/*
    * Copyright 2011-2013 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.tagcloud.export;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.List;
  
  import javax.xml.parsers.DocumentBuilder;
  import javax.xml.parsers.DocumentBuilderFactory;
  import javax.xml.parsers.ParserConfigurationException;
  import javax.xml.transform.OutputKeys;
  import javax.xml.transform.Transformer;
  import javax.xml.transform.TransformerException;
  import javax.xml.transform.TransformerFactory;
  import javax.xml.transform.dom.DOMSource;
  import javax.xml.transform.stream.StreamResult;
  
  import org.w3c.dom.DOMException;
  import org.w3c.dom.Document;
  import org.w3c.dom.Element;
  
  import de.smartics.tagcloud.Tag;
  import de.smartics.tagcloud.TagCloud;
  
  /**
   * Exports the tag cloud to an XML file.
   *
   * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
   * @version $Revision:591 $
   */
  public class XmlTagCloudExport
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    /**
     * The URI of the XML schema instance.
     * <p>
     * The value of this constant is {@value}.
     * </p>
     */
    private static final String XML_SCHEMA_INSTANCE =
        "http://www.w3.org/2001/XMLSchema-instance";
  
    /**
     * The URI of the test documentation doctype.
     * <p>
     * The value of this constant is {@value}.
     * </p>
     */
    private static final String CODE_URI =
        "http://www.smartics.de/project/references/domain/tagcloud";
  
    // --- members --------------------------------------------------------------
  
    /**
     * The builder for XML documents.
     */
    private final DocumentBuilder builder; // NOPMD
  
    /**
     * The flag determines whether or not the XML file should be pretty-printed (
     * <code>true</code>) or not (<code>false</code>).
     */
    private final boolean prettyPrint;
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     */
    public XmlTagCloudExport(final boolean prettyPrint)
      throws ParserConfigurationException
    {
      final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
      this.builder = factory.newDocumentBuilder();
      this.prettyPrint = prettyPrint;
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
 
   // --- init -----------------------------------------------------------------
 
   // --- get&set --------------------------------------------------------------
 
   // --- business -------------------------------------------------------------
 
   public void export(final TagCloud tagCloud, final OutputStream output)
     throws IOException
   {
     final Document document = createDocument(tagCloud);
     serialize(document, output);
   }
 
   protected Document createDocument(final TagCloud tagCloud)
   {
     final Document document = builder.newDocument();
     final Element rootElement = createDocRoot(document);
 
     final List<Tag> tags = tagCloud.getTags();
     for (final Tag tag : tags)
     {
       final Element tagElement = document.createElement("tag");
       tagElement.setAttribute("name", tag.getName());
       tagElement.setAttribute("score", String.valueOf(tag.getScore()));
       tagElement.setAttribute("weight", String.valueOf(tag.getWeight()));
       rootElement.appendChild(tagElement);
     }
     return document;
   }
 
   private Element createDocRoot(final Document document) throws DOMException
   {
     final Element docRoot = document.createElement("tagcloud");
     docRoot.setAttribute("xmlns:xsi", XML_SCHEMA_INSTANCE);
     docRoot.setAttribute("xmlns", CODE_URI);
     docRoot.setAttribute("xsi:schemaLocation", CODE_URI + ' ' + CODE_URI);
     document.appendChild(docRoot);
     return docRoot;
   }
 
   /**
    * Writes the DOM document to the given stream.
    *
    * @param document the document to write.
    * @param out the stream to write to.
    * @throws IOException on any problem writing to the stream.
    */
   private void serialize(final Document document, final OutputStream out)
     throws IOException
   {
     try
     {
       final TransformerFactory factory = TransformerFactory.newInstance();
       final Transformer serializer = factory.newTransformer();
       if (prettyPrint)
       {
         serializer.setOutputProperty(OutputKeys.INDENT, "yes");
         serializer.setOutputProperty(
             "{http://xml.apache.org/xslt}indent-amount", "2");
       }
 
       serializer.transform(new DOMSource(document), new StreamResult(out));
     }
     catch (final TransformerException e)
     {
       throw new IOException("Cannot write XML document.", e);
     }
   }
   // --- object basics --------------------------------------------------------
 
 }