/*
 * This program is free software; you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
 * Foundation.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 * or from the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * 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.
 *
 * Copyright (c) 2006 - 2009 Pentaho Corporation and Contributors.  All rights reserved.
 */

package org.pentaho.reporting.libraries.formula.function.text;

import org.pentaho.reporting.libraries.formula.EvaluationException;
import org.pentaho.reporting.libraries.formula.FormulaContext;
import org.pentaho.reporting.libraries.formula.LibFormulaErrorValue;
import org.pentaho.reporting.libraries.formula.function.Function;
import org.pentaho.reporting.libraries.formula.function.ParameterCallback;
import org.pentaho.reporting.libraries.formula.lvalues.TypeValuePair;
import org.pentaho.reporting.libraries.formula.typing.Type;
import org.pentaho.reporting.libraries.formula.typing.coretypes.TextType;

/**
 * This function returns the given text free of leading spaces.
 * Removes all leading and trailing spaces and all extra spaces inside the text.
 *
 * @author Cedric Pronzato
 * @link http://mercury.ccil.org/%7Ecowan/OF/textfuncs.html
 */
public class TrimFunction implements Function
{
  private static final long serialVersionUID = 7379670108270974597L;

  public TrimFunction()
  {
  }

  public TypeValuePair evaluate(final FormulaContext context, final ParameterCallback parameters) throws EvaluationException
  {
    final int parameterCount = parameters.getParameterCount();
    if (parameterCount < 1)
    {
      throw EvaluationException.getInstance(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
    }
    final Type type1 = parameters.getType(0);
    final Object value1 = parameters.getValue(0);
    final String result = context.getTypeRegistry().convertToText(type1, value1);

    if(result == null)
    {
      throw EvaluationException.getInstance(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
    }

    // remove all unnecessary spaces ..
    // we dont use regexps, because they are JDK 1.4, but this library is aimed
    // for JDK 1.2.2

    final char[] chars = result.toCharArray();
    final StringBuffer b = new StringBuffer(chars.length);
    boolean removeNextWs = true;

    for (int i = 0; i < chars.length; i++)
    {
      final char c = chars[i];
      if (Character.isWhitespace(c))
      {
        if (removeNextWs)
        {
          continue;
        }
        b.append(c);
        removeNextWs = true;
        continue;
      }

      b.append(c);
      removeNextWs = false;
    }

    // now check whether the last char is a whitespace and remove that one
    // if neccessary
    final String trimmedResult;
    if (removeNextWs && b.length() > 0)
    {
      trimmedResult = b.substring(0, b.length() - 1);
    }
    else
    {
      trimmedResult = b.toString();
    }

    return new TypeValuePair(TextType.TYPE, trimmedResult);
  }

  public String getCanonicalName()
  {
    return "TRIM";
  }

}
