/*
 * Copyright 1999-2007 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.xml.security.transforms.implementations;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Method;

import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.apache.xml.security.exceptions.XMLSecurityException;
import org.apache.xml.security.signature.XMLSignatureInput;
import org.apache.xml.security.transforms.Transform;
import org.apache.xml.security.transforms.TransformSpi;
import org.apache.xml.security.transforms.TransformationException;
import org.apache.xml.security.transforms.Transforms;
import org.apache.xml.security.utils.XMLUtils;
import org.w3c.dom.Element;

/**
 * Class TransformXSLT
 *
 * Implements the <CODE>http://www.w3.org/TR/1999/REC-xslt-19991116</CODE>
 * transform.
 *
 * @author Christian Geuer-Pollmann
 */
public class TransformXSLT extends TransformSpi {

   /** Field implementedTransformURI */
   public static final String implementedTransformURI =
      Transforms.TRANSFORM_XSLT;
   //J-
   static final String XSLTSpecNS              = "http://www.w3.org/1999/XSL/Transform";
   static final String defaultXSLTSpecNSprefix = "xslt";
   static final String XSLTSTYLESHEET          = "stylesheet";

   // check for secure processing feature
   private static Class xClass = null;
   static {
      try {
         xClass = Class.forName("javax.xml.XMLConstants");
      } catch (Exception e) {}
   }

   static org.apache.commons.logging.Log log =
      org.apache.commons.logging.LogFactory.getLog(
         TransformXSLT.class.getName());

   /**
    * Method engineGetURI
    *
    * @inheritDoc
    */
   protected String engineGetURI() {
      return implementedTransformURI;
   }

   /**
    * Method enginePerformTransform
    * 
    * @param input the input for this transform
    * @return the result of this Transform
    * @throws IOException
    * @throws TransformationException
    */
   protected XMLSignatureInput enginePerformTransform
	(XMLSignatureInput input, Transform _transformObject)
           throws IOException,
                  TransformationException {
   	return enginePerformTransform(input, null, _transformObject);
   }

    protected XMLSignatureInput enginePerformTransform(XMLSignatureInput input,OutputStream baos, Transform _transformObject)
    throws IOException,
           TransformationException {
      if (xClass == null) {
         Object exArgs[] = { "SECURE_PROCESSING_FEATURE not supported" };
         throw new TransformationException("generic.EmptyMessage", exArgs);
      }
      try {
         Element transformElement = _transformObject.getElement();        

         Element _xsltElement =
            XMLUtils.selectNode(transformElement.getFirstChild(),
                                                XSLTSpecNS,"stylesheet", 0);

         if (_xsltElement == null) {
            Object exArgs[] = { "xslt:stylesheet", "Transform" };

            throw new TransformationException("xml.WrongContent", exArgs);
         }

         TransformerFactory tFactory = TransformerFactory.newInstance();
         Class c = tFactory.getClass();
         Method m = c.getMethod("setFeature", new Class[] {String.class, boolean.class});
         // Process XSLT stylesheets in a secure manner
         m.invoke(tFactory, new Object[] {"http://javax.xml.XMLConstants/feature/secure-processing", Boolean.TRUE});

         /*
          * This transform requires an octet stream as input. If the actual
          * input is an XPath node-set, then the signature application should
          * attempt to convert it to octets (apply Canonical XML]) as described
          * in the Reference Processing Model (section 4.3.3.2).
          */
         Source xmlSource =
            new StreamSource(new ByteArrayInputStream(input.getBytes()));
         Source stylesheet;

         /*
          * This complicated transformation of the stylesheet itself is necessary
          * because of the need to get the pure style sheet. If we simply say
          * Source stylesheet = new DOMSource(this._xsltElement);
          * whereby this._xsltElement is not the rootElement of the Document,
          * this causes problems;
          * so we convert the stylesheet to byte[] and use this as input stream
          */
         {
            ByteArrayOutputStream os = new ByteArrayOutputStream();
            Transformer transformer = tFactory.newTransformer();
            DOMSource source = new DOMSource(_xsltElement);
            StreamResult result = new StreamResult(os);

            transformer.transform(source, result);

            stylesheet =
               new StreamSource(new ByteArrayInputStream(os.toByteArray()));
         }

         Transformer transformer = tFactory.newTransformer(stylesheet);

	 // Force Xalan to use \n as line separator on all OSes. This 
	 // avoids OS specific signature validation failures due to line
	 // separator differences in the transformed output. Unfortunately,
	 // this is not a standard JAXP property so will not work with non-Xalan
	 // implementations.
	 try {
	    transformer.setOutputProperty
	       ("{http://xml.apache.org/xalan}line-separator", "\n");
	 } catch (Exception e) {
	    log.warn("Unable to set Xalan line-separator property: " 
	       + e.getMessage());
	 }

         if (baos==null) {
            ByteArrayOutputStream baos1 = new ByteArrayOutputStream();
            StreamResult outputTarget = new StreamResult(baos1);
            transformer.transform(xmlSource, outputTarget);
            return new XMLSignatureInput(baos1.toByteArray());
         }
         StreamResult outputTarget = new StreamResult(baos);

         transformer.transform(xmlSource, outputTarget);         
         XMLSignatureInput output=new XMLSignatureInput((byte[])null);
         output.setOutputStream(baos);
         return output;
      } catch (XMLSecurityException ex) {
         Object exArgs[] = { ex.getMessage() };

         throw new TransformationException("generic.EmptyMessage", exArgs, ex);
      } catch (TransformerConfigurationException ex) {
         Object exArgs[] = { ex.getMessage() };

         throw new TransformationException("generic.EmptyMessage", exArgs, ex);
      } catch (TransformerException ex) {
         Object exArgs[] = { ex.getMessage() };

         throw new TransformationException("generic.EmptyMessage", exArgs, ex);
      } catch (NoSuchMethodException ex) {
         Object exArgs[] = { ex.getMessage() };

         throw new TransformationException("generic.EmptyMessage", exArgs, ex);
      } catch (IllegalAccessException ex) {
         Object exArgs[] = { ex.getMessage() };

         throw new TransformationException("generic.EmptyMessage", exArgs, ex);
      } catch (java.lang.reflect.InvocationTargetException ex) {
         Object exArgs[] = { ex.getMessage() };

         throw new TransformationException("generic.EmptyMessage", exArgs, ex);
      }
   }
}
