src/main/java/net/pterodactylus/sone/database/memory/MemoryDatabase.java

   1 /*
   2  * Sone - MemoryDatabase.java - Copyright © 2013 David Roden
   3  *
   4  * This program is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 package net.pterodactylus.sone.database.memory;
  19
  20 import static com.google.common.base.Optional.fromNullable;
  21 import static com.google.common.base.Preconditions.checkNotNull;
  22 import static com.google.common.base.Predicates.not;
  23 import static com.google.common.collect.FluentIterable.from;
  24 import static java.util.Collections.emptyList;
  25 import static net.pterodactylus.sone.data.Sone.LOCAL_SONE_FILTER;
  26
  27 import java.util.ArrayList;
  28 import java.util.Collection;
  29 import java.util.Collections;
  30 import java.util.Comparator;
  31 import java.util.HashMap;
  32 import java.util.HashSet;
  33 import java.util.List;
  34 import java.util.Map;
  35 import java.util.Set;
  36 import java.util.SortedSet;
  37 import java.util.TreeSet;
  38 import java.util.concurrent.locks.ReadWriteLock;
  39 import java.util.concurrent.locks.ReentrantReadWriteLock;
  40
  41 import net.pterodactylus.sone.data.Album;
  42 import net.pterodactylus.sone.data.Image;
  43 import net.pterodactylus.sone.data.Post;
  44 import net.pterodactylus.sone.data.PostReply;
  45 import net.pterodactylus.sone.data.Reply;
  46 import net.pterodactylus.sone.data.Sone;
  47 import net.pterodactylus.sone.database.Database;
  48 import net.pterodactylus.sone.database.DatabaseException;
  49 import net.pterodactylus.sone.database.PostDatabase;
  50 import net.pterodactylus.sone.database.SoneBuilder;
  51 import net.pterodactylus.util.config.Configuration;
  52 import net.pterodactylus.util.config.ConfigurationException;
  53
  54 import com.google.common.base.Function;
  55 import com.google.common.base.Optional;
  56 import com.google.common.collect.ArrayListMultimap;
  57 import com.google.common.collect.ListMultimap;
  58 import com.google.common.collect.SortedSetMultimap;
  59 import com.google.common.collect.TreeMultimap;
  60 import com.google.common.util.concurrent.AbstractService;
  61 import com.google.inject.Inject;
  62
  63 /**
  64  * Memory-based {@link PostDatabase} implementation.
  65  *
  66  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  67  */
  68 public class MemoryDatabase extends AbstractService implements Database {
  69
  70         /** The lock. */
  71         private final ReadWriteLock lock = new ReentrantReadWriteLock();
  72
  73         /** The configuration. */
  74         private final Configuration configuration;
  75
  76         private final Map<String, Sone> sones = new HashMap<String, Sone>();
  77
  78         /** All posts by their ID. */
  79         private final Map<String, Post> allPosts = new HashMap<String, Post>();
  80
  81         /** All posts by their Sones. */
  82         private final Map<String, Collection<Post>> sonePosts = new HashMap<String, Collection<Post>>();
  83
  84         /** All posts by their recipient. */
  85         private final Map<String, Collection<Post>> recipientPosts = new HashMap<String, Collection<Post>>();
  86
  87         /** Whether posts are known. */
  88         private final Set<String> knownPosts = new HashSet<String>();
  89
  90         /** All post replies by their ID. */
  91         private final Map<String, PostReply> allPostReplies = new HashMap<String, PostReply>();
  92
  93         /** Replies sorted by Sone. */
  94         private final SortedSetMultimap<String, PostReply> sonePostReplies = TreeMultimap.create(new Comparator<String>() {
  95
  96                 @Override
  97                 public int compare(String leftString, String rightString) {
  98                         return leftString.compareTo(rightString);
  99                 }
 100         }, PostReply.TIME_COMPARATOR);
 101
 102         /** Replies by post. */
 103         private final Map<String, SortedSet<PostReply>> postReplies = new HashMap<String, SortedSet<PostReply>>();
 104
 105         /** Whether post replies are known. */
 106         private final Set<String> knownPostReplies = new HashSet<String>();
 107
 108         private final Map<String, Album> allAlbums = new HashMap<String, Album>();
 109         private final ListMultimap<String, String> albumChildren = ArrayListMultimap.create();
 110         private final ListMultimap<String, String> albumImages = ArrayListMultimap.create();
 111
 112         private final Map<String, Image> allImages = new HashMap<String, Image>();
 113
 114         /**
 115          * Creates a new memory database.
