/*

  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/StartsWithFunction.java,v 1.11 2006/02/05 21:47:41 elharo Exp $

  * $Revision: 1.11 $

  * $Date: 2006/02/05 21:47:41 $

  *

  * ====================================================================

  *

  * Copyright 2000-2002 bob mcwhirter & James Strachan.

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions are

  * met:

  * 

  *   * Redistributions of source code must retain the above copyright

  *     notice, this list of conditions and the following disclaimer.

  * 

  *   * Redistributions in binary form must reproduce the above copyright

  *     notice, this list of conditions and the following disclaimer in the

  *     documentation and/or other materials provided with the distribution.

  * 

  *   * Neither the name of the Jaxen Project nor the names of its

  *     contributors may be used to endorse or promote products derived 

  *     from this software without specific prior written permission.

  * 

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER

  * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  *

  * ====================================================================

  * This software consists of voluntary contributions made by many 

  * individuals on behalf of the Jaxen Project and was originally 

  * created by bob mcwhirter <bob@werken.com> and 

  * James Strachan <jstrachan@apache.org>.  For more information on the 

  * Jaxen Project, please see <http://www.jaxen.org/>.

  * 

  * $Id: StartsWithFunction.java,v 1.11 2006/02/05 21:47:41 elharo Exp $

  */

 package org.jaxen.function;

 import java.util.List;

 import org.jaxen.Context;

 import org.jaxen.Function;

 import org.jaxen.FunctionCallException;

 import org.jaxen.Navigator;

 /**

  * <p><b>4.2</b> <code><i>boolean</i> starts-with(<i>string</i>,<i>string</i>)</code></p> 

  * 

  * 

  * <blockquote src="http://www.w3.org/TR/xpath">

  * The <b>starts-with</b> function returns true if the first argument string starts 

  * with the second argument string, and otherwise returns false.

  * </blockquote>

  * 

  * @author bob mcwhirter (bob @ werken.com)

  * @see <a href="http://www.w3.org/TR/xpath#function-starts-with" target="_top">Section 4.2 of the XPath Specification</a>

  */

 public class StartsWithFunction implements Function

 {

     /**

      * Create a new <code>StartsWithFunction</code> object.

      */

     public StartsWithFunction() {}

     /** 

      * Returns true if the string-value of the first item in <code>args</code>

      * starts with the string-value of the second item in <code>args</code>. 

      * Otherwise it returns false.

      *

      * @param context the context at the point in the

      *         expression when the function is called

      * @param args a list that contains two items

      * 

      * @return <code>Boolean.TRUE</code> if the first item in <code>args</code>

      *     starts with the string-value of the second item in <code>args</code>;

      *     otherwise <code>Boolean.FALSE</code>

      * 

      * @throws FunctionCallException if <code>args</code> does not have length two

      */

     public Object call(Context context,

                        List args) throws FunctionCallException

     {

         if (args.size() == 2)

         {

             return evaluate( args.get(0),

                              args.get(1),

                              context.getNavigator() );

         }

         throw new FunctionCallException( "starts-with() requires two arguments." );

     }

     /** 

      * Returns true if the string-value of <code>strArg</code>

      * starts with the string-value of <code>matchArg</code>. 

      * Otherwise it returns false.

      * 

      * @param strArg the object whose string-value searched for the prefix

      * @param matchArg the object whose string-value becomes the prefix string to compare against

      * @param nav the navigator used to calculate the string-values of the arguments

      * 

      * @return <code>Boolean.TRUE</code> if the string-value of <code>strArg</code>

      *     starts with the string-value of <code>matchArg</code>;

      *     otherwise <code>Boolean.FALSE</code>

      * 

      */

     public static Boolean evaluate(Object strArg,

                                    Object matchArg,

                                    Navigator nav)

     {

         String str   = StringFunction.evaluate( strArg,

                                                 nav );

         String match = StringFunction.evaluate( matchArg,

                                                 nav );

         return ( str.startsWith(match)

                  ? Boolean.TRUE

                  : Boolean.FALSE

                  );

     }

 }