AdministratorInterface.java

import java.util.Scanner;

/**
 * AdministratorInterface provides the command line menu for admins.
 */
public class AdministratorInterface {
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        System.out.println("Welcome to the Course Enrollment and Grade Management System!");
        boolean running = true;

        while (running) {
            displayMenu();
            int choice = getIntInput("Enter your choice: ");

            switch (choice) {
                case 1:
                    addNewCourse();
                    break;
                case 2:
                    enrollStudentInCourse();
                    break;
                case 3:
                    assignGradeToStudent();
                    break;
                case 4:
                    calculateStudentOverallGrade();
                    break;
                case 5:
                    viewTotalEnrollments();
                    break;
                case 6:
                    System.out.println("Goodbye!");
                    running = false;
                    break;
                default:
                    System.out.println("Invalid choice. Please try again.");
            }
        }
        scanner.close();
    }

    /**
     * Displays the main menu.
     */
    private static void displayMenu() {
        System.out.println("\n========== MAIN MENU ==========");
        System.out.println("1. Add a new course");
        System.out.println("2. Enroll student in course");
        System.out.println("3. Assign grade to student");
        System.out.println("4. Calculate overall course grade");
        System.out.println("5. View total enrolled students");
        System.out.println("6. Exit");
        System.out.println("===============================");
    }

    /**
     * Handles adding a new course.
     */
    private static void addNewCourse() {
        System.out.println("\n--- Add New Course ---");
        String code = getStringInput("Enter course code: ");
        String name = getStringInput("Enter course name: ");
        int capacity = getIntInput("Enter maximum capacity: ");

        CourseManagement.addCourse(code, name, capacity);
        System.out.println("Course added successfully!");
    }

    /**
     * Handles enrolling a student in a course.
     */
    private static void enrollStudentInCourse() {
        System.out.println("\n--- Enroll Student ---");
        String studentName = getStringInput("Enter student name: ");
        String studentId = getStringInput("Enter student ID: ");
        Student student = new Student(studentName, studentId);

        System.out.println("Available courses:");
        for (int i = 0; i < CourseManagement.getCourses().size(); i++) {
            Course c = CourseManagement.getCourses().get(i);
            System.out.println((i + 1) + ". " + c.getCourseCode() + " - " + c.getName());
        }

        int courseChoice = getIntInput("Select course number: ") - 1;
        if (courseChoice >= 0 && courseChoice < CourseManagement.getCourses().size()) {
            Course selected = CourseManagement.getCourses().get(courseChoice);
            CourseManagement.enrollStudent(student, selected);
        } else {
            System.out.println("Invalid course selection.");
        }
    }

    /**
     * Handles assigning a grade.
     */
    private static void assignGradeToStudent() {
        System.out.println("\n--- Assign Grade ---");
        String studentName = getStringInput("Enter student name: ");
        String studentId = getStringInput("Enter student ID: ");
        Student student = new Student(studentName, studentId);

        String courseCode = getStringInput("Enter course code: ");
        double grade = getDoubleInput("Enter grade (0-100): ");

        for (Course c : CourseManagement.getCourses()) {
            if (c.getCourseCode().equals(courseCode)) {
                CourseManagement.assignGrade(student, c, grade);
                return;
            }
        }
        System.out.println("Course not found.");
    }

    /**
     * Handles calculating overall grade.
     */
    private static void calculateStudentOverallGrade() {
        System.out.println("\n--- Calculate Overall Grade ---");
        String studentName = getStringInput("Enter student name: ");
        String studentId = getStringInput("Enter student ID: ");
        Student student = new Student(studentName, studentId);

        double overall = CourseManagement.calculateOverallGrade(student);
        System.out.printf("Overall grade for " + student.getName() + ": %.2f%n", overall);
    }

    /**
     * Shows total enrollments across all courses.
     */
    private static void viewTotalEnrollments() {
        System.out.println("\nTotal enrolled students across all courses: " + Course.getTotalEnrolledStudents());
    }

    /**
     * Helper to get string input.
     */
    private static String getStringInput(String prompt) {
        System.out.print(prompt);
        return scanner.nextLine();
    }

    /**
     * Helper to get integer input with error handling.
     */
    private static int getIntInput(String prompt) {
        while (true) {
            System.out.print(prompt);
            try {
                return Integer.parseInt(scanner.nextLine());
            } catch (NumberFormatException e) {
                System.out.println("Please enter a valid number.");
            }
        }
    }

    /**
     * Helper to get double input with error handling.
     */
    private static double getDoubleInput(String prompt) {
        while (true) {
            System.out.print(prompt);
            try {
                return Double.parseDouble(scanner.nextLine());
            } catch (NumberFormatException e) {
                System.out.println("Please enter a valid number.");
            }
        }
    }
}