001    /**
002     * =========================================
003     * LibFormula : a free Java formula library
004     * =========================================
005     *
006     * Project Info:  http://reporting.pentaho.org/libformula/
007     *
008     * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors.
009     *
010     * This library is free software; you can redistribute it and/or modify it under the terms
011     * of the GNU Lesser General Public License as published by the Free Software Foundation;
012     * either version 2.1 of the License, or (at your option) any later version.
013     *
014     * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
015     * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
016     * See the GNU Lesser General Public License for more details.
017     *
018     * You should have received a copy of the GNU Lesser General Public License along with this
019     * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
020     * Boston, MA 02111-1307, USA.
021     *
022     * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
023     * in the United States and other countries.]
024     *
025     *
026     * ------------
027     * $Id: HourFunction.java 2822 2007-05-20 21:47:52Z mimil $
028     * ------------
029     * (C) Copyright 2006-2007, by Pentaho Corporation.
030     */
031    package org.jfree.formula.function.datetime;
032    
033    import java.math.BigDecimal;
034    
035    import org.jfree.formula.EvaluationException;
036    import org.jfree.formula.FormulaContext;
037    import org.jfree.formula.LibFormulaErrorValue;
038    import org.jfree.formula.function.Function;
039    import org.jfree.formula.function.ParameterCallback;
040    import org.jfree.formula.lvalues.TypeValuePair;
041    import org.jfree.formula.typing.TypeRegistry;
042    import org.jfree.formula.typing.coretypes.NumberType;
043    import org.jfree.formula.util.NumberUtil;
044    
045    /**
046     * This function extracts the hour (0 through 23) from a time.
047     * 
048     * @author Cedric Pronzato
049     */
050    public class HourFunction implements Function
051    {
052      private static final BigDecimal HOUR_24 = new BigDecimal(24);
053    
054      public HourFunction()
055      {
056      }
057    
058      public String getCanonicalName()
059      {
060        return "HOUR";
061      }
062    
063      public TypeValuePair evaluate(final FormulaContext context,
064          final ParameterCallback parameters) throws EvaluationException
065      {
066        if (parameters.getParameterCount() != 1)
067        {
068          throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
069        }
070    
071        final TypeRegistry typeRegistry = context.getTypeRegistry();
072        final Number n = typeRegistry.convertToNumber(parameters.getType(0),
073            parameters.getValue(0));
074    
075        if (n == null)
076        {
077          throw new EvaluationException(
078              LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
079        }
080    
081        final BigDecimal bd = NumberUtil.getAsBigDecimal(n);
082        final BigDecimal round1 = new BigDecimal(NumberUtil
083                .performIntRounding(bd).intValue());
084        final BigDecimal dayFraction = bd.subtract(round1);
085        final Integer hour = NumberUtil.performIntRounding(dayFraction
086            .multiply(HOUR_24));
087    
088        return new TypeValuePair(NumberType.GENERIC_NUMBER, hour);
089      }
090    }