
/*
 * @(#)PolicyFinderModule.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
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 */

package com.sun.xacml.finder;

import com.sun.xacml.EvaluationCtx;

import java.net.URI;


/**
 * This is the abstract class that all <code>PolicyFinder</code> modules
 * extend. All methods have default values to represent that the given
 * feature isn't supported by this module, so module writers needs only
 * implement the methods for the features they're supporting.
 *
 * @since 1.0
 * @author Seth Proctor
 */
public abstract class PolicyFinderModule
{

    /**
     * Returns this module's identifier. A module does not need to provide
     * a unique identifier, but it is a good idea, especially in support of
     * management software. Common identifiers would be the full package
     * and class name (the default if this method isn't overridden), just the
     * class name, or some other well-known string that identifies this class.
     *
     * @return this module's identifier
     */
    public String getIdentifier() {
        return getClass().getName();
    }

    /**
     * Returns true if the module supports finding policies based on a
     * request (ie, target matching). By default this method returns false.
     *
     * @return true if request retrieval is supported
     */
    public boolean isRequestSupported() {
        return false;
    }

    /**
     * Returns true if the module supports finding policies based on an
     * id reference (in a PolicySet). By default this method returns false.
     *
     * @return true if idReference retrieval is supported
     */
    public boolean isIdReferenceSupported() {
        return false;
    }

    /**
     * Initializes this module for use by the given finder. Typically this
     * is called when a <code>PDP</code> is initialized with a
     * <code>PDPConfig</code> containing the given <code>PolicyFinder</code>.
     * Because <code>PolicyFinderModule</code>s usually need to parse
     * policies, and this requires knowing their <code>PolicyFinder<code>,
     * parsing is usually done at or after this point in the lifetime
     * of this module. This might also be a good time to reset any internal
     * caches or temporary data. Note that this method may be called more
     * than once in the lifetime of a module.
     *
     * @param finder the <code>PolicyFinder</code> using this module
     */
    public abstract void init(PolicyFinder finder);

    /**
     * This is an experimental method that asks the module to invalidate any
     * cache values it may contain. This is not used by any of the core
     * processing code, but it may be used by management software that wants
     * to have some control over these modules. Since a module is free to
     * decide how or if it caches values, and whether it is capable of
     * updating values once in a cache, a module is free to intrepret this
     * message in any way it sees fit (including igoring the message). It
     * is preferable, however, for a module to make every effort to clear
     * any dynamically cached values it contains.
     * <p>
     * This method has been introduced to see what people think of this
     * functionality, and how they would like to use it. It may be removed
     * in future versions, or it may be changed to a more general
     * message-passing system (if other useful messages are identified).
     * 
     * @since 1.2
     */
    public void invalidateCache() {

    }

    /**
     * Tries to find one and only one matching policy given the request
     * represented by the context data. If more than one policy is found,
     * this is an error and must be reported as such. If no policies are
     * found, then an empty result must be returned. By default this
     * method returns an empty result. This method should never return null.
     *
     * @param context the representation of the request
     *
     * @return the result of looking for a matching policy
     */
    public PolicyFinderResult findPolicy(EvaluationCtx context) {
        return new PolicyFinderResult();
    }

    /**
     * Tries to find one and only one matching policy given the idReference
     * If more than one policy is found, this is an error and must be reported
     * as such. If no policies are found, then an empty result must be
     * returned. By default this method returns an empty result. This method
     * should never return null.
     *
     * @param idReference an identifier specifying some policy
     * @param type type of reference (policy or policySet) as identified by
     *             the fields in <code>PolicyReference</code>
     *
     * @return the result of looking for a matching policy
     */
    public PolicyFinderResult findPolicy(URI idReference, int type) {
        return new PolicyFinderResult();
    }

}
