/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.apache.xpath.functions;

import org.apache.xalan.res.XSLMessages;
import org.apache.xalan.res.XSLTErrorResources;
import org.apache.xalan.templates.ElemTemplate;
import org.apache.xml.dtm.DTM;
import org.apache.xpath.ExpressionNode;
import org.apache.xpath.XPathContext;
import org.apache.xpath.axes.LocPathIterator;
import org.apache.xpath.axes.PredicatedNodeTest;
import org.apache.xpath.axes.SubContextList;
import org.apache.xpath.objects.XMLNodeCursorImpl;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.patterns.StepPattern;

/**
 * Implementation of XSLT 3.0 fn:current function.
 * 
 * @xsl.usage advanced
 */
public class FuncCurrent extends Function
{
    static final long serialVersionUID = 5715316804877715008L;
    
    /**
     * Default constructor.
     */
    public FuncCurrent() {
    	m_defined_arity = new Short[] { 0 };	
    }

  /**
   * Evaluate 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
  {
   
	  SubContextList subContextList = xctxt.getCurrentNodeList();
	  int currentNode = DTM.NULL;	  

	  if (null != subContextList) {
		  if (subContextList instanceof PredicatedNodeTest) {
			  LocPathIterator iter = ((PredicatedNodeTest)subContextList).getLocPathIterator();
			  currentNode = iter.getCurrentContextNode();
		  }
		  else if (getExpressionOwner() instanceof ElemTemplate) {
			  /**
			   * An XPath fn:current function call, occurs within
			   * xsl:template instruction 'match' attribute's value.
			   */
			  
			  currentNode = xctxt.getCurrentNode();
			  
			  ExpressionNode parentNode = exprGetParent();
			  while (parentNode != null) {
				 if ((parentNode instanceof PredicatedNodeTest) 
						                                     || (parentNode instanceof StepPattern)) {					
					break; 
				 }
				 
				 parentNode = parentNode.exprGetParent();
			  }
			  
			  if (parentNode instanceof PredicatedNodeTest) {				  
				  ExpressionNode exprNode = parentNode.exprGetParent();
				  if ((exprNode instanceof StepPattern) && (((StepPattern)exprNode).getPredicateCount() > 0)) {
					  // XPath fn:current function call, is there within 
					  // nested predicate.					  
					  DTM dtm = xctxt.getDTM(currentNode);
					  currentNode = dtm.getParent(currentNode); 
				  }
			  }
		  }
		  else if (subContextList instanceof StepPattern) {        	         	 
			  throw new RuntimeException(XSLMessages.createMessage(XSLTErrorResources.ER_PROCESSOR_ERROR, null));

		  }
	  } 
	  else {
		  // not predicate => ContextNode == CurrentNode
		  currentNode = xctxt.getContextNode();
	  }

	  return new XMLNodeCursorImpl(currentNode, xctxt.getDTMManager());
  }

/**
   * No arguments to process, so this does nothing.
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize)
  {
    // no-op
  }

}
