public class Student_Manage {
    static Scanner scan = new Scanner(System.in);
    static LinkedList<Student> studentList = new LinkedList<>();

    // Đọc danh sách sinh viên từ file
    @SuppressWarnings("unchecked")
    public static LinkedList<Student> readFromFile(String path) {
        LinkedList<Student> list = null;
        try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(path))) {
            list = (LinkedList<Student>) ois.readObject();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list != null ? list : new LinkedList<>();
    }

    // Lưu danh sách sinh viên ra file
    public static boolean saveToFile(LinkedList<Student> list, String path) {
        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(path))) {
            oos.writeObject(list);
            return true;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    // Xuất thông tin danh sách sinh viên
    public static void displayStudentList(LinkedList<Student> list) {
        System.out.printf("%-10s %-20s %-10s %-10s\n", "ID", "Name", "Result", "Rank");
        for (Student student : list) {
            System.out.println(student);
        }
    }

    // Thêm sinh viên mới vào danh sách
    public static void addStudent(LinkedList<Student> list) {
        System.out.println("Enter Student ID: ");
        String id = scan.nextLine();
        System.out.println("Enter Student Name: ");
        String name = scan.nextLine();
        Student student = new Student(id, name);
        list.add(student);
    }

    // Tìm kiếm sinh viên theo mã sinh viên
    public static int findStudentById(LinkedList<Student> list, String id) {
        for (int i = 0; i < list.size(); i++) {
            if (list.get(i).getStudent_id().equalsIgnoreCase(id)) {
                return i;
            }
        }
        return -1;
    }

    // Xóa sinh viên khỏi danh sách
    public static void deleteStudent(LinkedList<Student> list) {
        System.out.println("Enter Student ID to delete: ");
        String id = scan.nextLine();
        int index = findStudentById(list, id);
        if (index != -1) {
            list.remove(index);
            System.out.println("Student deleted successfully.");
        } else {
            System.out.println("Student not found.");
        }
    }

    // Sắp xếp danh sách sinh viên theo họ tên
    public static void sortStudentsByName(LinkedList<Student> list) {
        list.sort((s1, s2) -> s1.getStudent_name().compareToIgnoreCase(s2.getStudent_name()));
        System.out.println("List sorted by name.");
    }

    // Cập nhật điểm trung bình của sinh viên
    public static void updateStudentResult(LinkedList<Student> list) {
        System.out.println("Enter Student ID to update result: ");
        String id = scan.nextLine();
        int index = findStudentById(list, id);
        if (index != -1) {
            System.out.println("Enter new result: ");
            double result = scan.nextDouble();
            scan.nextLine(); // Clear buffer
            list.get(index).setStudent_result(result);
            System.out.println("Student result updated.");
        } else {
            System.out.println("Student not found.");
        }
    }

    // Menu chính
    public static void main(String[] args) {
        String filePath = "students.dat";
        int choice;
        do {
            System.out.println("\n--- STUDENT MANAGEMENT SYSTEM ---");
            System.out.println("1. Read Student List from File");
            System.out.println("2. Save Student List to File");
            System.out.println("3. Display Student List");
            System.out.println("4. Add Student");
            System.out.println("5. Find Student by ID");
            System.out.println("6. Delete Student by ID");
            System.out.println("7. Sort Students by Name");
            System.out.println("8. Update Student Result");
            System.out.println("0. Exit");
            System.out.print("Enter your choice: ");
            choice = scan.nextInt();
            scan.nextLine(); // Clear buffer
            switch (choice) {
                case 1 -> studentList = readFromFile(filePath);
                case 2 -> {
                    if (saveToFile(studentList, filePath)) System.out.println("Data saved successfully.");
                    else System.out.println("Error saving data.");
                }
                case 3 -> displayStudentList(studentList);
                case 4 -> addStudent(studentList);
                case 5 -> {
                    System.out.println("Enter Student ID to search: ");
                    String id = scan.nextLine();
                    int index = findStudentById(studentList, id);
                    if (index != -1) System.out.println(studentList.get(index));
                    else System.out.println("Student not found.");
                }
                case 6 -> deleteStudent(studentList);
                case 7 -> sortStudentsByName(studentList);
                case 8 -> updateStudentResult(studentList);
                case 0 -> System.out.println("Exiting program.");
                default -> System.out.println("Invalid choice. Please try again.");
            }
        } while (choice != 0);
    }
}