CORD-1071 Refactor VTN node service

Done
- Separated interface, implementation and store for node management
- Added unit tests for node manager and handler
- Offloaded more of the event handling off of the Atomix event thread

Todo
- Add REST interface for the node service

Change-Id: Ibf90d3a621013497cc891ca3086db6648f5d49df
diff --git a/src/main/java/org/opencord/cordvtn/api/node/CordVtnNodeService.java b/src/main/java/org/opencord/cordvtn/api/node/CordVtnNodeService.java
new file mode 100644
index 0000000..afa9b17
--- /dev/null
+++ b/src/main/java/org/opencord/cordvtn/api/node/CordVtnNodeService.java
@@ -0,0 +1,57 @@
+/*
+ * 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.opencord.cordvtn.api.node;
+
+import org.onosproject.event.ListenerService;
+import org.onosproject.net.DeviceId;
+
+import java.util.Set;
+
+/**
+ * Service for interfacing with the inventory of {@link CordVtnNode}.
+ */
+public interface CordVtnNodeService extends ListenerService<CordVtnNodeEvent, CordVtnNodeListener> {
+
+    /**
+     * Returns all nodes.
+     *
+     * @return set of nodes; empty set if no node presents
+     */
+    Set<CordVtnNode> nodes();
+
+    /**
+     * Returns nodes in complete state.
+     *
+     * @return set of nodes; empty set if no complete node presents
+     */
+    Set<CordVtnNode> completeNodes();
+
+    /**
+     * Returns the node with the given hostname.
+     *
+     * @param hostname hostname of the node
+     * @return cordvtn node; null if no node present with the hostname
+     */
+    CordVtnNode node(String hostname);
+
+    /**
+     * Returns the node with the given integration bridge device identifier.
+     *
+     * @param deviceId integration bridge device id
+     * @return cordvtn node; null if no node present with the device id
+     */
+    CordVtnNode node(DeviceId deviceId);
+}