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.PostBuilder;
  50 import net.pterodactylus.sone.database.PostDatabase;
  51 import net.pterodactylus.sone.database.PostReplyBuilder;
  52 import net.pterodactylus.sone.database.SoneBuilder;
  53 import net.pterodactylus.util.config.Configuration;
  54 import net.pterodactylus.util.config.ConfigurationException;
  55
  56 import com.google.common.base.Function;
  57 import com.google.common.base.Optional;
  58 import com.google.common.collect.ArrayListMultimap;
  59 import com.google.common.collect.ListMultimap;
  60 import com.google.common.collect.SortedSetMultimap;
  61 import com.google.common.collect.TreeMultimap;
  62 import com.google.common.util.concurrent.AbstractService;
  63 import com.google.inject.Inject;
  64
  65 /**
  66  * Memory-based {@link PostDatabase} implementation.
  67  *
  68  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  69  */
  70 public class MemoryDatabase extends AbstractService implements Database {
  71
  72         /** The lock. */
  73         private final ReadWriteLock lock = new ReentrantReadWriteLock();
  74
  75         /** The configuration. */
  76         private final Configuration configuration;
  77
  78         private final Map<String, Sone> sones = new HashMap<String, Sone>();
  79
  80         /** All posts by their ID. */
  81         private final Map<String, Post> allPosts = new HashMap<String, Post>();
  82
  83         /** All posts by their Sones. */
  84         private final Map<String, Collection<Post>> sonePosts = new HashMap<String, Collection<Post>>();
  85
  86         /** All posts by their recipient. */
  87         private final Map<String, Collection<Post>> recipientPosts = new HashMap<String, Collection<Post>>();
  88
  89         /** Whether posts are known. */
  90         private final Set<String> knownPosts = new HashSet<String>();
  91
  92         /** All post replies by their ID. */
  93         private final Map<String, PostReply> allPostReplies = new HashMap<String, PostReply>();
  94
  95         /** Replies sorted by Sone. */
  96         private final SortedSetMultimap<String, PostReply> sonePostReplies = TreeMultimap.create(new Comparator<String>() {
  97
  98                 @Override
  99                 public int compare(String leftString, String rightString) {
 100                         return leftString.compareTo(rightString);
 101                 }
 102         }, PostReply.TIME_COMPARATOR);
 103
 104         /** Replies by post. */
 105         private final Map<String, SortedSet<PostReply>> postReplies = new HashMap<String, SortedSet<PostReply>>();
 106
 107         /** Whether post replies are known. */
 108         private final Set<String> knownPostReplies = new HashSet<String>();
 109
 110         private final Map<String, Album> allAlbums = new HashMap<String, Album>();
 111         private final ListMultimap<String, String> albumChildren = ArrayListMultimap.create();
 112         private final ListMultimap<String, String> albumImages = ArrayListMultimap.create();
 113
 114         private final Map<String, Image> allImages = new HashMap<String, Image>();
 115
 116         /**
 117          * Creates a new memory database.
 118          *
 119          * @param configuration
 120          *              The configuration for loading and saving elements
 121          */
 122         @Inject
 123         public MemoryDatabase(Configuration configuration) {
 124                 this.configuration = configuration;
 125         }
 126
 127         //
 128         // DATABASE METHODS
 129         //
 130
 131         /**
 132          * Saves the database.
