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: MidFunction.java 2752 2007-04-10 14:10:41Z taqua $
028     * ------------
029     * (C) Copyright 2006-2007, by Pentaho Corporation.
030     */
031    package org.jfree.formula.function.text;
032    
033    import org.jfree.formula.EvaluationException;
034    import org.jfree.formula.FormulaContext;
035    import org.jfree.formula.LibFormulaErrorValue;
036    import org.jfree.formula.function.Function;
037    import org.jfree.formula.function.ParameterCallback;
038    import org.jfree.formula.lvalues.TypeValuePair;
039    import org.jfree.formula.typing.Type;
040    import org.jfree.formula.typing.TypeRegistry;
041    import org.jfree.formula.typing.coretypes.TextType;
042    
043    /**
044     * This function returns extracted text, given an original text, starting position, and length.
045     *
046     * @author Cedric Pronzato
047     *
048     */
049    public class MidFunction implements Function
050    {
051      public MidFunction()
052      {
053      }
054    
055      public TypeValuePair evaluate(final FormulaContext context,
056                                    final ParameterCallback parameters) throws EvaluationException
057      {
058        final int parameterCount = parameters.getParameterCount();
059        if (parameterCount != 3)
060        {
061          throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
062        }
063        final TypeRegistry typeRegistry = context.getTypeRegistry();
064    
065        final Type textType = parameters.getType(0);
066        final Object textValue = parameters.getValue(0);
067        final Type startType = parameters.getType(1);
068        final Object startValue = parameters.getValue(1);
069        final Type lengthType = parameters.getType(2);
070        final Object lengthValue = parameters.getValue(2);
071    
072        final String text = typeRegistry.convertToText(textType, textValue);
073        final Number start = typeRegistry.convertToNumber(startType, startValue);
074        final Number length = typeRegistry.convertToNumber(lengthType, lengthValue);
075    
076        if(length.doubleValue() < 0 || start.doubleValue() < 1)
077        {
078          throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
079        }
080    
081        return new TypeValuePair(TextType.TYPE, process(text, start, length));
082      }
083    
084      public String process(final String text, final Number start, final Number length)
085      {
086        int lengthValue = length.intValue();
087        final int startValue = start.intValue()-1;
088        if(startValue >= text.length())
089        {
090          return "";
091        }
092    
093        if((lengthValue +startValue) > text.length())
094        {
095          lengthValue = text.length()-startValue;
096        }
097    
098        return text.substring(startValue, startValue +lengthValue);
099      }
100    
101      public String getCanonicalName()
102      {
103        return "MID";
104      }
105    
106    }