+ public static List<Post> filterPosts(Collection<Post> posts, Sone currentSone) {
+ List<Post> filteredPosts = new ArrayList<Post>();
+ for (Post post : posts) {
+ if (isPostVisible(currentSone, post)) {
+ filteredPosts.add(post);
+ }
+ }
+ return filteredPosts;
+ }
+
+ /**
+ * Checks whether a post is visible to the given Sone. A post is not
+ * considered visible if one of the following statements is true:
+ * <ul>
+ * <li>The post does not have a Sone.</li>
+ * <li>The post’s {@link Post#getTime() time} is in the future.</li>
+ * </ul>
+ * <p>
+ * If {@code post} is not {@code null} more checks are performed, and the
+ * post will be invisible if:
+ * </p>
+ * <ul>
+ * <li>The Sone of the post is not the given Sone, the given Sone does not
+ * follow the post’s Sone, and the given Sone is not the recipient of the
+ * post.</li>
+ * <li>The trust relationship between the two Sones can not be retrieved.</li>
+ * <li>The given Sone has explicitely assigned negative trust to the post’s
+ * Sone.</li>
+ * <li>The given Sone has not explicitely assigned negative trust to the
+ * post’s Sone but the implicit trust is negative.</li>
+ * </ul>
+ * If none of these statements is true the post is considered visible.
+ *
+ * @param sone
+ * The Sone that checks for a post’s visibility (may be
+ * {@code null} to skip Sone-specific checks, such as trust)
+ * @param post
+ * The post to check for visibility
+ * @return {@code true} if the post is considered visible, {@code false}
+ * otherwise
+ */
+ public static boolean isPostVisible(Sone sone, Post post) {
+ checkNotNull(post, "post must not be null");
+ Sone postSone = post.getSone();
+ if (postSone == null) {
+ return false;
+ }
+ if (sone != null) {
+ Trust trust = postSone.getIdentity().getTrust((OwnIdentity) sone.getIdentity());
+ if (trust != null) {
+ if ((trust.getExplicit() != null) && (trust.getExplicit() < 0)) {
+ return false;
+ }
+ if ((trust.getExplicit() == null) && (trust.getImplicit() != null) && (trust.getImplicit() < 0)) {
+ return false;
+ }
+ } else {
+ /*
+ * a null trust means that the trust updater has not yet
+ * received a trust value for this relation. if we return false,
+ * the post feed will stay empty until the trust updater has
+ * received trust values. to prevent this we simply assume that
+ * posts are visible if there is no trust.
+ */