsIgnoreCase("Y")) {
                    return true;
                } else {
                    return false;
                }
            } catch (InputMismatchException ex){
                System.out.println("\n----> ERROR! Please enter the correct word <----");
                input.nextLine();
            }

        }

    }

    public static void RemoveMember() {
        line();
        try {
            loadBooks();   // Load books from file (to check if member has borrowed any)
        } catch (Exception e) {
            System.out.println("Error loading data from file.");
            return;
        }

        if (NotEmpty(members) == 0) {
            System.out.println("The Database is Already Empty");
            return;
        }

        while (true) {
            try {
                System.out.print("Enter Membership ID: ");
                String id = input.nextLine().trim();

                boolean idExists = false;
                for (int i = 0; i < NotEmpty(members); i++) {
                    if (members[i][0].equals(id)) {
                        idExists = true;
                        break;
                    }
                }
                if (!idExists) {
                    System.out.println("Invalid ID!");
                    return;
                }

                int check = 0;
                int index = 0;

                for (int i = 0; i < NotEmpty(members); i++) {
                    if (members[i][0].equalsIgnoreCase(id)) {
                        check = 1;
                        index = i;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.println("Membership ID " + id + " Does Not Exist In The Database");
                    return;
                }

                if (!(members[index][5].equalsIgnoreCase("None"))) {
                    System.out.println("The Membership ID " + id + " has Pending Dues!\nClear All Dues to Remove Member!");
                    return;
                }

                for (int i = 0; i < NotEmpty(books); i++) {
                    if (books[i][4].equalsIgnoreCase(id)) {
                        System.out.println("Cannot remove Membership ID " + id + " as they Still have Borrowed Books.\nReturn All Borrowed Books First.");
                        return;
                    }
                }


                System.out.printf("\n%-15s %-25s %-20s %-20s %-20s", "MemberID", "NAME", "CNIC", "PHONE", "LATEFEES");

                line();

                System.out.printf("%-15s %-25s %-20s %-20s %-20s\n", members[index][0], members[index][1], members[index][2], members[index][3], members[index][5]);


                if (!(Confirmation())) {
                    System.out.println("\nMember Removal Operation Cancelled!");
                    return;
                }

                NullifyRow(index, members);
                Normalize(index, members);

                UpdateFile("member", null, id);

                System.out.println("Membership ID " + id + " Has Been Removed From The Database.");

                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }
    }


    public static void ViewMembers() {
        line();
        if (NotEmpty(members) == 0) {
            System.out.printf("%52s\n", "No Records Found!");
            return;
        }

        System.out.printf("\n%-15s %-25s %-20s %-20s %-20s", "MemberID", "NAME", "CNIC", "PHONE", "LATEFEES");

        line();

        for (int i = 0; i < NotEmpty(members); i++) {
            System.out.printf("%-15s %-25s %-20s %-20s %-20s\n", members[i][0], members[i][1], members[i][2], members[i][3], members[i][5]);
        }
        line();

    }


    public static void SearchMembers() {
        line();
        if (NotEmpty(members) == 0) {
            System.out.println("The Database is Already Empty");
            return;
        }

        while (true) {
            System.out.println("\n1. Search By Name");
            System.out.println("2. Search By CNIC");
            System.out.println("3. Search by Membership ID");
            System.out.println("4. Exit");
            System.out.print("Enter Choice(1-4): ");
            try {
                int choice = input.nextInt();
                input.nextLine();

                switch (choice) {
                    case 1:
                        delay(1500);
                        SearchByName();
                        break;
                    case 2:
                        delay(1500);
                        SearchByCNIC();
                        break;
                    case 3:
                        delay(1500);
                        SearchByID();
                        break;
                    case 4:
                        delay(1500);
                        return;
                    default:
                        System.out.println("ERROR! Invalid Input");
                        delay(1500);
                        break;
                }
                line();

            } catch (InputMismatchException ex){
                System.out.println("ERROR! Enter correct information");
            }
        }
    }


    public static void SearchByName(){
        line();
        while (true) {
            try {
                System.out.print("\nEnter Name: ");
                String name = input.nextLine();
                name = name.trim();

                int check = 0;
                System.out.printf("\n%-15s %-25s %-20s %-20s %-20s", "MemberID", "NAME", "CNIC", "PHONE", "LATEFEES");

                line();

                for (int i = 0; i < NotEmpty(members); i++) {
                    if ((members[i][1].toLowerCase()).contains(name.toLowerCase())) {
                        System.out.printf("%-15s %-25s %-20s %-20s %-20s\n", members[i][0], members[i][1], members[i][2], members[i][3], members[i][5]);
                        check = 1;
                    }
                }

                if (!(check == 1)) {
                    System.out.printf("%52s\n", "No Records Found!");
                }
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }

