/*
 * @(#)AttributeFinder.java
 *
 * Copyright 2003-2006 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 org.wso2.balana.finder;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.wso2.balana.attr.AttributeValue;
import org.wso2.balana.ctx.EvaluationCtx;

import org.wso2.balana.attr.BagAttribute;

import org.wso2.balana.cond.EvaluationResult;

import java.net.URI;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.w3c.dom.Node;

/**
 * This class is used by the PDP to find attribute values that weren't originally supplied in the
 * request. It can be called with the data supplied in
 * <code>AttributeDesignator<code>s or <code>AttributeSelector</code>s. Because the modules in this
 * finder may themselves need attribute data to search for attribute data, it's possible that the
 * modules will look for values in the <code>EvaluationCtx</code>, which may in turn result in the
 * invocation of this finder again, so module writers need to be careful about how they build their
 * modules.
 * <p>
 * Note that unlike the PolicyFinder, this class doesn't always need to use every module it has to
 * find a value. The ordering is maintained, however, so it will always start with the first module,
 * and proceed in order until it finds a value or runs out of modules.
 * 
 * @since 1.0
 * @author Seth Proctor
 */
public class AttributeFinder {

    // the list of all modules
    private List<AttributeFinderModule> allModules;

    //
    private List<AttributeFinderModule> designatorModules;

    //
    private List<AttributeFinderModule> selectorModules;

    // the logger we'll use for all messages
    private static final Log logger = LogFactory.getLog(AttributeFinder.class);

    /**
     * Default constructor.
     */
    public AttributeFinder() {
        allModules = new ArrayList<AttributeFinderModule>();
        designatorModules = new ArrayList<AttributeFinderModule>();
        selectorModules = new ArrayList<AttributeFinderModule>();
    }

    /**
     * Returns the ordered <code>List</code> of <code>AttributeFinderModule</code>s used by this
     * class to find attribute values.
     * 
     * @return a <code>List</code> of <code>AttributeFinderModule</code>s
     */
    public List<AttributeFinderModule> getModules() {
        return new ArrayList<AttributeFinderModule>(allModules);
    }

    /**
     * Sets the ordered <code>List</code> of <code>AttributeFinderModule</code>s used by this class
     * to find attribute values. The ordering will be maintained.
     * 
     * @param modules a <code>List</code> of <code>AttributeFinderModule</code>s
     */
    public void setModules(List<AttributeFinderModule> modules) {
        Iterator it = modules.iterator();

        allModules = new ArrayList<AttributeFinderModule>(modules);
        designatorModules = new ArrayList<AttributeFinderModule>();
        selectorModules = new ArrayList<AttributeFinderModule>();

        while (it.hasNext()) {
            AttributeFinderModule module = (AttributeFinderModule) (it.next());

            if (module.isDesignatorSupported())
                designatorModules.add(module);

            if (module.isSelectorSupported())
                selectorModules.add(module);
        }
    }

    /**
     * Tries to find attribute values based on the given designator data. The result, if successful,
     * will always contain a <code>BagAttribute</code>, even if only one value was found. If no
     * values were found, but no other error occurred, an empty bag is returned.
     * 
     * @param attributeType the datatype of the attributes to find
     * @param attributeId the identifier of the attributes to find
     * @param issuer the issuer of the attributes, or null if unspecified
     * @param category the category of the attribute if the designatorType is SUBJECT_TARGET,
     *            otherwise null
     * @param context the representation of the request data
     * 
     * @return the result of attribute retrieval, which will be a bag of attributes or an error
     */
    public EvaluationResult findAttribute(URI attributeType, URI attributeId, String issuer,
            URI category, EvaluationCtx context) {
        Iterator it = designatorModules.iterator();

        // start with empty list of Attribute ValuesS
        List<AttributeValue> attributeValues = new ArrayList<AttributeValue>();

        // go through each module in order
        while (it.hasNext()) {
            AttributeFinderModule module = (AttributeFinderModule) (it.next());

            // see if the module supports this type, note: if supportedIds and supportedCategories are null
            // it implies that the module will resolve any type attributes
            if(module.getSupportedIds() != null && module.getSupportedCategories() != null){
                if (!module.getSupportedCategories().contains(category.toString()) ||
                        !module.getSupportedIds().contains(attributeId.toString())){
                       continue;
                }
            }

            // see if the module can find an attribute value
            EvaluationResult result = module.findAttribute(attributeType, attributeId, issuer,
                    category, context);

            // if there was an error, we stop right away
            if (result.indeterminate()) {
                logger.error("Error while trying to resolve values: "
                        + result.getStatus().getMessage());
                return result;
            }

