Added region-based filtering for the GUI to make sure only the relevant
events get sent to the session.

Change-Id: I649eb1b33fdf9ed4b82e29d7ba7eb3cfac5eadbb
diff --git a/core/api/src/main/java/org/onosproject/ui/model/topo/UiModelEvent.java b/core/api/src/main/java/org/onosproject/ui/model/topo/UiModelEvent.java
new file mode 100644
index 0000000..5448b88
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/ui/model/topo/UiModelEvent.java
@@ -0,0 +1,85 @@
+/*
+ * Copyright 2017-present 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.ui.model.topo;
+
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.onosproject.event.AbstractEvent;
+
+/**
+ * UI Topology model events.
+ */
+public class UiModelEvent extends AbstractEvent<UiModelEvent.Type, UiElement> {
+
+    /**
+     * Enumeration of event types.
+     */
+    public enum Type {
+        CLUSTER_MEMBER_ADDED_OR_UPDATED,
+        CLUSTER_MEMBER_REMOVED,
+
+        REGION_ADDED_OR_UPDATED,
+        REGION_REMOVED,
+
+        DEVICE_ADDED_OR_UPDATED,
+        DEVICE_REMOVED,
+
+        LINK_ADDED_OR_UPDATED,
+        LINK_REMOVED,
+
+        HOST_ADDED_OR_UPDATED,
+        HOST_MOVED,
+        HOST_REMOVED
+    }
+
+    private final ObjectNode data;
+    private final String memo;
+
+    /**
+     * Creates a UI model event. Note that the memo field can be used to
+     * pass a hint to the listener about the event.
+     *
+     * @param type    event type
+     * @param subject subject of the event
+     * @param data    data containing details of the subject
+     * @param memo    a note about the event
+     */
+    public UiModelEvent(Type type, UiElement subject, ObjectNode data,
+                        String memo) {
+        super(type, subject);
+        this.data = data;
+        this.memo = memo;
+    }
+
+    /**
+     * Returns the data of the subject.
+     *
+     * @return the subject data
+     */
+    public ObjectNode data() {
+        return data;
+    }
+
+    /**
+     * Returns the memo.
+     *
+     * @return the memo
+     */
+    public String memo() {
+        return memo;
+    }
+
+}