Extract memory-based identity database into its own class.
[Sone.git] / src / main / java / net / pterodactylus / sone / database / memory / MemoryDatabase.java
index 264571e..bace9d9 100644 (file)
 
 package net.pterodactylus.sone.database.memory;
 
+import static com.google.common.base.Optional.fromNullable;
 import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Predicates.not;
+import static com.google.common.collect.FluentIterable.from;
+import static java.util.Collections.emptyList;
+import static java.util.logging.Logger.getLogger;
+import static net.pterodactylus.sone.data.Sone.LOCAL_SONE_FILTER;
 
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.SortedSet;
-import java.util.TreeSet;
-import java.util.UUID;
 import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
+import net.pterodactylus.sone.data.Album;
+import net.pterodactylus.sone.data.Image;
 import net.pterodactylus.sone.data.Post;
 import net.pterodactylus.sone.data.PostReply;
-import net.pterodactylus.sone.data.Reply;
 import net.pterodactylus.sone.data.Sone;
-import net.pterodactylus.sone.data.impl.AbstractPostReplyBuilder;
+import net.pterodactylus.sone.data.impl.DefaultSoneBuilder;
 import net.pterodactylus.sone.database.Database;
 import net.pterodactylus.sone.database.DatabaseException;
-import net.pterodactylus.sone.database.PostBuilder;
-import net.pterodactylus.sone.database.PostDatabase;
-import net.pterodactylus.sone.database.PostReplyBuilder;
-import net.pterodactylus.sone.database.SoneProvider;
+import net.pterodactylus.sone.database.SoneBuilder;
+import net.pterodactylus.sone.freenet.wot.Identity;
 import net.pterodactylus.util.config.Configuration;
 import net.pterodactylus.util.config.ConfigurationException;
 
+import com.google.common.base.Function;
 import com.google.common.base.Optional;
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.HashMultimap;
+import com.google.common.collect.ListMultimap;
+import com.google.common.collect.SetMultimap;
+import com.google.common.collect.SortedSetMultimap;
+import com.google.common.collect.TreeMultimap;
 import com.google.common.util.concurrent.AbstractService;
 import com.google.inject.Inject;
 
 /**
- * Memory-based {@link PostDatabase} implementation.
+ * Memory-based {@link Database} implementation.
  *
  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  */
 public class MemoryDatabase extends AbstractService implements Database {
 
+       private static final Logger logger = getLogger(MemoryDatabase.class.getName());
+
        /** The lock. */
        private final ReadWriteLock lock = new ReentrantReadWriteLock();
 
-       /** The Sone provider. */
-       private final SoneProvider soneProvider;
-
        /** The configuration. */
        private final Configuration configuration;
 
-       /** All posts by their ID. */
-       private final Map<String, Post> allPosts = new HashMap<String, Post>();
-
-       /** All posts by their Sones. */
-       private final Map<String, Collection<Post>> sonePosts = new HashMap<String, Collection<Post>>();
-
-       /** All posts by their recipient. */
-       private final Map<String, Collection<Post>> recipientPosts = new HashMap<String, Collection<Post>>();
-
-       /** Whether posts are known. */
-       private final Set<String> knownPosts = new HashSet<String>();
+       private final Map<String, Sone> sones = new HashMap<String, Sone>();
+       private final MemoryIdentityDatabase memoryIdentityDatabase;
+       private final MemoryPostDatabase memoryPostDatabase;
 
        /** All post replies by their ID. */
        private final Map<String, PostReply> allPostReplies = new HashMap<String, PostReply>();
+       private final SetMultimap<String, String> likedPostRepliesBySone = HashMultimap.create();
+       private final SetMultimap<String, String> postReplyLikingSones = HashMultimap.create();
+
+       /** Replies sorted by Sone. */
+       private final SortedSetMultimap<String, PostReply> sonePostReplies = TreeMultimap.create(new Comparator<String>() {
+
+               @Override
+               public int compare(String leftString, String rightString) {
+                       return leftString.compareTo(rightString);
+               }
+       }, PostReply.TIME_COMPARATOR);
 
        /** Replies by post. */
-       private final Map<String, SortedSet<PostReply>> postReplies = new HashMap<String, SortedSet<PostReply>>();
+       private final SortedSetMultimap<String, PostReply> postReplies = TreeMultimap.create(new Comparator<String>() {
+
+               @Override
+               public int compare(String leftString, String rightString) {
+                       return leftString.compareTo(rightString);
+               }
+       }, PostReply.TIME_COMPARATOR);
 
