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;
  
  import java.util.HashMap;
  
  /** Simple default implementation of <code>FunctionContext</code>.
   *
   *  <p>
   *  This is a simple table-based key-lookup implementation
   *  for <code>FunctionContext</code> which can be programmatically
   *  extended by registering additional functions.
   *  </p>
   *
   *  @see XPathFunctionContext
   *
   *  @author <a href="mailto:bob@werken.com">bob mcwhirter</a>
   */
  public class SimpleFunctionContext implements FunctionContext
  {
      /** Table of functions. */
      private HashMap functions;
  
      /** 
       *  <p>
       *  Construct an empty function context.
       *  </p>
       */
      public SimpleFunctionContext()
      {
          this.functions = new HashMap();
      }
  
      /** Register a new function.
       *
       *  <p>
       *  By registering a new function, any XPath expression
       *  that utilizes this <code>FunctionContext</code> may
       *  refer to and use the new function.
       *  </p>
       *
       *  <p>
       *  Functions may exist either in a namespace or not.
       *  Namespace prefix-to-URI resolution is the responsibility
       *  of a {@link NamespaceContext}.  Within this <code>FunctionContext</code>
       *  functions are only referenced using the URI, <strong>not</strong>
       *  the prefix.
       *  </p>
       *
       *  <p>
       *  The namespace URI of a function may be <code>null</code>
       *  to indicate that it exists without a namespace.
       *  </p>
       *
       *  @param namespaceURI the namespace URI of the function to
       *         be registered with this context
       *  @param localName the non-prefixed local portion of the
       *         function to be registered with this context
       *  @param function a {@link Function} implementation object
       *         to be used when evaluating the function
       */
      public void registerFunction(String namespaceURI,
                                   String localName,
                                   Function function )
      {
          this.functions.put( new QualifiedName(namespaceURI, localName),
                              function );
      }
  
      public Function getFunction(String namespaceURI,
                                  String prefix,
                                  String localName )
          throws UnresolvableException
      {
          QualifiedName key = new QualifiedName( namespaceURI, localName );
  
          if ( this.functions.containsKey(key) ) {
              return (Function) this.functions.get( key );
          }
          else {
              throw new UnresolvableException( "No Such Function " + key.getClarkForm() );
          }
      }
  }
  