            // if the result wasn't empty, add the found attributes to list of AttributeValues and continue iterating
            BagAttribute bag = (BagAttribute) (result.getAttributeValue());
            if (!bag.isEmpty()) {
                Iterator iterator = bag.iterator();
                while (iterator.hasNext()) {
                    AttributeValue attr = (AttributeValue) (iterator.next());
                    attributeValues.add(attr);
                }
            }

        }

        // check whether we were able to find any attributes, if not return an empty bag
        if (attributeValues.isEmpty()){
            // if we got here then there were no errors but there were also no
            // matches
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to resolve any values for " + attributeId.toString());
            }

        }

        return new EvaluationResult(new BagAttribute(attributeType,attributeValues));
    }

    /**
     * Tries to find attribute values based on the given selector data. The result, if successful,
     * must always contain a <code>BagAttribute</code>, even if only one value was found. If no
     * values were found, but no other error occurred, an empty bag is returned.
     * 
     * @param contextPath the XPath expression to search against
     * @param attributeType the datatype of the attributes to find
     * @param context the representation of the request data
     * @param xpathVersion the XPath version to use
     * 
     * @return the result of attribute retrieval, which will be a bag of attributes or an error
     */
    public EvaluationResult findAttribute(String contextPath, URI attributeType,
                                          EvaluationCtx context, String xpathVersion) {
        Iterator it = selectorModules.iterator();

        // start with empty list of Attribute Values
        List<AttributeValue> attributeValues = new ArrayList<AttributeValue>();

        // go through each module in order
        while (it.hasNext()) {
            AttributeFinderModule module = (AttributeFinderModule) (it.next());

            // see if the module can find an attribute value
            EvaluationResult result = module.findAttribute(contextPath,
                    attributeType, null, null, context, xpathVersion);

            // if there was an error, we stop right away
            if (result.indeterminate()) {
                logger.error("Error while trying to resolve values: "
                        + result.getStatus().getMessage());
                return result;
            }

            // if the result wasn't empty, add the found attributes to list of AttributeValues and continue iterating
            BagAttribute bag = (BagAttribute) (result.getAttributeValue());
            if (!bag.isEmpty()) {
                Iterator iterator = bag.iterator();
                while (iterator.hasNext()) {
                    AttributeValue attr = (AttributeValue) (iterator.next());
                    attributeValues.add(attr);
                }
            }
        }

        // check whether we were able to find any attributes, if not return an empty bag
        if (attributeValues.isEmpty()) {
            // if we got here then there were no errors but there were also no
            // matches
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to resolve any values for " + contextPath);
            }
        }

        return new EvaluationResult(new BagAttribute(attributeType,attributeValues));
    }

    /**
     * Tries to find attribute values based on the given selector data. The result, if successful,
     * must always contain a <code>BagAttribute</code>, even if only one value was found. If no
     * values were found, but no other error occurred, an empty bag is returned.
     *
     * @param contextPath the XPath expression to search against
     * @param contextSelector select the context to evaluate
     * @param attributeType the datatype of the attributes to find
     * @param root root XML node
     * @param context the representation of the request data
     * @param xpathVersion the XPath version to use
     *
     * @return the result of attribute retrieval, which will be a bag of attributes or an error
     */    
    public EvaluationResult findAttribute(String contextPath, String contextSelector, URI attributeType,
                        Node root, EvaluationCtx context, String xpathVersion) {

        Iterator it = selectorModules.iterator();

        // start with empty list of Attribute Values
        List<AttributeValue> attributeValues = new ArrayList<AttributeValue>();

        // go through each module in order
        while (it.hasNext()) {
            AttributeFinderModule module = (AttributeFinderModule) (it.next());

            // see if the module can find an attribute value
            EvaluationResult result = module.findAttribute(contextPath, 
                    attributeType, contextSelector, root, context, xpathVersion);

            // if there was an error, we stop right away
            if (result.indeterminate()) {
                logger.error("Error while trying to resolve values: "
                        + result.getStatus().getMessage());
                return result;
            }

            // if the result wasn't empty, add the found attributes to list of AttributeValues and continue iterating
            BagAttribute bag = (BagAttribute) (result.getAttributeValue());
            if (!bag.isEmpty()) {
                Iterator iterator = bag.iterator();
                while (iterator.hasNext()) {
                    AttributeValue attr = (AttributeValue) (iterator.next());
                    attributeValues.add(attr);
                }
            }
        }

        // check whether we were able to find any attributes, if not return an empty bag
        if (attributeValues.isEmpty()) {
            // if we got here then there were no errors but there were also no
            // matches
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to resolve any values for " + contextPath);
            }
        }

        return new EvaluationResult(new BagAttribute(attributeType,attributeValues));
    }

}