        /** Whether post replies are known. */
        private final Set<String> knownPostReplies = new HashSet<String>();
 
+       private final Map<String, Album> allAlbums = new HashMap<String, Album>();
+       private final ListMultimap<String, String> albumChildren = ArrayListMultimap.create();
+       private final ListMultimap<String, String> albumImages = ArrayListMultimap.create();
+
+       private final Map<String, Image> allImages = new HashMap<String, Image>();
+
        /**
         * Creates a new memory database.
         *
-        * @param soneProvider
-        *            The Sone provider
         * @param configuration
-        *            The configuration for loading and saving elements
+        *              The configuration for loading and saving elements
         */
        @Inject
-       public MemoryDatabase(SoneProvider soneProvider, Configuration configuration) {
-               this.soneProvider = soneProvider;
+       public MemoryDatabase(Configuration configuration) {
                this.configuration = configuration;
-       }
-
-       //
-       // DATABASE METHODS
-       //
-
-       /**
-        * Saves the database.
-        *
-        * @throws DatabaseException
-        *             if an error occurs while saving
-        */
-       @Override
-       public void save() throws DatabaseException {
-               saveKnownPosts();
-               saveKnownPostReplies();
+               memoryPostDatabase = new MemoryPostDatabase(this, lock, configuration);
+               memoryIdentityDatabase = new MemoryIdentityDatabase(lock);
        }
 
        //
        // SERVICE METHODS
        //
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        protected void doStart() {
-               loadKnownPosts();
+               memoryPostDatabase.start();
                loadKnownPostReplies();
                notifyStarted();
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        protected void doStop() {
                try {
-                       save();
-                       notifyStopped();
+                       memoryPostDatabase.stop();
                } catch (DatabaseException de1) {
-                       notifyFailed(de1);
+                       logger.log(Level.WARNING, "Could not stop post database!", de1);
                }
+               notifyStopped();
        }
 
-       //
-       // POSTPROVIDER METHODS
-       //
+       @Override
+       public Optional<Identity> getIdentity(String identityId) {
+               return memoryIdentityDatabase.getIdentity(identityId);
+       }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
-       public Optional<Post> getPost(String postId) {
+       public void storeIdentity(Identity identitiy) {
+               memoryIdentityDatabase.storeIdentity(identitiy);
+       }
+
+       @Override
+       public Function<String, Optional<Sone>> getSone() {
+               return new Function<String, Optional<Sone>>() {
+                       @Override
+                       public Optional<Sone> apply(String soneId) {
+                               return (soneId == null) ? Optional.<Sone>absent() : getSone(soneId);
+                       }
+               };
+       }
+
+       @Override
+       public Optional<Sone> getSone(String soneId) {
                lock.readLock().lock();
                try {
-                       return Optional.fromNullable(allPosts.get(postId));
+                       return fromNullable(sones.get(soneId));
                } finally {
                        lock.readLock().unlock();
                }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
-       public Collection<Post> getPosts(String soneId) {
-               return new HashSet<Post>(getPostsFrom(soneId));
+       public Collection<Sone> getSones() {
+               lock.readLock().lock();
+               try {
+                       return Collections.unmodifiableCollection(sones.values());
+               } finally {
+                       lock.readLock().unlock();
+               }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
-       public Collection<Post> getDirectedPosts(String recipientId) {
+       public Collection<Sone> getLocalSones() {
+               lock.readLock().lock();
+               try {
+                       return from(getSones()).filter(LOCAL_SONE_FILTER).toSet();
+               } finally {
+                       lock.readLock().unlock();
+               }
+       }
+
+       @Override
+       public Collection<Sone> getRemoteSones() {
                lock.readLock().lock();
                try {
-                       Collection<Post> posts = recipientPosts.get(recipientId);
-                       return (posts == null) ? Collections.<Post> emptySet() : new HashSet<Post>(posts);
+                       return from(getSones()).filter(not(LOCAL_SONE_FILTER)).toSet();
                } finally {
                        lock.readLock().unlock();
                }
        }
 