 133          *
 134          * @throws DatabaseException
 135          *              if an error occurs while saving
 136          */
 137         @Override
 138         public void save() throws DatabaseException {
 139                 saveKnownPosts();
 140                 saveKnownPostReplies();
 141         }
 142
 143         //
 144         // SERVICE METHODS
 145         //
 146
 147         /** {@inheritDocs} */
 148         @Override
 149         protected void doStart() {
 150                 loadKnownPosts();
 151                 loadKnownPostReplies();
 152                 notifyStarted();
 153         }
 154
 155         /** {@inheritDocs} */
 156         @Override
 157         protected void doStop() {
 158                 try {
 159                         save();
 160                         notifyStopped();
 161                 } catch (DatabaseException de1) {
 162                         notifyFailed(de1);
 163                 }
 164         }
 165
 166         @Override
 167         public Optional<Sone> getSone(String soneId) {
 168                 lock.readLock().lock();
 169                 try {
 170                         return fromNullable(sones.get(soneId));
 171                 } finally {
 172                         lock.readLock().unlock();
 173                 }
 174         }
 175
 176         @Override
 177         public Collection<Sone> getSones() {
 178                 lock.readLock().lock();
 179                 try {
 180                         return Collections.unmodifiableCollection(sones.values());
 181                 } finally {
 182                         lock.readLock().unlock();
 183                 }
 184         }
 185
 186         @Override
 187         public Collection<Sone> getLocalSones() {
 188                 lock.readLock().lock();
 189                 try {
 190                         return from(getSones()).filter(LOCAL_SONE_FILTER).toSet();
 191                 } finally {
 192                         lock.readLock().unlock();
 193                 }
 194         }
 195
 196         @Override
 197         public Collection<Sone> getRemoteSones() {
 198                 lock.readLock().lock();
 199                 try {
 200                         return from(getSones()).filter(not(LOCAL_SONE_FILTER)).toSet();
 201                 } finally {
 202                         lock.readLock().unlock();
 203                 }
 204         }
 205
 206         @Override
 207         public SoneBuilder newSoneBuilder() {
 208                 return null;
 209         }
 210
 211         //
 212         // POSTPROVIDER METHODS
 213         //
 214
 215         /** {@inheritDocs} */
 216         @Override
 217         public Optional<Post> getPost(String postId) {
 218                 lock.readLock().lock();
 219                 try {
 220                         return fromNullable(allPosts.get(postId));
 221                 } finally {
 222                         lock.readLock().unlock();
 223                 }
 224         }
 225
 226         /** {@inheritDocs} */
 227         @Override
 228         public Collection<Post> getPosts(String soneId) {
 229                 return new HashSet<Post>(getPostsFrom(soneId));
 230         }
 231
 232         /** {@inheritDocs} */
 233         @Override
 234         public Collection<Post> getDirectedPosts(String recipientId) {
 235                 lock.readLock().lock();
 236                 try {
 237                         Collection<Post> posts = recipientPosts.get(recipientId);
 238                         return (posts == null) ? Collections.<Post>emptySet() : new HashSet<Post>(posts);
 239                 } finally {
 240                         lock.readLock().unlock();
 241                 }
 242         }
 243
 244         //
 245         // POSTSTORE METHODS
 246         //
 247
 248         /** {@inheritDocs} */
 249         @Override
 250         public void storePost(Post post) {
 251                 checkNotNull(post, "post must not be null");
 252                 lock.writeLock().lock();
 253                 try {
 254                         allPosts.put(post.getId(), post);
 255                         getPostsFrom(post.getSone().getId()).add(post);
 256                         if (post.getRecipientId().isPresent()) {
 257                                 getPostsTo(post.getRecipientId().get()).add(post);
 258                         }
 259                 } finally {
 260                         lock.writeLock().unlock();
 261                 }
 262         }
 263
 264         /** {@inheritDocs} */
 265         @Override
 266         public void removePost(Post post) {
 267                 checkNotNull(post, "post must not be null");
 268                 lock.writeLock().lock();
 269                 try {
 270                         allPosts.remove(post.getId());
 271                         getPostsFrom(post.getSone().getId()).remove(post);
 272                         if (post.getRecipientId().isPresent()) {
 273                                 getPostsTo(post.getRecipientId().get()).remove(post);
 274                         }
