/*

  * #%L

  * Header.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * 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.

  * #L%

  */

 package com.allanbank.mongodb.client.message;

 import java.io.IOException;

 import com.allanbank.mongodb.bson.io.BsonInputStream;

 import com.allanbank.mongodb.client.Operation;

 /**

  * The header of a message.

  * 

  * <pre>

  * <code>

  * struct MsgHeader {

  *     int32   messageLength; // total message size, including this

  *     int32   requestID;     // identifier for this message

  *     int32   responseTo;    // requestID from the original request

  *                            //   (used in reponses from db)

  *     int32   opCode;        // request type - see table below

  * }

  * </code>

  * </pre>

  * 

  * @api.no This class is <b>NOT</b> part of the drivers API. This class may be

  *         mutated in incompatible ways between any two releases of the driver.

  * @copyright 2011-2013, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class Header {

     /** The size of a message header. */

     public static final int SIZE = 16;

     /**

      * The length of the message in bytes. This includes the length of the

      * header (16 bytes).

      */

     private final int myLength;

     /** The operation for the message. */

     private final Operation myOperation;

     /** The request id for the message. */

     private final int myRequestId;

     /** The response id for the message. */

     private final int myResponseId;

     /**

      * Creates a new header.

      * 

      * @param in

      *            The stream to read the header from.

      * @throws IOException

      *             On a failure reading the header.

      */

     public Header(final BsonInputStream in) throws IOException {

         myLength = in.readInt();

         myRequestId = in.readInt();

         myResponseId = in.readInt();

         myOperation = Operation.fromCode(in.readInt());

     }

     /**

      * Creates a new header.

      * 

      * @param length

      *            The length of the message in bytes.

      * @param requestId

      *            The request id for the message.

      * @param responseId

      *            The response id for the message.

      * @param operation

      *            The operation for the message.

      */

     public Header(final int length, final int requestId, final int responseId,

             final Operation operation) {

         myLength = length;

         myRequestId = requestId;

         myResponseId = responseId;

         myOperation = operation;

     }

     /**

      * Determines if the passed object is of this same type as this object and

      * if so that its fields are equal.

      * 

      * @param object

      *            The object to compare to.

      * 

      * @see java.lang.Object#equals(java.lang.Object)

      */

     @Override

     public boolean equals(final Object object) {

         boolean result = false;

         if (this == object) {

             result = true;

         }

         else if ((object != null) && (getClass() == object.getClass())) {

             final Header other = (Header) object;

             result = (myLength == other.myLength)

                     && (myOperation == other.myOperation)

                     && (myRequestId == other.myRequestId)

                     && (myResponseId == other.myResponseId);

         }

         return result;

     }

     /**

      * Returns the length of the message in bytes. This includes the

      * {@link #SIZE} of the header.

      * 

      * @return The length of the message in bytes.

      */

     public int getLength() {

         return myLength;

     }

     /**

      * Returns the operation for the message.

      * 

      * @return The operation for the message.

      */

     public Operation getOperation() {

         return myOperation;

     }

     /**

      * Returns the request id for the message.

      * 

      * @return The request id for the message.

      */

     public int getRequestId() {

         return myRequestId;

     }

     /**

      * Returns the response id for the message.

      * 

      * @return The response id for the message.

      */

     public int getResponseId() {

         return myResponseId;

     }

     /**

      * Computes a reasonable hash code.

      * 

      * @return The hash code value.

      */

     @Override

     public int hashCode() {

         int result = 1;

         result = (31 * result) + myLength;

         result = (31 * result) + myRequestId;

         result = (31 * result) + myResponseId;

         result = (31 * result) + myOperation.hashCode();

         return result;

     }

 }