/*
 * @(#)LogicalFunction.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.cond;

import com.sun.xacml.EvaluationCtx;

import com.sun.xacml.attr.AttributeValue;
import com.sun.xacml.attr.BooleanAttribute;

import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;


/**
 * A class that implements the logical functions "or" and "and".
 * These functions take any number of boolean arguments and evaluate
 * them one at a time, starting with the first argument. As soon as
 * the result of the function can be determined, evaluation stops and
 * that result is returned. During this process, if any argument
 * evaluates to indeterminate, an indeterminate result is returned.
 *
 * @since 1.0
 * @author Steve Hanna
 * @author Seth Proctor
 */
public class LogicalFunction extends FunctionBase
{

    /**
     * Standard identifier for the or function.
     */
    public static final String NAME_OR = FUNCTION_NS + "or";

    /**
     * Standard identifier for the and function.
     */
    public static final String NAME_AND = FUNCTION_NS + "and";

    // internal identifiers for each of the supported functions
    private static final int ID_OR = 0;
    private static final int ID_AND = 1;

    /**
     * Creates a new <code>LogicalFunction</code> object.
     *
     * @param functionName the standard XACML name of the function to be
     *                     handled by this object, including the full namespace
     *
     * @throws IllegalArgumentException if the functionName is unknown
     */
    public LogicalFunction(String functionName) {
        super(functionName, getId(functionName), BooleanAttribute.identifier,
              false, -1, BooleanAttribute.identifier, false);
    }

    /**
     * Private helper that looks up the private id based on the function name.
     */
    private static int getId(String functionName) {
        if (functionName.equals(NAME_OR)) {
            return ID_OR;
        } else if (functionName.equals(NAME_AND)) {
            return ID_AND;
        } else {
            throw new IllegalArgumentException("unknown logical function: " +
                                               functionName);
        }
    }

    /**
     * Returns a <code>Set</code> containing all the function identifiers
     * supported by this class.
     *
     * @return a <code>Set</code> of <code>String</code>s
     */
    public static Set<String> getSupportedIdentifiers() {
        Set<String> set = new HashSet<String>();

        set.add(NAME_OR);
        set.add(NAME_AND);

        return set;
    }

    /**
     * Evaluate the function, using the specified parameters.
     *
     * @param inputs a <code>List</code> of <code>Evaluatable</code>
     *               objects representing the arguments passed to the function
     * @param context an <code>EvaluationCtx</code> so that the
     *                <code>Evaluatable</code> objects can be evaluated
     * @return an <code>EvaluationResult</code> representing the
     *         function's result
     */
    public EvaluationResult evaluate(List<Expression> inputs, EvaluationCtx context) {

        // Evaluate the arguments one by one. As soon as we can
        // return a result, do so. Return Indeterminate if any argument
        // evaluated is indeterminate.
        Iterator<Expression> it = inputs.iterator();
        while (it.hasNext()) {
            Evaluatable eval = (Evaluatable)(it.next());

            // Evaluate the argument
            EvaluationResult result = eval.evaluate(context);
            if (result.indeterminate()) {
                return result;
            }

            AttributeValue value = result.getAttributeValue();
            boolean argBooleanValue = ((BooleanAttribute)value).getValue();

            if (getFunctionId() == ID_OR) {
                if (argBooleanValue) {
                    return EvaluationResult.getTrueInstance();
                }
            } else if (getFunctionId() == ID_AND) {
                if (!argBooleanValue) {
                    return EvaluationResult.getFalseInstance();
                }
            }
        }

        if (getFunctionId() == ID_OR) {
            return EvaluationResult.getFalseInstance();
        }
        return EvaluationResult.getTrueInstance();
    }
}