/*

  * Copyright 2007 - 2007 JEuclid, http://jeuclid.sf.net

  *

  * 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.

  */

 /* $Id: Processor.java,v 5a7becda9147 2009/10/23 10:57:54 max $ */

 package net.sourceforge.jeuclid.converter;

 import java.io.IOException;

 import javax.xml.transform.Result;

 import javax.xml.transform.Source;

 import javax.xml.transform.Transformer;

 import javax.xml.transform.TransformerException;

 import javax.xml.transform.TransformerFactory;

 import javax.xml.transform.dom.DOMResult;

 import javax.xml.transform.dom.DOMSource;

 import net.sourceforge.jeuclid.LayoutContext;

 import net.sourceforge.jeuclid.context.LayoutContextImpl;

 import net.sourceforge.jeuclid.converter.ConverterPlugin.DocumentWithDimension;

 import net.sourceforge.jeuclid.elements.AbstractJEuclidElement;

 import net.sourceforge.jeuclid.elements.generic.MathImpl;

 import net.sourceforge.jeuclid.parser.Parser;

 import org.apache.commons.logging.Log;

 import org.apache.commons.logging.LogFactory;

 import org.w3c.dom.Element;

 import org.w3c.dom.Node;

 import org.w3c.dom.NodeList;

 import org.xml.sax.SAXException;

 /**

  * Contains the actual processing routines.

  * <p>

  * To use this class obtain an instance of the Processor singleton instance.

  * Then use the {@link #process(Source, Result)} function to process your

  * Document.

  * <p>

  * This will replace all occurrences of MathML within fo:instream tags by the

  * equivalent SVG code. It will also add a baseline-shift attribute so that the

  * formula is in line with the rest of the text.

  * 

  * @version $Revision: 5a7becda9147 $

  */

 public final class Processor {

     private static final class SingletonHolder {

         private static final Processor INSTANCE = new Processor();

         private SingletonHolder() {

         }

     }

     /**

      * Logger for this class

      */

     private static final Log LOGGER = LogFactory.getLog(Processor.class);

     // private static final String NAMESPACE_HTML =

     // "http://www.w3.org/1999/xhtml";

     private final Transformer transformer;

     /**

      * Default constructor.

      */

     protected Processor() {

         Transformer t;

         try {

             t = TransformerFactory.newInstance().newTransformer();

         } catch (final TransformerException e) {

             t = null;

             Processor.LOGGER.warn(e.getMessage());

             assert false;

         }

         this.transformer = t;

     }

     /**

      * Retrieve the processor singleton object.

      * 

      * @return the Processor.

      */

     public static Processor getInstance() {

         return Processor.SingletonHolder.INSTANCE;

     }

     /**

      * use {@link #getInstance()} instead.

      * 

      * @return see {@link #getInstance()}

      * @throws TransformerException

      *             see {@link #getInstance()}

      * @deprecated use {@link #getInstance()} instead.

      */

     @Deprecated

     public static Processor getProcessor() throws TransformerException {

         return Processor.getInstance();

     }

     /**

      * Pre-process a .fo file.

      * 

      * @param inputSource

      *            Input File

      * @param result

      *            Output File

      * @param context

      *            LayoutContext.

      * @throws TransformerException

      *             an error occurred during the processing.

      */

     public void process(final Source inputSource, final Result result,

             final LayoutContext context) throws TransformerException {

         Processor.LOGGER.info("Processing " + inputSource.getSystemId()

                 + " to " + result.getSystemId());

         try {

             final Node doc = Parser.getInstance().parse(inputSource);

             this.processSubtree(doc, context);

             final DOMSource source = new DOMSource(doc);

             this.transformer.transform(source, result);

         } catch (final IOException e) {

             throw new TransformerException("IOException", e);

         } catch (final SAXException e) {

             throw new TransformerException("SAXException", e);

         }

     }

     /**

      * Pre-process a .fo file.

      * 

      * @param inputSource

      *            Input File

      * @param result

      *            Output File

      * @throws TransformerException

      *             an error occurred during the processing.

      */

     public void process(final Source inputSource, final Result result)

             throws TransformerException {

         this.process(inputSource, result, LayoutContextImpl

                 .getDefaultLayoutContext());

     }

     private void processSubtree(final Node node, final LayoutContext context) {

         if (AbstractJEuclidElement.URI.equals(node.getNamespaceURI())

                 && MathImpl.ELEMENT.equals(node.getLocalName())) {

             final DocumentWithDimension svgdocdim = Converter

                     .getInstance()

                     .convert(

                             node,

                             net.sourceforge.jeuclid.converter.Converter.TYPE_SVG,

                             context);

             final float baselinePercent = -(svgdocdim.getBaseline() / (float) svgdocdim

                     .getDimension().getHeight()) * 100f;

             final Node parent = node.getParentNode();

             if ("http://www.w3.org/1999/XSL/Format".equals(parent

                     .getNamespaceURI())

                     && "instream-foreign-object".equals(parent.getLocalName())) {

                 final Element pElement = (Element) parent;

                 pElement

                         .setAttribute("alignment-adjust", baselinePercent + "%");

             }

             this.safeReplaceChild(parent, node, svgdocdim.getDocument()

                     .getFirstChild());

         } else {

             this.processChildren(node, context);

             // TODO: This is an IE-Fix, but does not work yet.

             // final Node parent = node.getParentNode();

             // if ((parent != null)

             // && (Processor.NAMESPACE_HTML.equals(parent

             // .getNamespaceURI()))

             // && ("html".equals(parent.getLocalName()))

             // && ("head".equals(node.getLocalName()))) {

             // ((Element) parent).setAttribute("xmlns:svg",

             // "http://www.w3.org/2000/svg");

             // final Document ownerDoc = node.getOwnerDocument();

             // final Element objectElement = ownerDoc

             // .createElement("object");

             // objectElement.setAttribute("id", "AdobeSVG");

             // objectElement.setAttribute("classid",

             // "clsid:78156a80-c6a1-4bbf-8e6a-3cd390eeb4e2");

             // node.appendChild(objectElement);

             // final ProcessingInstruction pi = ownerDoc

             // .createProcessingInstruction("import",

             // "namespace=\"svg\" implementation=\"#AdobeSVG\"");

             // node.appendChild(pi);

             // }

         }

     }

     private void safeReplaceChild(final Node parent, final Node oldChild,

             final Node newChild) {

         try {

             final DOMSource source = new DOMSource(newChild);

             final DOMResult result = new DOMResult(parent);

             this.transformer.transform(source, result);

         } catch (final TransformerException e) {

             Processor.LOGGER.warn("TranformerException: " + e.getMessage());

         }

         parent.removeChild(oldChild);

     }

     private void processChildren(final Node node, final LayoutContext context) {

         final NodeList childList = node.getChildNodes();

         if (childList != null) {

             for (int i = 0; i < childList.getLength(); i++) {

                 final Node child = childList.item(i);

                 this.processSubtree(child, context);

             }

         }

     }

 }