+       @Override
+       public void storeSone(Sone sone) {
+               lock.writeLock().lock();
+               try {
+                       sones.put(sone.getId(), sone);
+               } finally {
+                       lock.writeLock().unlock();
+               }
+       }
+
+       @Override
+       public SoneBuilder newSoneBuilder() {
+               return new DefaultSoneBuilder(this) {
+                       @Override
+                       public Sone build(Optional<SoneCreated> soneCreated) throws IllegalStateException {
+                               Sone sone = super.build(soneCreated);
+                               lock.writeLock().lock();
+                               try {
+                                       sones.put(sone.getId(), sone);
+                               } finally {
+                                       lock.writeLock().unlock();
+                               }
+                               return sone;
+                       }
+               };
+       }
+
        //
-       // POSTBUILDERFACTORY METHODS
+       // POSTPROVIDER METHODS
        //
 
+       @Override
+       public Function<String, Optional<Post>> getPost() {
+               return memoryPostDatabase.getPost();
+       }
+
+       @Override
+       public Optional<Post> getPost(String postId) {
+               return memoryPostDatabase.getPost(postId);
+       }
+
+       @Override
+       public Collection<Post> getPosts(String soneId) {
+               return memoryPostDatabase.getPosts(soneId);
+       }
+
+       @Override
+       public Collection<Post> getDirectedPosts(String recipientId) {
+               return memoryPostDatabase.getDirectedPosts(recipientId);
+       }
+
        /**
-        * {@inheritDocs}
+        * Returns whether the given post is known.
+        *
+        * @param post
+        *              The post
+        * @return {@code true} if the post is known, {@code false} otherwise
+        */
+       @Override
+       public boolean isPostKnown(Post post) {
+               return memoryPostDatabase.isPostKnown(post);
+       }
+
+       /**
+        * Sets whether the given post is known.
+        *
+        * @param post
+        *              The post
         */
        @Override
-       public PostBuilder newPostBuilder() {
-               return new MemoryPostBuilder(this, soneProvider);
+       public void setPostKnown(Post post) {
+               memoryPostDatabase.setPostKnown(post);
+       }
+
+       @Override
+       public void likePost(Post post, Sone localSone) {
+               memoryPostDatabase.likePost(post, localSone);
+       }
+
+       @Override
+       public void unlikePost(Post post, Sone localSone) {
+               memoryPostDatabase.unlikePost(post, localSone);
+       }
+
+       public boolean isLiked(Post post, Sone sone) {
+               return memoryPostDatabase.isLiked(post, sone);
+       }
+
+       @Override
+       public Set<Sone> getLikes(Post post) {
+               return memoryPostDatabase.getLikes(post);
        }
 
        //
        // POSTSTORE METHODS
        //
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        public void storePost(Post post) {
-               checkNotNull(post, "post must not be null");
-               lock.writeLock().lock();
-               try {
-                       allPosts.put(post.getId(), post);
-                       getPostsFrom(post.getSone().getId()).add(post);
-                       if (post.getRecipientId().isPresent()) {
-                               getPostsTo(post.getRecipientId().get()).add(post);
-                       }
-               } finally {
-                       lock.writeLock().unlock();
-               }
+               memoryPostDatabase.storePost(post);
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        public void removePost(Post post) {
-               checkNotNull(post, "post must not be null");
-               lock.writeLock().lock();
+               memoryPostDatabase.removePost(post);
+       }
+
+       @Override
+       public void storePosts(Sone sone, Collection<Post> posts) throws IllegalArgumentException {
+               /* verify that all posts are from the same Sone. */
+
+               memoryPostDatabase.storePosts(sone, posts);
+       }
+
+       @Override
+       public void removePosts(Sone sone) {
+               memoryPostDatabase.removePosts(sone);
+       }
+
+       //
+       // POSTREPLYPROVIDER METHODS
+       //
+
+       @Override
+       public Optional<PostReply> getPostReply(String id) {
+               lock.readLock().lock();
                try {
-                       allPosts.remove(post.getId());
-                       getPostsFrom(post.getSone().getId()).remove(post);
-                       if (post.getRecipientId().isPresent()) {
-                               getPostsTo(post.getRecipientId().get()).remove(post);
-                       }
-                       post.getSone().removePost(post);
+                       return fromNullable(allPostReplies.get(id));
                } finally {
-                       lock.writeLock().unlock();
+                       lock.readLock().unlock();
                }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
-       public void storePosts(Sone sone, Collection<Post> posts) throws IllegalArgumentException {
-               checkNotNull(sone, "sone must not be null");
-               /* verify that all posts are from the same Sone. */
-               for (Post post : posts) {
-                       if (!sone.equals(post.getSone())) {
-                               throw new IllegalArgumentException(String.format("Post from different Sone found: %s", post));
+       public List<PostReply> getReplies(String postId) {
+               lock.readLock().lock();
+               try {
+                       if (!postReplies.containsKey(postId)) {
+                               return emptyList();
                        }
+                       return new ArrayList<PostReply>(postReplies.get(postId));
+               } finally {
+                       lock.readLock().unlock();
                }
+       }
 