 116          *
 117          * @param configuration
 118          *              The configuration for loading and saving elements
 119          */
 120         @Inject
 121         public MemoryDatabase(Configuration configuration) {
 122                 this.configuration = configuration;
 123         }
 124
 125         //
 126         // DATABASE METHODS
 127         //
 128
 129         @Override
 130         public void save() throws DatabaseException {
 131                 saveKnownPosts();
 132                 saveKnownPostReplies();
 133         }
 134
 135         //
 136         // SERVICE METHODS
 137         //
 138
 139         @Override
 140         protected void doStart() {
 141                 loadKnownPosts();
 142                 loadKnownPostReplies();
 143                 notifyStarted();
 144         }
 145
 146         @Override
 147         protected void doStop() {
 148                 try {
 149                         save();
 150                         notifyStopped();
 151                 } catch (DatabaseException de1) {
 152                         notifyFailed(de1);
 153                 }
 154         }
 155
 156         @Override
 157         public Optional<Sone> getSone(String soneId) {
 158                 lock.readLock().lock();
 159                 try {
 160                         return fromNullable(sones.get(soneId));
 161                 } finally {
 162                         lock.readLock().unlock();
 163                 }
 164         }
 165
 166         @Override
 167         public Collection<Sone> getSones() {
 168                 lock.readLock().lock();
 169                 try {
 170                         return Collections.unmodifiableCollection(sones.values());
 171                 } finally {
 172                         lock.readLock().unlock();
 173                 }
 174         }
 175
 176         @Override
 177         public Collection<Sone> getLocalSones() {
 178                 lock.readLock().lock();
 179                 try {
 180                         return from(getSones()).filter(LOCAL_SONE_FILTER).toSet();
 181                 } finally {
 182                         lock.readLock().unlock();
 183                 }
 184         }
 185
 186         @Override
 187         public Collection<Sone> getRemoteSones() {
 188                 lock.readLock().lock();
 189                 try {
 190                         return from(getSones()).filter(not(LOCAL_SONE_FILTER)).toSet();
 191                 } finally {
 192                         lock.readLock().unlock();
 193                 }
 194         }
 195
 196         @Override
 197         public SoneBuilder newSoneBuilder() {
 198                 return null;
 199         }
 200
 201         //
 202         // POSTPROVIDER METHODS
 203         //
 204
 205         @Override
 206         public Optional<Post> getPost(String postId) {
 207                 lock.readLock().lock();
 208                 try {
 209                         return fromNullable(allPosts.get(postId));
 210                 } finally {
 211                         lock.readLock().unlock();
 212                 }
 213         }
 214
 215         @Override
 216         public Collection<Post> getPosts(String soneId) {
 217                 return new HashSet<Post>(getPostsFrom(soneId));
 218         }
 219
 220         @Override
 221         public Collection<Post> getDirectedPosts(String recipientId) {
 222                 lock.readLock().lock();
 223                 try {
 224                         Collection<Post> posts = recipientPosts.get(recipientId);
 225                         return (posts == null) ? Collections.<Post>emptySet() : new HashSet<Post>(posts);
 226                 } finally {
 227                         lock.readLock().unlock();
 228                 }
 229         }
 230
 231         //
 232         // POSTSTORE METHODS
 233         //
 234
 235         @Override
 236         public void storePost(Post post) {
 237                 checkNotNull(post, "post must not be null");
 238                 lock.writeLock().lock();
 239                 try {
 240                         allPosts.put(post.getId(), post);
 241                         getPostsFrom(post.getSone().getId()).add(post);
 242                         if (post.getRecipientId().isPresent()) {
 243                                 getPostsTo(post.getRecipientId().get()).add(post);
 244                         }
 245                 } finally {
 246                         lock.writeLock().unlock();