 275                         post.getSone().removePost(post);
 276                 } finally {
 277                         lock.writeLock().unlock();
 278                 }
 279         }
 280
 281         /** {@inheritDocs} */
 282         @Override
 283         public void storePosts(Sone sone, Collection<Post> posts) throws IllegalArgumentException {
 284                 checkNotNull(sone, "sone must not be null");
 285                 /* verify that all posts are from the same Sone. */
 286                 for (Post post : posts) {
 287                         if (!sone.equals(post.getSone())) {
 288                                 throw new IllegalArgumentException(String.format("Post from different Sone found: %s", post));
 289                         }
 290                 }
 291
 292                 lock.writeLock().lock();
 293                 try {
 294                         /* remove all posts by the Sone. */
 295                         getPostsFrom(sone.getId()).clear();
 296                         for (Post post : posts) {
 297                                 allPosts.remove(post.getId());
 298                                 if (post.getRecipientId().isPresent()) {
 299                                         getPostsTo(post.getRecipientId().get()).remove(post);
 300                                 }
 301                         }
 302
 303                         /* add new posts. */
 304                         getPostsFrom(sone.getId()).addAll(posts);
 305                         for (Post post : posts) {
 306                                 allPosts.put(post.getId(), post);
 307                                 if (post.getRecipientId().isPresent()) {
 308                                         getPostsTo(post.getRecipientId().get()).add(post);
 309                                 }
 310                         }
 311                 } finally {
 312                         lock.writeLock().unlock();
 313                 }
 314         }
 315
 316         /** {@inheritDocs} */
 317         @Override
 318         public void removePosts(Sone sone) {
 319                 checkNotNull(sone, "sone must not be null");
 320                 lock.writeLock().lock();
 321                 try {
 322                         /* remove all posts by the Sone. */
 323                         getPostsFrom(sone.getId()).clear();
 324                         for (Post post : sone.getPosts()) {
 325                                 allPosts.remove(post.getId());
 326                                 if (post.getRecipientId().isPresent()) {
 327                                         getPostsTo(post.getRecipientId().get()).remove(post);
 328                                 }
 329                         }
 330                 } finally {
 331                         lock.writeLock().unlock();
 332                 }
 333         }
 334
 335         //
 336         // POSTREPLYPROVIDER METHODS
 337         //
 338
 339         /** {@inheritDocs} */
 340         @Override
 341         public Optional<PostReply> getPostReply(String id) {
 342                 lock.readLock().lock();
 343                 try {
 344                         return fromNullable(allPostReplies.get(id));
 345                 } finally {
 346                         lock.readLock().unlock();
 347                 }
 348         }
 349
 350         /** {@inheritDocs} */
 351         @Override
 352         public List<PostReply> getReplies(String postId) {
 353                 lock.readLock().lock();
 354                 try {
 355                         if (!postReplies.containsKey(postId)) {
 356                                 return emptyList();
 357                         }
 358                         return new ArrayList<PostReply>(postReplies.get(postId));
 359                 } finally {
 360                         lock.readLock().unlock();
 361                 }
 362         }
 363
 364         //
 365         // POSTREPLYSTORE METHODS
 366         //
 367
 368         /** {@inheritDocs} */
 369         @Override
 370         public void storePostReply(PostReply postReply) {
 371                 lock.writeLock().lock();
 372                 try {
 373                         allPostReplies.put(postReply.getId(), postReply);
 374                         if (postReplies.containsKey(postReply.getPostId())) {
 375                                 postReplies.get(postReply.getPostId()).add(postReply);
 376                         } else {
 377                                 TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
 378                                 replies.add(postReply);
 379                                 postReplies.put(postReply.getPostId(), replies);
 380                         }
 381                 } finally {
 382                         lock.writeLock().unlock();
 383                 }
 384         }
 385
 386         /** {@inheritDocs} */
 387         @Override
 388         public void storePostReplies(Sone sone, Collection<PostReply> postReplies) {
 389                 checkNotNull(sone, "sone must not be null");
