cs151/hw3/src/model/PhotoAlbumModel.java

package model;

import strategy.SortingStrategy;
import iterator.AlbumIterator;
import iterator.PhotoIterator;

import java.util.*;

/**
 * A model that represents a photo album.
 * <p>
 * This class is responsible for managing the photos in the album, as well as
 * the sorting strategy used to sort the photos.
 * The model notifies its listeners when the model changes.
 * It also provides methods to add and delete photos,
 * as well as to navigate through the photos.
 *
 * @author Yuri Tatishchev
 * @version 0.1 2025-03-26
 * @see Photo
 * @see SortingStrategy
 * @see AlbumIterator
 * @see PhotoIterator
 * @see ModelChangeListener
 */
public class PhotoAlbumModel {
    private List<Photo> photos;
    private SortingStrategy<Photo> sortingStrategy;
    private final List<ModelChangeListener> listeners;
    private AlbumIterator iterator;

    /**
     * A listener interface for model changes.
     * The method {@link #onModelChanged()} is called when the model changes.
     */
    public interface ModelChangeListener {
        /**
         * Called when the model changes.
         */
        void onModelChanged();
    }

    public PhotoAlbumModel() {
        photos = new ArrayList<>();
        listeners = new ArrayList<>();
        iterator = new PhotoIterator(photos);
    }

    /**
     * Adds a photo to the album.
     * Resets the iterator and notifies the listeners.
     *
     * @param photo the photo to add
     */
    public void addPhoto(Photo photo) {
        photos.add(photo);
        sortPhotos();
        notifyListeners();
    }

    /**
     * Deletes a photo from the album by name.
     * If the deleted photo is the current photo or the album is empty,
     * the iterator is reset.
     *
     * @param name the name of the photo to delete
     */
    public void deletePhoto(String name) {
        Photo currentPhoto = iterator.current();
        photos.removeIf(photo -> photo.name().equals(name));
        if (photos.isEmpty() || (currentPhoto != null && currentPhoto.name().equals(name))) {
            iterator = new PhotoIterator(photos);
        }
        notifyListeners();
    }

    /**
     * Sets the sorting strategy for the photos.
     * Sorts the photos using the new strategy and resets the iterator.
     *
     * @param strategy the sorting strategy to set
     */
    public void setSortingStrategy(SortingStrategy<Photo> strategy) {
        this.sortingStrategy = strategy;
        sortPhotos();
        iterator = new PhotoIterator(photos);
        notifyListeners();
    }

    private void sortPhotos() {
        if (sortingStrategy != null) {
            photos = sortingStrategy.sort(photos);
            iterator = new PhotoIterator(photos);
        }
    }

    /**
     * Adds a listener for model changes.
     *
     * @param listener the listener to add
     */
    public void addListener(ModelChangeListener listener) {
        listeners.add(listener);
    }

    /**
     * Notifies all listeners that the model has changed,
     * calling the {@link ModelChangeListener#onModelChanged()} method.
     */
    private void notifyListeners() {
        for (ModelChangeListener listener : listeners) {
            listener.onModelChanged();
        }
    }

    /**
     * Returns an unmodifiable list of photos in the album.
     *
     * @return an unmodifiable list of photos
     */
    public List<Photo> getPhotos() {
        return Collections.unmodifiableList(photos);
    }

    /**
     * Returns the photo in the album that the iterator is currently pointing to.
     *
     * @return the current photo
     */
    public Photo getCurrentPhoto() {
        try {
            return iterator.current();
        } catch (NoSuchElementException e) {
            return null;
        }
    }

    /**
     * Returns whether there is a next photo in the album.
     *
     * @return {@code true} if there is a next photo, {@code false} otherwise
     */
    public boolean hasNext() {
        return iterator.hasNext();
    }

    /**
     * Returns whether there is a previous photo in the album.
     *
     * @return {@code true} if there is a previous photo, {@code false} otherwise
     */
    public boolean hasPrevious() {
        return iterator.hasPrevious();
    }

    /**
     * Advances the iterator to the next photo in the album.
     * Notifies the listeners.
     *
     * @return the next photo or {@code null} if there is no next photo
     */
    public Photo next() {
        try {
            Photo next = iterator.next();
            notifyListeners();
            return next;
        } catch (NoSuchElementException e) {
            return null;
        }
    }

    /**
     * Advances the iterator to the previous photo in the album.
     * Notifies the listeners.
     *
     * @return the previous photo or {@code null} if there is no previous photo
     */
    public Photo previous() {
        try {
            Photo prev = iterator.previous();
            notifyListeners();
            return prev;
        } catch (NoSuchElementException e) {
            return null;
        }
    }
}