+       @Override
+       public void likePostReply(PostReply postReply, Sone localSone) {
                lock.writeLock().lock();
                try {
-                       /* remove all posts by the Sone. */
-                       getPostsFrom(sone.getId()).clear();
-                       for (Post post : posts) {
-                               allPosts.remove(post.getId());
-                               if (post.getRecipientId().isPresent()) {
-                                       getPostsTo(post.getRecipientId().get()).remove(post);
-                               }
-                       }
-
-                       /* add new posts. */
-                       getPostsFrom(sone.getId()).addAll(posts);
-                       for (Post post : posts) {
-                               allPosts.put(post.getId(), post);
-                               if (post.getRecipientId().isPresent()) {
-                                       getPostsTo(post.getRecipientId().get()).add(post);
-                               }
-                       }
+                       likedPostRepliesBySone.put(localSone.getId(), postReply.getId());
+                       postReplyLikingSones.put(postReply.getId(), localSone.getId());
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
-       public void removePosts(Sone sone) {
-               checkNotNull(sone, "sone must not be null");
+       public void unlikePostReply(PostReply postReply, Sone localSone) {
                lock.writeLock().lock();
                try {
-                       /* remove all posts by the Sone. */
-                       getPostsFrom(sone.getId()).clear();
-                       for (Post post : sone.getPosts()) {
-                               allPosts.remove(post.getId());
-                               if (post.getRecipientId().isPresent()) {
-                                       getPostsTo(post.getRecipientId().get()).remove(post);
-                               }
-                       }
+                       likedPostRepliesBySone.remove(localSone.getId(), postReply.getId());
+                       postReplyLikingSones.remove(postReply.getId(), localSone.getId());
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
-       //
-       // POSTREPLYPROVIDER METHODS
-       //
-
-       /**
-        * {@inheritDocs}
-        */
        @Override
-       public Optional<PostReply> getPostReply(String id) {
+       public boolean isLiked(PostReply postReply, Sone sone) {
                lock.readLock().lock();
                try {
-                       return Optional.fromNullable(allPostReplies.get(id));
+                       return postReplyLikingSones.containsEntry(postReply.getId(), sone.getId());
                } finally {
                        lock.readLock().unlock();
                }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
-       public List<PostReply> getReplies(String postId) {
+       public Set<Sone> getLikes(PostReply postReply) {
                lock.readLock().lock();
                try {
-                       if (!postReplies.containsKey(postId)) {
-                               return Collections.emptyList();
-                       }
-                       return new ArrayList<PostReply>(postReplies.get(postId));
+                       return from(postReplyLikingSones.get(postReply.getId())).transform(getSone()).transformAndConcat(this.<Sone>unwrap()).toSet();
                } finally {
                        lock.readLock().unlock();
                }
        }
 
        //
-       // POSTREPLYBUILDERFACTORY METHODS
+       // POSTREPLYSTORE METHODS
        //
 
        /**
-        * {@inheritDocs}
+        * Returns whether the given post reply is known.
+        *
+        * @param postReply
+        *              The post reply
+        * @return {@code true} if the given post reply is known, {@code false}
+        *         otherwise
         */
-       @Override
-       public PostReplyBuilder newPostReplyBuilder() {
-               return new MemoryPostReplyBuilder();
+       public boolean isPostReplyKnown(PostReply postReply) {
+               lock.readLock().lock();
+               try {
+                       return knownPostReplies.contains(postReply.getId());
+               } finally {
+                       lock.readLock().unlock();
+               }
        }
 