 390                 /* verify that all posts are from the same Sone. */
 391                 for (PostReply postReply : postReplies) {
 392                         if (!sone.equals(postReply.getSone())) {
 393                                 throw new IllegalArgumentException(String.format("PostReply from different Sone found: %s", postReply));
 394                         }
 395                 }
 396
 397                 lock.writeLock().lock();
 398                 try {
 399                         /* remove all post replies of the Sone. */
 400                         for (PostReply postReply : getRepliesFrom(sone.getId())) {
 401                                 removePostReply(postReply);
 402                         }
 403                         for (PostReply postReply : postReplies) {
 404                                 allPostReplies.put(postReply.getId(), postReply);
 405                                 sonePostReplies.put(postReply.getSone().getId(), postReply);
 406                                 if (this.postReplies.containsKey(postReply.getPostId())) {
 407                                         this.postReplies.get(postReply.getPostId()).add(postReply);
 408                                 } else {
 409                                         TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
 410                                         replies.add(postReply);
 411                                         this.postReplies.put(postReply.getPostId(), replies);
 412                                 }
 413                         }
 414                 } finally {
 415                         lock.writeLock().unlock();
 416                 }
 417         }
 418
 419         /** {@inheritDocs} */
 420         @Override
 421         public void removePostReply(PostReply postReply) {
 422                 lock.writeLock().lock();
 423                 try {
 424                         allPostReplies.remove(postReply.getId());
 425                         if (postReplies.containsKey(postReply.getPostId())) {
 426                                 postReplies.get(postReply.getPostId()).remove(postReply);
 427                                 if (postReplies.get(postReply.getPostId()).isEmpty()) {
 428                                         postReplies.remove(postReply.getPostId());
 429                                 }
 430                         }
 431                 } finally {
 432                         lock.writeLock().unlock();
 433                 }
 434         }
 435
 436         /** {@inheritDocs} */
 437         @Override
 438         public void removePostReplies(Sone sone) {
 439                 checkNotNull(sone, "sone must not be null");
 440
 441                 lock.writeLock().lock();
 442                 try {
 443                         for (PostReply postReply : sone.getReplies()) {
 444                                 removePostReply(postReply);
 445                         }
 446                 } finally {
 447                         lock.writeLock().unlock();
 448                 }
 449         }
 450
 451         //
 452         // ALBUMPROVDER METHODS
 453         //
 454
 455         @Override
 456         public Optional<Album> getAlbum(String albumId) {
 457                 lock.readLock().lock();
 458                 try {
 459                         return fromNullable(allAlbums.get(albumId));
 460                 } finally {
 461                         lock.readLock().unlock();
 462                 }
 463         }
 464
 465         @Override
 466         public List<Album> getAlbums(Album parent) {
 467                 lock.readLock().lock();
 468                 try {
 469                         return from(albumChildren.get(parent.getId())).transformAndConcat(getAlbum()).toList();
 470                 } finally {
 471                         lock.readLock().unlock();
 472                 }
 473         }
 474
 475         @Override
 476         public void moveUp(Album album) {
 477                 lock.writeLock().lock();
 478                 try {
 479                         List<String> albums = albumChildren.get(album.getParent().getId());
 480                         int currentIndex = albums.indexOf(album.getId());
 481                         if (currentIndex == 0) {
 482                                 return;
 483                         }
 484                         albums.remove(album.getId());
 485                         albums.add(currentIndex - 1, album.getId());
 486                 } finally {
 487                         lock.writeLock().unlock();
 488                 }
 489         }
 490
 491         @Override
 492         public void moveDown(Album album) {
 493                 lock.writeLock().lock();
 494                 try {
 495                         List<String> albums = albumChildren.get(album.getParent().getId());
 496                         int currentIndex = albums.indexOf(album.getId());
 497                         if (currentIndex == (albums.size() - 1)) {
 498                                 return;
 499                         }
