/*
 * 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.xalan.templates;

import java.util.Vector;

import javax.xml.transform.SourceLocator;

import org.apache.xalan.transformer.TransformerImpl;
import org.apache.xpath.XPathContext;
import org.apache.xpath.functions.Function;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.types.StringWithCollation;
import org.apache.xpath.types.XslForEachGroupCompositeGroupingKey;

/**   
 * Implementation of an XSLT 3.0 function fn:current-grouping-key.
 * 
 * @author Mukul Gandhi <mukulg@apache.org>
 * 
 * @xsl.usage advanced
 */
public class FuncCurrentGroupingKey extends Function
{

    private static final long serialVersionUID = 936495388930718095L;
    
    public static final String XSL_GROUPING_KEY_ABSENT = "XSL_GROUPING_KEY_ABSENT";

    /**
      * Evaluate the function. The function must return a valid object.
      * 
      * @param xctxt                          An XPath context object
      * @return                               A valid XObject
      *
      * @throws javax.xml.transform.TransformerException
    */
    public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException
    {
    	XObject result = null;
    	
    	SourceLocator srcLocator = xctxt.getSAXLocator();
    	
    	ElemTemplateElement elemTemplateElement = (ElemTemplateElement)getExpressionOwner();
  	  
    	boolean isFnCurrentGroupingKeyRefValidContext = false; 
    	while (elemTemplateElement != null) {
    		if (elemTemplateElement instanceof ElemForEachGroup) {
    			isFnCurrentGroupingKeyRefValidContext = true;

    			break; 
    		}

    		elemTemplateElement = elemTemplateElement.getParentElem();
    	}

    	if (!isFnCurrentGroupingKeyRefValidContext) {
    		elemTemplateElement = (ElemTemplateElement)getExpressionOwner();
    		(elemTemplateElement.m_groupingKeyStack).clear();
    	} 
    	
        TransformerImpl transformer = (TransformerImpl) xctxt.getOwnerObject();                            
        ElemTemplateElement currElemTemplateElement = transformer.getCurrentElement();
        
        Object groupingKeyObj = currElemTemplateElement.getGroupingKey();
        
        while ((groupingKeyObj == null) && (currElemTemplateElement != null)) {            
           currElemTemplateElement = currElemTemplateElement.getParentElem();
           if (currElemTemplateElement != null) {
               groupingKeyObj = currElemTemplateElement.getGroupingKey();
           }
        }
        
        if (groupingKeyObj == null) {
           groupingKeyObj = XSL_GROUPING_KEY_ABSENT; 
        }
        
        if (groupingKeyObj instanceof StringWithCollation) {
        	groupingKeyObj = ((StringWithCollation)groupingKeyObj).getStrValue();	
        }
        else if (XSL_GROUPING_KEY_ABSENT.equals(groupingKeyObj.toString())) {
        	throw new javax.xml.transform.TransformerException("XTDE1071 : An XSL 'for-each-group' instruction's current-grouping-key "
        			                                                                                                            + "value is not available.", srcLocator);
        }
        
        if (groupingKeyObj instanceof XslForEachGroupCompositeGroupingKey) {
           result = ((XslForEachGroupCompositeGroupingKey)groupingKeyObj).getValue(); 
        }
        else {
           result = XObject.create(groupingKeyObj);
        }
      
        return result;
    }

    @Override
    public void fixupVariables(Vector vars, int globalsSize) {
       // no op    
    }
}
