/* 
 *  eXist Open Source Native XML Database 
 *  Copyright (C) 2001-06 The eXist Project 
 *  http://exist-db.org 
 *  http://exist.sourceforge.net 
 *   
 *  This program is free software; you can redistribute it and/or 
 *  modify it under the terms of the GNU Lesser General Public License 
 *  as published by the Free Software Foundation; either version 2 
 *  of the License, or (at your option) any later version. 
 *   
 *  This program is distributed in the hope that it will be useful, 
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of 
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 *  GNU Lesser General Public License for more details. 
 *   
 *  You should have received a copy of the GNU Lesser General Public License 
 *  along with this program; if not, write to the Free Software 
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
 *   
 *  $Id$ 
 */ 
package org.exist.xquery.value;

import java.util.Hashtable;
import java.util.Iterator;

import org.exist.xquery.GroupSpec;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;

/**
* An Hashtable that containts a GroupedValueSequence for each group.
* Groups are specified by the group specs of a "group by" clause. Used by
* {@link org.exist.xquery.ForExpr} et al.
*
* WARNING : don't use except for experimental "group by" clause
*
* @author Boris Verhaegen (boris.verhaegen@gmail.com)
*/

public class GroupedValueSequenceTable extends Hashtable {
	
	 private GroupSpec groupSpecs[]; 
	    private String toGroupVarName; 
	    private XQueryContext context; 
	 
	    public GroupedValueSequenceTable(GroupSpec groupSpecs[], String varName, XQueryContext aContext) { 
	    	super(11,(float)0.75); //Hashtable parameters
	        this.groupSpecs = groupSpecs;     
	        this.toGroupVarName = varName; 
	        this.context = aContext; 
	    } 
	     
	    public void setToGroupVarName(String varName){ 
	        toGroupVarName = varName; 
	    } 
	     
	    public String getToGroupVarName(){ 
	        return toGroupVarName; 
	    } 
	    
	    public Iterator iterate(){
        	Iterator it = this.keySet().iterator();
            return it;
	    }
	     
	    /** 
	     * Add <code>item</code> in the correct <code>GroupedValueSequence</code>. 
	     * Create correct GroupedValueSequence if needed. Insertion based on  
	     * the group specs of a "group by" clause. 
	     *   
	     * @throws     XPathException 
	     */ 
	    public void add(Item item) throws XPathException { 
	        Sequence specEvaluation[] = new Sequence[groupSpecs.length]; 
	        ValueSequence keySequence = new ValueSequence(); 
               
	        for(int i = 0; i < groupSpecs.length ; i++){ 
	            //evaluates the values of the grouping keys 
	            specEvaluation[i] =  groupSpecs[i].getGroupExpression().eval(item.toSequence()); //TODO : too early evaluation !
	            keySequence.add(specEvaluation[i].itemAt(0)); 
	        } 
	        
	        String hashKey = keySequence.getHashKey();
	            
	        if( this.containsKey(hashKey) ){
	        	GroupedValueSequence currentGroup = (GroupedValueSequence)super.get(hashKey);
	        	currentGroup.add(item);
	        }
	        else{ 
	            //this group doesn't exists, then creates this group 
	            GroupedValueSequence newGroup = new GroupedValueSequence(groupSpecs, 1, keySequence,context); 
	            newGroup.add(item); 
	            super.put(hashKey,newGroup); 
	        } 
	    } 
	     
	    /** 
	     * Add all items of a sequence 
	     *  
	     * @param sequence 
	     * @throws XPathException 
	     */ 
	    public void addAll(Sequence sequence) throws XPathException{ 
	        for (SequenceIterator i = sequence.iterate(); i.hasNext(); ) { 
	            this.add(i.nextItem()); 
	        } 
	    } 
	}