/*

  * #%L

  * ReplyLongCallback.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.callback;

 import java.util.List;

 import com.allanbank.mongodb.Callback;

 import com.allanbank.mongodb.MongoDbException;

 import com.allanbank.mongodb.bson.Document;

 import com.allanbank.mongodb.bson.Element;

 import com.allanbank.mongodb.bson.NumericElement;

 import com.allanbank.mongodb.client.message.Reply;

 import com.allanbank.mongodb.error.ReplyException;

 /**

  * Callback to expect and extract a single document from the reply and then

  * extract a contained {@link NumericElement} and coerce it to a long value.

  * 

  * @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 ReplyLongCallback extends AbstractReplyCallback<Long> {

     /** The default name for the long value to return. */

     public static final String DEFAULT_NAME = "n";

     /**

      * The name of the {@link NumericElement value} expected in the reply

      * document.

      */

     private final String myName;

     /**

      * Create a new ReplyLongCallback.

      * 

      * @param results

      *            The callback to notify of the value.

      */

     public ReplyLongCallback(final Callback<Long> results) {

         this(DEFAULT_NAME, results);

     }

     /**

      * Create a new ReplyLongCallback.

      * 

      * @param name

      *            The name of the {@link NumericElement numeric} value.

      * @param results

      *            The callback to notify of the value.

      */

     public ReplyLongCallback(final String name, final Callback<Long> results) {

         super(results);

         myName = name;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Creates an exception from the {@link Reply} if the 'n' field is missing.

      * </p>

      * 

      * @param reply

      *            The raw reply.

      * @return The exception created.

      */

     @Override

     protected MongoDbException asError(final Reply reply) {

         MongoDbException error = super.asError(reply);

         if (error == null) {

             final List<Document> results = reply.getResults();

             if (results.size() == 1) {

                 final Document doc = results.get(0);

                 final Element nElem = doc.get(myName);

                 if (!(nElem instanceof NumericElement)) {

                     error = new ReplyException(reply, "Missing '" + myName

                             + "' field in reply.");

                 }

             }

         }

         return error;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to return the 'n' field in the reply document.

      * </p>

      * 

      * @see AbstractReplyCallback#convert(Reply)

      */

     @Override

     protected Long convert(final Reply reply) throws MongoDbException {

         final List<Document> results = reply.getResults();

         if (results.size() == 1) {

             final Document doc = results.get(0);

             final Element nElem = doc.get(myName);

             return Long.valueOf(toLong(nElem));

         }

         return Long.valueOf(-1);

     }

     /**

      * Converts a {@link NumericElement} into a <tt>long</tt> value. If not a

      * {@link NumericElement} then -1 is returned.

      * 

      * @param element

      *            The element to convert.

      * @return The element's long value or -1.

      */

     protected long toLong(final Element element) {

         if (element instanceof NumericElement) {

             return ((NumericElement) element).getLongValue();

         }

         return -1;

     }

 }