/*
    * 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);
             }
         }
     }
 
 }