    }

    public static void SearchByCNIC(){
        line();
        while (true) {
            try {
                System.out.print("Enter CNIC: ");
                String cnic = input.nextLine();
                cnic = cnic.trim();

                if (!(ValidateCNIC(cnic))) {
                    System.out.println("ERROR! Invalid CNIC!");
                    return;
                }

                int check = 0;
                System.out.printf("\n%-15s %-25s %-20s %-20s %-20s", "MemberID", "NAME", "CNIC", "PHONE", "LATEFEES");

                line();

                for (int i = 0; i < NotEmpty(members); i++) {
                    if ((members[i][2]).equals(cnic)) {
                        System.out.printf("%-15s %-25s %-20s %-20s %-20s\n", members[i][0], members[i][1], members[i][2], members[i][3], members[i][5]);
                        check = 1;
                        break;
                    }
                }

                if (check == 0) {
                    System.out.printf("%52s\n", "No Records Found!");
                }
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }

    }

    public static void SearchByID(){
        line();
        while (true) {
            try {
                System.out.print("Enter Membership ID: ");
                String id = input.nextLine();
                id = id.trim();

                boolean found = false;
                for (int i = 0; i < NotEmpty(members); i++) {
                    if (members[i][0].equals(id)) {
                        found = true;
                        break;
                    }
                }
                if (!found) {
                    System.out.println("Invalid ID!");
                    return;
                }

                int check = 0;
                System.out.printf("\n%-15s %-25s %-20s %-20s %-20s", "MemberID", "NAME", "CNIC", "PHONE", "LATEFEES");

                line();

                for (int i = 0; i < NotEmpty(members); i++) {
                    if ((members[i][0]).equals(id)) {
                        System.out.printf("%-15s %-25s %-20s %-20s %-20s\n", members[i][0], members[i][1], members[i][2], members[i][3], members[i][5]);
                        check = 1;
                        break;
                    }
                }

                if (!(check == 1)) {
                    System.out.printf("%52s\n", "No Records Found!");
                }
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }

    }

    // Function to update a password of any user (memeber, admin or System Admin)
    public static void UpdatePassword(String userType, String newPassword, String id, int idIndex) {
         
        // Check File name
        String fileName = "";

        //Encrypt new Password
        String encryptedPassword = EncryptPassword(userType, newPassword, id);

        if (userType.equalsIgnoreCase("admin")) {
            fileName = "admins";
            admin[idIndex][4] = encryptedPassword;
        } else if (userType.equalsIgnoreCase("member")) {
            fileName = "members";
            members[idIndex][4] = encryptedPassword;
        } else {
            fileName = "sysAdmins";
            systemAdmin[idIndex][4] = encryptedPassword;
        }

        // Open required file
        File file = new File(fileName + ".txt");

        // Create a new file if it does not exist
        if (!file.exists()) {
        try {
            file.createNewFile();
        } catch (IOException e) {
            System.out.println("Error creating " + fileName + ".txt: " + e.getMessage());
            return;
        }
    }
   
        // Open temporary file to save data of all the users except the one which is being updated
        File tempFile = new File("temp.txt");

        // Open data file as reader and temporary file as writer
        try (Scanner reader = new Scanner(file);
             FileWriter writer = new FileWriter(tempFile, true)) {

            // Loop to read each line of data file
            while (reader.hasNextLine()) {

                // Store each line
                String line = reader.nextLine();

                // Split the line by space to save id, name and other information as an array
                String[] credentials = line.trim().split(" ");

                // If the ID matches skip that line
                if (credentials.length > 0 && credentials[0].equals(id)) {
                    continue; // Skip the line with the old password
                }

                // Write other lines in temporary file
                writer.write(line + "\n");
            }
        } catch (IOException e) {
            System.out.println("An error occurred. Please try again later.");
            return;
        }

        // Call UpdateFile to update the changes
        UpdateFile(userType, "yes", id);

    }

    public static void MemberPasswordChangeAdmin() {
        line();

        if (NotEmpty(members) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        while(true) {
            try {
                System.out.print("\nEnter member ID: ");
                String id = input.nextLine().trim();

                if (!(Integer.parseInt(id) > 0 && Integer.parseInt(id) <= members.length)) {
                    System.out.println("ERROR! Invalid ID!");
                    return;
                }

