/**
    *    Copyright 2011 meltmedia
    *
    *    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.xchain.framework.sax.util;
  
  import org.xchain.framework.sax.HandlerWrapper;
  import org.xml.sax.ErrorHandler;
  import org.xml.sax.Attributes;
  import org.xml.sax.helpers.AttributesImpl;
  import org.xml.sax.SAXException;
  
  /**
   * This class wraps an apache serializer for html.  It will remap the html namespace (http://www.w3c.org/1999/xhtml) into the
   * default namespace and then pass the elements along.  It also caches namespace mapping to prevent extra namespaces from being passed to the document.
   *
   * @author Christian Trimble
   */
  public class XHtmlHandler
    extends HandlerWrapper
  {
    public static String HTML_NAMESPACE = "http://www.w3.org/1999/xhtml";
  
    protected NamespaceContext inputNamespaceContext = new NamespaceContext();
  
    public void startElement( String namespaceUri, String localName, String qName, Attributes attributes )
      throws SAXException
    {
      if( HTML_NAMESPACE.equals(namespaceUri) ) {
        super.startElement("", localName, localName, filterAttributes(attributes));
      }
      else {
        super.startElement(namespaceUri, localName, qName, attributes);
      }
    }
  
    public void endElement( String namespaceUri, String localName, String qName )
      throws SAXException
    {
      if( HTML_NAMESPACE.equals(namespaceUri) ) {
        super.endElement("", localName, localName);
      }
      else {
        super.endElement(namespaceUri, localName, qName);
      }
    }
  
    public void startPrefixMapping( String prefix, String namespaceUri )
      throws SAXException
    {
      inputNamespaceContext.startPrefixMapping(prefix, namespaceUri);
  
      // only pass the mapping if it is not the html namespace.
      if( HTML_NAMESPACE.equals(namespaceUri) ) {
        // translate this into the default mapping.
        super.startPrefixMapping("", "");
      }
      else if( inputNamespaceContext.isPrefixMappingNeeded(prefix) ) {
        // only pass mappings that are needed.
        super.startPrefixMapping(prefix, namespaceUri);
      }
      
    }
  
    public void endPrefixMapping( String prefix )
      throws SAXException
    {
      String namespaceUri = inputNamespaceContext.lookupUri( prefix );
  
      if( HTML_NAMESPACE.equals(namespaceUri) ) {
        super.endPrefixMapping("");
      }
      else if( inputNamespaceContext.isPrefixMappingNeeded(prefix) ) {
        super.endPrefixMapping(prefix);
      }
  
      inputNamespaceContext.endPrefixMapping(prefix);
    }
  
    public Attributes filterAttributes( Attributes attributes )
    {
      if( attributes.getLength() == 0 ) {
        return attributes;
      }
  
      // if any of the attributes is in the html namespace, then filter them into the default namespace.
      AttributesImpl filteredAttributes = new AttributesImpl();
      for( int i = 0; i < attributes.getLength(); i++ ) {
       if( HTML_NAMESPACE.equals(attributes.getURI(i)) ) {
         if( attributes.getIndex(attributes.getLocalName(i)) == -1 ) {
           filteredAttributes.addAttribute("", attributes.getLocalName(i), attributes.getLocalName(i), attributes.getType(i), attributes.getValue(i));
         }
       }
       else {
         filteredAttributes.addAttribute(attributes.getURI(i), attributes.getLocalName(i), attributes.getQName(i), attributes.getType(i), attributes.getValue(i));
       }
     }
 
     return filteredAttributes;
   }
 }