/*

  * #%L

  * NullElement.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.element;

 import com.allanbank.mongodb.bson.Element;

 import com.allanbank.mongodb.bson.ElementType;

 import com.allanbank.mongodb.bson.Visitor;

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

 /**

  * A wrapper for a BSON null.

  * 

  * @api.yes This class 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 2011-2013, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class NullElement extends AbstractElement {

     /** The BSON type for a binary. */

     public static final ElementType TYPE = ElementType.NULL;

     /** Serialization version for the class. */

     private static final long serialVersionUID = -4974513577366947524L;

     /**

      * Computes and returns the number of bytes that are used to encode the

      * element.

      * 

      * @param name

      *            The name for the element.

      * @return The size of the element when encoded in bytes.

      */

     private static long computeSize(final String name) {

         long result = 2; // type (1) + name null byte (1).

         result += StringEncoder.utf8Size(name);

         return result;

     }

     /**

      * Constructs a new {@link NullElement}.

      * 

      * @param name

      *            The name for the BSON null.

      * @throws IllegalArgumentException

      *             If the {@code name} is <code>null</code>.

      */

     public NullElement(final String name) {

         this(name, computeSize(name));

     }

     /**

      * Constructs a new {@link NullElement}.

      * 

      * @param name

      *            The name for the BSON null.

      * @param size

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

      *            then use the {@link NullElement#NullElement(String)}

      *            constructor instead.

      * @throws IllegalArgumentException

      *             If the {@code name} is <code>null</code>.

      */

     public NullElement(final String name, final long size) {

         super(name, size);

     }

     /**

      * Accepts the visitor and calls the {@link Visitor#visitNull} method.

      * 

      * @see Element#accept(Visitor)

      */

     @Override

     public void accept(final Visitor visitor) {

         visitor.visitNull(getName());

     }

     /**

      * {@inheritDoc}

      */

     @Override

     public ElementType getType() {

         return TYPE;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Returns <code>null</code>.

      * </p>

      */

     @Override

     public Object getValueAsObject() {

         return null;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Returns the result of {@link String#valueOf(Object) String.valueOf(null)}

      * .

      * </p>

      */

     @Override

     public String getValueAsString() {

         return String.valueOf((Object) null);

     }

     /**

      * {@inheritDoc}

      * <p>

      * Returns a new {@link NullElement}.

      * </p>

      */

     @Override

     public NullElement withName(final String name) {

         if (getName().equals(name)) {

             return this;

         }

         return new NullElement(name);

     }

 }