                // Determine the index of the member with this ID
                int memberExistanceIndex = -1;
                for (int i = 0; i < NotEmpty(members); i++) {
                    if (members[i][0].equals(id)) {
                        memberExistanceIndex = i;
                        break;
                    }
                }

                if (memberExistanceIndex == -1) {
                    System.out.println("Member with this ID does not exist.");
                    return;
                }

                System.out.print("\nEnter your password (Admin): ");
                String password = input.nextLine().trim();

                System.out.print("\nEnter member's new password: ");
                String newPassword = input.nextLine().trim();

                System.out.print("\nConfirm the new password: ");
                String confirmPassword = input.nextLine().trim();

                if (!(password.equals(DecryptPassword("admin", loggedInAdminPassword, loggedInAdminID)))) {
                    System.out.println("ERROR! Invalid Password");
                    return;
                }

                if (!(newPassword.equals(confirmPassword))) {
                    System.out.println("Both \"password\" and \"confirm password\" should be same");
                    return;
                }

                UpdatePassword("member", newPassword, id, memberExistanceIndex);

                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }
    }


    public static void MemberPasswordChangeSelf() {
        line();
        if (NotEmpty(members) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        String id = loggedInMemberID.trim();

        // Find index of logged-in member in array
        int memberExistanceIndex = -1;
        for (int i = 0; i < NotEmpty(members); i++) {
            if (members[i][0].equalsIgnoreCase(id)) {
                memberExistanceIndex = i;
                break;
            }
        }

        if (memberExistanceIndex == -1) {
            System.out.println("ERROR! Invalid ID!");
            return;
        }

        while(true) {
            try {
                System.out.print("\nEnter your old password: ");
                String password = input.nextLine().trim();

                System.out.print("\nEnter new password: ");
                String newPassword = input.nextLine().trim();

                System.out.print("\nConfirm the new password: ");
                String confirmPassword = input.nextLine().trim();

                // Check old password
                if (!(password.equals(DecryptPassword("member", loggedInMemberPassword, loggedInMemberID)))) {
                    System.out.println("ERROR! Invalid Password");
                    return;
                }

                // Check if new password matches confirmation
                if (!(newPassword.equals(confirmPassword))) {
                    System.out.println("Both \"password\" and \"confirm password\" should be same");
                    return;
                }

                // Update password in memory and file
                UpdatePassword("member", newPassword, id, memberExistanceIndex);
                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }
    }


    public static void AdminPasswordChangeSysAdmin() {
        line();
        if (NotEmpty(admin) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        while(true) {
            try {
                System.out.print("\nEnter admin ID: ");
                String id = input.nextLine().trim();

                // Find the index of the admin in the array
                int adminExistanceIndex = -1;
                for (int i = 0; i < NotEmpty(admin); i++) {
                    if (admin[i][0].equals(id)) {
                        adminExistanceIndex = i;
                        break;
                    }
                }

                if (adminExistanceIndex == -1) {
                    System.out.println("ERROR! Invalid ID!");
                    return;
                }

                System.out.print("\nEnter your password (System Admin): ");
                String password = input.nextLine().trim();

                System.out.print("\nEnter admin's new password: ");
                String newPassword = input.nextLine().trim();

                System.out.print("\nConfirm the new password: ");
                String confirmPassword = input.nextLine().trim();

                if (!(password.equals(DecryptPassword("sysAdmin", loggedInSysAdminPassword, loggedInSysAdminID)))) {
                    System.out.println("ERROR! Invalid Password");
                    return;
                }

                if (!(newPassword.equals(confirmPassword))) {
                    System.out.println("Both password and confirm password should be same");
                    return;
                }

                UpdatePassword("admin", newPassword, id, adminExistanceIndex);
                line();

                break;
            } catch (InputMismatchException ex){
                System.out.println("ERROR! Enter correct information");
            }
        }
    }


    public static void AdminPasswordChangeSelf() {
        line();
        if (NotEmpty(admin) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        String id = loggedInAdminID;

        // Find the correct index of the logged-in admin
        int adminExistanceIndex = -1;
        for (int i = 0; i < NotEmpty(admin); i++) {
            if (admin[i][0].equals(id)) {
                adminExistanceIndex = i;
                break;
            }
        }

        if (adminExistanceIndex == -1) {
            System.out.println("ERROR! Invalid ID!");
            return;
        }

        while (true) {
            try {
                System.out.print("\nEnter your old password: ");
                String password = input.nextLine().trim();

                System.out.print("\nEnter new password: ");
                String newPassword = input.nextLine().trim();