 247                 }
 248         }
 249
 250         @Override
 251         public void removePost(Post post) {
 252                 checkNotNull(post, "post must not be null");
 253                 lock.writeLock().lock();
 254                 try {
 255                         allPosts.remove(post.getId());
 256                         getPostsFrom(post.getSone().getId()).remove(post);
 257                         if (post.getRecipientId().isPresent()) {
 258                                 getPostsTo(post.getRecipientId().get()).remove(post);
 259                         }
 260                         post.getSone().removePost(post);
 261                 } finally {
 262                         lock.writeLock().unlock();
 263                 }
 264         }
 265
 266         @Override
 267         public void storePosts(Sone sone, Collection<Post> posts) throws IllegalArgumentException {
 268                 checkNotNull(sone, "sone must not be null");
 269                 /* verify that all posts are from the same Sone. */
 270                 for (Post post : posts) {
 271                         if (!sone.equals(post.getSone())) {
 272                                 throw new IllegalArgumentException(String.format("Post from different Sone found: %s", post));
 273                         }
 274                 }
 275
 276                 lock.writeLock().lock();
 277                 try {
 278                         /* remove all posts by the Sone. */
 279                         getPostsFrom(sone.getId()).clear();
 280                         for (Post post : posts) {
 281                                 allPosts.remove(post.getId());
 282                                 if (post.getRecipientId().isPresent()) {
 283                                         getPostsTo(post.getRecipientId().get()).remove(post);
 284                                 }
 285                         }
 286
 287                         /* add new posts. */
 288                         getPostsFrom(sone.getId()).addAll(posts);
 289                         for (Post post : posts) {
 290                                 allPosts.put(post.getId(), post);
 291                                 if (post.getRecipientId().isPresent()) {
 292                                         getPostsTo(post.getRecipientId().get()).add(post);
 293                                 }
 294                         }
 295                 } finally {
 296                         lock.writeLock().unlock();
 297                 }
 298         }
 299
 300         @Override
 301         public void removePosts(Sone sone) {
 302                 checkNotNull(sone, "sone must not be null");
 303                 lock.writeLock().lock();
 304                 try {
 305                         /* remove all posts by the Sone. */
 306                         getPostsFrom(sone.getId()).clear();
 307                         for (Post post : sone.getPosts()) {
 308                                 allPosts.remove(post.getId());
 309                                 if (post.getRecipientId().isPresent()) {
 310                                         getPostsTo(post.getRecipientId().get()).remove(post);
 311                                 }
 312                         }
 313                 } finally {
 314                         lock.writeLock().unlock();
 315                 }
 316         }
 317
 318         //
 319         // POSTREPLYPROVIDER METHODS
 320         //
 321
 322         @Override
 323         public Optional<PostReply> getPostReply(String id) {
 324                 lock.readLock().lock();
 325                 try {
 326                         return fromNullable(allPostReplies.get(id));
 327                 } finally {
 328                         lock.readLock().unlock();
 329                 }
 330         }
 331
 332         @Override
 333         public List<PostReply> getReplies(String postId) {
 334                 lock.readLock().lock();
 335                 try {
 336                         if (!postReplies.containsKey(postId)) {
 337                                 return emptyList();
 338                         }
 339                         return new ArrayList<PostReply>(postReplies.get(postId));
 340                 } finally {
 341                         lock.readLock().unlock();
 342                 }
 343         }
 344
 345         //
 346         // POSTREPLYSTORE METHODS
 347         //
 348
 349         /**
 350          * Returns whether the given post reply is known.
