/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xalan.templates;

import javax.xml.transform.TransformerException;
import org.apache.xalan.res.XSLMessages;
import org.apache.xalan.res.XSLTErrorResources;
import org.apache.xalan.transformer.TransformerImpl;
import org.apache.xpath.XPathContext;


/**
 * Implement an unknown element
 * @xsl.usage advanced
 */
public class ElemUnknown extends ElemLiteralResult
{

  /**
   * Get an int constant identifying the type of element.
   * @see org.apache.xalan.templates.Constants
   *
   *@return The token ID for this element
   */
  public int getXSLToken()
  {
    return Constants.ELEMNAME_UNDEFINED;
  }
  
  /**
   * Execute the fallbacks when an extension is not available.
   *
   * @param transformer non-null reference to the the current transform-time state.
   * @param sourceNode non-null reference to the <a href="http://www.w3.org/TR/xslt#dt-current-node">current source node</a>.
   * @param mode reference, which may be null, to the <a href="http://www.w3.org/TR/xslt#modes">current mode</a>.
   *
   * @throws TransformerException
   */
  private void executeFallbacks(
          TransformerImpl transformer)
            throws TransformerException
  {
    for (ElemTemplateElement child = m_firstChild; child != null;
             child = child.m_nextSibling)
    {
      if (child.getXSLToken() == Constants.ELEMNAME_FALLBACK)
      {
        try
        {
          transformer.pushElemTemplateElement(child);
          ((ElemFallback) child).executeFallback(transformer);
        }
        finally
        {
          transformer.popElemTemplateElement();
        }
      }
    }

  }
  
  /**
   * Return true if this extension element has a <xsl:fallback> child element.
   *
   * @return true if this extension element has a <xsl:fallback> child element.
   */
  private boolean hasFallbackChildren()
  {
    for (ElemTemplateElement child = m_firstChild; child != null;
             child = child.m_nextSibling)
    {
      if (child.getXSLToken() == Constants.ELEMNAME_FALLBACK)
        return true;
    }
    
    return false;
  }


  /**
   * Execute an unknown element.
   * Execute fallback if fallback child exists or do nothing
   *
   * @param transformer non-null reference to the the current transform-time state.
   * @param sourceNode non-null reference to the <a href="http://www.w3.org/TR/xslt#dt-current-node">current source node</a>.
   * @param mode reference, which may be null, to the <a href="http://www.w3.org/TR/xslt#modes">current mode</a>.
   *
   * @throws TransformerException
   */
  public void execute(TransformerImpl transformer)
            throws TransformerException
  {


	if (TransformerImpl.S_DEBUG)
		transformer.getTraceManager().fireTraceEvent(this);

	try {

		if (hasFallbackChildren()) {
			executeFallbacks(transformer);
		} else {
			// do nothing
		}
		
	} catch (TransformerException e) {
		transformer.getErrorListener().fatalError(e);
	}
	if (TransformerImpl.S_DEBUG)
		transformer.getTraceManager().fireTraceEndEvent(this);
  }

}