/**

  * Distribution License:

  * JSword is free software; you can redistribute it and/or modify it under

  * the terms of the GNU Lesser General Public License, version 2.1 or later

  * as published by the Free Software Foundation. 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.

  *

  * The License is available on the internet at:

  *      http://www.gnu.org/copyleft/lgpl.html

  * or by writing to:

  *      Free Software Foundation, Inc.

  *      59 Temple Place - Suite 330

  *      Boston, MA 02111-1307, USA

  *

  * © CrossWire Bible Society, 2005 - 2016

  */

 package org.crosswire.jsword.index.query;

 import org.crosswire.jsword.book.BookException;

 import org.crosswire.jsword.index.Index;

 import org.crosswire.jsword.passage.Key;

 /**

  * An "And Not" query specifies that a result needs to be in the left but not in

  * the right query result.

  * 

  * @see gnu.lgpl.License The GNU Lesser General Public License for details.

  * @author DM Smith

  */

 public class AndNotQuery extends AbstractBinaryQuery {

     /**

      * Create a query where the right query result is subtracted from the left

      * query result.

      * 

      * @param theLeftQuery

      * @param theRightQuery

      */

     public AndNotQuery(Query theLeftQuery, Query theRightQuery) {

         super(theLeftQuery, theRightQuery);

     }

     /*

      * (non-Javadoc)

      * 

      * @see

      * org.crosswire.jsword.index.search.parse.Query#find(org.crosswire.jsword

      * .index.search.Index)

      */

     public Key find(Index index) throws BookException {

         Key left = getLeftQuery().find(index);

         if (left.isEmpty()) {

             return left;

         }

         Key right = getRightQuery().find(index);

         if (right.isEmpty()) {

             return left;

         }

         left.removeAll(right);

         return left;

     }

 }