/*
    * Copyright 2000-2004 The Apache Software Foundation.
    * 
    * 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 org.apache.jetspeed.util;
  
  //java stuff
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.io.PipedInputStream;
  import java.io.PipedOutputStream;
  import java.io.Reader;
  import java.io.StringWriter;
  import java.io.Writer;
  import java.util.Iterator;
  import java.util.Map;
  
  //Trax support
  import javax.xml.transform.TransformerFactory;
  import javax.xml.transform.Transformer;
  import javax.xml.transform.Templates;
  //import javax.xml.transform.stream.StreamSource;
  import javax.xml.transform.stream.StreamResult;
  import javax.xml.transform.dom.DOMSource;
  import javax.xml.transform.sax.SAXSource;
  import javax.xml.transform.sax.SAXTransformerFactory;
  import javax.xml.transform.sax.TemplatesHandler;
  import javax.xml.transform.sax.TransformerHandler;              
  
  //xpath objects
  import org.apache.xpath.objects.XString;
  
  //SAX Suport
  import org.xml.sax.XMLReader;
  import org.xml.sax.SAXException;
  import org.xml.sax.helpers.XMLReaderFactory;
  import org.xml.sax.InputSource;
  
  //DOM Support
  import org.w3c.dom.Document;
  
  //Jetspeed stuff
  import org.apache.jetspeed.cache.disk.JetspeedDiskCache;
  import org.apache.jetspeed.services.logging.JetspeedLogFactoryService;
  import org.apache.jetspeed.services.logging.JetspeedLogger;
  import org.apache.jetspeed.xml.JetspeedXMLEntityResolver;
  
  
  
  
  /***
   * Provides a very simple mechanism to transform a document using XSLT using 
   * one XML document and another XSL document.  This implementation uses the TRAX API.
   * It can be used with any TRAX transformer.   This can be used for very 
   * simple XML -> XSL processing to reduce the complexity and possibility of a 
   * runtime failure.
   *
   * @author <a href="mailto:burton@apache.org">Kevin A. Burton</a>
   * @author <a href="mailto:sgala@apache.org">Santiago Gala</a>
   * @version $Id: SimpleTransform.java,v 1.23 2004/02/23 03:23:42 jford Exp $
   */
  public class SimpleTransform
  {
      /***
       * Static initialization of the logger for this class
       */    
      private static final JetspeedLogger logger = JetspeedLogFactoryService.getLogger(SimpleTransform.class.getName());
      
      //FIXME: This code should go into the Turbine XSLTservice.
      //Also, it is a temporary hack, as it should be configurable,
      // and done later.
      static
      {
          try 
          {
              if( System.getProperty( "org.xml.sax.driver" ) == null )
              {
                  System.setProperty( "org.xml.sax.driver",
                                      "org.apache.xerces.parsers.SAXParser" );
              }
          }
          catch (Throwable t)
          {
              //be very cautious here. We are in class initialization.
              t.printStackTrace();
          }
     }
     
     /***
      * Given a a DOM and a URL to a stylesheet,
      * transform the original document.
      */
     public static String transform( Document doc,
                                     String stylesheet_url)
         throws SAXException
     {
         return transform( doc, stylesheet_url, null );
     }
 
     
     /***
      * Given a a DOM and a URL to a stylesheet,
      * transform the original document,
      * passing parameters to the stylesheet
      */
     public static String transform( Document doc,
                                     String stylesheet_url,
                                     Map params)
         throws SAXException
     {
 
         // Instantiate a TransformerFactory.
         TransformerFactory tFactory = TransformerFactory.newInstance();
         // Determine whether the TransformerFactory supports the use of SAXSource 
         // and SAXResult
         if (!tFactory.getFeature(SAXTransformerFactory.FEATURE) )
         {
             logger.error( "SimpleTransform: nobody told you that we need a SAX Transformer?" );
             throw new SAXException( "Invalid SAX Tranformer" );
         }
         try
         {
             // Cast the TransformerFactory.
             SAXTransformerFactory saxTFactory = ((SAXTransformerFactory) tFactory);
             // Create a ContentHandler to handle parsing of the stylesheet.
             TemplatesHandler templatesHandler = saxTFactory.newTemplatesHandler();
 
             // Create an XMLReader and set its ContentHandler.
             XMLReader reader = XMLReaderFactory.createXMLReader();
             reader.setContentHandler(templatesHandler);
             // Set it to solve Entities through Jetspeed URL Manager
             reader.setEntityResolver( new JetspeedXMLEntityResolver() );
     
             // Parse the stylesheet.                       
             final InputSource xstyle = new InputSource( JetspeedDiskCache.getInstance()
                                                         .getEntry( stylesheet_url ).getReader() );
             xstyle.setSystemId( stylesheet_url );
             reader.parse( xstyle );
 
             //Get the Templates object from the ContentHandler.
             Templates templates = templatesHandler.getTemplates();
             // Create a ContentHandler to handle parsing of the XML source.  
             TransformerHandler handler 
                 = saxTFactory.newTransformerHandler(templates);
         
             // Reset the XMLReader's ContentHandler.
             reader.setContentHandler(handler);  
 
