
/*
 * @(#)AddFunction.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
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * 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,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * 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.cond;

import com.sun.xacml.EvaluationCtx;

import com.sun.xacml.attr.AttributeValue;
import com.sun.xacml.attr.DoubleAttribute;
import com.sun.xacml.attr.IntegerAttribute;

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


/**
 * A class that implements all the *-add functions. It takes two or more
 * operands of the appropriate type and returns the sum of the operands.
 * If any of the operands is indeterminate, an indeterminate result is
 * returned.
 *
 * @since 1.0
 * @author Steve Hanna
 * @author Seth Proctor
 */
public class AddFunction extends FunctionBase
{

    /**
     * Standard identifier for the integer-add function.
     */
    public static final String NAME_INTEGER_ADD =
        FUNCTION_NS + "integer-add";
    
    /**
     * Standard identifier for the double-add function.
     */
    public static final String NAME_DOUBLE_ADD =
        FUNCTION_NS + "double-add";

    // inernal identifiers for each of the supported functions
    private static final int ID_INTEGER_ADD = 0;
    private static final int ID_DOUBLE_ADD = 1;

    /**
     * Creates a new <code>AddFunction</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 function is unknown
     */
    public AddFunction(String functionName) {
        super(functionName, getId(functionName), getArgumentType(functionName),
              false, -1, 2, getArgumentType(functionName), false);
    }

    /**
     * Private helper that returns the internal identifier used for the
     * given standard function.
     */
    private static int getId(String functionName) {
        if (functionName.equals(NAME_INTEGER_ADD))
            return ID_INTEGER_ADD;
        else if (functionName.equals(NAME_DOUBLE_ADD))
            return ID_DOUBLE_ADD;
        else
            throw new IllegalArgumentException("unknown add function " +
                                               functionName);
    }

    /**
     * Private helper that returns the type used for the given standard
     * function. Note that this doesn't check on the return value since the
     * method always is called after getId, so we assume that the function
     * is present.
     */
    private static String getArgumentType(String functionName) {
        if (functionName.equals(NAME_INTEGER_ADD))
            return IntegerAttribute.identifier;
        else
            return DoubleAttribute.identifier;
    }

    /**
     * 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 getSupportedIdentifiers() {
        Set set = new HashSet();

        set.add(NAME_INTEGER_ADD);
        set.add(NAME_DOUBLE_ADD);

        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 inputs, EvaluationCtx context) {
        
        // Evaluate the arguments
        AttributeValue [] argValues = new AttributeValue[inputs.size()];
        EvaluationResult result = evalArgs(inputs, context, argValues);
        if (result != null)
            return result;
        
        // Now that we have real values, perform the add operation
        switch (getFunctionId()) {
        case ID_INTEGER_ADD: {
            long sum = 0;
            for (int index = 0; index < argValues.length; index++) {
                long arg = ((IntegerAttribute) argValues[index]).getValue();
                sum += arg;
            }
            
            result = new EvaluationResult(new IntegerAttribute(sum));
            break;
        }
        case ID_DOUBLE_ADD: {
            double sum = 0;
            for (int index = 0; index < argValues.length; index++) {
                double arg =
                    ((DoubleAttribute) argValues[index]).getValue();
                sum = sum + arg;
            }
            
            // Make it round half even, not round nearest
            double lower = Math.floor(sum);
            double higher = lower + 1;
            if ((sum - lower) == (higher - sum)) {
                if ((lower % 2) == 0)
                    sum = lower;
                else
                    sum = higher;
            }
            
            result = new EvaluationResult(new DoubleAttribute(sum));
            break;
        }
        }

        return result;
    }

}
