Design Library Management

// ========== Enums ==========
enum BookStatus { AVAILABLE, BORROWED, RESERVED, LOST }
enum MemberType { STUDENT, FACULTY, REGULAR }

// ========== Book ==========
class Book {
    private String isbn;
    private String title;
    private String author;
    private List<BookCopy> copies;
    
    public Book(String isbn, String title, String author) {
        this.isbn = isbn;
        this.title = title;
        this.author = author;
        this.copies = new ArrayList<>();
    }
    
    public void addCopy() {
        copies.add(new BookCopy(this, copies.size() + 1));
    }
    
    public BookCopy getAvailableCopy() {
        return copies.stream()
            .filter(c -> c.getStatus() == BookStatus.AVAILABLE)
            .findFirst()
            .orElse(null);
    }
    
    public String getTitle() { return title; }
    public String getIsbn() { return isbn; }
}

class BookCopy {
    private int id;
    private Book book;
    private BookStatus status;
    
    public BookCopy(Book book, int id) {
        this.book = book;
        this.id = id;
        this.status = BookStatus.AVAILABLE;
    }
    
    public void setStatus(BookStatus s) { this.status = s; }
    public BookStatus getStatus() { return status; }
    public Book getBook() { return book; }
}

// ========== Member ==========
abstract class Member {
    protected String id;
    protected String name;
    protected List<Loan> activeLoans;
    
    public Member(String id, String name) {
        this.id = id;
        this.name = name;
        this.activeLoans = new ArrayList<>();
    }
    
    public abstract int getMaxBooks();
    public abstract int getLoanDays();
    
    public boolean canBorrow() {
        return activeLoans.size() < getMaxBooks();
    }
    
    public void addLoan(Loan loan) {
        activeLoans.add(loan);
    }
    
    public void removeLoan(Loan loan) {
        activeLoans.remove(loan);
    }
}

class StudentMember extends Member {
    public StudentMember(String id, String name) { super(id, name); }
    public int getMaxBooks() { return 5; }
    public int getLoanDays() { return 14; }
}

class FacultyMember extends Member {
    public FacultyMember(String id, String name) { super(id, name); }
    public int getMaxBooks() { return 10; }
    public int getLoanDays() { return 30; }
}

// ========== Loan ==========
class Loan {
    private BookCopy bookCopy;
    private Member member;
    private LocalDate issueDate;
    private LocalDate dueDate;
    private LocalDate returnDate;
    private static final double FINE_PER_DAY = 0.50;
    
    public Loan(BookCopy copy, Member member) {
        this.bookCopy = copy;
        this.member = member;
        this.issueDate = LocalDate.now();
        this.dueDate = issueDate.plusDays(member.getLoanDays());
        copy.setStatus(BookStatus.BORROWED);
    }
    
    public double returnBook() {
        this.returnDate = LocalDate.now();
        bookCopy.setStatus(BookStatus.AVAILABLE);
        member.removeLoan(this);
        return calculateFine();
    }
    
    public double calculateFine() {
        if (returnDate == null || !returnDate.isAfter(dueDate)) return 0;
        long daysLate = ChronoUnit.DAYS.between(dueDate, returnDate);
        return daysLate * FINE_PER_DAY;
    }
}

// ========== Library ==========
class Library {
    private static Library instance;
    private Map<String, Book> booksByIsbn;
    private Map<String, Member> members;
    private List<Loan> allLoans;
    
    private Library() {
        booksByIsbn = new HashMap<>();
        members = new HashMap<>();
        allLoans = new ArrayList<>();
    }
    
    public static Library getInstance() {
        if (instance == null) instance = new Library();
        return instance;
    }
    
    public void addBook(Book book, int copies) {
        booksByIsbn.put(book.getIsbn(), book);
        for (int i = 0; i < copies; i++) book.addCopy();
    }
    
    public void registerMember(Member member) {
        members.put(member.id, member);
    }
    
    public Loan borrowBook(String memberId, String isbn) {
        Member member = members.get(memberId);
        Book book = booksByIsbn.get(isbn);
        
        if (member == null || book == null) return null;
        if (!member.canBorrow()) {
            System.out.println("Member has reached borrowing limit");
            return null;
        }
        
        BookCopy copy = book.getAvailableCopy();
        if (copy == null) {
            System.out.println("No copies available");
            return null;
        }
        
        Loan loan = new Loan(copy, member);
        member.addLoan(loan);
        allLoans.add(loan);
        System.out.println("Borrowed: " + book.getTitle());
        return loan;
    }
    
    public List<Book> searchByTitle(String title) {
        return booksByIsbn.values().stream()
            .filter(b -> b.getTitle().toLowerCase().contains(title.toLowerCase()))
            .collect(Collectors.toList());
    }
}