 500                         albums.remove(album.getId());
 501                         albums.add(currentIndex + 1, album.getId());
 502                 } finally {
 503                         lock.writeLock().unlock();
 504                 }
 505         }
 506
 507         //
 508         // ALBUMSTORE METHODS
 509         //
 510
 511         @Override
 512         public void storeAlbum(Album album) {
 513                 lock.writeLock().lock();
 514                 try {
 515                         allAlbums.put(album.getId(), album);
 516                         albumChildren.put(album.getParent().getId(), album.getId());
 517                 } finally {
 518                         lock.writeLock().unlock();
 519                 }
 520         }
 521
 522         @Override
 523         public void removeAlbum(Album album) {
 524                 lock.writeLock().lock();
 525                 try {
 526                         allAlbums.remove(album.getId());
 527                         albumChildren.remove(album.getParent().getId(), album.getId());
 528                 } finally {
 529                         lock.writeLock().unlock();
 530                 }
 531         }
 532
 533         //
 534         // IMAGEPROVIDER METHODS
 535         //
 536
 537         @Override
 538         public Optional<Image> getImage(String imageId) {
 539                 lock.readLock().lock();
 540                 try {
 541                         return fromNullable(allImages.get(imageId));
 542                 } finally {
 543                         lock.readLock().unlock();
 544                 }
 545         }
 546
 547         @Override
 548         public List<Image> getImages(Album parent) {
 549                 lock.readLock().lock();
 550                 try {
 551                         return from(albumImages.get(parent.getId())).transformAndConcat(getImage()).toList();
 552                 } finally {
 553                         lock.readLock().unlock();
 554                 }
 555         }
 556
 557         @Override
 558         public void moveUp(Image image) {
 559                 lock.writeLock().lock();
 560                 try {
 561                         List<String> images = albumImages.get(image.getAlbum().getId());
 562                         int currentIndex = images.indexOf(image.getId());
 563                         if (currentIndex == 0) {
 564                                 return;
 565                         }
 566                         images.remove(image.getId());
 567                         images.add(currentIndex - 1, image.getId());
 568                 } finally {
 569                         lock.writeLock().unlock();
 570                 }
 571         }
 572
 573         @Override
 574         public void moveDown(Image image) {
 575                 lock.writeLock().lock();
 576                 try {
 577                         List<String> images = albumChildren.get(image.getAlbum().getId());
 578                         int currentIndex = images.indexOf(image.getId());
 579                         if (currentIndex == (images.size() - 1)) {
 580                                 return;
 581                         }
 582                         images.remove(image.getId());
 583                         images.add(currentIndex + 1, image.getId());
 584                 } finally {
 585                         lock.writeLock().unlock();
 586                 }
 587         }
 588
 589         //
 590         // IMAGESTORE METHODS
 591         //
 592
 593         @Override
 594         public void storeImage(Image image) {
 595                 lock.writeLock().lock();
 596                 try {
 597                         allImages.put(image.getId(), image);
 598                         albumImages.put(image.getAlbum().getId(), image.getId());
 599                 } finally {
 600                         lock.writeLock().unlock();
 601                 }
 602         }
 603
 604         @Override
 605         public void removeImage(Image image) {
 606                 lock.writeLock().lock();
 607                 try {
 608                         allImages.remove(image.getId());
 609                         albumImages.remove(image.getAlbum().getId(), image.getId());
 610                 } finally {
 611                         lock.writeLock().unlock();
 612                 }
 613         }
 614
 615         //
 616         // PACKAGE-PRIVATE METHODS
 617         //
 618
 619         /**
 620          * Returns whether the given post is known.
 621          *
 622          * @param post
 623          *              The post
 624          * @return {@code true} if the post is known, {@code false} otherwise
 625          */
 626         boolean isPostKnown(Post post) {
 627                 lock.readLock().lock();
 628                 try {
 629                         return knownPosts.contains(post.getId());
 630                 } finally {
 631                         lock.readLock().unlock();
 632                 }
 633         }
 634
 635         /**
 636          * Sets whether the given post is known.
