MemoryBookmarkDatabase.java

package net.pterodactylus.sone.database.memory;

import static com.google.common.collect.FluentIterable.from;

import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import net.pterodactylus.sone.data.Post;
import net.pterodactylus.sone.data.Post.EmptyPost;
import net.pterodactylus.sone.database.BookmarkDatabase;

import com.google.common.base.Function;

/**
 * Memory-based {@link BookmarkDatabase} implementation.
 *
 * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 */
public class MemoryBookmarkDatabase implements BookmarkDatabase {

	private final ReadWriteLock lock = new ReentrantReadWriteLock();
	private final MemoryDatabase memoryDatabase;
	private final ConfigurationLoader configurationLoader;
	private final Set<String> bookmarkedPosts = new HashSet<String>();

	public MemoryBookmarkDatabase(MemoryDatabase memoryDatabase,
			ConfigurationLoader configurationLoader) {
		this.memoryDatabase = memoryDatabase;
		this.configurationLoader = configurationLoader;
	}

	public void start() {
		loadBookmarkedPosts();
	}

	private void loadBookmarkedPosts() {
		Set<String> bookmarkedPosts = configurationLoader.loadBookmarkedPosts();
		lock.writeLock().lock();
		try {
			this.bookmarkedPosts.clear();
			this.bookmarkedPosts.addAll(bookmarkedPosts);
		} finally {
			lock.writeLock().unlock();
		}
	}

	public void stop() {
		saveBookmarkedPosts();
	}

	private void saveBookmarkedPosts() {
		lock.readLock().lock();
		try {
			configurationLoader.saveBookmarkedPosts(this.bookmarkedPosts);
		} finally {
			lock.readLock().unlock();
		}
	}

	@Override
	public void bookmarkPost(Post post) {
		lock.writeLock().lock();
		try {
			bookmarkedPosts.add(post.getId());
			saveBookmarkedPosts();
		} finally {
			lock.writeLock().unlock();
		}
	}

	@Override
	public void unbookmarkPost(Post post) {
		lock.writeLock().lock();
		try {
			bookmarkedPosts.remove(post.getId());
			saveBookmarkedPosts();
		} finally {
			lock.writeLock().unlock();
		}
	}

	@Override
	public boolean isPostBookmarked(Post post) {
		lock.readLock().lock();
		try {
			return bookmarkedPosts.contains(post.getId());
		} finally {
			lock.readLock().unlock();
		}
	}

	@Override
	public Set<Post> getBookmarkedPosts() {
		lock.readLock().lock();
		try {
			return from(bookmarkedPosts).transform(
					new Function<String, Post>() {
						@Override
						public Post apply(String postId) {
							return memoryDatabase.getPost(postId)
									.or(new EmptyPost(postId));
						}
					}).toSet();
		} finally {
			lock.readLock().unlock();
		}
	}

}