 351          *
 352          * @param postReply
 353          *              The post reply
 354          * @return {@code true} if the given post reply is known, {@code false}
 355          *         otherwise
 356          */
 357         public boolean isPostReplyKnown(PostReply postReply) {
 358                 lock.readLock().lock();
 359                 try {
 360                         return knownPostReplies.contains(postReply.getId());
 361                 } finally {
 362                         lock.readLock().unlock();
 363                 }
 364         }
 365
 366         @Override
 367         public void setPostReplyKnown(PostReply postReply) {
 368                 lock.writeLock().lock();
 369                 try {
 370                         knownPostReplies.add(postReply.getId());
 371                 } finally {
 372                         lock.writeLock().unlock();
 373                 }
 374         }
 375
 376         @Override
 377         public void storePostReply(PostReply postReply) {
 378                 lock.writeLock().lock();
 379                 try {
 380                         allPostReplies.put(postReply.getId(), postReply);
 381                         if (postReplies.containsKey(postReply.getPostId())) {
 382                                 postReplies.get(postReply.getPostId()).add(postReply);
 383                         } else {
 384                                 TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
 385                                 replies.add(postReply);
 386                                 postReplies.put(postReply.getPostId(), replies);
 387                         }
 388                 } finally {
 389                         lock.writeLock().unlock();
 390                 }
 391         }
 392
 393         @Override
 394         public void storePostReplies(Sone sone, Collection<PostReply> postReplies) {
 395                 checkNotNull(sone, "sone must not be null");
 396                 /* verify that all posts are from the same Sone. */
 397                 for (PostReply postReply : postReplies) {
 398                         if (!sone.equals(postReply.getSone())) {
 399                                 throw new IllegalArgumentException(String.format("PostReply from different Sone found: %s", postReply));
 400                         }
 401                 }
 402
 403                 lock.writeLock().lock();
 404                 try {
 405                         /* remove all post replies of the Sone. */
 406                         for (PostReply postReply : getRepliesFrom(sone.getId())) {
 407                                 removePostReply(postReply);
 408                         }
 409                         for (PostReply postReply : postReplies) {
 410                                 allPostReplies.put(postReply.getId(), postReply);
 411                                 sonePostReplies.put(postReply.getSone().getId(), postReply);
 412                                 if (this.postReplies.containsKey(postReply.getPostId())) {
 413                                         this.postReplies.get(postReply.getPostId()).add(postReply);
 414                                 } else {
 415                                         TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
 416                                         replies.add(postReply);
 417                                         this.postReplies.put(postReply.getPostId(), replies);
 418                                 }
 419                         }
 420                 } finally {
 421                         lock.writeLock().unlock();
 422                 }
 423         }
 424
 425         @Override
 426         public void removePostReply(PostReply postReply) {
 427                 lock.writeLock().lock();
 428                 try {
 429                         allPostReplies.remove(postReply.getId());
 430                         if (postReplies.containsKey(postReply.getPostId())) {
 431                                 postReplies.get(postReply.getPostId()).remove(postReply);
 432                                 if (postReplies.get(postReply.getPostId()).isEmpty()) {
 433                                         postReplies.remove(postReply.getPostId());
 434                                 }
 435                         }
 436                 } finally {
 437                         lock.writeLock().unlock();
 438                 }
 439         }
 440
 441         @Override
 442         public void removePostReplies(Sone sone) {
 443                 checkNotNull(sone, "sone must not be null");
 444
 445                 lock.writeLock().lock();
 446                 try {
 447                         for (PostReply postReply : sone.getReplies()) {
 448                                 removePostReply(postReply);
 449                         }
 450                 } finally {
 451                         lock.writeLock().unlock();
 452                 }
 453         }
 454
 455         //
 456         // ALBUMPROVDER METHODS
 457         //
 458
 459         @Override
 460         public Optional<Album> getAlbum(String albumId) {
 461                 lock.readLock().lock();
 462                 try {
 463                         return fromNullable(allAlbums.get(albumId));
 464                 } finally {
 465                         lock.readLock().unlock();
 466                 }
 467         }
 468
 469         @Override
 470         public List<Album> getAlbums(Album parent) {
 471                 lock.readLock().lock();
 472                 try {
 473                         return from(albumChildren.get(parent.getId())).transformAndConcat(getAlbum()).toList();
 474                 } finally {
 475                         lock.readLock().unlock();
