/*
 *************************************************************************
 * Copyright (c) 2004, 2008 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *  Actuate Corporation  - initial API and implementation
 *  
 *************************************************************************
 */
package org.eclipse.birt.data.aggregation.impl;

import org.eclipse.birt.core.data.DataType;
import org.eclipse.birt.data.aggregation.api.IBuildInAggregation;
import org.eclipse.birt.data.aggregation.i18n.Messages;
import org.eclipse.birt.data.engine.api.aggregation.Accumulator;
import org.eclipse.birt.data.engine.api.aggregation.IParameterDefn;

/**
 * 
 * Implements the built-in Total.last aggregation
 */
public class TotalLast extends AggrFunction
{

    /*
     * (non-Javadoc)
     * 
     * @see org.eclipse.birt.data.engine.aggregation.Aggregation#getName()
     */
    public String getName()
    {
        return IBuildInAggregation.TOTAL_LAST_FUNC;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.eclipse.birt.data.engine.aggregation.Aggregation#getType()
     */
    public int getType()
    {
        return SUMMARY_AGGR;
    }
    
    /*
     * (non-Javadoc)
     * @see org.eclipse.birt.data.engine.api.aggregation.IAggregation#getDateType()
     */
	public int getDataType( )
	{
		return DataType.ANY_TYPE;
	}

    /*
     * (non-Javadoc)
     * 
     * @see org.eclipse.birt.data.engine.aggregation.Aggregation#getParameterDefn()
     */
    public IParameterDefn[] getParameterDefn( )
	{
		return new IParameterDefn[]{
			new ParameterDefn( Constants.EXPRESSION_NAME,
					Constants.EXPRESSION_DISPLAY_NAME,
					false,
					true,
					SupportedDataTypes.ANY,
					"" )//$NON-NLS-1$
		};
	}
    
    /* (non-Javadoc)
	 * @see org.eclipse.birt.data.engine.api.aggregation.IAggrFunction#isDataOrderSensitive()
	 */
	public boolean isDataOrderSensitive( )
	{
		return true;
	}

    /*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.data.engine.aggregation.Aggregation#newAccumulator()
	 */
    public Accumulator newAccumulator()
    {
        return new MyAccumulator();
    }

    private class MyAccumulator extends SummaryAccumulator
    {
        private Object last = null;

        private boolean isRowAvailable = false;

        public void start()
        {
            super.start();
            last = null;
            isRowAvailable = false;
        }

        /*
         * (non-Javadoc)
         * 
         * @see org.eclipse.birt.data.engine.aggregation.Accumulator#onRow(java.lang.Object[])
         */
        public void onRow(Object[] args)
        {
            assert (args.length > 0);
            if (args[0] != null)
            {
                if (!isRowAvailable)
                {
                    isRowAvailable = true;
                }
                last = args[0];
            }
        }

        /*
         * (non-Javadoc)
         * 
         * @see org.eclipse.birt.data.engine.aggregation.SummaryAccumulator#getSummaryValue()
         */
        public Object getSummaryValue()
        {
            return last;
        }

    }

    /*
     * (non-Javadoc)
     * @see org.eclipse.birt.data.engine.api.aggregation.IAggrFunction#getDescription()
     */
	public String getDescription( )
	{
		return Messages.getString("TotalLast.description"); //$NON-NLS-1$
	}

	/*
	 * (non-Javadoc)
	 * @see org.eclipse.birt.data.engine.api.aggregation.IAggrFunction#getDisplayName()
	 */
	public String getDisplayName( )
	{
		return Messages.getString("TotalLast.displayName"); //$NON-NLS-1$
	}
}