diff --git a/briar-api/src/org/briarproject/api/clients/MessageTree.java b/briar-api/src/org/briarproject/api/clients/MessageTree.java
new file mode 100644
index 0000000000000000000000000000000000000000..500db6a583435f5371ff4e403b7b37778a7f3098
--- /dev/null
+++ b/briar-api/src/org/briarproject/api/clients/MessageTree.java
@@ -0,0 +1,21 @@
+package org.briarproject.api.clients;
+
+import org.briarproject.api.sync.MessageId;
+
+import java.util.Collection;
+import java.util.Comparator;
+
+public interface MessageTree<T extends MessageTree.MessageNode> {
+
+ void add(Collection<T> nodes);
+ void clear();
+ Collection<T> depthFirstOrder();
+ void setComparator(Comparator<T> comparator);
+
+ interface MessageNode {
+ MessageId getId();
+ MessageId getParentId();
+ long getTimestamp();
+ }
+
+}
diff --git a/briar-api/src/org/briarproject/api/forum/ForumPostHeader.java b/briar-api/src/org/briarproject/api/forum/ForumPostHeader.java
index 00924f98ab0834de48700d4f855128f1de6dcb02..40779390539cd3dff457cc70470d1443780f1755 100644
--- a/briar-api/src/org/briarproject/api/forum/ForumPostHeader.java
+++ b/briar-api/src/org/briarproject/api/forum/ForumPostHeader.java
@@ -1,9 +1,10 @@
package org.briarproject.api.forum;
+import org.briarproject.api.clients.MessageTree;
import org.briarproject.api.identity.Author;
import org.briarproject.api.sync.MessageId;
-public class ForumPostHeader {
+public class ForumPostHeader implements MessageTree.MessageNode {
private final MessageId id;
private final MessageId parentId;
diff --git a/briar-core/src/org/briarproject/clients/MessageTreeImpl.java b/briar-core/src/org/briarproject/clients/MessageTreeImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..55f69cf54008adbcb57e57788a24afe25f0284d7
--- /dev/null
+++ b/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;
+ }
+
+}
diff --git a/briar-core/src/org/briarproject/forum/ForumModule.java b/briar-core/src/org/briarproject/forum/ForumModule.java
index bde6a057df777386641fc75c4656c4e9272175b7..04d934a21ccccaabdae511448eee6d6fa55d5d4d 100644
--- a/briar-core/src/org/briarproject/forum/ForumModule.java
+++ b/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;
+ }
}
diff --git a/briar-tests/src/org/briarproject/clients/MessageTreeTest.java b/briar-tests/src/org/briarproject/clients/MessageTreeTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..1c6e165311ea13955c7124704dd568bf7732e499
--- /dev/null
+++ b/briar-tests/src/org/briarproject/clients/MessageTreeTest.java
@@ -0,0 +1,102 @@
+package org.briarproject.clients;
+
+import org.briarproject.TestUtils;
+import org.briarproject.api.clients.MessageTree;
+import org.briarproject.api.sync.MessageId;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.logging.Logger;
+
+import static org.junit.Assert.assertEquals;
+
+public class MessageTreeTest {
+
+ private static final Logger LOG =
+ Logger.getLogger(MessageTreeTest.class.getName());
+
+ private MessageTree<TestNode> tree;
+
+ @Test
+ public void testMessageTree() {
+ tree = new MessageTreeImpl<>();
+ testSimpleTree();
+ tree.clear();
+ testSimpleTree();
+ }
+
+ private void testSimpleTree() {
+ TestNode[] nodes = new TestNode[5];
+ for (int i = 0; i < nodes.length; i++) {
+ nodes[i] = new TestNode();
+ }
+ /*
+ Construct the following tree:
+ 4
+ 1 ->
+ 0 ->
+ 2
+ 3
+ */
+ nodes[0].setParentId(nodes[1].getId());
+ nodes[2].setParentId(nodes[0].getId());
+ nodes[3].setParentId(nodes[1].getId());
+ long timestamp = System.currentTimeMillis();
+ nodes[4].setTimestamp(timestamp - 5);
+ nodes[1].setTimestamp(timestamp - 4);
+ nodes[0].setTimestamp(timestamp - 3);
+ nodes[3].setTimestamp(timestamp - 2);
+ nodes[2].setTimestamp(timestamp - 1);
+ // add all nodes except the last one
+ tree.add(Arrays.asList(Arrays.copyOf(nodes, nodes.length-1)));
+ tree.add(Collections.singletonList(nodes[nodes.length-1]));
+ TestNode[] sortedNodes = tree.depthFirstOrder().toArray(new TestNode[5]);
+ assertEquals(nodes[4], sortedNodes[0]);
+ assertEquals(nodes[1], sortedNodes[1]);
+ assertEquals(nodes[0], sortedNodes[2]);
+ assertEquals(nodes[2], sortedNodes[3]);
+ assertEquals(nodes[3], sortedNodes[4]);
+ }
+
+ private void printNodes(TestNode[] nodes, TestNode[] sortedNodes) {
+ for (int i = 0; i < sortedNodes.length; i++) {
+ for (int j = 0; j < nodes.length; j++) {
+ if (sortedNodes[i] == nodes[j]) {
+ LOG.info("index: " + j);
+ break;
+ }
+ }
+ }
+ }
+
+ class TestNode implements MessageTree.MessageNode {
+
+ private final MessageId id = new MessageId(TestUtils.getRandomId());
+ private MessageId parentId;
+ private long timestamp;
+
+ @Override
+ public MessageId getId() {
+ return id;
+ }
+
+ @Override
+ public MessageId getParentId() {
+ return parentId;
+ }
+
+ @Override
+ public long getTimestamp() {
+ return timestamp;
+ }
+
+ public void setParentId(MessageId parentId) {
+ this.parentId = parentId;
+ }
+
+ public void setTimestamp(long timestamp) {
+ this.timestamp = timestamp;
+ }
+ }
+}