[Emu][onos-2603] - Implement LinkState Link attributes-Prefix Attribute

Change-Id: I87884b14b22495bb4e8f716765d4bb634f5cb270

+/*
+ * Copyright 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.bgpio.types.attr;
+
+import java.util.Objects;
+
+import org.jboss.netty.buffer.ChannelBuffer;
+import org.onosproject.bgpio.exceptions.BGPParseException;
+import org.onosproject.bgpio.types.BGPErrorType;
+import org.onosproject.bgpio.types.BGPValueType;
+import org.onosproject.bgpio.util.Validation;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.base.MoreObjects;
+
+/**
+ * Implements BGP prefix metric attribute.
+ */
+public class BgpPrefixAttrMetric implements BGPValueType {
+
+    protected static final Logger log = LoggerFactory
+            .getLogger(BgpPrefixAttrMetric.class);
+
+    public static final int ATTR_PREFIX_METRIC = 1155;
+    public static final int ATTR_PREFIX_LEN = 4;
+
+    /* TE Default Metric */
+    private final int linkPfxMetric;
+
+    /**
+     * Constructor to initialize value.
+     *
+     * @param linkPfxMetric Prefix Metric
+     */
+    public BgpPrefixAttrMetric(int linkPfxMetric) {
+        this.linkPfxMetric = linkPfxMetric;
+    }
+
+    /**
+     * Returns object of this class with specified values.
+     *
+     * @param linkPfxMetric Prefix Metric
+     * @return object of BgpPrefixAttrMetric
+     */
+    public static BgpPrefixAttrMetric of(final int linkPfxMetric) {
+        return new BgpPrefixAttrMetric(linkPfxMetric);
+    }
+
+    /**
+     * Reads the Prefix Metric.
+     *
+     * @param cb ChannelBuffer
+     * @return object of BgpPrefixAttrMetric
+     * @throws BGPParseException while parsing BgpPrefixAttrMetric
+     */
+    public static BgpPrefixAttrMetric read(ChannelBuffer cb)
+            throws BGPParseException {
+        int linkPfxMetric;
+
+        short lsAttrLength = cb.readShort(); // 4 Bytes
+
+        if ((lsAttrLength != ATTR_PREFIX_LEN)
+                || (cb.readableBytes() < lsAttrLength)) {
+            Validation.validateLen(BGPErrorType.UPDATE_MESSAGE_ERROR,
+                                   BGPErrorType.ATTRIBUTE_LENGTH_ERROR,
+                                   lsAttrLength);
+        }
+
+        linkPfxMetric = cb.readInt();
+
+        return BgpPrefixAttrMetric.of(linkPfxMetric);
+    }
+
+    /**
+     * Returns the Prefix Metric.
+     *
+     * @return Prefix Metric
+     */
+    public int attrPfxMetric() {
+        return linkPfxMetric;
+    }
+
+    @Override
+    public short getType() {
+        return ATTR_PREFIX_METRIC;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(linkPfxMetric);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (obj instanceof BgpPrefixAttrMetric) {
+            BgpPrefixAttrMetric other = (BgpPrefixAttrMetric) obj;
+            return Objects.equals(linkPfxMetric, other.linkPfxMetric);
+        }
+        return false;
+    }
+
+    @Override
+    public int write(ChannelBuffer cb) {
+        // TODO This will be implemented in the next version
+        return 0;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("linkPfxMetric", linkPfxMetric).toString();
+    }
+}