/*

  * #%L

  * CommandCursorTranslator.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.ArrayList;

 import java.util.Collections;

 import java.util.List;

 import com.allanbank.mongodb.bson.Document;

 import com.allanbank.mongodb.bson.NumericElement;

 import com.allanbank.mongodb.bson.builder.BuilderFactory;

 import com.allanbank.mongodb.bson.element.ArrayElement;

 import com.allanbank.mongodb.bson.element.DocumentElement;

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

 /**

  * CommandCursorTranslator provides static utility methods to translate cursor

  * documents.

  * 

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

  */

 public class CommandCursorTranslator {

     /**

      * Translates the reply from a single document command reply into a standard

      * reply with the appropriate bit flips.

      * <p>

      * There are two possible formats we can receive:

      * <ul>

      * <li>

      * Traditional embedded documents under a {@code results} array. For this

      * format all of the Documents are in the single reply and there is no

      * cursor established.<blockquote>

      * 

      * <pre>

      * <code>

      * {

      *   results : [

      *      { ... },

      *      ...

      *   ],

      *   ok : 1

      * }

      * </code>

      * </pre>

      * 

      * </blockquote></li>

      * <li>

      * A {@code cursor} sub-document containing the cursor's {@code id} and

      * {@code firstBatch}. This reply establishes (possibly) a cursor for the

      * results.<blockquote>

      * 

      * <pre>

      * <code>

      * {

      *   cursor : {

      *     id : 1234567,

      *     firstBatch : [

      *       { ... },

      *       ...

      *     ]

      *   }

      *   ok : 1

      * }

      * </code>

      * </pre>

      * 

      * </blockquote></li>

      * 

      * 

      * @param reply

      *            The reply to translate.

      * @return The translated reply.

      */

     /* package */static Reply translate(final Reply reply) {

         Reply result = reply;

         final List<Reply> replies = translateAll(reply);

         if (replies.size() == 1) {

             result = replies.get(0);

         }

         return result;

     }

     /**

      * Translates the reply from a single document command reply into a list of

      * standard replies with the appropriate bit flips.

      * <p>

      * There are three possible formats we can receive:

      * <ul>

      * <li>

      * Traditional embedded documents under a {@code results} array. For this

      * format all of the Documents are in the single reply and there is no

      * cursor established.<blockquote>

      * 

      * <pre>

      * <code>

      * {

      *   results : [

      *      { ... },

      *      ...

      *   ],

      *   ok : 1

      * }

      * </code>

      * </pre>

      * 

      * </blockquote></li>

      * <li>

      * A {@code cursor} sub-document containing the cursor's {@code id} and

      * {@code firstBatch}. This reply establishes (possibly) a cursor for the

      * results.<blockquote>

      * 

      * <pre>

      * <code>

      * {

      *   cursor : {

      *     id : 1234567,

      *     firstBatch : [

      *       { ... },

      *       ...

      *     ]

      *   }

      *   ok : 1

      * }

      * </code>

      * </pre>

      * 

      * </blockquote></li>

      * <li>

      * A {@code cursor} sub-array with a sub-document as each element of the

      * array. Each sub-document contains a {@code cursor} document as described

      * above.<blockquote>

      * 

      * <pre>

      * <code>

      * {

      *   cursors: [

      *     {

      *       cursor : {

      *         id : 1234567,

      *         firstBatch : [

      *           { ... },

      *           ...

      *         ]

      *       }

      *     },

      *     {

      *       cursor : {

      *         id : 1234568,

      *         firstBatch : [

      *           { ... },

      *           ...

      *         ]

      *       }

      *     },

      *     ...

      *   ]

      *   ok : 1

      * }

      * </code>

      * </pre>

      * 

      * </blockquote></li>

      * 

      * 

      * @param reply

      *            The reply to translate.

      * @return The translated reply.

      */

     /* package */static List<Reply> translateAll(final Reply reply) {

         List<Reply> results = Collections.singletonList(reply);

         // Check for a single Document. All formats to translate are single

         // documents.

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

         if (docs.size() == 1) {

             final Document replyDoc = docs.get(0);

             List<DocumentElement> resultDocs;

             // Traditional first since it is more probable in the short term.

             final ArrayElement resultArray = replyDoc.get(ArrayElement.class,

                     "result");

             if (resultArray != null) {

                 resultDocs = replyDoc.find(DocumentElement.class, "result",

                         ".*");

                 results = Collections.singletonList(translate(reply, 0L,

                         resultDocs));

             }

             else {

                 final DocumentElement cursor = replyDoc.get(

                         DocumentElement.class, "cursor");

                 if (cursor != null) {

                     results = translate(reply,

                             Collections.singletonList(cursor));

                 }

                 else {

                     final List<DocumentElement> cursors = replyDoc.find(

                             DocumentElement.class, "cursors", ".*", "cursor");

                     if (!cursors.isEmpty()) {

                         results = translate(reply, cursors);

                     }

                 }

             }

         }

         return results;

     }

     /**

      * Translates a list of cursor documents into a list of {@link Reply}

      * objects.

      * 

      * @param reply

      *            The original reply.

      * @param cursors

      *            The cursor sub documents.

      * @return The translated replies.

      */

     private static List<Reply> translate(final Reply reply,

             final List<DocumentElement> cursors) {

         final List<Reply> results = new ArrayList<Reply>(cursors.size());

         for (final DocumentElement cursor : cursors) {

             final NumericElement id = cursor.get(NumericElement.class, "id");

             final List<DocumentElement> resultDocs = cursor.find(

                     DocumentElement.class, "firstBatch", ".*");

             results.add(translate(reply, (id == null) ? 0 : id.getLongValue(),

                     resultDocs));

         }

         return results;

     }

     /**

      * Creates a new reply based on the original reply and the specified cursor

      * id and document list.

      * 

      * @param reply

      *            The original reply to copy from.

      * @param cursorId

      *            The cursor id that has been established.

      * @param results

      *            The results to include in the reply.

      * @return The translated reply.

      */

     private static Reply translate(final Reply reply, final long cursorId,

             final List<DocumentElement> results) {

         // Strip off the element-ness of the documents.

         final List<Document> docs = new ArrayList<Document>(results.size());

         for (final DocumentElement docElement : results) {

             docs.add(BuilderFactory.start(docElement).build());

         }

         return new Reply(reply.getResponseToId(), cursorId,

                 reply.getCursorOffset(), docs, reply.isAwaitCapable(),

                 reply.isCursorNotFound(), reply.isQueryFailed(),

                 reply.isShardConfigStale());

     }

     /**

      * Creates a new CommandCursorTranslator.

      */

     private CommandCursorTranslator() {

         // Static class.

     }

 }