-       //
-       // POSTREPLYSTORE METHODS
-       //
+       @Override
+       public void setPostReplyKnown(PostReply postReply) {
+               lock.writeLock().lock();
+               try {
+                       knownPostReplies.add(postReply.getId());
+               } finally {
+                       lock.writeLock().unlock();
+               }
+       }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        public void storePostReply(PostReply postReply) {
                lock.writeLock().lock();
                try {
                        allPostReplies.put(postReply.getId(), postReply);
-                       if (postReplies.containsKey(postReply.getPostId())) {
-                               postReplies.get(postReply.getPostId()).add(postReply);
-                       } else {
-                               TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
-                               replies.add(postReply);
-                               postReplies.put(postReply.getPostId(), replies);
-                       }
+                       postReplies.put(postReply.getPostId(), postReply);
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        public void storePostReplies(Sone sone, Collection<PostReply> postReplies) {
                checkNotNull(sone, "sone must not be null");
@@ -379,43 +450,31 @@ public class MemoryDatabase extends AbstractService implements Database {
 
                lock.writeLock().lock();
                try {
+                       /* remove all post replies of the Sone. */
+                       for (PostReply postReply : getRepliesFrom(sone.getId())) {
+                               removePostReply(postReply);
+                       }
                        for (PostReply postReply : postReplies) {
                                allPostReplies.put(postReply.getId(), postReply);
-                               if (this.postReplies.containsKey(postReply.getPostId())) {
-                                       this.postReplies.get(postReply.getPostId()).add(postReply);
-                               } else {
-                                       TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
-                                       replies.add(postReply);
-                                       this.postReplies.put(postReply.getPostId(), replies);
-                               }
+                               sonePostReplies.put(postReply.getSone().getId(), postReply);
+                               this.postReplies.put(postReply.getPostId(), postReply);
                        }
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        public void removePostReply(PostReply postReply) {
                lock.writeLock().lock();
                try {
                        allPostReplies.remove(postReply.getId());
-                       if (postReplies.containsKey(postReply.getPostId())) {
-                               postReplies.get(postReply.getPostId()).remove(postReply);
-                               if (postReplies.get(postReply.getPostId()).isEmpty()) {
-                                       postReplies.remove(postReply.getPostId());
-                               }
-                       }
+                       postReplies.remove(postReply.getPostId(), postReply);
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
-       /**
-        * {@inheritDocs}
-        */
        @Override
        public void removePostReplies(Sone sone) {
                checkNotNull(sone, "sone must not be null");
@@ -431,194 +490,195 @@ public class MemoryDatabase extends AbstractService implements Database {
        }
 
        //
-       // PACKAGE-PRIVATE METHODS
+       // ALBUMPROVDER METHODS
        //
 
-       /**
-        * Returns whether the given post is known.
-        *
-        * @param post
-        *            The post
-        * @return {@code true} if the post is known, {@code false} otherwise
-        */
-       boolean isPostKnown(Post post) {
+       @Override
+       public Optional<Album> getAlbum(String albumId) {
                lock.readLock().lock();
                try {
-                       return knownPosts.contains(post.getId());
+                       return fromNullable(allAlbums.get(albumId));
                } finally {
                        lock.readLock().unlock();
                }
        }
 
-       /**
-        * Sets whether the given post is known.
-        *
-        * @param post
-        *            The post
-        * @param known
-        *            {@code true} if the post is known, {@code false} otherwise
-        */
-       void setPostKnown(Post post, boolean known) {
+       @Override
+       public List<Album> getAlbums(Album parent) {
+               lock.readLock().lock();
+               try {
+                       return from(albumChildren.get(parent.getId())).transformAndConcat(getAlbum()).toList();
+               } finally {
+                       lock.readLock().unlock();
+               }
+       }
+
+       @Override
+       public void moveUp(Album album) {
                lock.writeLock().lock();
                try {
-                       if (known) {
-                               knownPosts.add(post.getId());
-                       } else {
-                               knownPosts.remove(post.getId());
+                       List<String> albums = albumChildren.get(album.getParent().getId());
+                       int currentIndex = albums.indexOf(album.getId());
+                       if (currentIndex == 0) {
+                               return;
                        }
+                       albums.remove(album.getId());
+                       albums.add(currentIndex - 1, album.getId());
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
-       /**
-        * Returns whether the given post reply is known.
-        *
-        * @param postReply
-        *            The post reply
-        * @return {@code true} if the given post reply is known, {@code false}
-        *         otherwise
-        */
-       boolean isPostReplyKnown(PostReply postReply) {
-               lock.readLock().lock();
+       @Override
+       public void moveDown(Album album) {
+               lock.writeLock().lock();
                try {
-                       return knownPostReplies.contains(postReply.getId());
+                       List<String> albums = albumChildren.get(album.getParent().getId());
+                       int currentIndex = albums.indexOf(album.getId());
+                       if (currentIndex == (albums.size() - 1)) {
+                               return;
+                       }
+                       albums.remove(album.getId());
+                       albums.add(currentIndex + 1, album.getId());
                } finally {
-                       lock.readLock().unlock();
+                       lock.writeLock().unlock();
                }
        }
 
