Refactor OpenstackTelemetry App for better readability

Change-Id: I93353de31fb9671d8670ee44fc248fe7f36ac12b
diff --git a/apps/openstacktelemetry/app/src/main/java/org/onosproject/openstacktelemetry/codec/TinaFlowInfoByteBufferCodec.java b/apps/openstacktelemetry/app/src/main/java/org/onosproject/openstacktelemetry/codec/TinaFlowInfoByteBufferCodec.java
index 35547b2..8b28797 100644
--- a/apps/openstacktelemetry/app/src/main/java/org/onosproject/openstacktelemetry/codec/TinaFlowInfoByteBufferCodec.java
+++ b/apps/openstacktelemetry/app/src/main/java/org/onosproject/openstacktelemetry/codec/TinaFlowInfoByteBufferCodec.java
@@ -35,14 +35,19 @@
 public class TinaFlowInfoByteBufferCodec extends ByteBufferCodec<FlowInfo> {
 
     private static final int MESSAGE_SIZE = 88;
+    private static final String OF_PREFIX = "of:";
 
     @Override
     public ByteBuffer encode(FlowInfo flowInfo) {
 
         ByteBuffer byteBuffer = ByteBuffer.allocate(MESSAGE_SIZE);
 
+        String  deviceId = flowInfo.deviceId().toString();
+        short switchId = (short) Integer.parseInt(deviceId.substring(3,
+                                                  deviceId.length()), 16);
+
         byteBuffer.put(flowInfo.flowType())
-                .putShort(Short.valueOf(flowInfo.deviceId().toString()))
+                .putShort(switchId)
                 .putInt(flowInfo.inputInterfaceId())
                 .putInt(flowInfo.outputInterfaceId())
                 .putShort(flowInfo.vlanId().toShort())
@@ -67,7 +72,8 @@
     public FlowInfo decode(ByteBuffer byteBuffer) {
 
         byte flowType = byteBuffer.get();
-        DeviceId deviceId = DeviceId.deviceId(String.valueOf(byteBuffer.getShort()));
+        String deviceIdStr = String.format("%016x", byteBuffer.getShort());
+        DeviceId deviceId = DeviceId.deviceId(OF_PREFIX + deviceIdStr);
         int inputInterfaceId = byteBuffer.getInt();
         int outputInterfaceId = byteBuffer.getInt();
         VlanId vlanId = VlanId.vlanId(byteBuffer.getShort());
diff --git a/apps/openstacktelemetry/app/src/main/java/org/onosproject/openstacktelemetry/codec/TinaMessageByteBufferCodec.java b/apps/openstacktelemetry/app/src/main/java/org/onosproject/openstacktelemetry/codec/TinaMessageByteBufferCodec.java
new file mode 100644
index 0000000..3b849d1
--- /dev/null
+++ b/apps/openstacktelemetry/app/src/main/java/org/onosproject/openstacktelemetry/codec/TinaMessageByteBufferCodec.java
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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.openstacktelemetry.codec;
+
+import org.onosproject.openstacktelemetry.api.FlowInfo;
+
+import java.nio.ByteBuffer;
+import java.util.Set;
+
+/**
+ * Tina Message ByteBuffer Codec.
+ */
+public class TinaMessageByteBufferCodec {
+
+    private static final int HEADER_SIZE = 8;
+    private static final int ENTRY_SIZE = 88;
+    private static final int MILLISECONDS = 1000;
+    private static final short KAFKA_MESSAGE_TYPE = 1;
+
+    /**
+     * Encodes a collection flow infos into byte buffer.
+     *
+     * @param flowInfos a collection of flow info
+     * @return encoded byte buffer
+     */
+    public ByteBuffer encode(Set<FlowInfo> flowInfos) {
+        ByteBuffer byteBuffer =
+                ByteBuffer.allocate(HEADER_SIZE + flowInfos.size() * ENTRY_SIZE);
+
+        byteBuffer.put(buildMessageHeader(flowInfos));
+        byteBuffer.put(buildMessageBody(flowInfos));
+
+        return byteBuffer;
+    }
+
+    private byte[] buildMessageHeader(Set<FlowInfo> flowInfos) {
+        ByteBuffer byteBuffer = ByteBuffer.allocate(HEADER_SIZE);
+
+        byteBuffer.putShort((short) flowInfos.size());
+        byteBuffer.putShort(KAFKA_MESSAGE_TYPE);
+        byteBuffer.putInt((int) (System.currentTimeMillis() / MILLISECONDS));
+
+        return byteBuffer.array();
+    }
+
+    private byte[] buildMessageBody(Set<FlowInfo> flowInfos) {
+        ByteBuffer byteBuffer = ByteBuffer.allocate(flowInfos.size() * ENTRY_SIZE);
+
+        TinaFlowInfoByteBufferCodec codec = new TinaFlowInfoByteBufferCodec();
+        flowInfos.forEach(flowInfo -> byteBuffer.put(codec.encode(flowInfo)));
+
+        return byteBuffer.array();
+    }
+}