ONOS-3182 Starting on path visualization app.

Change-Id: Id9b074afb22599473b1849acc380fa189061e8bb
diff --git a/apps/pathpainter/src/main/java/org/onosproject/pathpainter/PathLink.java b/apps/pathpainter/src/main/java/org/onosproject/pathpainter/PathLink.java
new file mode 100644
index 0000000..5724170
--- /dev/null
+++ b/apps/pathpainter/src/main/java/org/onosproject/pathpainter/PathLink.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2014,2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.pathpainter;
+
+import org.onosproject.net.Link;
+import org.onosproject.net.LinkKey;
+import org.onosproject.ui.topo.BiLink;
+import org.onosproject.ui.topo.LinkHighlight;
+import org.onosproject.ui.topo.LinkHighlight.Flavor;
+
+import java.util.Set;
+
+/**
+ * Bi-directional link capable of different hilights.
+ */
+public class PathLink extends BiLink {
+
+    private boolean primary = false;
+    private boolean secondary = false;
+
+    public PathLink(LinkKey key, Link link) {
+        super(key, link);
+    }
+
+    public void computeHilight(Set<Link> selectedLinks, Set<Link> allLinks) {
+        primary = selectedLinks.contains(this.one()) ||
+                (two() != null && selectedLinks.contains(two()));
+        secondary = allLinks.contains(this.one()) ||
+                (two() != null && allLinks.contains(two()));
+    }
+
+    @Override
+    public LinkHighlight highlight(Enum<?> anEnum) {
+        Flavor flavor = primary ? Flavor.PRIMARY_HIGHLIGHT :
+                (secondary ? Flavor.SECONDARY_HIGHLIGHT : Flavor.NO_HIGHLIGHT);
+        return new LinkHighlight(this.linkId(), flavor);
+    }
+}