-       /**
-        * Sets whether the given post reply is known.
-        *
-        * @param postReply
-        *            The post reply
-        * @param known
-        *            {@code true} if the post reply is known, {@code false}
-        *            otherwise
-        */
-       void setPostReplyKnown(PostReply postReply, boolean known) {
+       //
+       // ALBUMSTORE METHODS
+       //
+
+       @Override
+       public void storeAlbum(Album album) {
                lock.writeLock().lock();
                try {
-                       if (known) {
-                               knownPostReplies.add(postReply.getId());
-                       } else {
-                               knownPostReplies.remove(postReply.getId());
+                       allAlbums.put(album.getId(), album);
+                       if (!album.isRoot()) {
+                               albumChildren.put(album.getParent().getId(), album.getId());
                        }
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
+       @Override
+       public void removeAlbum(Album album) {
+               lock.writeLock().lock();
+               try {
+                       allAlbums.remove(album.getId());
+                       albumChildren.remove(album.getParent().getId(), album.getId());
+               } finally {
+                       lock.writeLock().unlock();
+               }
+       }
+
        //
-       // PRIVATE METHODS
+       // IMAGEPROVIDER METHODS
        //
 
-       /**
-        * Gets all posts for the given Sone, creating a new collection if there is
-        * none yet.
-        *
-        * @param soneId
-        *            The ID of the Sone to get the posts for
-        * @return All posts
-        */
-       private Collection<Post> getPostsFrom(String soneId) {
-               Collection<Post> posts = null;
+       @Override
+       public Optional<Image> getImage(String imageId) {
                lock.readLock().lock();
                try {
-                       posts = sonePosts.get(soneId);
+                       return fromNullable(allImages.get(imageId));
                } finally {
                        lock.readLock().unlock();
                }
-               if (posts != null) {
-                       return posts;
+       }
+
+       @Override
+       public List<Image> getImages(Album parent) {
+               lock.readLock().lock();
+               try {
+                       return from(albumImages.get(parent.getId())).transformAndConcat(getImage()).toList();
+               } finally {
+                       lock.readLock().unlock();
                }
+       }
 
-               posts = new HashSet<Post>();
+       @Override
+       public void moveUp(Image image) {
                lock.writeLock().lock();
                try {
-                       sonePosts.put(soneId, posts);
+                       List<String> images = albumImages.get(image.getAlbum().getId());
+                       int currentIndex = images.indexOf(image.getId());
+                       if (currentIndex == 0) {
+                               return;
+                       }
+                       images.remove(image.getId());
+                       images.add(currentIndex - 1, image.getId());
                } finally {
                        lock.writeLock().unlock();
                }
-
-               return posts;
        }
 
-       /**
-        * Gets all posts that are directed the given Sone, creating a new
-        * collection if there is none yet.
-        *
-        * @param recipientId
-        *            The ID of the Sone to get the posts for
-        * @return All posts
-        */
-       private Collection<Post> getPostsTo(String recipientId) {
-               Collection<Post> posts = null;
-               lock.readLock().lock();
+       @Override
+       public void moveDown(Image image) {
+               lock.writeLock().lock();
                try {
-                       posts = recipientPosts.get(recipientId);
+                       List<String> images = albumChildren.get(image.getAlbum().getId());
+                       int currentIndex = images.indexOf(image.getId());
+                       if (currentIndex == (images.size() - 1)) {
+                               return;
+                       }
+                       images.remove(image.getId());
+                       images.add(currentIndex + 1, image.getId());
                } finally {
-                       lock.readLock().unlock();
-               }
-               if (posts != null) {
-                       return posts;
+                       lock.writeLock().unlock();
                }
+       }
 
