
/*
 * @(#)FunctionBase.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.ctx.Status;

import java.net.URI;
import java.net.URISyntaxException;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


/**
 * An abstract utility superclass for functions. Supplies several useful
 * methods, making it easier to implement a <code>Function</code>. You can
 * extend this class or implement <code>Function</code> directly, depending
 * on your needs.
 *
 * @since 1.0
 * @author Steve Hanna
 * @author Seth Proctor
 */
public abstract class FunctionBase implements Function
{
    
    /**
     * The standard namespace where all the spec-defined functions live
     */
    public static final String FUNCTION_NS =
        "urn:oasis:names:tc:xacml:1.0:function:";

    // A List used by makeProcessingError() to save some steps.
    private static List processingErrList = null;

    // the name of this function
    private String functionName;

    // the id used by this function
    private int functionId;

    // the return type of this function, and whether it's a bag
    private String returnType;
    private boolean returnsBag;

    // flag that tells us which of the two constructors was used
    private boolean singleType;
    
    // parameter data if we're only using a single type
    private String paramType;
    private boolean paramIsBag;
    private int numParams;
    private int minParams;
    
    // paramater data if we're using different types
    private String [] paramTypes;
    private boolean [] paramsAreBags;

    /**
     * Constructor that sets up the function as having some number of
     * parameters all of the same given type. If <code>numParams</code> is
     * -1, then the length is variable
     *
     * @param functionName the name of this function as used by the factory
     *                     and any XACML policies
     * @param functionId an optional identifier that can be used by your
     *                   code for convenience
     * @param paramType the type of all parameters to this function, as used
     *                  by the factory and any XACML documents
     * @param paramIsBag whether or not every parameter is actually a bag
     *                   of values
     * @param numParams the number of parameters required by this function,
     *                  or -1 if any number are allowed
     * @param returnType the type returned by this function, as used by
     *                   the factory and any XACML documents
     * @param returnsBag whether or not this function returns a bag of values
     */
    public FunctionBase(String functionName, int functionId, String paramType,
                        boolean paramIsBag, int numParams,
                        String returnType, boolean returnsBag) {
        this(functionName, functionId, returnType, returnsBag);

        singleType = true;

        this.paramType = paramType;
        this.paramIsBag = paramIsBag;
        this.numParams = numParams;
        this.minParams = 0;
    }

    /**
     * Constructor that sets up the function as having some number of
     * parameters all of the same given type. If <code>numParams</code> is
     * -1, then the length is variable, and then <code>minParams</code> may
     * be used to specify a minimum number of parameters. If
     * <code>numParams</code> is not -1, then <code>minParams</code> is
     * ignored.
     *
     * @param functionName the name of this function as used by the factory
     *                     and any XACML policies
     * @param functionId an optional identifier that can be used by your
     *                   code for convenience
     * @param paramType the type of all parameters to this function, as used
     *                  by the factory and any XACML documents
     * @param paramIsBag whether or not every parameter is actually a bag
     *                   of values
     * @param numParams the number of parameters required by this function,
     *                  or -1 if any number are allowed
     * @param minParams the minimum number of parameters required if 
     *                  <code>numParams</code> is -1
     * @param returnType the type returned by this function, as used by
     *                   the factory and any XACML documents
     * @param returnsBag whether or not this function returns a bag of values
     */
    public FunctionBase(String functionName, int functionId, String paramType,
                        boolean paramIsBag, int numParams, int minParams,
                        String returnType, boolean returnsBag) {
        this(functionName, functionId, returnType, returnsBag);

        singleType = true;

        this.paramType = paramType;
        this.paramIsBag = paramIsBag;
        this.numParams = numParams;
        this.minParams = minParams;
    }