 476                 }
 477         }
 478
 479         @Override
 480         public void moveUp(Album album) {
 481                 lock.writeLock().lock();
 482                 try {
 483                         List<String> albums = albumChildren.get(album.getParent().getId());
 484                         int currentIndex = albums.indexOf(album.getId());
 485                         if (currentIndex == 0) {
 486                                 return;
 487                         }
 488                         albums.remove(album.getId());
 489                         albums.add(currentIndex - 1, album.getId());
 490                 } finally {
 491                         lock.writeLock().unlock();
 492                 }
 493         }
 494
 495         @Override
 496         public void moveDown(Album album) {
 497                 lock.writeLock().lock();
 498                 try {
 499                         List<String> albums = albumChildren.get(album.getParent().getId());
 500                         int currentIndex = albums.indexOf(album.getId());
 501                         if (currentIndex == (albums.size() - 1)) {
 502                                 return;
 503                         }
 504                         albums.remove(album.getId());
 505                         albums.add(currentIndex + 1, album.getId());
 506                 } finally {
 507                         lock.writeLock().unlock();
 508                 }
 509         }
 510
 511         //
 512         // ALBUMSTORE METHODS
 513         //
 514
 515         @Override
 516         public void storeAlbum(Album album) {
 517                 lock.writeLock().lock();
 518                 try {
 519                         allAlbums.put(album.getId(), album);
 520                         albumChildren.put(album.getParent().getId(), album.getId());
 521                 } finally {
 522                         lock.writeLock().unlock();
 523                 }
 524         }
 525
 526         @Override
 527         public void removeAlbum(Album album) {
 528                 lock.writeLock().lock();
 529                 try {
 530                         allAlbums.remove(album.getId());
 531                         albumChildren.remove(album.getParent().getId(), album.getId());
 532                 } finally {
 533                         lock.writeLock().unlock();
 534                 }
 535         }
 536
 537         //
 538         // IMAGEPROVIDER METHODS
 539         //
 540
 541         @Override
 542         public Optional<Image> getImage(String imageId) {
 543                 lock.readLock().lock();
 544                 try {
 545                         return fromNullable(allImages.get(imageId));
 546                 } finally {
 547                         lock.readLock().unlock();
 548                 }
 549         }
 550
 551         @Override
 552         public List<Image> getImages(Album parent) {
 553                 lock.readLock().lock();
 554                 try {
 555                         return from(albumImages.get(parent.getId())).transformAndConcat(getImage()).toList();
 556                 } finally {
 557                         lock.readLock().unlock();
 558                 }
 559         }
 560
 561         @Override
 562         public void moveUp(Image image) {
 563                 lock.writeLock().lock();
 564                 try {
 565                         List<String> images = albumImages.get(image.getAlbum().getId());
 566                         int currentIndex = images.indexOf(image.getId());
 567                         if (currentIndex == 0) {
 568                                 return;
 569                         }
 570                         images.remove(image.getId());
 571                         images.add(currentIndex - 1, image.getId());
 572                 } finally {
 573                         lock.writeLock().unlock();
 574                 }
 575         }
 576
 577         @Override
 578         public void moveDown(Image image) {
 579                 lock.writeLock().lock();
 580                 try {
 581                         List<String> images = albumChildren.get(image.getAlbum().getId());
 582                         int currentIndex = images.indexOf(image.getId());
 583                         if (currentIndex == (images.size() - 1)) {
 584                                 return;
 585                         }
 586                         images.remove(image.getId());
 587                         images.add(currentIndex + 1, image.getId());
 588                 } finally {
 589                         lock.writeLock().unlock();
 590                 }
 591         }
 592
 593         //
 594         // IMAGESTORE METHODS
 595         //
 596
 597         @Override
 598         public void storeImage(Image image) {
 599                 lock.writeLock().lock();
 600                 try {
 601                         allImages.put(image.getId(), image);
 602                         albumImages.put(image.getAlbum().getId(), image.getId());
 603                 } finally {
 604                         lock.writeLock().unlock();
 605                 }
 606         }
 607
 608         @Override
 609         public void removeImage(Image image) {
 610                 lock.writeLock().lock();
 611                 try {
 612                         allImages.remove(image.getId());
 613                         albumImages.remove(image.getAlbum().getId(), image.getId());
 614                 } finally {
 615                         lock.writeLock().unlock();
 616                 }
 617         }
 618
 619         //
 620         // PACKAGE-PRIVATE METHODS
 621         //
 622
 623         /**
 624          * Returns whether the given post is known.
