generic sorted message tree

briar-core/src/org/briarproject/clients/MessageTreeImpl.java

@@ -0,0 +1,89 @@
+package org.briarproject.clients;
+
+import org.briarproject.api.clients.MessageTree;
+import org.briarproject.api.sync.MessageId;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import javax.inject.Inject;
+
+public class MessageTreeImpl<T extends MessageTree.MessageNode>
+		implements MessageTree<T> {
+
+	Map<MessageId, List<T>> nodeMap = new HashMap<MessageId, List<T>>();
+	List<T> roots = new ArrayList<T>();
+
+	private Comparator<T> comparator = new Comparator<T>() {
+		@Override
+		public int compare(T o1, T o2) {
+			return Long.valueOf(o1.getTimestamp()).compareTo(o2.getTimestamp());
+		}
+	};
+
+	@Inject
+	public MessageTreeImpl() {
+
+	}
+
+	@Override
+	public void clear() {
+		roots.clear();
+		nodeMap.clear();
+	}
+
+	@Override
+	public void add(Collection<T> nodes) {
+		// add all nodes to the node map
+		for (T node : nodes) {
+			nodeMap.put(node.getId(), new ArrayList<T>());
+		}
+		// parse the nodes for dependencies
+		for (T node : nodes) {
+			if (node.getParentId() == null) {
+				roots.add(node);
+			}
+			else {
+				// retrieve the parent's children
+				List<T> pChildren = nodeMap.get(node.getParentId());
+				pChildren.add(node);
+			}
+		}
+		sortAll();
+	}
+
+	private void sortAll() {
+		Collections.sort(roots, comparator);
+		// Sort all the sub-lists
+		for (Map.Entry<MessageId, List<T>> entry: nodeMap.entrySet()) {
+			Collections.sort(entry.getValue(), comparator);
+		}
+	}
+
+	private void traverse(List<T> list, T node) {
+		list.add(node);
+		for (T child : nodeMap.get(node.getId())) {
+			traverse(list, child);
+		}
+	}
+
+	@Override
+	public Collection<T> depthFirstOrder() {
+		List<T> orderedList = new ArrayList<T>();
+		for (T root : roots) {
+			traverse(orderedList, root);
+		}
+		return Collections.unmodifiableList(orderedList);
+	}
+
+	@Override
+	public void setComparator(Comparator<T> comparator) {
+		this.comparator = comparator;
+	}
+
+}

briar-core/src/org/briarproject/forum/ForumModule.java

@@ -2,6 +2,7 @@ package org.briarproject.forum;
 
 import org.briarproject.api.clients.ClientHelper;
 import org.briarproject.api.clients.MessageQueueManager;
+import org.briarproject.api.clients.MessageTree;
 import org.briarproject.api.contact.ContactManager;
 import org.briarproject.api.crypto.CryptoComponent;
 import org.briarproject.api.data.MetadataEncoder;
@@ -9,12 +10,14 @@ import org.briarproject.api.db.DatabaseComponent;
 import org.briarproject.api.forum.ForumFactory;
 import org.briarproject.api.forum.ForumManager;
 import org.briarproject.api.forum.ForumPostFactory;
+import org.briarproject.api.forum.ForumPostHeader;
 import org.briarproject.api.forum.ForumSharingManager;
 import org.briarproject.api.identity.AuthorFactory;
 import org.briarproject.api.lifecycle.LifecycleManager;
 import org.briarproject.api.sync.GroupFactory;
 import org.briarproject.api.sync.ValidationManager;
 import org.briarproject.api.system.Clock;
+import org.briarproject.clients.MessageTreeImpl;
 
 import java.security.SecureRandom;
 
@@ -100,4 +103,11 @@ public class ForumModule {
 
 		return forumSharingManager;
 	}
+
+	@Provides
+	@Singleton
+	MessageTree<ForumPostHeader> provideForumMessageTree(
+			MessageTreeImpl<ForumPostHeader> messageTree) {
+		return messageTree;
+	}
 }