Refactor notification filtering

[Sone.git] / src / main / java / net / pterodactylus / sone / notify / PostVisibilityFilter.java

diff --git a/src/main/java/net/pterodactylus/sone/notify/PostVisibilityFilter.java b/src/main/java/net/pterodactylus/sone/notify/PostVisibilityFilter.java
new file mode 100644 (file)
index 0000000..edcd148
--- /dev/null
+++ b/src/main/java/net/pterodactylus/sone/notify/PostVisibilityFilter.java
@@ -0,0 +1,98 @@
+package net.pterodactylus.sone.notify;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.inject.Singleton;
+
+import net.pterodactylus.sone.data.Post;
+import net.pterodactylus.sone.data.Sone;
+import net.pterodactylus.sone.freenet.wot.OwnIdentity;
+import net.pterodactylus.sone.freenet.wot.Trust;
+import net.pterodactylus.util.notify.Notification;
+
+import com.google.common.base.Predicate;
+
+/**
+ * Filters {@link Notification}s involving {@link Post}s.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+@Singleton
+public class PostVisibilityFilter {
+
+       /**
+        * 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
+        */
+       boolean isPostVisible(@Nullable Sone sone, @Nonnull Post post) {
+               checkNotNull(post, "post must not be null");
+               if (!post.isLoaded()) {
+                       return false;
+               }
+               Sone postSone = post.getSone();
+               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.
+                                */
+                       }
+                       if ((!postSone.equals(sone)) && !sone.hasFriend(postSone.getId()) && !sone.getId().equals(post.getRecipientId().orNull())) {
+                               return false;
+                       }
+               }
+               return post.getTime() <= System.currentTimeMillis();
+       }
+
+       @Nonnull
+       public Predicate<Post> isVisible(@Nullable final Sone currentSone) {
+               return new Predicate<Post>() {
+                       @Nonnull
+                       @Override
+                       public boolean apply(@Nullable Post post) {
+                               return isPostVisible(currentSone, post);
+                       }
+               };
+       }
+
+}