/*
 * @(#)CurrentEnvModule.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.finder.impl;

import com.sun.xacml.EvaluationCtx;

import com.sun.xacml.attr.AttributeDesignator;
import com.sun.xacml.attr.AttributeValue;
import com.sun.xacml.attr.BagAttribute;
import com.sun.xacml.attr.DateAttribute;
import com.sun.xacml.attr.DateTimeAttribute;
import com.sun.xacml.attr.TimeAttribute;

import com.sun.xacml.cond.EvaluationResult;

import com.sun.xacml.ctx.Status;

import com.sun.xacml.finder.AttributeFinderModule;

import java.net.URI;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;


/**
 * Supports the current date, time, and dateTime values. The XACML
 * specification states that these three values must always be available to
 * a PDP. They may be included in the request, but if they're not, a PDP
 * must be able to recognize the attribute and generate the correct value.
 * The module provides support for this feature by generating real-time
 * values as known at the host where this module is running.
 * <p>
 * This class uses the caching functions of <code>EvaluationCtx</code> to
 * make sure that values are constant within an evaluation, if that is the
 * desired behavior.
 *
 * @since 1.0
 * @author Seth Proctor
 */
public class CurrentEnvModule extends AttributeFinderModule
{
    
    /**
     * Standard environment variable that represents the current time
     */
    public static final String ENVIRONMENT_CURRENT_TIME =
        "urn:oasis:names:tc:xacml:1.0:environment:current-time";

    /**
     * Standard environment variable that represents the current date
     */
    public static final String ENVIRONMENT_CURRENT_DATE =
        "urn:oasis:names:tc:xacml:1.0:environment:current-date";

    /**
     * Standard environment variable that represents the current date and time
     */
    public static final String ENVIRONMENT_CURRENT_DATETIME =
        "urn:oasis:names:tc:xacml:1.0:environment:current-dateTime";

    /**
     * Returns true always because this module supports designators.
     *
     * @return true always
     */
    public boolean isDesignatorSupported() {
        return true;
    }

    /**
     * Returns a <code>Set</code> with a single <code>Integer</code>
     * specifying that environment attributes are supported by this
     * module.
     *
     * @return a <code>Set</code> with
     * <code>AttributeDesignator.ENVIRONMENT_TARGET</code> included
     */
    public Set getSupportedDesignatorTypes() {
        HashSet set = new HashSet();
        set.add(new Integer(AttributeDesignator.ENVIRONMENT_TARGET));
        return set;
    }

    /**
     * Used to get the current time, date, or dateTime. If one of those
     * values isn't being asked for, or if the types are wrong, then an
     * empty bag is returned.
     *
     * @param attributeType the datatype of the attributes to find, which
     *                      must be time, date, or dateTime for this module
     *                      to resolve a value
     * @param attributeId the identifier of the attributes to find, which
     *                    must be one of the three ENVIRONMENT_* fields for
     *                    this module to resolve a value
     * @param issuer the issuer of the attributes, or null if unspecified
     * @param subjectCategory the category of the attribute or null, which
     *                        ignored since this only handles non-subjects
     * @param context the representation of the request data
     * @param designatorType the type of designator, which must be
     *                       ENVIRONMENT_TARGET for this module to resolve
     *                       a value
     *
     * @return the result of attribute retrieval, which will be a bag with
     *         a single attribute, an empty bag, or an error
     */
    public EvaluationResult findAttribute(URI attributeType, URI attributeId,
                                          URI issuer, URI subjectCategory,
                                          EvaluationCtx context,
                                          int designatorType) {
        // we only know about environment attributes
        if (designatorType != AttributeDesignator.ENVIRONMENT_TARGET)
            return new EvaluationResult(BagAttribute.
                                        createEmptyBag(attributeType));

        // figure out which attribute we're looking for
        String attrName = attributeId.toString();

        if (attrName.equals(ENVIRONMENT_CURRENT_TIME)) {
            return handleTime(attributeType, issuer, context);
        } else if (attrName.equals(ENVIRONMENT_CURRENT_DATE)) {
            return handleDate(attributeType, issuer, context);
        } else if (attrName.equals(ENVIRONMENT_CURRENT_DATETIME)) {
            return handleDateTime(attributeType, issuer, context);
        }

        // if we got here, then it's an attribute that we don't know
        return new EvaluationResult(BagAttribute.
                                    createEmptyBag(attributeType));
    }

    /**
     * Handles requests for the current Time.
     */
    private EvaluationResult handleTime(URI type, URI issuer,
                                        EvaluationCtx context) {
        // make sure they're asking for a time attribute
        if (! type.toString().equals(TimeAttribute.identifier))
            return new EvaluationResult(BagAttribute.
                                        createEmptyBag(type));

        // see if there's a value already cached that we should use
        TimeAttribute attr = context.getCurrentTime();
        
        if (attr == null) {
            // create the current time data
            attr = new TimeAttribute();
            context.setCurrentTime(attr);
        }

        return makeBag(attr);
    }
    
    /**
     * Handles requests for the current Date.
     */
    private EvaluationResult handleDate(URI type, URI issuer,
                                        EvaluationCtx context) {
        // make sure they're asking for a date attribute
        if (! type.toString().equals(DateAttribute.identifier))
            return new EvaluationResult(BagAttribute.
                                        createEmptyBag(type));

        // see if there's a value already cached that we should use
        DateAttribute attr = context.getCurrentDate();

        if (attr == null) {
            // create the current date data
            attr = new DateAttribute();
            context.setCurrentDate(attr);
        }

        return makeBag(attr);
    }

    /**
     * Handles requests for the current DateTime.
     */
    private EvaluationResult handleDateTime(URI type, URI issuer,
                                            EvaluationCtx context) {
        // make sure they're asking for a dateTime attribute
        if (! type.toString().equals(DateTimeAttribute.identifier))
            return new EvaluationResult(BagAttribute.
                                        createEmptyBag(type));
        
        // see if there's a value already cached that we should use
        DateTimeAttribute attr = context.getCurrentDateTime();

        if (attr == null) {
            // create the current dateTime data
            attr = new DateTimeAttribute();
            context.setCurrentDateTime(attr);
        }

        return makeBag(attr);
    }

    /**
     * Private helper that generates a new processing error status and
     * includes the given string.
     */
    private EvaluationResult makeProcessingError(String message) {
        ArrayList code = new ArrayList();
        code.add(Status.STATUS_PROCESSING_ERROR);
        return new EvaluationResult(new Status(code, message));
    }

    /**
     * Private helper that makes a bag containing only the given attribute.
     */
    private EvaluationResult makeBag(AttributeValue attribute) {
        Set set = new HashSet();
        set.add(attribute);

        BagAttribute bag = new BagAttribute(attribute.getType(), set);

        return new EvaluationResult(bag);
    }

}