             // Set the ContentHandler to also function as a LexicalHandler, which
             // includes "lexical" events (e.g., comments and CDATA).
             try
             { 
                 reader.setProperty("http://xml.org/sax/properties/lexical-handler", handler);
             } 
             catch( org.xml.sax.SAXNotRecognizedException e ) {}
 
             final Transformer processor = handler.getTransformer();
 
             if( params != null ) {
                 Iterator keys = params.keySet().iterator();
                 while( keys.hasNext() )
                 {
                     String name  = (String) keys.next();
                     String value = (String) params.get(name);
                     processor.setParameter(name, 
                                            value ); //FIXME: maybe we need to quote again...
                     // was processor.createXString( value)
                 }
             }
         
             StringWriter pw = new StringWriter();
         
             // Have the XSLTProcessor processor object transform "foo.xml" to
             // System.out, using the XSLT instructions found in "foo.xsl".
             processor.transform( new DOMSource( doc ),
                                  new StreamResult( pw ) );
                       
             try
             {
 
                 pw.flush();
                 pw.close();
             
             } 
             catch (IOException e)
             {
                 //should never really happen
                 logger.error("Exception",  e);
             }
             return pw.toString();
         } 
         catch (Exception e)
         {
             logger.error( "Invalid SAX Transformer: " , e );
             throw new SAXException( "problem in SAX transform: " + e.toString() );
         }    
     }
     
     /***
      * Given a URL to an XML file and a URL to a stylesheet, transform the 
      * original document.
      */
     public static String transform( String url,
                                     String stylesheet_url )
         throws SAXException
     {
 
         return transform( url, stylesheet_url, null );
     
     }
     
     /***
      * Given a URL to an XML file and a URL to a stylesheet, transform the 
      * original document.
      */
     public static String transform( String url,
                                     String stylesheet_url,
                                     Map params )
         throws SAXException
     {
 
         //bring these URLs local if they happen to be remote
 
         InputSource in;
         InputSource style;
         try
         {
             in = new InputSource( JetspeedDiskCache.getInstance().getEntry( url ).getReader() );
             style = new InputSource( JetspeedDiskCache.getInstance().getEntry( stylesheet_url ).getReader() );
         } 
         catch (IOException e)
         {
             logger.error("Exception",  e);
             //at this point we can just use the original url and stylesheet_url so this shouldn't be a problem
             in = new InputSource( url ); 
             style = new InputSource( stylesheet_url );
         }
         
         if ( logger.isInfoEnabled() )
         {
             logger.info( "SimpleTransform:  transforming url: " + 
                   url + 
                   " with stylesheet: " + 
                   stylesheet_url );
         }
 
         in.setSystemId( url );
         style.setSystemId( stylesheet_url );
 
         return transform( in,
                           style,
                           params );
     
     }
     
     /***
      * Used internally to handle doing XSLT transformations directly.
      */
     public static String transform( InputSource content, 
                                     InputSource stylesheet,
                                     Map params)
         throws SAXException
     {
 
         // Instantiate a TransformerFactory.
         TransformerFactory tFactory = TransformerFactory.newInstance();
         // Determine whether the TransformerFactory supports the use of SAXSource 
         // and SAXResult
         if (!tFactory.getFeature(SAXTransformerFactory.FEATURE) )
         {
             logger.error( "SimpleTransform: nobody told you that we need a SAX Transformer?" );
             throw new SAXException( "Invalid SAX Tranformer" );
         }
         try
         {
             // Cast the TransformerFactory.
             SAXTransformerFactory saxTFactory = ((SAXTransformerFactory) tFactory);
             // Create a ContentHandler to handle parsing of the stylesheet.
             TemplatesHandler templatesHandler = saxTFactory.newTemplatesHandler();
 
             // Create an XMLReader and set its ContentHandler.
             XMLReader reader = XMLReaderFactory.createXMLReader();
             reader.setContentHandler(templatesHandler);
     
             // Parse the stylesheet.                       
             reader.parse( stylesheet );
 
             //Get the Templates object from the ContentHandler.
             Templates templates = templatesHandler.getTemplates();
             // Create a ContentHandler to handle parsing of the XML source.  
             TransformerHandler handler 
                 = saxTFactory.newTransformerHandler(templates);
         
             // Reset the XMLReader's ContentHandler.
             reader.setContentHandler(handler);  
 
             // Set the ContentHandler to also function as a LexicalHandler, which
             // includes "lexical" events (e.g., comments and CDATA). 
             try
             {
                 reader.setProperty("http://xml.org/sax/properties/lexical-handler", handler);
             } 
             catch( org.xml.sax.SAXNotRecognizedException e ) {}
             
             final Transformer processor = handler.getTransformer();
 
         
             if( params != null )
             {
                 Iterator keys = params.keySet().iterator();
                 while( keys.hasNext() )
                 {
                     String name  = (String) keys.next();
                     String value = (String) params.get(name);
                     processor.setParameter(name, 
                                            new XString( value ) 
                          /*FIXME: was processor.createXString( value) */ );
                 }
             }
 
             StringWriter pw = new StringWriter();
         
