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/*
 * $Header$
 * $Revision$
 * $Date$
 *
 * ====================================================================
 *
 * 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  and 
 * James Strachan .  For more information on the 
 * Jaxen Project, please see .
 * 
 * $Id$
 */


package org.jaxen.function;

import java.util.List;

import org.jaxen.Context;
import org.jaxen.Function; 
import org.jaxen.Navigator;

/**
 * 
 * 4.2 string normalize-space(string)
 * 
 * 
 *  
 * The normalize-space function
 * returns the argument string with whitespace normalized by stripping
 * leading and trailing whitespace and replacing sequences of whitespace
 * characters by a single space. Whitespace characters are the same as
 * those allowed by the S
 * production in XML. If the argument is omitted, it defaults to the
 * context node converted to a string, in other words the string-value of the context node.
 * 
 * 
 * @author James Strachan ([email protected])
 * @see Section 4.2 of the XPath Specification
 */
@SuppressWarnings({"rawtypes"})
public class NormalizeSpaceFunction implements Function
{


    /**
     * Create a new NormalizeSpaceFunction object.
     */
    public NormalizeSpaceFunction() {}
    
    /** 
     * Returns the string-value of the first item in args
     * after removing all leading and trailing white space, and 
     * replacing each other sequence of whitespace by a single space.
     * Whitespace consists of the characters space (0x32), carriage return (0x0D),
     * linefeed (0x0A), and tab (0x09).
     *
     * @param context the context at the point in the
     *         expression when the function is called
     * @param args a list that contains exactly one item
     * 
     * @return a normalized String
     * 
     * @ if args does not have length one
     */
    public Object call(Context context,
                       List args) 
    {
        
        if (args.size() == 0) {
            return evaluate( context.getNodeSet(),
                             context.getNavigator() );
        }
        else if (args.size() == 1)
        {
            return evaluate( args.get(0),
                             context.getNavigator() );
        }
    
        throw new RuntimeException( "normalize-space() cannot have more than one argument" );
    }

    /** 
     * Returns the string-value of strArg after removing
     * all leading and trailing white space, and 
     * replacing each other sequence of whitespace by a single space.
     * Whitespace consists of the characters space (0x32), carriage return (0x0D),
     * linefeed (0x0A), and tab (0x09).
     *
     * @param strArg the object whose string-value is normalized
     * @param nav the context at the point in the
     *         expression when the function is called
     * 
     * @return the normalized string-value
     */
    public static String evaluate(Object strArg,
                                  Navigator nav) 
    {
        String str = StringFunction.evaluate( strArg,
                                              nav );

        char[] buffer = str.toCharArray();
        int write = 0;
        int lastWrite = 0;
        boolean wroteOne = false;
        int read = 0;
        while (read < buffer.length)
        {
            if (isXMLSpace(buffer[read]))
            {
                if (wroteOne)
                {
                    buffer[write++] = ' ';
                }
                do
                {
                    read++;
                }
                while(read < buffer.length && isXMLSpace(buffer[read]));
            }
            else
            {
                buffer[write++] = buffer[read++];
                wroteOne = true;
                lastWrite = write;
            }
        }

        return new String(buffer, 0, lastWrite);
    }
    
    
    private static boolean isXMLSpace(char c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t';
    }
    
}