/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.common.content.transformer;
  
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.Iterator;
  import java.util.List;
  
  import javax.xml.transform.sax.TransformerHandler;
  
  import org.jdom2.Content;
  import org.jdom2.DefaultJDOMFactory;
  import org.jdom2.Document;
  import org.jdom2.JDOMFactory;
  import org.jdom2.Text;
  import org.jdom2.transform.JDOMResult;
  import org.mycore.common.MCRCache;
  import org.mycore.common.MCRConstants;
  import org.mycore.common.config.MCRConfigurationException;
  import org.mycore.common.content.MCRContent;
  import org.mycore.common.content.MCRJDOMContent;
  import org.xml.sax.SAXException;
  import org.xml.sax.XMLReader;
  
  /**
   * Transforms XML content using a static XSL stylesheet.
   * The stylesheet is configured via
   * 
   * MCR.ContentTransformer.{ID}.Stylesheet
   * 
   * Resulting MCRContent holds XML.
   * Use {@link MCRXSLTransformer} if you want to produce non XML output.
   * @author Thomas Scheffler (yagee)
   *
   */
  public class MCRXSL2XMLTransformer extends MCRXSLTransformer {
  
      private static MCRCache<String, MCRXSL2XMLTransformer> INSTANCE_CACHE = new MCRCache<>(100,
          "MCRXSLTransformer instance cache");
  
      public MCRXSL2XMLTransformer() {
          super();
      }
  
      public MCRXSL2XMLTransformer(String... stylesheets) {
          super(stylesheets);
      }
  
      public static MCRXSL2XMLTransformer getInstance(String... stylesheets) {
          String key = stylesheets.length == 1 ? stylesheets[0] : Arrays.toString(stylesheets);
          MCRXSL2XMLTransformer instance = INSTANCE_CACHE.get(key);
          if (instance == null) {
              instance = new MCRXSL2XMLTransformer(stylesheets);
              INSTANCE_CACHE.put(key, instance);
          }
          return instance;
      }
  
      @Override
      protected MCRContent getTransformedContent(MCRContent source, XMLReader reader,
          TransformerHandler transformerHandler) throws IOException, SAXException {
          JDOMResult result = new JDOMResult();
          transformerHandler.setResult(result);
          // Parse the source XML, and send the parse events to the
          // TransformerHandler.
          reader.parse(source.getInputSource());
          Document resultDoc = getDocument(result);
          if (resultDoc == null) {
              throw new MCRConfigurationException("Stylesheets " + Arrays.asList(templateSources)
                  + " does not return any content for " + source.getSystemId());
          }
          return new MCRJDOMContent(resultDoc);
      }
  
      private Document getDocument(JDOMResult result) {
          Document resultDoc = result.getDocument();
          if (resultDoc == null) {
              //Sometimes a transformation produces whitespace strings
              //JDOM would produce a empty document if it detects those
              //So we remove them, if they exists.
              List<Content> transformResult = result.getResult();
              int origSize = transformResult.size();
             Iterator<Content> iterator = transformResult.iterator();
             while (iterator.hasNext()) {
                 Content content = iterator.next();
                 if (content instanceof Text) {
                     String trimmedText = ((Text) content).getTextTrim();
                     if (trimmedText.length() == 0) {
                         iterator.remove();
                     }
                 }
             }
             if (transformResult.size() < origSize) {
                 JDOMFactory f = result.getFactory();
                 if (f == null) {
                     f = new DefaultJDOMFactory();
                 }
                 resultDoc = f.document(null);
                 resultDoc.setContent(transformResult);
             }
         }
         return resultDoc;
     }
 
     @Override
     protected String getDefaultExtension() {
         return "xml";
     }
 
     @Override
     public String getEncoding() {
         return MCRConstants.DEFAULT_ENCODING;
     }
 
 }