/*
    * Copyright 2007-2013 smartics, Kronseder & Reiner GmbH
    *
    * 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.
   */
  package de.smartics.exceptions.report.utils;
  
  import java.io.StringReader;
  import java.util.Iterator;
  
  import javax.xml.stream.XMLEventReader;
  import javax.xml.stream.XMLInputFactory;
  import javax.xml.stream.XMLStreamException;
  import javax.xml.stream.XMLStreamWriter;
  import javax.xml.stream.events.Attribute;
  import javax.xml.stream.events.Characters;
  import javax.xml.stream.events.StartElement;
  import javax.xml.stream.events.XMLEvent;
  
  /**
   * Copies XML information read from one source to another.
   */
  public class CopyReader
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    /**
     * The generic identifier (GI) of the artificial element that is added if the
     * fragment is not enclosed in an element.
     * <p>
     * The value of this constant is {@value}.
     */
    private static final String ARTIFICIAL_GI = "root";
  
    /**
     * The artificial start tag with the {@link #ARTIFICIAL_GI}.
     * <p>
     * The value of this constant is {@value}.
     */
    private static final String ARTIFICIAL_START_TAG = '<' + ARTIFICIAL_GI + '>';
  
    /**
     * The artificial end tag with the {@link #ARTIFICIAL_GI}.
     * <p>
     * The value of this constant is {@value}.
     */
    private static final String ARTIFICIAL_END_TAG = "</" + ARTIFICIAL_GI + '>';
  
    // --- members --------------------------------------------------------------
  
    /**
     * The writer to write to. The caller is responsible to release the resource.
     */
    private final XMLStreamWriter xmlWriter;
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     *
     * @param xmlWriter the writer to write to.
     */
    public CopyReader(final XMLStreamWriter xmlWriter)
    {
      this.xmlWriter = xmlWriter;
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    // --- get&set --------------------------------------------------------------
  
    // --- business -------------------------------------------------------------
  
    /**
     * Copies the XML fragment to the writer.
     *
     * @param xmlFragment the XML fragment to read and write to the writer.
     * @throws XMLStreamException on any problem reading from the fragment.
     */
    public void copy(final String xmlFragment) throws XMLStreamException
    {
     final XMLInputFactory factory = XMLInputFactory.newInstance();
     final boolean isFragment = isFragment(xmlFragment);
     final XMLEventReader eventReader;
     if (isFragment)
     {
       eventReader = factory.createXMLEventReader(new StringReader(
           ARTIFICIAL_START_TAG + xmlFragment + ARTIFICIAL_END_TAG));
       boolean run = true;
       while (run && eventReader.hasNext())
       {
         final XMLEvent event = eventReader.nextEvent();
         if (event.getEventType() == XMLEvent.START_ELEMENT)
         {
           run = false;
         }
       }
     }
     else
     {
       eventReader = factory.createXMLEventReader(new StringReader(xmlFragment));
     }
     parse(eventReader);
   }
 
   /**
    * Checks if the given XML fragment is not enclosed within an element.
    *
    * @param xmlFragment the XML fragment to check.
    * @return <code>true</code> if the fragment is not enclosed in an element,
    *         <code>false</code> otherwise.
    */
   private static boolean isFragment(final String xmlFragment)
   {
     return xmlFragment.charAt(0) != '<';
   }
 
   /**
    * Parses the events from the given event reader.
    *
    * @param eventReader the event reader to read the events from.
    * @throws XMLStreamException on any problem reading the events.
    */
   private void parse(final XMLEventReader eventReader)
       throws XMLStreamException
   {
     int level = 0; // NOPMD
     while (eventReader.hasNext())
     {
       final XMLEvent event = eventReader.nextEvent();
       switch (event.getEventType())
       {
         case XMLEvent.START_ELEMENT:
           level++; // NOPMD
           handleStartElement(event);
           break;
         case XMLEvent.END_ELEMENT:
           level--;
           if (level >= 0)
           {
             xmlWriter.writeEndElement();
           }
           break;
         case XMLEvent.CHARACTERS:
           final Characters chars = event.asCharacters();
           xmlWriter.writeCharacters(chars.getData());
         default:
           // Just skip...
           break;
       }
     }
   }
 
   /**
    * Handles the start element with all of its attributes.
    *
    * @param event the event required to be a {@link StartElement}.
    * @throws XMLStreamException on any parsing problem.
    */
   @SuppressWarnings("unchecked")
   private void handleStartElement(final XMLEvent event)
       throws XMLStreamException
   {
     final StartElement element = event.asStartElement();
     final String gi = element.getName().toString();
     xmlWriter.writeStartElement(gi);
     for (final Iterator<Attribute> i = element.getAttributes(); i.hasNext();)
     {
       final Attribute attribute = i.next();
       xmlWriter.writeAttribute(attribute.getName().toString(), attribute
           .getValue());
     }
   }
 
   // --- object basics --------------------------------------------------------
 
 }