Add sone change detector that finds new and removed elements.

[Sone.git] / src / main / java / net / pterodactylus / sone / core / SoneChangeDetector.java

diff --git a/src/main/java/net/pterodactylus/sone/core/SoneChangeDetector.java b/src/main/java/net/pterodactylus/sone/core/SoneChangeDetector.java
new file mode 100644 (file)
index 0000000..efcdc6e
--- /dev/null
+++ b/src/main/java/net/pterodactylus/sone/core/SoneChangeDetector.java
@@ -0,0 +1,114 @@
+package net.pterodactylus.sone.core;
+
+import static com.google.common.base.Optional.absent;
+import static com.google.common.base.Optional.fromNullable;
+import static com.google.common.collect.FluentIterable.from;
+
+import java.util.Collection;
+
+import net.pterodactylus.sone.data.Post;
+import net.pterodactylus.sone.data.PostReply;
+import net.pterodactylus.sone.data.Sone;
+
+import com.google.common.base.Optional;
+import com.google.common.base.Predicate;
+import com.google.common.collect.FluentIterable;
+
+/**
+ * Compares the contents of two {@link Sone}s and fires events for new and
+ * removed elements.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class SoneChangeDetector {
+
+       private final Sone oldSone;
+       private Optional<PostProcessor> newPostProcessor = absent();
+       private Optional<PostProcessor> removedPostProcessor = absent();
+       private Optional<PostReplyProcessor> newPostReplyProcessor = absent();
+       private Optional<PostReplyProcessor> removedPostReplyProcessor = absent();
+
+       public SoneChangeDetector(Sone oldSone) {
+               this.oldSone = oldSone;
+       }
+
+       public void onNewPosts(PostProcessor newPostProcessor) {
+               this.newPostProcessor = fromNullable(newPostProcessor);
+       }
+
+       public void onRemovedPosts(PostProcessor removedPostProcessor) {
+               this.removedPostProcessor = fromNullable(removedPostProcessor);
+       }
+
+       public void onNewPostReplies(PostReplyProcessor newPostReplyProcessor) {
+               this.newPostReplyProcessor = fromNullable(newPostReplyProcessor);
+       }
+
+       public void onRemovedPostReplies(
+                       PostReplyProcessor removedPostReplyProcessor) {
+               this.removedPostReplyProcessor = fromNullable(removedPostReplyProcessor);
+       }
+
+       public void detectChanges(Sone newSone) {
+               processPosts(from(newSone.getPosts()).filter(
+                               notContainedIn(oldSone.getPosts())), newPostProcessor);
+               processPosts(from(oldSone.getPosts()).filter(
+                               notContainedIn(newSone.getPosts())), removedPostProcessor);
+               processPostReplies(from(newSone.getReplies()).filter(
+                               notContainedIn(oldSone.getReplies())), newPostReplyProcessor);
+               processPostReplies(from(oldSone.getReplies()).filter(
+                               notContainedIn(newSone.getReplies())), removedPostReplyProcessor);
+       }
+
+       private void processPostReplies(FluentIterable<PostReply> postReplies,
+                       Optional<PostReplyProcessor> postReplyProcessor) {
+               for (PostReply postReply : postReplies) {
+                       notifyPostReplyProcessor(postReplyProcessor, postReply);
+               }
+       }
+
+       private void notifyPostReplyProcessor(
+                       Optional<PostReplyProcessor> postReplyProcessor,
+                       PostReply postReply) {
+               if (postReplyProcessor.isPresent()) {
+                       postReplyProcessor.get()
+                                       .processPostReply(postReply);
+               }
+       }
+
+       private void processPosts(FluentIterable<Post> posts,
+                       Optional<PostProcessor> newPostProcessor) {
+               for (Post post : posts) {
+                       notifyPostProcessor(newPostProcessor, post);
+               }
+       }
+
+       private void notifyPostProcessor(Optional<PostProcessor> postProcessor,
+                       Post newPost) {
+               if (postProcessor.isPresent()) {
+                       postProcessor.get().processPost(newPost);
+               }
+       }
+
+       private <T> Predicate<T> notContainedIn(final Collection<T> posts) {
+               return new Predicate<T>() {
+                       @Override
+                       public boolean apply(T element) {
+                               return !posts.contains(element);
+                       }
+               };
+       }
+
+       public interface PostProcessor {
+
+               void processPost(Post post);
+
+       }
+
+       public interface PostReplyProcessor {
+
+               void processPostReply(PostReply postReply);
+
+       }
+
+}