/*

  * #%L

  * AbstractMessage.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 com.allanbank.mongodb.ReadPreference;

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

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

 import com.allanbank.mongodb.client.Message;

 import com.allanbank.mongodb.client.Operation;

 import com.allanbank.mongodb.client.VersionRange;

 /**

  * Base class for a MongoDB message.

  * 

  * @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 abstract class AbstractMessage implements Message {

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

     public static final int HEADER_SIZE = Header.SIZE;

     /** The name of the collection to operate on. */

     protected String myCollectionName;

     /** The name of the database to operate on. */

     protected String myDatabaseName;

     /** The details on which servers may be sent the message. */

     private final ReadPreference myReadPreference;

     /** The required version of the server to support processing the message. */

     private final VersionRange myRequiredServerVersionRange;

     /**

      * Create a new AbstractMessage.

      */

     public AbstractMessage() {

         myDatabaseName = "";

         myCollectionName = "";

         myReadPreference = ReadPreference.PRIMARY;

         myRequiredServerVersionRange = null;

     }

     /**

      * Create a new AbstractMessage.

      * 

      * @param databaseName

      *            The name of the database.

      * @param collectionName

      *            The name of the collection.

      * @param readPreference

      *            The preferences for which servers to send the message.

      */

     public AbstractMessage(final String databaseName,

             final String collectionName, final ReadPreference readPreference) {

         myDatabaseName = databaseName;

         myCollectionName = collectionName;

         myReadPreference = readPreference;

         myRequiredServerVersionRange = null;

     }

     /**

      * Creates a new AbstractMessage.

      * 

      * @param databaseName

      *            The name of the database.

      * @param collectionName

      *            The name of the collection.

      * @param readPreference

      *            The preferences for which servers to send the message.

      * @param versionRange

      *            The required range of versions of the server to support

      *            processing the message.

      */

     public AbstractMessage(final String databaseName,

             final String collectionName, final ReadPreference readPreference,

             final VersionRange versionRange) {

         myDatabaseName = databaseName;

         myCollectionName = collectionName;

         myReadPreference = readPreference;

         myRequiredServerVersionRange = versionRange;

     }

     /**

      * 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;

         // This should never return false as derived classes should have

         // verified.

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

             final AbstractMessage other = (AbstractMessage) object;

             result = myCollectionName.equals(other.myCollectionName)

                     && myDatabaseName.equals(other.myDatabaseName)

                     && myReadPreference.equals(other.myReadPreference);

         }

         return result;

     }

     /**

      * Returns the name of the collection.

      * 

      * @return The name of the collection.

      */

     public String getCollectionName() {

         return myCollectionName;

     }

     /**

      * Returns the name of the database.

      * 

      * @return The name of the database.

      */

     @Override

     public String getDatabaseName() {

         return myDatabaseName;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Returns the message's read preference.

      * </p>

      */

     @Override

     public ReadPreference getReadPreference() {

         return myReadPreference;

     }

     /**

      * {@inheritDoc}

      */

     @Override

     public VersionRange getRequiredVersionRange() {

         return myRequiredServerVersionRange;

     }

     /**

      * Computes a reasonable hash code.

      * 

      * @return The hash code value.

      */

     @Override

     public int hashCode() {

         int result = 1;

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

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

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

         return result;

     }

     /**

      * Writes the MsgHeader messageLengthField in the header <tt>stream</tt>.

      * 

      * <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>

      * 

      * @param stream

      *            The stream to write to.

      * @param start

      *            The position of the start of the header for the message.

      */

     protected void finishHeader(final BufferingBsonOutputStream stream,

             final long start) {

         final long end = stream.getPosition();

         stream.writeIntAt(start, (int) (end - start));

     }

     /**

      * Initializes the database and collection name from the full database name.

      * 

      * @param name

      *            The full database name.

      */

     protected void init(final String name) {

         final int firstDot = name.indexOf('.');

         if (firstDot >= 0) {

             myDatabaseName = name.substring(0, firstDot);

             myCollectionName = name.substring(firstDot + 1);

         }

         else {

             myDatabaseName = name;

         }

     }

     /**

      * Writes the MsgHeader to the <tt>stream</tt>.

      * 

      * <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>

      * 

      * @param stream

      *            The stream to write to.

      * @param requestId

      *            The requestID from above.

      * @param responseTo

      *            The responseTo from above.

      * @param op

      *            The operation for the opCode field.

      * @param length

      *            The length of the message including the header.

      */

     protected void writeHeader(final BsonOutputStream stream,

             final int requestId, final int responseTo, final Operation op,

             final int length) {

         stream.writeInt(length);

         stream.writeInt(requestId);

         stream.writeInt(responseTo);

         stream.writeInt(op.getCode());

     }

     /**

      * Writes the MsgHeader to the <tt>stream</tt>.

      * 

      * <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>

      * 

      * @param stream

      *            The stream to write to.

      * @param requestId

      *            The requestID from above.

      * @param responseTo

      *            The responseTo from above.

      * @param op

      *            The operation for the opCode field.

      * @return The position of the start of the header for the message.

      */

     protected long writeHeader(final BufferingBsonOutputStream stream,

             final int requestId, final int responseTo, final Operation op) {

         final long start = stream.getPosition();

         stream.writeInt(0);

         stream.writeInt(requestId);

         stream.writeInt(responseTo);

         stream.writeInt(op.getCode());

         return start;

     }

 }