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.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.StringTokenizer;
  
  import org.jaxen.Context;
  import org.jaxen.Function;
  import org.jaxen.FunctionCallException;
  import org.jaxen.Navigator;
  
  /**
   * <p><b>4.1</b> <code><i>node-set</i> id(<i>object</i>)</code> </p>
   *  
   * <p>The <b>id</b> function returns a <code>List</code>
   * of all the elements in the context document that have an ID
   * matching one of a specified list of IDs. How an attribute is determined
   * to be of type ID depends on the navigator, but it normally requires that
   * the attribute be declared to have type ID in the DTD. 
   * </p>
   * 
   * <p>
   * There should be no more than one element in any document with a 
   * certain ID. However, if there are multiple such elements--i.e. if 
   * there are duplicate IDs--then this function selects only the first element 
   * in document order with the specified ID. 
   * </p>
   * 
   * @author Erwin Bolwidt (ejb @ klomp.org)
   * @author J\u00e9r\u00f4me N\u00e8gre (jerome.negre @ e-xmlmedia.fr)
   * 
   * @see <a href="http://www.w3.org/TR/xpath#function-id" target="_top">Section 4.1 of the XPath Specification</a>
   */
  public class IdFunction implements Function
  {
  
      /**
       * Create a new <code>IdFunction</code> object.
       */
      public IdFunction() {}
      
      /** 
       * Returns a list of the nodes with the specified IDs.
       *
       * @param context the context at the point in the
       *         expression when the function is called
       * @param args a list with exactly one item which is either a string
       *     a node-set
       * 
       * @return a <code>List</code> containing the first node in document 
       *     with each of the specified IDs; or 
       *     an empty list if there are no such nodes
       * 
       * @throws FunctionCallException if <code>args</code> has more or less than one item
       */
      public Object call(Context context, List args) throws FunctionCallException
      {
          if ( args.size() == 1 ) {
              return evaluate( context.getNodeSet(),
                               args.get(0), context.getNavigator() );
          }
  
          throw new FunctionCallException( "id() requires one argument" );
      }
  
      /** 
       * Returns a list of the nodes with the specified IDs.
       * 
       * @param contextNodes the context node-set. The first item in this list
       *     determines the document in which the search is performed.
       * @param arg the ID or IDs to search for
       * @param nav the navigator used to calculate string-values and search
       *     by ID
       * 
       * @return a <code>List</code> containing the first node in document 
       *     with each of the specified IDs; or 
       *     an empty list if there are no such nodes
       * 
       */
      public static List evaluate(List contextNodes, Object arg, Navigator nav)
      {
          if (contextNodes.size() == 0) return Collections.EMPTY_LIST;
        
          List nodes = new ArrayList();
  
          Object contextNode = contextNodes.get(0);
  
          if (arg instanceof List) {
              Iterator iter = ((List)arg).iterator();
              while (iter.hasNext()) {
                  String id = StringFunction.evaluate(iter.next(), nav);
                  nodes.addAll( evaluate( contextNodes, id, nav ) );
              }
          } 
          else {
              String ids = StringFunction.evaluate(arg, nav);
              StringTokenizer tok = new StringTokenizer(ids, " \t\n\r");
              while (tok.hasMoreTokens()) {
                  String id = tok.nextToken();
                  Object node = nav.getElementById(contextNode, id);
                  if (node != null) {
                      nodes.add(node);
                  }
              }
          }
          return nodes;
      }
      
  }
  
  