/*
 * $Header: /l/extreme/cvs/codes/XPP3/java/src/java/xpath/org/xmlpull/v1/builder/xpath/jaxen/SimpleFunctionContext.java,v 1.2 2005/08/11 22:44:00 aslom Exp $
 * $Revision: 1.2 $
 * $Date: 2005/08/11 22:44:00 $
 *
 * ====================================================================
 *
 * Copyright (C) 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:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions, and the disclaimer that follows 
 *    these conditions in the documentation and/or other materials 
 *    provided with the distribution.
 *
 * 3. The name "Jaxen" must not be used to endorse or promote products
 *    derived from this software without prior written permission.  For
 *    written permission, please contact license@jaxen.org.
 * 
 * 4. Products derived from this software may not be called "Jaxen", nor
 *    may "Jaxen" appear in their name, without prior written permission
 *    from the Jaxen Project Management (pm@jaxen.org).
 * 
 * In addition, we request (but do not require) that you include in the 
 * end-user documentation provided with the redistribution and/or in the 
 * software itself an acknowledgement equivalent to the following:
 *     "This product includes software developed by the
 *      Jaxen Project (http://www.jaxen.org/)."
 * Alternatively, the acknowledgment may be graphical using the logos 
 * available at http://www.jaxen.org/
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 Jaxen AUTHORS OR THE PROJECT
 * 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: SimpleFunctionContext.java,v 1.2 2005/08/11 22:44:00 aslom Exp $
 */


package org.xmlpull.v1.builder.xpath.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;

    /** Construct.
     *
     *  <p>
     *  Construct with an empty function lookup table.
     *  </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 an 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, <b>not</b>
     *  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
    {
        Object key = new QualifiedName( namespaceURI, localName );

        if ( this.functions.containsKey(key) )
            return (Function) this.functions.get( key );
        else
            throw new UnresolvableException( "Function " +
                                             prefix + ":" + localName );
    }
}
