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/*
 * NodeExtractor.java January 2010
 *
 * Copyright (C) 2010, Niall Gallagher 
 *
 * 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
 * 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.
 */

package org.simpleframework.xml.stream;

import static org.w3c.dom.Node.COMMENT_NODE;

import java.util.LinkedList;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
 * The NodeExtractor object is used to extract nodes 
 * from a provided DOM document. This is used so that the nodes of
 * a given document can be read with queue like semantics, such 
 * that the first node encountered is the first node taken from 
 * the queue. Queue semantics help transform DOM documents to an
 * event stream much like the StAX framework.
 *  
 * @author Niall Gallagher
 */
class NodeExtractor extends LinkedList {

   /**
    * Constructor for the NodeExtractor object. This
    * is used to instantiate an object that flattens a document
    * in to a queue so that the nodes can be used for streaming.
    * 
    * @param source this is the source document to be flattened
    */
   public NodeExtractor(Document source) {
      this.extract(source);
   }
   
   /**
    * This is used to extract the nodes of the document in such a
    * way that it can be navigated as a queue. In order to do this
    * each node encountered is pushed in to the queue so that
    * when finished the nodes can be dealt with as a stream.
    * 
    * @param source this is the source document to be flattened
    */
   private void extract(Document source) {
      Node node = source.getDocumentElement();
      
      if(node != null) {
         offer(node);
         extract(node);
      }
   }

   /**
    * This is used to extract the nodes of the element in such a
    * way that it can be navigated as a queue. In order to do this
    * each node encountered is pushed in to the queue so that
    * when finished the nodes can be dealt with as a stream.
    * 
    * @param source this is the source element to be flattened
    */
   private void extract(Node source) {
      NodeList list = source.getChildNodes();
      int length = list.getLength();
      
      for(int i = 0; i < length; i++) {
         Node node = list.item(i);
         short type = node.getNodeType();
         
         if(type != COMMENT_NODE) {
            offer(node);
            extract(node);
         }
      }
   }
}