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Cristal-ise is a description-driven software platform originally developed to track the construction of the CMS ECAL detector of the LHC at CERN. This is its core library, known as the kernel, which manages business objects called Items. Items are entirely configured from data, called descriptions, held in other Items. Every change of a state in an Item is a consequence of an execution of an activity in that Item's lifecycle, meaning that Cristal-ise applications are completely traceable, even in their design. It also supports extensive versioning of Item description data, giving the system a high level of flexibility.

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/**
 * This file is part of the CRISTAL-iSE kernel.
 * Copyright (c) 2001-2015 The CRISTAL Consortium. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; with out even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * http://www.fsf.org/licensing/licenses/lgpl.html
 */
package org.cristalise.kernel.lifecycle.routingHelpers;

import org.cristalise.kernel.common.InvalidDataException;
import org.cristalise.kernel.common.ObjectNotFoundException;
import org.cristalise.kernel.common.PersistencyException;
import org.cristalise.kernel.lookup.ItemPath;
import org.cristalise.kernel.process.Gateway;
import org.cristalise.kernel.utils.Logger;

/**
 * Utility class to retrieve and resolve DataHelpers
 */
public class DataHelperUtility {

    /**
     * First checks the configuration properties to instantiate the requested Datahelper.
     * If there is such no property, it uses the given id to instantiate one of these classes:
     * {@link ViewpointDataHelper}, {@link PropertyDataHelper}, {@link ActivityDataHelper}
     *
     * @param id the string used to identify the DataHelper in the cristal-ise configuration
     * @return the DataHelper instance
     * @throws InvalidDataException could not configure DataHelper
     */
    public static DataHelper getDataHelper(String id) throws InvalidDataException {
        Object configHelper = Gateway.getProperties().getObject("DataHelper."+id);

        if (configHelper != null) {
            if (configHelper instanceof DataHelper)
                return (DataHelper)configHelper;
            else
                throw new InvalidDataException("Config value is not an instance of DataHelper - 'DataHelper."+id+"'=" +configHelper.toString());
        }
        else {
            switch (BuiltInDataHelpers.getValue(id)) {
                case VIEWPOINT_DH: return new ViewpointDataHelper();
                case PROPERTY_DH:  return new PropertyDataHelper();
                case ACTIVITY_DH:  return new ActivityDataHelper();

                default: throw new InvalidDataException("UNKOWN DataHelper id:"+id);
            }
        }
    }

    /**
     * If the
     *
     * @param itemPath the actual Item context
     * @param value the value to be evaluated
     * @param actContext activity path
     * @param locker database transaction locker
     * @return String value which was evaluated using {@link DataHelper} implementation
     *
     * @throws InvalidDataException data inconsistency
     * @throws PersistencyException persistency issue
     * @throws ObjectNotFoundException  object was not found
     */
    public static Object evaluateValue(ItemPath itemPath, Object value, String actContext, Object locker)
            throws InvalidDataException, PersistencyException, ObjectNotFoundException
    {
        if (value == null || !(value instanceof String) || !((String)value).contains("//"))
            return value;

        if(itemPath == null) throw new InvalidDataException("DataHelper must have ItemPath initialised");

        //Finding the first occurrence of '//' because DataHelper uses XPath which can start with '//'
        int i = ((String)value).indexOf("//");

        if (i == -1) throw new InvalidDataException("DataHelperUtility.evaluateValue() - Cannot locate '//' in value:"+value);

        String pathType = ((String)value).substring(0, i);
        String dataPath = ((String)value).substring(i+2);

        Logger.msg(5, "DataHelperUtility.evaluateValue() - pathType:"+pathType+" dataPath:"+dataPath);

        DataHelper dataHelper = getDataHelper(pathType);

        if (dataHelper != null) return dataHelper.get(itemPath, actContext, dataPath, locker);
        else                    return value;
    }
}