 637          *
 638          * @param post
 639          *              The post
 640          * @param known
 641          *              {@code true} if the post is known, {@code false} otherwise
 642          */
 643         void setPostKnown(Post post, boolean known) {
 644                 lock.writeLock().lock();
 645                 try {
 646                         if (known) {
 647                                 knownPosts.add(post.getId());
 648                         } else {
 649                                 knownPosts.remove(post.getId());
 650                         }
 651                 } finally {
 652                         lock.writeLock().unlock();
 653                 }
 654         }
 655
 656         /**
 657          * Returns whether the given post reply is known.
 658          *
 659          * @param postReply
 660          *              The post reply
 661          * @return {@code true} if the given post reply is known, {@code false}
 662          *         otherwise
 663          */
 664         boolean isPostReplyKnown(PostReply postReply) {
 665                 lock.readLock().lock();
 666                 try {
 667                         return knownPostReplies.contains(postReply.getId());
 668                 } finally {
 669                         lock.readLock().unlock();
 670                 }
 671         }
 672
 673         /**
 674          * Sets whether the given post reply is known.
 675          *
 676          * @param postReply
 677          *              The post reply
 678          * @param known
 679          *              {@code true} if the post reply is known, {@code false} otherwise
 680          */
 681         void setPostReplyKnown(PostReply postReply, boolean known) {
 682                 lock.writeLock().lock();
 683                 try {
 684                         if (known) {
 685                                 knownPostReplies.add(postReply.getId());
 686                         } else {
 687                                 knownPostReplies.remove(postReply.getId());
 688                         }
 689                 } finally {
 690                         lock.writeLock().unlock();
 691                 }
 692         }
 693
 694         //
 695         // PRIVATE METHODS
 696         //
 697
 698         /**
 699          * Gets all posts for the given Sone, creating a new collection if there is
 700          * none yet.
 701          *
 702          * @param soneId
 703          *              The ID of the Sone to get the posts for
 704          * @return All posts
 705          */
 706         private Collection<Post> getPostsFrom(String soneId) {
 707                 Collection<Post> posts = null;
 708                 lock.readLock().lock();
 709                 try {
 710                         posts = sonePosts.get(soneId);
 711                 } finally {
 712                         lock.readLock().unlock();
 713                 }
 714                 if (posts != null) {
 715                         return posts;
 716                 }
 717
 718                 posts = new HashSet<Post>();
 719                 lock.writeLock().lock();
 720                 try {
 721                         sonePosts.put(soneId, posts);
 722                 } finally {
 723                         lock.writeLock().unlock();
 724                 }
 725
 726                 return posts;
 727         }
 728
 729         /**
 730          * Gets all posts that are directed the given Sone, creating a new collection
 731          * if there is none yet.
 732          *
 733          * @param recipientId
 734          *              The ID of the Sone to get the posts for
 735          * @return All posts
 736          */
 737         private Collection<Post> getPostsTo(String recipientId) {
 738                 Collection<Post> posts = null;
 739                 lock.readLock().lock();
 740                 try {
 741                         posts = recipientPosts.get(recipientId);
 742                 } finally {
 743                         lock.readLock().unlock();
 744                 }
 745                 if (posts != null) {
 746                         return posts;
 747                 }
 748
 749                 posts = new HashSet<Post>();
 750                 lock.writeLock().lock();
 751                 try {
 752                         recipientPosts.put(recipientId, posts);
 753                 } finally {
 754                         lock.writeLock().unlock();
 755                 }
 756
 757                 return posts;
 758         }
 759
 760         /** Loads the known posts. */
 761         private void loadKnownPosts() {
 762                 lock.writeLock().lock();
 763                 try {
 764                         int postCounter = 0;
 765                         while (true) {
 766                                 String knownPostId = configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").getValue(null);
 767                                 if (knownPostId == null) {
 768                                         break;
 769                                 }
 770                                 knownPosts.add(knownPostId);
 771                         }
 772                 } finally {
 773                         lock.writeLock().unlock();
 774                 }
 775         }
 776
 777         /**
 778          * Saves the known posts to the configuration.
