/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 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.xpath.functions;

import javax.xml.transform.TransformerException;

import org.apache.xalan.res.XSLMessages;
import org.apache.xalan.res.XSLTErrorResources;
import org.apache.xml.dtm.DTMSequence;
import org.apache.xpath.XPathContext;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.objects.XJavaObject;

/**
 * <meta name="usage" content="advanced"/>
 * Execute the data() function. Not supported before
 * XPath/XSLT 2.0.
 */
public class FuncData extends FunctionOneArg
{
  /**
   * Execute the function.  The function must return
   * a valid object.
   * @param xctxt The current execution context.
   * @return A valid XObject.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException
  {
    XObject src=m_arg0.execute(xctxt);
    
//    /* This should have been checked at stylesheet build,
//     * and hence ought to be superfluous.
//     * %REVIEW% %OPT%
//     * */
//    if("1.0".equals(xctxt.getXPathVersion()))
//    {
//    	xctxt.getErrorListener().error(
//    		new TransformerException(
//    		XSLMessages.createMessage(XSLTErrorResources.ER_NOT_SUPPORTED,
//    			new Object[]{"XSLT 2.0 data()"}), 
//    			xctxt.getSAXLocator())); 
//    		//"Illegal value for xml:space", locator));
//    	// If error listener returns...
//    	return src;
//    }
    
    if(src.getType()==src.CLASS_NODESET)
    {      
    	int sourceHandle=src.iter().item(0);
    	
	    if(sourceHandle==org.apache.xml.dtm.DTM.NULL)
    	return /*new XJavaObject*/(org.apache.xpath.objects.XSequence.EMPTY);
    	
    	org.apache.xml.dtm.DTM sourceDTM=xctxt.getDTM(sourceHandle);

		DTMSequence seq=sourceDTM.getTypedValue(sourceHandle);
		
		// %TODO% Other kinds of objects?
		return new org.apache.xpath.objects.XDTMSequence(seq);
    }
    
    // %TODO% %REVIEW% See issues 80, 81, 231, ....
    // There seem to be some conflicts here.
    //
    // "Consensus is to define data() on only singleton node and empty sequence"
    // "Open issue as to whether data() should be defined on node sequences."
    // "NB: Current definition of data() applied to a text node is the empty sequence."
    // "data() applied to simple value is identity function (no-op)"
    //
    // "xf:data(): decided that it should return the error object when applied to document, PI,
    // comment and namespace nodes." (What is "the error object"?)
    
    else return src; // %TODO% Awaiting typed non-nodes...
  }
  
}