-               posts = new HashSet<Post>();
+       //
+       // IMAGESTORE METHODS
+       //
+
+       @Override
+       public void storeImage(Image image) {
                lock.writeLock().lock();
                try {
-                       recipientPosts.put(recipientId, posts);
+                       allImages.put(image.getId(), image);
+                       albumImages.put(image.getAlbum().getId(), image.getId());
                } finally {
                        lock.writeLock().unlock();
                }
-
-               return posts;
        }
 
-       /**
-        * Loads the known posts.
-        */
-       private void loadKnownPosts() {
+       @Override
+       public void removeImage(Image image) {
                lock.writeLock().lock();
                try {
-                       int postCounter = 0;
-                       while (true) {
-                               String knownPostId = configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").getValue(null);
-                               if (knownPostId == null) {
-                                       break;
-                               }
-                               knownPosts.add(knownPostId);
-                       }
+                       allImages.remove(image.getId());
+                       albumImages.remove(image.getAlbum().getId(), image.getId());
                } finally {
                        lock.writeLock().unlock();
                }
        }
 
+       //
+       // PRIVATE METHODS
+       //
+
        /**
-        * Saves the known posts to the configuration.
+        * Returns all replies by the given Sone.
         *
-        * @throws DatabaseException
-        *             if a configuration error occurs
+        * @param id
+        *              The ID of the Sone
+        * @return The post replies of the Sone, sorted by time (newest first)
         */
-       private void saveKnownPosts() throws DatabaseException {
+       private Collection<PostReply> getRepliesFrom(String id) {
                lock.readLock().lock();
                try {
-                       int postCounter = 0;
-                       for (String knownPostId : knownPosts) {
-                               configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").setValue(knownPostId);
+                       if (sonePostReplies.containsKey(id)) {
+                               return Collections.unmodifiableCollection(sonePostReplies.get(id));
                        }
-                       configuration.getStringValue("KnownPosts/" + postCounter + "/ID").setValue(null);
-               } catch (ConfigurationException ce1) {
-                       throw new DatabaseException("Could not save database.", ce1);
+                       return Collections.emptySet();
                } finally {
                        lock.readLock().unlock();
                }
        }
 
-       /**
-        * Loads the known post replies.
-        */
+       /** Loads the known post replies. */
        private void loadKnownPostReplies() {
                lock.writeLock().lock();
                try {
@@ -639,7 +699,7 @@ public class MemoryDatabase extends AbstractService implements Database {
         * Saves the known post replies to the configuration.
         *
         * @throws DatabaseException
-        *             if a configuration error occurs
+        *              if a configuration error occurs
         */
        private void saveKnownPostReplies() throws DatabaseException {
                lock.readLock().lock();
@@ -656,26 +716,31 @@ public class MemoryDatabase extends AbstractService implements Database {
                }
        }
 
-       /**
-        * {@link PostReplyBuilder} implementation that creates
-        * {@link MemoryPostReply} objects.
-        *
-        * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
-        */
-       private class MemoryPostReplyBuilder extends AbstractPostReplyBuilder {
-
-               /**
-                * {@inheritDocs}
-                */
-               @Override
-               public PostReply build() throws IllegalStateException {
-                       validate();
+       private Function<String, Iterable<Album>> getAlbum() {
+               return new Function<String, Iterable<Album>>() {
+                       @Override
+                       public Iterable<Album> apply(String input) {
+                               return (input == null) ? Collections.<Album>emptyList() : getAlbum(input).asSet();
+                       }
+               };
+       }
 
-                       PostReply postReply = new MemoryPostReply(MemoryDatabase.this, soneProvider, randomId ? UUID.randomUUID().toString() : id, senderId, currentTime ? System.currentTimeMillis() : time, text, postId);
-                       postReply.setKnown(isPostReplyKnown(postReply));
-                       return postReply;
-               }
+       private Function<String, Iterable<Image>> getImage() {
+               return new Function<String, Iterable<Image>>() {
+                       @Override
+                       public Iterable<Image> apply(String input) {
+                               return (input == null) ? Collections.<Image>emptyList() : getImage(input).asSet();
+                       }
+               };
+       }
 
+       static <T> Function<Optional<T>, Iterable<T>> unwrap() {
+               return new Function<Optional<T>, Iterable<T>>() {
+                       @Override
+                       public Iterable<T> apply(Optional<T> input) {
+                               return (input == null) ? Collections.<T>emptyList() : input.asSet();
+                       }
+               };
        }
 
 }