/*
* 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 - 2013 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.TypeRegistry;
import org.pentaho.reporting.libraries.formula.typing.coretypes.TextType;

/**
 * This function returns extracted text, given an original text, starting position, and length.
 *
 * @author Cedric Pronzato
 */
public class MidFunction implements Function {
  private static final long serialVersionUID = 4190365695032245709L;

  public MidFunction() {
  }

  public TypeValuePair evaluate( final FormulaContext context,
                                 final ParameterCallback parameters ) throws EvaluationException {
    final int parameterCount = parameters.getParameterCount();
    if ( parameterCount != 3 ) {
      throw EvaluationException.getInstance( LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE );
    }
    final TypeRegistry typeRegistry = context.getTypeRegistry();

    final Type textType = parameters.getType( 0 );
    final Object textValue = parameters.getValue( 0 );
    final Type startType = parameters.getType( 1 );
    final Object startValue = parameters.getValue( 1 );
    final Type lengthType = parameters.getType( 2 );
    final Object lengthValue = parameters.getValue( 2 );

    final String text = typeRegistry.convertToText( textType, textValue );
    final Number start = typeRegistry.convertToNumber( startType, startValue );
    final Number length = typeRegistry.convertToNumber( lengthType, lengthValue );

    if ( length.doubleValue() < 0 || start.doubleValue() < 1 ) {
      throw EvaluationException.getInstance( LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE );
    }

    return new TypeValuePair( TextType.TYPE, process( text, start.intValue(), length.intValue() ) );
  }

  /**
   * Computes the substring for the given text, using the 1-based start index and the given length.
   *
   * @param text
   * @param start
   * @param lengthValue
   * @return
   */
  public static String process( final String text, final int start, int lengthValue ) {
    final int startValue = start - 1;
    if ( startValue >= text.length() || startValue < 0 ) {
      return "";
    }

    if ( ( lengthValue + startValue ) > text.length() ) {
      lengthValue = text.length() - startValue;
    }

    return text.substring( startValue, startValue + lengthValue );
  }

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

}