/*
 * $Header$
 * $Revision$
 * $Date$
 *
 * ====================================================================
 *
 * 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/>.
 * 
 * $Id$
 */


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>4.1</b> <code><i>string</i> local-name(<i>node-set?</i>)</code></p> 
 *  
 * 
 * <blockquote cite="http://www.w3.org/TR/xpath">
 * The <b>local-name</b> function returns the local part of the 
 * expanded-name of the node in the argument node-set that is first in document order. 
 * If the argument node-set is empty or the first node has no expanded-name, an 
 * empty string is returned. If the argument is omitted, it defaults to a node-set with the context node as its only member.
 *
 * </blockquote>
 * 
 * @author bob mcwhirter (bob @ werken.com)
 * @see <a href="https://www.w3.org/TR/xpath#function-local-name" target="_top">Section 4.1 of the XPath Specification</a>
 */
public class LocalNameFunction implements Function
{
    
    /**
     * Create a new <code>LocalNameFunction</code> object.
     */
    public LocalNameFunction() {}
    
    /**
     * Returns the local-name of the specified node or the context node if 
     * no arguments are provided.
     * 
     * @param context the context at the point in the
     *         expression where the function is called
     * @param args a <code>List</code> containing zero or one items
     * 
     * @return a <code>String</code> containing the local-name
     * 
     * @throws FunctionCallException if <code>args</code> has more than one item
     */
    public Object call(Context context,
                       List args) throws FunctionCallException
    {
        if ( args.size() == 0 )
        {
            return evaluate( context.getNodeSet(),
                             context.getNavigator() ); 
        }

        if ( args.size() == 1 )
        {
            return evaluate( args,
                             context.getNavigator() );
        }

        throw new FunctionCallException( "local-name() requires zero or one argument." );
    }

    /**
     * Returns the local-name of <code>list.get(0)</code>
     * 
     * @param list a list of nodes
     * @param nav the <code>Navigator</code> used to retrieve the local name
     * 
     * @return the local-name of <code>list.get(0)</code>
     * 
     * @throws FunctionCallException if <code>list.get(0)</code> is not a node
     */
    public static String evaluate(List list,
                                  Navigator nav) throws FunctionCallException
    {
        if ( ! list.isEmpty() )
        {            
            Object first = list.get(0);

            if (first instanceof List)
            {
                return evaluate( (List) first,
                                 nav );
            }
            else if ( nav.isElement( first ) )
            {
                return nav.getElementName( first );
            }
            else if ( nav.isAttribute( first ) )
            {
                return nav.getAttributeName( first );
            }
            else if ( nav.isProcessingInstruction( first ) )
            {
                return nav.getProcessingInstructionTarget( first );
            }
            else if ( nav.isNamespace( first ) )
            {
                return nav.getNamespacePrefix( first );
            }
            else if ( nav.isDocument( first ) )
            {
                return "";
            }
            else if ( nav.isComment( first ) )
            {
                return "";
            }
            else if ( nav.isText( first ) )
            {
                return "";
            }
            else {
                throw new FunctionCallException("The argument to the local-name function must be a node-set");   
            }
        }

        return "";
    }
    
}

