/*
 * 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.
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 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
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 * 5. Products derived from this software may not be called "Apache",
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 *
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 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * 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 org.apache.xml.dtm.DTM;
import org.apache.xml.dtm.DTMIterator;
import org.apache.xpath.XPathContext;
import org.apache.xpath.axes.SubContextList;
import org.apache.xpath.compiler.Compiler;
import org.apache.xpath.objects.XNumber;
import org.apache.xpath.objects.XObject;

/**
 * Execute the Position() function.
 * @xsl.usage advanced
 */
public class FuncPosition extends Function
{
  private boolean m_isTopLevel;
  
  /**
   * Figure out if we're executing a toplevel expression.
   * If so, we can't be inside of a predicate. 
   */
  public void postCompileStep(Compiler compiler)
  {
    m_isTopLevel = compiler.getLocationPathDepth() == -1;
  }

  /**
   * Get the position in the current context node list.
   *
   * @param xctxt Runtime XPath context.
   *
   * @return The current position of the itteration in the context node list, 
   *         or -1 if there is no active context node list.
   */
  public int getPositionInContextNodeList(XPathContext xctxt)
  {

    // System.out.println("FuncPosition- entry");
    // If we're in a predicate, then this will return non-null.
    SubContextList iter = m_isTopLevel ? null : xctxt.getSubContextList();

    if (null != iter)
    {
      int prox = iter.getProximityPosition(xctxt);
 
      // System.out.println("FuncPosition- prox: "+prox);
      return prox;
    }

    DTMIterator cnl = xctxt.getContextNodeList();

    if (null != cnl)
    {
      int n = cnl.getCurrentNode();
      if(n == DTM.NULL)
      {
        if(cnl.getCurrentPos() == 0)
          return 0;
          
        // Then I think we're in a sort.  See sort21.xsl. So the iterator has 
        // already been spent, and is not on the node we're processing. 
        // It's highly possible that this is an issue for other context-list 
        // functions.  Shouldn't be a problem for last(), and it shouldn't be 
        // a problem for current().
        try 
        { 
          cnl = cnl.cloneWithReset(); 
        }
        catch(CloneNotSupportedException cnse)
        {
          throw new org.apache.xml.utils.WrappedRuntimeException(cnse);
        }
        int currentNode = xctxt.getContextNode();
        // System.out.println("currentNode: "+currentNode);
        while(DTM.NULL != (n = cnl.nextNode()))
        {
          if(n == currentNode)
            break;
        }
      }
      // System.out.println("n: "+n);
      // System.out.println("FuncPosition- cnl.getCurrentPos(): "+cnl.getCurrentPos());
      return cnl.getCurrentPos();
    }

    // System.out.println("FuncPosition - out of guesses: -1");
    return -1;
  }

  /**
   * 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
  {
    double pos = (double) getPositionInContextNodeList(xctxt);
    
    return new XNumber(pos);
  }
  
  /**
   * No arguments to process, so this does nothing.
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize)
  {
    // no-op
  }
}