/**
    * Copyright 2005-2012 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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 org.kuali.rice.ken.util;
  
  import java.io.StringReader;
  import java.io.StringWriter;
  import java.util.HashMap;
  import java.util.Iterator;
  
  import javax.xml.transform.ErrorListener;
  import javax.xml.transform.Source;
  import javax.xml.transform.Transformer;
  import javax.xml.transform.TransformerException;
  import javax.xml.transform.TransformerFactory;
  import javax.xml.transform.stream.StreamResult;
  import javax.xml.transform.stream.StreamSource;
  
  import org.apache.log4j.Logger;
  
  /**
   * This class handles XSLT transformations.
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class ContentTransformer {
      private static final Logger LOG = Logger.getLogger(ContentTransformer.class);
  
      private static final class LoggingErrorListener implements ErrorListener {
          private final ErrorListener delegate;
          public LoggingErrorListener(ErrorListener delegate) {
              this.delegate = delegate;
          }
  
          public void error(TransformerException exception) throws TransformerException {
              LOG.error("Error transforming document", exception);
          }
  
          public void fatalError(TransformerException exception) throws TransformerException {
              if (delegate != null) {
                  delegate.fatalError(exception);
              } else {
                  throw exception;
              }
              
          }
  
          public void warning(TransformerException exception) throws TransformerException {
              LOG.warn("Error transforming document", exception);
          }
          
      };
  
      private Transformer transformer;
  
      /**
       * Constructs a ContentTransformer.java.
       * @param aStyleSheet
       * @throws Exception
       */
      public ContentTransformer(StreamSource aStyleSheet) throws Exception {
          // create transformer        
          TransformerFactory factory = TransformerFactory.newInstance();
          transformer = factory.newTransformer( aStyleSheet );
      }
  
      /**
       * Constructs a ContentTransformer.java.
       * @param aStyleSheet
       * @param parametermap
       * @throws Exception
       */
      public ContentTransformer(StreamSource aStyleSheet, HashMap parametermap) throws Exception {
         // create transformer
         TransformerFactory factory = TransformerFactory.newInstance();
         transformer = factory.newTransformer( aStyleSheet );
         Iterator iter = parametermap.keySet().iterator();
         while (iter.hasNext()) {
            Object o = iter.next();
            String param = o.toString();
            String value = (String) parametermap.get(param);
            transformer.setParameter(param, value);
         }
         transformer.setErrorListener(new LoggingErrorListener(transformer.getErrorListener()));
      }
  
      /**
       * This method performs the actual transformation.
      * @param xml
      * @return
      * @throws Exception
      */
     public String transform(String xml) throws Exception {
 
         // perform transformation
         Source xmlsource = new StreamSource(new StringReader(xml));
         StringWriter sout = new StringWriter();
          
         transformer.transform(xmlsource, new StreamResult(sout));
 
         // return resulting document
         return sout.toString();
     }
 }