content: /*
   * $Header$
   * $Revision$
   * $Date$
   *
   * ====================================================================
   *
   * 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>4.2</b> <code><i>string</i> normalize-space(<i>string</i>)</code>
   * </p>
   * 
   * <blockquote src="http://www.w3.org/TR/xpath#function-normalize-space"> 
   * The <b>normalize-space</b> 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 <a href="http://www.w3.org/TR/REC-xml#NT-S" target="_top">S</a>
   * production in XML. If the argument is omitted, it defaults to the
   * context node converted to a string, in other words the <a
   * href="http://www.w3.org/TR/xpath#dt-string-value"  
   * target="_top">string-value</a> of the context node.
   * </blockquote>
   * 
   * @author James Strachan (james@metastuff.com)
   * @see <a href="http://www.w3.org/TR/xpath#function-normalize-space"
   *      target="_top">Section 4.2 of the XPath Specification</a>
   */
  public class NormalizeSpaceFunction implements Function
  {
  
  
      /**
       * Create a new <code>NormalizeSpaceFunction</code> object.
       */
      public NormalizeSpaceFunction() {}
      
      /** 
       * Returns the string-value of the first item in <code>args</code>
       * 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 <code>String</code>
       * 
       * @throws FunctionCallException if <code>args</code> does not have length one
       */
      public Object call(Context context,
                         List args) throws FunctionCallException
      {
          
          if (args.size() == 0) {
              return evaluate( context.getNodeSet(),
                               context.getNavigator() );
          }
          else if (args.size() == 1)
          {
              return evaluate( args.get(0),
                               context.getNavigator() );
          }
      
          throw new FunctionCallException( "normalize-space() cannot have more than one argument" );
      }
  
      /** 
       * Returns the string-value of <code>strArg</code> 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';
      }
      
  }
  