/*
 * @(#)CombiningAlgFactory.java
 *
 * Copyright 2003-2004 Sun Microsystems, Inc. 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. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution 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 Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
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 */

package com.sun.xacml.combine;

import com.sun.xacml.UnknownIdentifierException;

import java.net.URI;

import java.util.Set;


/**
 * Provides a factory mechanism for installing and retrieving combining
 * algorithms.
 *
 * @since 1.0
 * @author Seth Proctor
 */
public abstract class CombiningAlgFactory
{

    // the proxy used to get the default factory
    private static CombiningAlgFactoryProxy defaultFactoryProxy;

    /**
     * static intialiazer that sets up the default factory proxy
     * NOTE: this will change when the right setup mechanism is in place
     */
    static {
        defaultFactoryProxy = new CombiningAlgFactoryProxy() {
                public CombiningAlgFactory getFactory() {
                    return StandardCombiningAlgFactory.getFactory();
                }
            };
    };

    /**
     * Default constructor. Used only by subclasses.
     */
    protected CombiningAlgFactory() {
        
    }

    /**
     * Returns the default factory. Depending on the default factory's
     * implementation, this may return a singleton instance or new instances
     * with each invokation.
     *
     * @return the default <code>CombiningAlgFactory</code>
     */
    public static final CombiningAlgFactory getInstance() {
        return defaultFactoryProxy.getFactory();
    }

    /**
     * Sets the default factory. Note that this is just a placeholder for
     * now, and will be replaced with a more useful mechanism soon.
     */
    public static final void setDefaultFactory(CombiningAlgFactoryProxy proxy)
    {
        defaultFactoryProxy = proxy;
    }

    /**
     * Adds a combining algorithm to the factory. This single instance will
     * be returned to anyone who asks the factory for an algorithm with the
     * id given here.
     *
     * @param alg the combining algorithm to add
     *
     * @throws IllegalArgumentException if the algorithm is already registered
     */
    public abstract void addAlgorithm(CombiningAlgorithm alg);

    /**
     * Adds a combining algorithm to the factory. This single instance will
     * be returned to anyone who asks the factory for an algorithm with the
     * id given here.
     *
     * @deprecated As of version 1.2, replaced by
     *        {@link #addAlgorithm(CombiningAlgorithm)}.
     *             The new factory system requires you to get a factory
     *             instance and then call the non-static methods on that
     *             factory. The static versions of these methods have been
     *             left in for now, but are slower and will be removed in
     *             a future version.
     *
     * @param alg the combining algorithm to add
     *
     * @throws IllegalArgumentException if the algorithm is already registered
     */
    public static void addCombiningAlg(CombiningAlgorithm alg) {
        getInstance().addAlgorithm(alg);
    }

    /**
     * Returns the algorithm identifiers supported by this factory.
     *
     * @return a <code>Set</code> of <code>String</code>s
     */
    public abstract Set getSupportedAlgorithms();

    /**
     * Tries to return the correct combinging algorithm based on the
     * given algorithm ID.
     *
     * @param algId the identifier by which the algorithm is known
     *
     * @return a combining algorithm
     *
     * @throws UnknownIdentifierException algId is unknown
     */
    public abstract CombiningAlgorithm createAlgorithm(URI algId)
        throws UnknownIdentifierException;

    /**
     * Tries to return the correct combinging algorithm based on the
     * given algorithm ID.
     *
     * @deprecated As of version 1.2, replaced by
     *        {@link #createAlgorithm(URI)}.
     *             The new factory system requires you to get a factory
     *             instance and then call the non-static methods on that
     *             factory. The static versions of these methods have been
     *             left in for now, but are slower and will be removed in
     *             a future version.
     *
     * @param algId the identifier by which the algorithm is known
     *
     * @return a combining algorithm
     *
     * @throws UnknownIdentifierException algId is unknown
     */
    public static CombiningAlgorithm createCombiningAlg(URI algId)
        throws UnknownIdentifierException
    {
        return getInstance().createAlgorithm(algId);
    }


}