    /**
     * Constructor that sets up the function as having different types for
     * each given parameter.
     *
     * @param functionName the name of this function as used by the factory
     *                     and any XACML policies
     * @param functionId an optional identifier that can be used by your
     *                   code for convenience
     * @param paramTypes the type of each parameter, in order, required by
     *                   this function, as used by the factory and any XACML
     *                    documents
     * @param paramIsBag whether or not each parameter is actually a bag
     *                   of values
     * @param returnType the type returned by this function, as used by
     *                   the factory and any XACML documents
     * @param returnsBag whether or not this function returns a bag of values
     */
    public FunctionBase(String functionName, int functionId,
                        String [] paramTypes, boolean [] paramIsBag,
                        String returnType, boolean returnsBag) {
        this(functionName, functionId, returnType, returnsBag);

        singleType = false;

        this.paramTypes = paramTypes;
        this.paramsAreBags = paramIsBag;
    }

    /**
     * Constructor that sets up some basic values for functions that will
     * take care of parameter checking on their own. If you use this
     * constructor for your function class, then you must override the
     * two check methods to make sure that parameters are correct.
     *
     * @param functionName the name of this function as used by the factory
     *                     and any XACML policies
     * @param functionId an optional identifier that can be used by your
     *                   code for convenience
     * @param returnType the type returned by this function, as used by
     *                   the factory and any XACML documents
     * @param returnsBag whether or not this function returns a bag of values
     */
    public FunctionBase(String functionName, int functionId,
                        String returnType, boolean returnsBag) {
        this.functionName = functionName;
        this.functionId = functionId;
        this.returnType = returnType;
        this.returnsBag = returnsBag;
    }

    /**
     * Returns the full identifier of this function, as known by the factories.
     *
     * @return the function's identifier
     *
     * @throws IllegalArgumentException if the identifier isn't a valid URI
     */
    public URI getIdentifier() {
        // this is to get around the exception handling problems, but may
        // change if this code changes to include exceptions from the
        // constructors
        try {
            return new URI(functionName);
        } catch (URISyntaxException use) {
            throw new IllegalArgumentException("invalid URI");
        }
    }

    /**
     * Returns the name of the function to be handled by this particular
     * object.
     *
     * @return the function name
     */
    public String getFunctionName() {
        return functionName;
    }

    /**
     * Returns the Identifier of the function to be handled by this
     * particular object.
     *
     * @return the function Id
     */
    public int getFunctionId() {
        return functionId;
    }

    /**
     * Get the attribute type returned by this function.
     *
     * @return a <code>URI</code> indicating the attribute type
     *         returned by this function
     */
    public URI getReturnType() {
        try {
            return new URI(returnType);
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * Returns true if this function returns a bag of values.
     *
     * @return true if the function returns a bag, false otherwise
     */
    public boolean returnsBag() {
        return returnsBag;
    }

    /**
     * Returns the return type for this particular object.
     *
     * @return the return type
     */
    public String getReturnTypeAsString() {
        return returnType;
    }

    /**
     * Create an <code>EvaluationResult</code> that indicates a
     * processing error with the specified message. This method
     * may be useful to subclasses.
     *
     * @param message a description of the error
     *                (<code>null</code> if none)
     * @return the desired <code>EvaluationResult</code>
     */
    protected static EvaluationResult makeProcessingError(String message) {
        // Build up the processing error Status.
        if (processingErrList == null) {
            String [] errStrings = { Status.STATUS_PROCESSING_ERROR };
            processingErrList = Arrays.asList(errStrings);
        }
        Status errStatus = new Status(processingErrList, message);
        EvaluationResult processingError = new EvaluationResult(errStatus);

        return processingError;
    }

    /**
     * Evaluates each of the parameters, in order, filling in the argument
     * array with the resulting values. If any error occurs, this method
     * returns the error, otherwise null is returned, signalling that
     * evaluation was successful for all inputs, and the resulting argument
     * list can be used.
     *
     * @param params a <code>List</code> of <code>Evaluatable</code>
     *               objects representing the parameters to evaluate
     * @param context the representation of the request
     * @param args an array as long as the params <code>List</code> that
     *             will, on return, contain the <code>AttributeValue</code>s
     *             generated from evaluating all parameters
     *
     * @return <code>null</code> if no errors were encountered, otherwise
     *         an <code>EvaluationResult</code> representing the error
     */
    protected EvaluationResult evalArgs(List params, EvaluationCtx context,
                                        AttributeValue [] args) {
        Iterator it = params.iterator();
        int index = 0;

        while (it.hasNext()) {
            // get and evaluate the next parameter
            Evaluatable eval = (Evaluatable)(it.next());
            EvaluationResult result = eval.evaluate(context);

