/*

  * #%L

  * ImmutableDocument.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.bson.impl;

 import java.io.IOException;

 import java.io.ObjectInputStream;

 import java.util.ArrayList;

 import java.util.Collections;

 import java.util.HashMap;

 import java.util.List;

 import java.util.Map;

 import com.allanbank.mongodb.bson.DocumentAssignable;

 import com.allanbank.mongodb.bson.Element;

 /**

  * A root level document that is truly immutable.

  * <p>

  * Documents normally returned from the document builders have the ability to be

  * modified by injecting an {@code _id} field into the document. This document

  * class does not have that ability.

  * </p>

  * <p>

  * Most users will not need to use this class except when creating static

  * documents within classes. The intended usage is then to use the builder when

  * constructing the immutable document: <blockquote>

  * 

  * <pre>

  * <code>

  * public static final Document QUERY;

  * 

  * ...

  * static {

  *    DocumentBuilder builder = BuilderFactory.start();

  * 

  *    builder.add(...);

  *    ...

  * 

  *    QUERY = new ImmutableDocument(builder);

  * }

  * </code>

  * </pre>

  * 

  * </blockquote>

  * 

  * @api.yes This interface is part of the driver's API. Public and protected

  *          members will be deprecated for at least 1 non-bugfix release

  *          (version numbers are <major>.<minor>.<bugfix>)

  *          before being removed or modified.

  * @copyright 2011-2014, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class ImmutableDocument extends AbstractDocument {

     /** Serialization version for the class. */

     private static final long serialVersionUID = -2875918328146027037L;

     /**

      * Constructed when a user tries to access the elements of the document by

      * name.

      */

     private volatile Map<String, Element> myElementMap;

     /** The elements of the document. */

     private final List<Element> myElements;

     /** The size of the document when encoded as bytes. */

     private transient long mySize;

     /**

      * Constructs a new {@link ImmutableDocument}.

      * 

      * @param document

      *            The elements for the BSON document.

      */

     public ImmutableDocument(final DocumentAssignable document) {

         final List<Element> elements = document.asDocument().getElements();

         myElements = Collections.unmodifiableList(new ArrayList<Element>(

                 elements));

         myElementMap = null;

         mySize = computeSize();

     }

     /**

      * Constructs a new {@link ImmutableDocument}.

      * 

      * @param document

      *            The elements for the BSON document.

      * @param size

      *            The size of the document when encoded in bytes. If not known

      *            then use the

      *            {@link ImmutableDocument#ImmutableDocument(DocumentAssignable)}

      *            constructor instead.

      */

     public ImmutableDocument(final DocumentAssignable document, final long size) {

         final List<Element> elements = document.asDocument().getElements();

         myElements = Collections.unmodifiableList(new ArrayList<Element>(

                 elements));

         myElementMap = null;

         mySize = size;

     }

     /**

      * Returns the elements in the document.

      * 

      * @return The elements in the document.

      */

     @Override

     public List<Element> getElements() {

         return myElements;

     }

     /**

      * Returns the size of the document when encoded as bytes.

      * 

      * @return The size of the document when encoded as bytes.

      */

     @Override

     public long size() {

         return mySize;

     }

     /**

      * Returns a map from the element names to the elements in the document.

      * Used for faster by-name access.

      * 

      * @return The element name to element mapping.

      */

     @Override

     protected Map<String, Element> getElementMap() {

         if (myElementMap == null) {

             final Map<String, Element> mapping = new HashMap<String, Element>(

                     myElements.size() << 1);

             for (final Element element : myElements) {

                 mapping.put(element.getName(), element);

             }

             // Swap the finished map into position.

             myElementMap = mapping;

         }

         return myElementMap;

     }

     /**

      * Computes and returns the length of the document in bytes.

      * 

      * @return The length of the document in bytes.

      */

     private long computeSize() {

         long result = 5; // int length (4) + terminal null byte (1).

         for (final Element element : myElements) {

             result += element.size();

         }

         return result;

     }

     /**

      * Sets the transient state of this document.

      * 

      * @param in

      *            The input stream.

      * @throws ClassNotFoundException

      *             On a failure loading a class in this classed reachable tree.

      * @throws IOException

      *             On a failure reading from the stream.

      */

     private void readObject(final ObjectInputStream in)

             throws ClassNotFoundException, IOException {

         in.defaultReadObject();

         mySize = computeSize();

     }

 }