 625          *
 626          * @param post
 627          *              The post
 628          * @return {@code true} if the post is known, {@code false} otherwise
 629          */
 630         boolean isPostKnown(Post post) {
 631                 lock.readLock().lock();
 632                 try {
 633                         return knownPosts.contains(post.getId());
 634                 } finally {
 635                         lock.readLock().unlock();
 636                 }
 637         }
 638
 639         /**
 640          * Sets whether the given post is known.
 641          *
 642          * @param post
 643          *              The post
 644          * @param known
 645          *              {@code true} if the post is known, {@code false} otherwise
 646          */
 647         void setPostKnown(Post post, boolean known) {
 648                 lock.writeLock().lock();
 649                 try {
 650                         if (known) {
 651                                 knownPosts.add(post.getId());
 652                         } else {
 653                                 knownPosts.remove(post.getId());
 654                         }
 655                 } finally {
 656                         lock.writeLock().unlock();
 657                 }
 658         }
 659
 660         //
 661         // PRIVATE METHODS
 662         //
 663
 664         /**
 665          * Gets all posts for the given Sone, creating a new collection if there is
 666          * none yet.
 667          *
 668          * @param soneId
 669          *              The ID of the Sone to get the posts for
 670          * @return All posts
 671          */
 672         private Collection<Post> getPostsFrom(String soneId) {
 673                 Collection<Post> posts = null;
 674                 lock.readLock().lock();
 675                 try {
 676                         posts = sonePosts.get(soneId);
 677                 } finally {
 678                         lock.readLock().unlock();
 679                 }
 680                 if (posts != null) {
 681                         return posts;
 682                 }
 683
 684                 posts = new HashSet<Post>();
 685                 lock.writeLock().lock();
 686                 try {
 687                         sonePosts.put(soneId, posts);
 688                 } finally {
 689                         lock.writeLock().unlock();
 690                 }
 691
 692                 return posts;
 693         }
 694
 695         /**
 696          * Gets all posts that are directed the given Sone, creating a new collection
 697          * if there is none yet.
 698          *
 699          * @param recipientId
 700          *              The ID of the Sone to get the posts for
 701          * @return All posts
 702          */
 703         private Collection<Post> getPostsTo(String recipientId) {
 704                 Collection<Post> posts = null;
 705                 lock.readLock().lock();
 706                 try {
 707                         posts = recipientPosts.get(recipientId);
 708                 } finally {
 709                         lock.readLock().unlock();
 710                 }
 711                 if (posts != null) {
 712                         return posts;
 713                 }
 714
 715                 posts = new HashSet<Post>();
 716                 lock.writeLock().lock();
 717                 try {
 718                         recipientPosts.put(recipientId, posts);
 719                 } finally {
 720                         lock.writeLock().unlock();
 721                 }
 722
 723                 return posts;
 724         }
 725
 726         /** Loads the known posts. */
 727         private void loadKnownPosts() {
 728                 lock.writeLock().lock();
 729                 try {
 730                         int postCounter = 0;
 731                         while (true) {
 732                                 String knownPostId = configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").getValue(null);
 733                                 if (knownPostId == null) {
 734                                         break;
 735                                 }
 736                                 knownPosts.add(knownPostId);
 737                         }
 738                 } finally {
 739                         lock.writeLock().unlock();
 740                 }
 741         }
 742
 743         /**
 744          * Saves the known posts to the configuration.
