Mini-challenge: Thư viện đa phương tiện với sealed và record

import java.util.*;
import java.util.stream.Collectors;

public class LibraryCatalogApp {

    public sealed interface LibraryAsset permits PrintedBook, AudioBook, DigitalEbook, ReferenceJournal {
        String id();
        String title();

        default String assetType() {
            return getClass().getSimpleName();
        }
    }

    public record PrintedBook(String id, String title, int pageCount, double weightGrams) implements LibraryAsset {
        public PrintedBook {
            validateIdAndTitle(id, title);
            if (pageCount <= 0) throw new IllegalArgumentException("pageCount must be positive, got: " + pageCount);
            if (weightGrams <= 0) throw new IllegalArgumentException("weightGrams must be positive, got: " + weightGrams);
        }
    }

    public record AudioBook(String id, String title, int durationMinutes, double bitrateKbps) implements LibraryAsset {
        public AudioBook {
            validateIdAndTitle(id, title);
            if (durationMinutes <= 0) throw new IllegalArgumentException("durationMinutes must be positive, got: " + durationMinutes);
            if (bitrateKbps <= 0) throw new IllegalArgumentException("bitrateKbps must be positive, got: " + bitrateKbps);
        }
    }

    public record DigitalEbook(String id, String title, long fileSizeBytes, String format) implements LibraryAsset {
        public DigitalEbook {
            validateIdAndTitle(id, title);
            if (fileSizeBytes <= 0) throw new IllegalArgumentException("fileSizeBytes must be positive, got: " + fileSizeBytes);
            Objects.requireNonNull(format, "format must not be null");
        }
    }

    public record ReferenceJournal(String id, String title, int issueNumber, boolean isRestricted) implements LibraryAsset {
        public ReferenceJournal {
            validateIdAndTitle(id, title);
            if (issueNumber <= 0) throw new IllegalArgumentException("issueNumber must be positive, got: " + issueNumber);
        }
    }

    private static void validateIdAndTitle(String id, String title) {
        Objects.requireNonNull(id, "id must not be null");
        if (id.isBlank()) throw new IllegalArgumentException("id must not be blank");
        Objects.requireNonNull(title, "title must not be null");
        if (title.isBlank()) throw new IllegalArgumentException("title must not be blank");
    }

    public static class LibraryCatalog {
        private final List<LibraryAsset> assets = new ArrayList<>();

        public void addAsset(LibraryAsset asset) {
            Objects.requireNonNull(asset, "asset must not be null");
            assets.add(asset);
        }

        public int totalAssets() {
            return assets.size();
        }

        public List<LibraryAsset> assets() {
            return List.copyOf(assets); // Tra ve immutable copy
        }

        public Map<String, Long> countByType() {
            return assets.stream()
                .collect(Collectors.groupingBy(LibraryAsset::assetType, Collectors.counting()));
        }
    }

    public static double calculateMonthlyMaintenanceCost(LibraryAsset asset) {
        return switch (asset) {
            case PrintedBook b -> b.weightGrams() * 2.0;
            case AudioBook a -> a.durationMinutes() * 15.0;
            case DigitalEbook e -> (e.fileSizeBytes() / (1024.0 * 1024.0)) * 500.0;
            case ReferenceJournal j -> j.isRestricted() ? 100000.0 : 30000.0;
        };
    }

    public static String describeAsset(LibraryAsset asset) {
        return switch (asset) {
            case PrintedBook b -> String.format("Sach in: '%s' (%d trang, %.1fg)", b.title(), b.pageCount(), b.weightGrams());
            case AudioBook a -> String.format("Sach noi: '%s' (%d phut, %.0f kbps)", a.title(), a.durationMinutes(), a.bitrateKbps());
            case DigitalEbook e -> String.format("Ebook: '%s' (Dinh dang %s, %d bytes)", e.title(), e.format(), e.fileSizeBytes());
            case ReferenceJournal j -> String.format("Tap chi: '%s' (Ky so %d, %s)",
                j.title(), j.issueNumber(), j.isRestricted() ? "Phong doc kin" : "Pho thong");
        };
    }

    public static void main(String[] args) {
        LibraryCatalog catalog = new LibraryCatalog();

        PrintedBook book = new PrintedBook("B-01", "Clean Code", 464, 600.0);
        AudioBook audio = new AudioBook("A-01", "Design Patterns Audio", 240, 320.0);
        DigitalEbook ebook = new DigitalEbook("E-01", "Java Concurrency in Practice", 3 * 1024 * 1024L, "PDF");
        ReferenceJournal journal = new ReferenceJournal("J-01", "ACM Computing Surveys", 108, true);

        catalog.addAsset(book);
        catalog.addAsset(audio);
        catalog.addAsset(ebook);
        catalog.addAsset(journal);

        System.out.println("=== HE THONG QUAN LY AN PHAM THU VIEN ===");
        System.out.println("Da nap: " + catalog.totalAssets() + " an pham vao danh muc.");
        System.out.println("Tong so an pham: " + catalog.totalAssets());

        System.out.println("Chi phi luu tru hang thang:");
        for (LibraryAsset asset : catalog.assets()) {
            double cost = calculateMonthlyMaintenanceCost(asset);
            System.out.println("  [" + asset.id() + "] " + asset.title() + ": " + String.format("%.2f VND", cost));
        }

        System.out.println("\nThong ke theo loai an pham: " + catalog.countByType());
    }
}