openaz-xacml-pdp/src/main/java/org/apache/openaz/xacml/pdp/policy/ExpressionResult.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 *
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/*
 *                        AT&T - PROPRIETARY
 *          THIS FILE CONTAINS PROPRIETARY INFORMATION OF
 *        AT&T AND IS NOT TO BE DISCLOSED OR USED EXCEPT IN
 *             ACCORDANCE WITH APPLICABLE AGREEMENTS.
 *
 *          Copyright (c) 2013 AT&T Knowledge Ventures
 *              Unpublished and Not for Publication
 *                     All Rights Reserved
 */
package org.apache.openaz.xacml.pdp.policy;

import java.util.Iterator;

import org.apache.openaz.xacml.api.AttributeValue;
import org.apache.openaz.xacml.api.Status;
import org.apache.openaz.xacml.std.StdStatus;

/**
 * ExpressionResult is the object returned by the <code>evaluate</code> method of {@link Expression} objects.
 */
public abstract class ExpressionResult implements FunctionArgument {
    private Status status;

    /**
     * ExpressionResultError extends <code>ExpressionResult</code> to represent error results.
     */
    private static class ExpressionResultError extends ExpressionResult {
        public ExpressionResultError(Status statusIn) {
            super(statusIn);
        }

        @Override
        public AttributeValue<?> getValue() {
            return null;
        }

        @Override
        public boolean isBag() {
            return false;
        }

        @Override
        public Bag getBag() {
            return null;
        }
    }

    /**
     * ExpressionResultSingle extends <code>ExpressionResult</code> to represent results with a single value.
     */
    private static class ExpressionResultSingle extends ExpressionResult {
        AttributeValue<?> attributeValue;

        public ExpressionResultSingle(AttributeValue<?> attributeValueIn) {
            super(StdStatus.STATUS_OK);
            this.attributeValue = attributeValueIn;
        }

        @Override
        public AttributeValue<?> getValue() {
            return this.attributeValue;
        }

        @Override
        public boolean isBag() {
            return false;
        }

        @Override
        public Bag getBag() {
            return null;
        }
    }

    private static class ExpressionResultBag extends ExpressionResult {
        private Bag bag;

        public ExpressionResultBag(Bag bagIn) {
            super(StdStatus.STATUS_OK);
            this.bag = bagIn;
        }

        @Override
        public AttributeValue<?> getValue() {
            Iterator<AttributeValue<?>> iter = this.bag.getAttributeValues();
            if (iter != null && iter.hasNext()) {
                return iter.next();
            } else {
                return null;
            }
        }

        @Override
        public boolean isBag() {
            return true;
        }

        @Override
        public Bag getBag() {
            return this.bag;
        }
    }

    private static class ExpressionResultEmptyBag extends ExpressionResult {
        public ExpressionResultEmptyBag() {
            super(StdStatus.STATUS_OK);
        }

        @Override
        public AttributeValue<?> getValue() {
            return null;
        }

        @Override
        public boolean isBag() {
            return true;
        }

        @Override
        public Bag getBag() {
            return Bag.EMPTY;
        }
    }

    /**
     * Creates a new <code>ExpressionResult</code> with the given {@link org.apache.openaz.xacml.api.Status}.
     *
     * @param statusIn the <code>Status</code> of this <code>ExpressionResult</code>
     */
    protected ExpressionResult(Status statusIn) {
        this.status = statusIn;
    }

    /**
     * Gets the <code>Status</code> for this <code>ExpressionResult</code>.
     *
     * @return the <code>Status</code> for this <code>ExpressionResult</code>
     */
    @Override
    public Status getStatus() {
        return this.status;
    }

    /**
     * Shortcut procedure for determining if the <code>Status</code> of this <code>ExpressionResult</code> is
     * OK.
     *
     * @return true if the <code>Status</code> is null or has a <code>StatusCode</code> value of
     *         <code>STATUS_CODE_OK</code>.
     */
    @Override
    public boolean isOk() {
        return this.getStatus() == null || this.getStatus().isOk();
    }

    /**
     * Gets the single {@link org.apache.openaz.xacml.api.AttributeValue} from this
     * <code>ExpressionResult</code>. If this <code>ExpressionResult</code> represents a bag, the first
     * element in the bag is returned.
     *
     * @return a single <code>AttributeValue</code> from this <code>ExpressionResult</code>
     */
    @Override
    public abstract AttributeValue<?> getValue();

    /**
     * Determines if this <code>ExpressionResult</code> represents a bag of <code>AttributeValue</code>s or
     * not.
     *
     * @return true if this <code>ExpressionResult</code> represents a bag of <code>AttributeValue</code>s,
     *         else false
     */
    @Override
    public abstract boolean isBag();

    /**
     * Gets the {@link Bag} of values for this <code>ExpressionResult</code> if there is one.
     *
     * @return the <code>Bag</code> of <code>AttributeValue</code>s for this <code>ExpressionResult</code>.
     */
    @Override
    public abstract Bag getBag();

    @Override
    public String toString() {
        StringBuilder stringBuilder = new StringBuilder("{");
        stringBuilder.append("isOk=" + this.isOk());
        stringBuilder.append(", isBag=" + this.isBag());
        Status thisStatus = this.getStatus();
        if (thisStatus != null) {
            stringBuilder.append(", status=");
            stringBuilder.append(thisStatus.toString());
        }
        AttributeValue<?> value = this.getValue();
        if (value != null) {
            stringBuilder.append(", value=");
            stringBuilder.append(value);
        }
        /*
         * Not sure if I want this dumped if (this.isBag()) { Bag bag = this.getBag(); if (bag != null) { } }
         */
        stringBuilder.append('}');
        return stringBuilder.toString();
    }

    /**
     * Creates a new instance of the <code>ExpressionResult</code> class representing an error.
     *
     * @param statusIn the <code>Status</code> containing the error information
     * @return a new <code>ExpressionResult</code> representing the error
     */
    public static ExpressionResult newError(Status statusIn) {
        return new ExpressionResultError(statusIn);
    }

    public static ExpressionResult newSingle(AttributeValue<?> attributeValue) {
        return new ExpressionResultSingle(attributeValue);
    }

    /**
     * Creates a new instance of the <code>ExpressionResult</code> class representing a bag of values from the
     * given <code>Bag</code>.
     *
     * @param bag the <code>Bag</code> for the new <code>ExpressionResult</code>
     * @return a new <code>ExpressionResult</code> representing the given <code>Bag</code>.
     */
    public static ExpressionResult newBag(Bag bag) {
        return new ExpressionResultBag(bag);
    }

    /**
     * Creates a new instance of the <code>ExpressionResult</code> class representing an empty bag of values.
     *
     * @return the <code>ExpressionResult</code> representing the empty bag of values of the expression
     */
    public static ExpressionResult newEmpty() {
        return new ExpressionResultEmptyBag();
    }

    public static ExpressionResult newInstance(Status statusIn) {
        if (statusIn.getStatusCode().equals(StdStatus.STATUS_OK.getStatusCode())) {
            return newEmpty();
        } else {
            return newError(statusIn);
        }
    }

}