
/*
 * @(#)ResourceFinder.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
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
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 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
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 *
 * You acknowledge that this software is not designed or intended for use in
 * the design, construction, operation or maintenance of any nuclear facility.
 */

package com.sun.xacml.finder;

import com.sun.xacml.EvaluationCtx;

import com.sun.xacml.attr.AttributeValue;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import java.util.logging.Level;
import java.util.logging.Logger;


/**
 * This class is used by the PDP to handle resource scopes other than
 * Immediate. In the case of a scope of Children or Descendants, the PDP
 * needs a list of Resource Ids to evaluate, each of which will get its
 * own Result. Like the PolicyFinder, this is not tied in any way to the
 * rest of the PDP code, and could be provided as a stand-alone resource.
 * <p>
 * This class basically is a coordinator that asks each module in turn
 * if it can handle the given identifier. Evaluation proceeds in order through
 * the given modules, and once a module returns a non-empty response (whether
 * or not it contains any errors or only errors), the evaluation is
 * finished and the result is returned. One of the issues here is ordering,
 * since a given resource may look to several modules like something that
 * they can handle. So, you must be careful when assigning to ordering of
 * the modules in this finder.
 * <p>
 * Note that in release 1.2 the interfaces were updated to include the
 * evaluation context. In the next major release the interfaces without the
 * context information will be removed, but for now both exist. This means
 * that if this finder is called with the context, then only the methods
 * in <code>ResourceFinderModule</code> supporting the context will be
 * called (and likewise only the methods without context will be called
 * when this finder is called without the context). In practice this
 * means that the methods with context will always get invoked, since this
 * is what the default PDP implementation calls.
 *
 * @since 1.0
 * @author Seth Proctor
 */
public class ResourceFinder
{

    // the list of all modules
    private List allModules;

    // the list of child modules
    private List childModules;

    // the list of descendant modules
    private List descendantModules;

    // the logger we'll use for all messages
    private static final Logger logger =
        Logger.getLogger(ResourceFinder.class.getName());

    /**
     * Default constructor.
     */
    public ResourceFinder() {
        allModules = new ArrayList();
        childModules = new ArrayList();
        descendantModules = new ArrayList();
    }

    /**
     * Returns the ordered <code>List</code> of modules used by this class
     * to find resources.
     *
     * @return the list of modules used by this class
     */
    public List getModules() {
        return new ArrayList(allModules);
    }

    /**
     * Sets the ordered <code>List</code> of modules used by this class
     * to find resources. The ordering will be maintained.
     *
     * @param modules the modules this class will use
     */
    public void setModules(List modules) {
        Iterator it = modules.iterator();

        allModules = new ArrayList(modules);
        childModules = new ArrayList();
        descendantModules = new ArrayList();
        
        while (it.hasNext()) {
            ResourceFinderModule module = (ResourceFinderModule)(it.next());
            
            if (module.isChildSupported())
                childModules.add(module);

            if (module.isDescendantSupported())
                descendantModules.add(module);
        }
    }

    /**
     * Finds Resource Ids using the Children scope, and returns all resolved
     * identifiers as well as any errors that occurred. If no modules can
     * handle the given Resource Id, then an empty result is returned.
     *
     * @param parentResourceId the root of the resources
     * @param context the representation of the request data
     *
     * @return the result of looking for child resources
     */
    public ResourceFinderResult findChildResources(AttributeValue
                                                   parentResourceId,
                                                   EvaluationCtx context) {
        Iterator it = childModules.iterator();

        while (it.hasNext()) {
            ResourceFinderModule module = (ResourceFinderModule)(it.next());

            // ask the module to find the resources
            ResourceFinderResult result =
                module.findChildResources(parentResourceId, context);

            // if we found something, then always return that result
            if (! result.isEmpty())
                return result;
        }

        // no modules applied, so we return an empty result
        if (logger.isLoggable(Level.INFO))
            logger.info("No ResourceFinderModule existed to handle the " +
                        "children of " + parentResourceId.encode());

        return new ResourceFinderResult();
    }
    
    /**
     * Finds Resource Ids using the Children scope, and returns all resolved
     * identifiers as well as any errors that occurred. If no modules can
     * handle the given Resource Id, then an empty result is returned.
     *
     * @deprecated As of version 1.2, replaced by
     *             {@link #findChildResources(AttributeValue,EvaluationCtx)}.
     *             This version does not provide the evaluation context to
     *             the modules, and will be removed in a future release.
     *
     * @param parentResourceId the root of the resources
     *
     * @return the result of looking for child resources
     */
    public ResourceFinderResult findChildResources(AttributeValue
                                                   parentResourceId) {
        Iterator it = childModules.iterator();

        while (it.hasNext()) {
            ResourceFinderModule module = (ResourceFinderModule)(it.next());

            // ask the module to find the resources
            ResourceFinderResult result =
                module.findChildResources(parentResourceId);

            // if we found something, then always return that result
            if (! result.isEmpty())
                return result;
        }

        // no modules applied, so we return an empty result
        if (logger.isLoggable(Level.INFO))
            logger.info("No ResourceFinderModule existed to handle the " +
                        "children of " + parentResourceId.encode());

        return new ResourceFinderResult();
    }

    /**
     * Finds Resource Ids using the Descendants scope, and returns all resolved
     * identifiers as well as any errors that occurred. If no modules can
     * handle the given Resource Id, then an empty result is returned.
     *
     * @param parentResourceId the root of the resources
     * @param context the representation of the request data
     *
     * @return the result of looking for descendant resources
     */
    public ResourceFinderResult findDescendantResources(AttributeValue
                                                        parentResourceId,
                                                        EvaluationCtx
                                                        context) {
        Iterator it = descendantModules.iterator();

        while (it.hasNext()) {
            ResourceFinderModule module = (ResourceFinderModule)(it.next());

            // ask the module to find the resources
            ResourceFinderResult result =
                module.findDescendantResources(parentResourceId, context);

            // if we found something, then always return that result
            if (! result.isEmpty())
                return result;
        }

        // no modules applied, so we return an empty result
        if (logger.isLoggable(Level.INFO))
            logger.info("No ResourceFinderModule existed to handle the " +
                        "descendants of " + parentResourceId.encode());
        
        return new ResourceFinderResult();
    }

    /**
     * Finds Resource Ids using the Descendants scope, and returns all resolved
     * identifiers as well as any errors that occurred. If no modules can
     * handle the given Resource Id, then an empty result is returned.
     *
     * @deprecated As of version 1.2, replaced by
     *          {@link #findDescendantResources(AttributeValue,EvaluationCtx)}.
     *             This version does not provide the evaluation context to
     *             the modules, and will be removed in a future release.
     *
     * @param parentResourceId the root of the resources
     *
     * @return the result of looking for child resources
     */
    public ResourceFinderResult findDescendantResources(AttributeValue
                                                        parentResourceId) {
        Iterator it = descendantModules.iterator();

        while (it.hasNext()) {
            ResourceFinderModule module = (ResourceFinderModule)(it.next());

            // ask the module to find the resources
            ResourceFinderResult result =
                module.findDescendantResources(parentResourceId);

            // if we found something, then always return that result
            if (! result.isEmpty())
                return result;
        }

        // no modules applied, so we return an empty result
        if (logger.isLoggable(Level.INFO))
            logger.info("No ResourceFinderModule existed to handle the " +
                        "descendants of " + parentResourceId.encode());
        
        return new ResourceFinderResult();
    }

}
