/*
    * Copyright 2012-2013 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.properties.utils;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  
  import org.apache.commons.lang.StringUtils;
  import org.htmlcleaner.CleanerProperties;
  import org.htmlcleaner.DefaultTagProvider;
  import org.htmlcleaner.HtmlCleaner;
  import org.htmlcleaner.ITagInfoProvider;
  import org.htmlcleaner.JDomSerializer;
  import org.htmlcleaner.SimpleXmlSerializer;
  import org.htmlcleaner.TagNode;
  import org.jdom.Document;
  
  import de.smartics.util.lang.Arguments;
  
  /**
   * Utilities to deal with HTML.
   */
  public final class HtmlUtils
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    // --- members --------------------------------------------------------------
  
    /**
     * The encoding used write.
     */
    private final String outputEncoding;
  
    /**
     * The cleaner instance to use.
     */
    private final HtmlCleaner cleaner;
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     *
     * @param outputEncoding the encoding used write.
     */
    public HtmlUtils(final String outputEncoding)
    {
      Arguments.checkNotBlank("outputEncoding", outputEncoding);
  
      this.outputEncoding = outputEncoding;
  
      cleaner = new HtmlCleaner();
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    // --- get&set --------------------------------------------------------------
  
    // --- business -------------------------------------------------------------
  
    /**
     * Cleans up the HTML fragment.
     *
     * @param htmlFragment the dirty fragment.
     * @return the cleaned up fragment.
     */
    public String clean(final String htmlFragment)
    {
      if (StringUtils.isBlank(htmlFragment))
      {
        return htmlFragment;
      }
      final TagNode tagNode = cleaner.clean(htmlFragment);
      final TagNode body = tagNode.findElementByName("body", false);
  
      final ByteArrayOutputStream out = new ByteArrayOutputStream(1024);
      final CleanerProperties cleanerProps = createCleanerProperties();
      try
     {
       final SimpleXmlSerializer serializer =
           new SimpleXmlSerializer(cleanerProps);
       serializer.writeToStream(body, out, outputEncoding, true);
       final String content = out.toString(outputEncoding);
       return content;
     }
     catch (final IOException e)
     {
       throw new IllegalStateException(
           "Streaming error with in memory stream or encoding.", e);
     }
   }
 
   /**
    * Cleans up the HTML fragment.
    *
    * @param htmlFragment the dirty fragment.
    * @return the cleaned up fragment.
    */
   public Document cleanJDom(final String htmlFragment)
   {
     if (StringUtils.isBlank(htmlFragment))
     {
       return null;
     }
 
     final TagNode tagNode = cleaner.clean(htmlFragment);
     final TagNode body = tagNode.findElementByName("body", false);
     final CleanerProperties cleanerProps = createCleanerProperties();
     final Document document =
         new JDomSerializer(cleanerProps, true).createJDom(body);
     return document;
   }
 
   private static CleanerProperties createCleanerProperties()
   {
     final CleanerProperties properties = new CleanerProperties()
     {
 
       // CHECKSTYLE:OFF analogous to the implementation that gets fixed here.
       ITagInfoProvider tagInfoProvider = new DefaultTagProvider(); // NOPMD
 
       // CHECKSTYLE:ON
 
       @Override
       public ITagInfoProvider getTagInfoProvider()
       {
         return tagInfoProvider;
       }
     };
 
     properties.setOmitHtmlEnvelope(true);
     properties.setOmitDoctypeDeclaration(true);
     properties.setOmitXmlDeclaration(true);
     properties.setUseEmptyElementTags(true);
 
     return properties;
   }
 
   // --- object basics --------------------------------------------------------
 
 }