            // If there was an error, pass it back...
            if (result.indeterminate())
                return result;

            // ...otherwise save it and keep going
            args[index++] = result.getAttributeValue();
        }

        // if no error occurred then we got here, so we return no errors
        return null;
    }
    
    /**
     * Default handling of input checking. This does some simple checking
     * based on the type of constructor used. If you need anything more
     * complex, or if you used the simple constructor, then you must
     * override this method.
     *
     * @param inputs a <code>List></code> of <code>Evaluatable</code>s
     *
     * @throws IllegalArgumentException if the inputs won't work
     */
    public void checkInputs(List inputs) throws IllegalArgumentException {
        // first off, see what kind of function we are
        if (singleType) {
            // first, check the length of the inputs, if appropriate
            if (numParams != -1) {
                if (inputs.size() != numParams)
                    throw new IllegalArgumentException("wrong number of args" +
                                                       " to " + functionName);
            } else {
                if (inputs.size() < minParams)
                    throw new IllegalArgumentException("not enough args" +
                                                       " to " + functionName);
            }

            // now, make sure everything is of the same, correct type
            Iterator it = inputs.iterator();
            while (it.hasNext()) {
                Evaluatable eval = (Evaluatable)(it.next());

                if ((! eval.getType().toString().equals(paramType)) ||
                    (eval.evaluatesToBag() != paramIsBag))
                    throw new IllegalArgumentException("illegal parameter");
            }
        } else {
            // first, check the length of the inputs
            if (paramTypes.length != inputs.size())
                throw new IllegalArgumentException("wrong number of args" +
                                                   " to " + functionName);
            
            // now, make sure everything is of the same, correct type
            Iterator it = inputs.iterator();
            int i = 0;
            while (it.hasNext()) {
                Evaluatable eval = (Evaluatable)(it.next());

                if ((! eval.getType().toString().equals(paramTypes[i])) ||
                    (eval.evaluatesToBag() != paramsAreBags[i]))
                    throw new IllegalArgumentException("illegal parameter");

                i++;
            }
        }
    }

    /**
     * Default handling of input checking. This does some simple checking
     * based on the type of constructor used. If you need anything more
     * complex, or if you used the simple constructor, then you must
     * override this method.
     *
     * @param inputs a <code>List></code> of <code>Evaluatable</code>s
     *
     * @throws IllegalArgumentException if the inputs won't work
     */
    public void checkInputsNoBag(List inputs) throws IllegalArgumentException {
        // first off, see what kind of function we are
        if (singleType) {
            // first check to see if we need bags
            if (paramIsBag)
                throw new IllegalArgumentException(functionName + "needs" +
                                                   "bags on input");

            // now check on the length
            if (numParams != -1) {
                if (inputs.size() != numParams)
                    throw new IllegalArgumentException("wrong number of args" +
                                                       " to " + functionName);
            } else {
                if (inputs.size() < minParams)
                    throw new IllegalArgumentException("not enough args" +
                                                       " to " + functionName);
            }

            // finally check param list
            Iterator it = inputs.iterator();
            while (it.hasNext()) {
                Evaluatable eval = (Evaluatable)(it.next());

                if (! eval.getType().toString().equals(paramType))
                    throw new IllegalArgumentException("illegal parameter");
            }
        } else {
            // first, check the length of the inputs
            if (paramTypes.length != inputs.size())
                throw new IllegalArgumentException("wrong number of args" +
                                                   " to " + functionName);

            // now, make sure everything is of the same, correct type
            Iterator it = inputs.iterator();
            int i = 0;
            while (it.hasNext()) {
                Evaluatable eval = (Evaluatable)(it.next());

                if ((! eval.getType().toString().equals(paramTypes[i])) ||
                    (paramsAreBags[i]))
                    throw new IllegalArgumentException("illegal parameter");

                i++;
            }
        }
    }

}