 779          *
 780          * @throws DatabaseException
 781          *              if a configuration error occurs
 782          */
 783         private void saveKnownPosts() throws DatabaseException {
 784                 lock.readLock().lock();
 785                 try {
 786                         int postCounter = 0;
 787                         for (String knownPostId : knownPosts) {
 788                                 configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").setValue(knownPostId);
 789                         }
 790                         configuration.getStringValue("KnownPosts/" + postCounter + "/ID").setValue(null);
 791                 } catch (ConfigurationException ce1) {
 792                         throw new DatabaseException("Could not save database.", ce1);
 793                 } finally {
 794                         lock.readLock().unlock();
 795                 }
 796         }
 797
 798         /**
 799          * Returns all replies by the given Sone.
 800          *
 801          * @param id
 802          *              The ID of the Sone
 803          * @return The post replies of the Sone, sorted by time (newest first)
 804          */
 805         private Collection<PostReply> getRepliesFrom(String id) {
 806                 lock.readLock().lock();
 807                 try {
 808                         if (sonePostReplies.containsKey(id)) {
 809                                 return Collections.unmodifiableCollection(sonePostReplies.get(id));
 810                         }
 811                         return Collections.emptySet();
 812                 } finally {
 813                         lock.readLock().unlock();
 814                 }
 815         }
 816
 817         /** Loads the known post replies. */
 818         private void loadKnownPostReplies() {
 819                 lock.writeLock().lock();
 820                 try {
 821                         int replyCounter = 0;
 822                         while (true) {
 823                                 String knownReplyId = configuration.getStringValue("KnownReplies/" + replyCounter++ + "/ID").getValue(null);
 824                                 if (knownReplyId == null) {
 825                                         break;
 826                                 }
 827                                 knownPostReplies.add(knownReplyId);
 828                         }
 829                 } finally {
 830                         lock.writeLock().unlock();
 831                 }
 832         }
 833
 834         /**
 835          * Saves the known post replies to the configuration.
 836          *
 837          * @throws DatabaseException
 838          *              if a configuration error occurs
 839          */
 840         private void saveKnownPostReplies() throws DatabaseException {
 841                 lock.readLock().lock();
 842                 try {
 843                         int replyCounter = 0;
 844                         for (String knownReplyId : knownPostReplies) {
 845                                 configuration.getStringValue("KnownReplies/" + replyCounter++ + "/ID").setValue(knownReplyId);
 846                         }
 847                         configuration.getStringValue("KnownReplies/" + replyCounter + "/ID").setValue(null);
 848                 } catch (ConfigurationException ce1) {
 849                         throw new DatabaseException("Could not save database.", ce1);
 850                 } finally {
 851                         lock.readLock().unlock();
 852                 }
 853         }
 854
 855         private Function<String, Iterable<Album>> getAlbum() {
 856                 return new Function<String, Iterable<Album>>() {
 857                         @Override
 858                         public Iterable<Album> apply(String input) {
 859                                 return (input == null) ? Collections.<Album>emptyList() : getAlbum(input).asSet();
 860                         }
 861                 };
 862         }
 863
 864         private Function<String, Iterable<Image>> getImage() {
 865                 return new Function<String, Iterable<Image>>() {
 866                         @Override
 867                         public Iterable<Image> apply(String input) {
 868                                 return (input == null) ? Collections.<Image>emptyList() : getImage(input).asSet();
 869                         }
 870                 };
 871         }
 872
 873 }