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>4.1</b>
   * <code><i>string</i> namespace-uri(<i>node-set?</i>)</code>
   * </p>
   * 
   * <blockquote src="http://www.w3.org/TR/xpath">
   * <p>
   * The <b>namespace-uri</b>
   * function returns the namespace URI of the <a
   * href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a> of the node in the
   * argument node-set that is first in <a
   * href="http://www.w3.org/TR/xpath#dt-document-order" target="_top">document order</a>. If the argument
   * node-set is empty, the first node has no <a
   * href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a>, or the namespace URI of
   * the <a href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a> is null, an empty
   * string is returned. If the argument is omitted, it defaults to a
   * node-set with the context node as its only member.
   * </p>
   * 
   * <blockquote> <b>NOTE: </b>The string returned by the <b>namespace-uri</b> function will
   * be empty except for element nodes and attribute nodes.</blockquote>
   * 
   * </blockquote>
   * 
   * @author bob mcwhirter (bob @ werken.com)
   * @see <a href="http://www.w3.org/TR/xpath#function-namespace-uri"
   *      target="_top">Section 4.1 of the XPath Specification</a>
   */
  public class NamespaceUriFunction implements Function
  {
  
      /**
       * Create a new <code>NamespaceUriFunction</code> object.
       */
      public NamespaceUriFunction() {}
  
      /**
       * Returns the namespace URI of the specified node or the namespace URI of 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 namespace URI
       * 
       * @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( "namespace-uri() requires zero or one argument." );
      }
  
      /**
       * Returns the namespace URI of <code>list.get(0)</code>
       * 
       * @param list a list of nodes
       * @param nav the <code>Navigator</code> used to retrieve the namespace
       * 
       * @return the namespace URI 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.getElementNamespaceUri( first );
              }
              else if ( nav.isAttribute( first ) )
              {
                  String uri = nav.getAttributeNamespaceUri( first );
                  if (uri == null) return "";
                  return uri;
              }
              else if ( nav.isProcessingInstruction( first ) )
              {
                  return "";
              }
              else if ( nav.isNamespace( first ) )
              {
                  return "";
              }
              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 namespace-uri function must be a node-set");   
              }
  
          }
  
          return "";
  
      }
  }
  
  