/*
 * @(#)GeneralSetFunction.java
 *
 * Copyright 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.BagAttribute;

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


/**
 * Specific <code>SetFunction</code> class that supports all of the
 * general-purpose set functions: type-intersection and type-union.
 *
 * @since 1.2
 * @author Seth Proctor
 */
public class GeneralSetFunction extends SetFunction
{

    // private identifiers for the supported functions
    private static final int ID_BASE_INTERSECTION = 0;
    private static final int ID_BASE_UNION = 1;

    // mapping of function name to its associated id and parameter type
    private static HashMap idMap;
    private static HashMap typeMap;

    /**
     * Static initializer that sets up the paramater info for all the
     * supported functions.
     */
    static {
        idMap = new HashMap();
        typeMap = new HashMap();

        idMap.put(NAME_BASE_INTERSECTION, new Integer(ID_BASE_INTERSECTION));
        idMap.put(NAME_BASE_UNION, new Integer(ID_BASE_UNION));

        for (int i = 0; i < baseTypes.length; i++) {
            String baseName = FUNCTION_NS + simpleTypes[i];
            String baseType = baseTypes[i];

            idMap.put(baseName + NAME_BASE_INTERSECTION,
                      new Integer(ID_BASE_INTERSECTION));
            idMap.put(baseName + NAME_BASE_UNION,
                      new Integer(ID_BASE_UNION));

            typeMap.put(baseName + NAME_BASE_INTERSECTION, baseType);
            typeMap.put(baseName + NAME_BASE_UNION, baseType);
        }
    };
    
    /**
     * Constructor that is used to create one of the general-purpose standard
     * set functions. The name supplied must be one of the standard XACML
     * functions supported by this class, including the full namespace,
     * otherwise an exception is thrown. Look in <code>SetFunction</code>
     * for details about the supported names.
     *
     * @param functionName the name of the function to create
     *
     * @throws IllegalArgumentException if the function is unknown
     */
    public GeneralSetFunction(String functionName) {
        super(functionName, getId(functionName), getArgumentType(functionName),
              getArgumentType(functionName), true);
    }

    /**
     * Constructor that is used to create instances of general-purpose set
     * functions for new (non-standard) datatypes. This is equivalent to
     * using the <code>getInstance</code> methods in <code>SetFunction</code>
     * and is generally only used by the run-time configuration code.
     *
     * @param functionName the name of the new function
     * @param datatype the full identifier for the supported datatype
     * @param functionType which kind of Set function, based on the
     *                     <code>NAME_BASE_*</code> fields
     */
    public GeneralSetFunction(String functionName, String datatype,
                              String functionType) {
        super(functionName, getId(functionType), datatype, datatype, true);
    }

    /**
     * Private helper that returns the internal identifier used for the
     * given standard function.
     */
    private static int getId(String functionName) {
        Integer id = (Integer)(idMap.get(functionName));

        if (id == null)
            throw new IllegalArgumentException("unknown set function " +
                                               functionName);

        return id.intValue();
    }

    /**
     * Private helper that returns the argument type 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) {
        return (String)(typeMap.get(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 getSupportedIdentifiers() {
        return Collections.unmodifiableSet(idMap.keySet());
    }

    /**
     * Evaluates 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 evalResult = evalArgs(inputs, context, argValues);
        if (evalResult != null)
            return evalResult;

        // setup the two bags we'll be using
        BagAttribute [] bags = new BagAttribute[2];
        bags[0] = (BagAttribute)(argValues[0]);
        bags[1] = (BagAttribute)(argValues[1]);

        AttributeValue result = null;
        Set set = new HashSet();
        
        switch(getFunctionId()) {

            // *-intersection takes two bags of the same type and returns
            // a bag of that type
        case ID_BASE_INTERSECTION:
            // create a bag with the common elements of both inputs, removing
            // all duplicate values

            Iterator it = bags[0].iterator();

            // find all the things in bags[0] that are also in bags[1]
            while (it.hasNext()) {
                AttributeValue value = (AttributeValue)(it.next());
                if (bags[1].contains(value)) {
                    // sets won't allow duplicates, so this addition is ok
                    set.add(value);
                }
            }

            result = new BagAttribute(bags[0].getType(), set);

            break;

            // *-union takes two bags of the same type and returns a bag of
            // that type
        case ID_BASE_UNION:
            // create a bag with all the elements from both inputs, removing
            // all duplicate values

            Iterator it0 = bags[0].iterator();
            while (it0.hasNext()) {
                // first off, add all elements from the first bag...the set
                // will ignore all duplicates
                set.add(it0.next());
            }
            
            Iterator it1 = bags[1].iterator();
            while (it1.hasNext()) {
                // now add all the elements from the second bag...again, all
                // duplicates will be ignored by the set
                set.add(it1.next());
            }

            result = new BagAttribute(bags[0].getType(), set);

            break;
        }
        
        return new EvaluationResult(result);
    }

}