             // Have the XSLTProcessor processor object transform "foo.xml" to
             // System.out, using the XSLT instructions found in "foo.xsl".
             processor.transform( new SAXSource( content ),
                                  new StreamResult( pw ) );
                       
             try
             {
                 pw.flush();
                 pw.close();
             } 
             catch (IOException e)
             {
                 //should never really happen
                 logger.error("Exception",  e);
             }
             return pw.toString();
         }
         catch (Exception e)
         {
             logger.error( "Invalid SAX Transformer: " , e);
             throw new SAXException( "problem in SAX transform: " + e.toString() );
         }    
     }
 
     /***
      * Perform a event based parsing of the given content_url, 
      * process it with the XSLT stylesheet stylesheet_url, using the params
      * parameters, and return a Reader that will do the transformation dynamically.
      *
      * @param content_url The url of the xml document
      * @param stylesheet_url The url of the stylesheet
      * @param params A Map containing stylesheet parameters
      * @return a Reader on the transformed document
      *
      */
     public static Reader SAXTransform( String content_url, 
                                        String stylesheet_url,
                                        Map params) throws IOException
     {
 
         // Instantiate a TransformerFactory.
         TransformerFactory tFactory = TransformerFactory.newInstance();
         // Determine whether the TransformerFactory supports the use of SAXSource 
         // and SAXResult
         if (!tFactory.getFeature(SAXTransformerFactory.FEATURE) )
         {
             logger.error( "SimpleTransform: nobody told you that we need a SAX Transformer?" );
             throw new IOException( "Invalid SAX Tranformer" );
         }
         try
         {
             // Cast the TransformerFactory.
             SAXTransformerFactory saxTFactory = ((SAXTransformerFactory) tFactory);
             // Create a ContentHandler to handle parsing of the stylesheet.
             TemplatesHandler templatesHandler = saxTFactory.newTemplatesHandler();
 
             // Create an XMLReader and set its ContentHandler.
             XMLReader reader = XMLReaderFactory.createXMLReader();
             reader.setContentHandler(templatesHandler);
             // Set it to solve Entities through Jetspeed URL Manager
             reader.setEntityResolver( new JetspeedXMLEntityResolver() );
 
             // Parse the stylesheet.                       
             InputSource style = new InputSource( JetspeedDiskCache.getInstance()
                                                  .getEntry( stylesheet_url ).getReader() );
             style.setSystemId( stylesheet_url );
             final InputSource xstyle = style;
 
             reader.parse( xstyle );
 
             //Get the Templates object from the ContentHandler.
             Templates templates = templatesHandler.getTemplates();
             // Create a ContentHandler to handle parsing of the XML source.  
             TransformerHandler handler 
                 = saxTFactory.newTransformerHandler(templates);
         
             // Reset the XMLReader's ContentHandler.
             reader.setContentHandler(handler);  
 
             // Set the ContentHandler to also function as a LexicalHandler, which
             // includes "lexical" events (e.g., comments and CDATA). 
             try
             {
                 reader.setProperty("http://xml.org/sax/properties/lexical-handler", handler);
             }
             catch( org.xml.sax.SAXNotRecognizedException e ) {}
 
             final Transformer processor = handler.getTransformer();
 
             //Set the parameters (if any)
             if( params != null )
             {
                 Iterator keys = params.keySet().iterator();
                 while( keys.hasNext() )
                 {
                     String name  = (String) keys.next();
                     String value = (String) params.get(name);
                     //FIXME: maybe we need to quote again...
                     // was processor.createXString( value)
                     processor.setParameter(name, 
                                            new XString( value ) );
                 }
             }
 
             PipedInputStream pis = new PipedInputStream();
             PipedOutputStream pos = new PipedOutputStream( pis );
             try
             {
 
                 final Writer pw = new OutputStreamWriter( pos, "utf-8" );
                 InputSource is = new InputSource( JetspeedDiskCache.getInstance()
                                                   .getEntry( content_url ).getReader() );
                 is.setSystemId( content_url );
 
                 final SAXSource xinput = new SAXSource( is );
                 //Perform the transformation on a new thread, using
                 // PipedStreams 
                 Thread t = new Thread( new Runnable()
                     {
                         public void run()
                         {
                             // Have the processor object transform 
                             // "foo.xml" to
                             // System.out, using the XSLT instructions 
                             //found in "foo.xsl".
                             logger.debug("Starting SAX thread...");
                             try 
                             {
                                 processor.transform( xinput,
                                                      new StreamResult( pw ) );
                                 pw.close();
                                 logger.debug("...ending SAX thread.");
                             } 
                             catch( Exception se)
                             {
                                 logger.debug("Error in SAXTransform" + se.toString(), se );
                             }
                         }
                     } );
                 t.start();
             } 
             catch (java.io.UnsupportedEncodingException uee)
             {
                 logger.error("Need utf-8 encoding to SAXTransform", uee);
             }
             return new InputStreamReader ( pis, "utf-8" );
         } 
         catch (Exception e)
         {
             logger.error( "Invalid SAX Transformer:" , e);
             throw new IOException( "problem in SAX transform: " + e.toString() );
         }    
     }
 
 }