 745          *
 746          * @throws DatabaseException
 747          *              if a configuration error occurs
 748          */
 749         private void saveKnownPosts() throws DatabaseException {
 750                 lock.readLock().lock();
 751                 try {
 752                         int postCounter = 0;
 753                         for (String knownPostId : knownPosts) {
 754                                 configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").setValue(knownPostId);
 755                         }
 756                         configuration.getStringValue("KnownPosts/" + postCounter + "/ID").setValue(null);
 757                 } catch (ConfigurationException ce1) {
 758                         throw new DatabaseException("Could not save database.", ce1);
 759                 } finally {
 760                         lock.readLock().unlock();
 761                 }
 762         }
 763
 764         /**
 765          * Returns all replies by the given Sone.
 766          *
 767          * @param id
 768          *              The ID of the Sone
 769          * @return The post replies of the Sone, sorted by time (newest first)
 770          */
 771         private Collection<PostReply> getRepliesFrom(String id) {
 772                 lock.readLock().lock();
 773                 try {
 774                         if (sonePostReplies.containsKey(id)) {
 775                                 return Collections.unmodifiableCollection(sonePostReplies.get(id));
 776                         }
 777                         return Collections.emptySet();
 778                 } finally {
 779                         lock.readLock().unlock();
 780                 }
 781         }
 782
 783         /** Loads the known post replies. */
 784         private void loadKnownPostReplies() {
 785                 lock.writeLock().lock();
 786                 try {
 787                         int replyCounter = 0;
 788                         while (true) {
 789                                 String knownReplyId = configuration.getStringValue("KnownReplies/" + replyCounter++ + "/ID").getValue(null);
 790                                 if (knownReplyId == null) {
 791                                         break;
 792                                 }
 793                                 knownPostReplies.add(knownReplyId);
 794                         }
 795                 } finally {
 796                         lock.writeLock().unlock();
 797                 }
 798         }
 799
 800         /**
 801          * Saves the known post replies to the configuration.
 802          *
 803          * @throws DatabaseException
 804          *              if a configuration error occurs
 805          */
 806         private void saveKnownPostReplies() throws DatabaseException {
 807                 lock.readLock().lock();
 808                 try {
 809                         int replyCounter = 0;
 810                         for (String knownReplyId : knownPostReplies) {
 811                                 configuration.getStringValue("KnownReplies/" + replyCounter++ + "/ID").setValue(knownReplyId);
 812                         }
 813                         configuration.getStringValue("KnownReplies/" + replyCounter + "/ID").setValue(null);
 814                 } catch (ConfigurationException ce1) {
 815                         throw new DatabaseException("Could not save database.", ce1);
 816                 } finally {
 817                         lock.readLock().unlock();
 818                 }
 819         }
 820
 821         private Function<String, Iterable<Album>> getAlbum() {
 822                 return new Function<String, Iterable<Album>>() {
 823                         @Override
 824                         public Iterable<Album> apply(String input) {
 825                                 return (input == null) ? Collections.<Album>emptyList() : getAlbum(input).asSet();
 826                         }
 827                 };
 828         }
 829
 830         private Function<String, Iterable<Image>> getImage() {
 831                 return new Function<String, Iterable<Image>>() {
 832                         @Override
 833                         public Iterable<Image> apply(String input) {
 834                                 return (input == null) ? Collections.<Image>emptyList() : getImage(input).asSet();
 835                         }
 836                 };
 837         }
 838
 839 }