                System.out.print("\nConfirm the new password: ");
                String confirmPassword = input.nextLine().trim();

                if (!(password.equals(DecryptPassword("admin", loggedInAdminPassword, loggedInAdminID)))) {
                    System.out.println("ERROR! Invalid Password");
                    return;
                }

                if (!(newPassword.equals(confirmPassword))) {
                    System.out.println("Both \"password\" and \"confirm password\" should be same");
                    return;
                }

                UpdatePassword("admin", newPassword, id, adminExistanceIndex);

                line();

                break;
            } catch (InputMismatchException ex) {
                System.out.println("ERROR! Enter correct information");
            }
        }
    }


    public static void SysAdminPasswordChange() {
        line();
        if (NotEmpty(systemAdmin) == 0) {
            System.out.println("The Database is Empty.");
            return;
        }

        String id = loggedInSysAdminID;

        // Find the correct index of the logged-in system admin
        int sysAdminExistanceIndex = -1;
        for (int i = 0; i < NotEmpty(systemAdmin); i++) {
            if (systemAdmin[i][0].equals(id)) {
                sysAdminExistanceIndex = i;
                break;
            }
        }

        if (sysAdminExistanceIndex == -1) {
            System.out.println("ERROR! Invalid ID!");
            return;
        }

        while (true) {
            try {
                System.out.print("\nEnter your old password: ");
                String password = input.nextLine().trim();

                System.out.print("\nEnter new password: ");
                String newPassword = input.nextLine().trim();

                System.out.print("\nConfirm the new password: ");
                String confirmPassword = input.nextLine().trim();

                if (!(password.equals(DecryptPassword("sysAdmin", loggedInSysAdminPassword, loggedInSysAdminID)))) {
                    System.out.println("Invalid Password");
                    return;
                }

                if (!(newPassword.equals(confirmPassword))) {
                    System.out.println("Both password and confirm password should be same");
                    return;
                }
                UpdatePassword("sysAdmin", newPassword, id, sysAdminExistanceIndex);

                line();

                break;
            } catch (InputMismatchException ex){
                System.out.println("ERROR! Enter correct information");
            }
        }
    }

    // Function to update file
    public static void UpdateFile(String userType, String addData, String id) {
        // File name to check user type
        String fileName = "";
        if (userType.equalsIgnoreCase("admin")) {
            fileName = "admins";
        } else if (userType.equalsIgnoreCase("member")) {
            fileName = "members";
        } else {
            fileName = "systemAdmins";
        }

        //Open file
        File file = new File(fileName + ".txt");

        // Create the file if it doesn't exist
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                System.out.println("Error creating " + fileName + ".txt: " + e.getMessage());
                return;
            }
        }

        // Write the entire array to the file
        try (PrintWriter writer = new PrintWriter(new FileOutputStream(file, false))){
            String[][] array = null;
            if (userType.equalsIgnoreCase("admin")) {
                array = admin;
            } else if (userType.equalsIgnoreCase("member")) {
                array = members;
            } else {
                array = systemAdmin;
            }

            int count = NotEmpty(array); // Find length of an array

            // Loop to write updated ddata in a file
            for (int i = 0; i < count; i++) {

                // Only add data if it is not empty or null
                if (array[i][0] != null && !array[i][0].isEmpty()) {

                    // If the file data is being updated for member then this condition otherwise else one
                    // Beacause members have 6 features
                    if (userType.equalsIgnoreCase("member")) {
                        writer.printf("%s %s %s %s %s %s%n",
                                array[i][0], array[i][1], array[i][2],
                                array[i][3], array[i][4], array[i][5]);
                    } else {
                        writer.printf("%s %s %s %s %s%n",
                                array[i][0], array[i][1], array[i][2],
                                array[i][3], array[i][4]);
                    }
                }
            }
        } catch (IOException e) {
            System.out.println("Error writing to " + fileName + ".txt: " + e.getMessage());
            return;
        }

        // Delete encryption file if we are removing user
        if (addData == null) {
            if (fileName.equals("members")) {
                File memberFile = new File("members", id + ".txt");
                if(memberFile.delete()){
                    System.out.println("\nData Updated Successfully.");
                }
            } else if (fileName.equals("admins")) {
                File memberFile = new File("admins", id + ".txt");
                if(memberFile.delete()){
                    System.out.println("\nData Updated Successfully.");
                }
            } else {
                File memberFile = new File("sysAdmins", id + ".txt");
                if(memberFile.delete()){
                    System.out.println("\nData Updated Successfully.");
                }
            }
        } else {
            System.out.println("\nData Updated Successfully.");
        }
    }
}