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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.entity.proxy;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.StringTokenizer;

import org.cristalise.kernel.common.ObjectNotFoundException;
import org.cristalise.kernel.entity.C2KLocalObject;
import org.cristalise.kernel.utils.Logger;


public class MemberSubscription implements Runnable {
    public static final String ERROR = "Error";
    public static final String END = "theEND";

    ItemProxy subject;
    String interest;
    // keep the subscriber by weak reference, so it is not kept from the garbage collector if no longer used
    WeakReference> observerReference;
    ArrayList contents = new ArrayList();
    boolean preLoad;

    public MemberSubscription(ProxyObserver observer, String interest, boolean preLoad) {
        setObserver(observer);
        this.interest = interest;
        this.preLoad = preLoad;
    }

    @Override
    public void run() {
        Thread.currentThread().setName("MemberSubscription:"+subject.getPath()+":"+interest);
        if (preLoad) loadChildren();
    }

    private void loadChildren() {
        C newMember;
        ProxyObserver observer = getObserver();
        if (observer == null) return; //reaped

        try {
            // fetch contents of path
            String children = subject.queryData(interest+"/all");
            StringTokenizer tok = new StringTokenizer(children, ",");
            ArrayList newContents = new ArrayList();
            
            while (tok.hasMoreTokens()) newContents.add(tok.nextToken());

            // look to see what's new
            for (String newChild: newContents) {
                // load child object
                try {
                    newMember = (C)subject.getObject(interest+"/"+newChild);
                    contents.remove(newChild);
                    observer.add(newMember);
                }
                catch (ObjectNotFoundException ex) {
                    observer.control(ERROR, "Listed member "+newChild+" was not found.");
                }
                catch (ClassCastException ex) {
                    Logger.error(ex);
                    observer.control(ERROR, "Listed member "+newChild+" was the wrong type.");
                }
            }
            // report what's left in old contents as deleted
            for (String oldChild: contents) {
                observer.remove(interest+"/"+oldChild);
            }
            //replace contents arraylist
            contents = newContents;
            //report that we're done
            observer.control(END, null);
        }
        catch (Exception ex) {
            observer.control(ERROR, "Query on "+interest+" failed with "+ex.getMessage());
        }
        Logger.msg(5, "MemberSubscription.loadChildren() -  DONE interest:"+interest);
    }

    public boolean isRelevant(String path) {
        Logger.msg(7, "MemberSubscription.isRelevant() - path "+path+" to "+interest);
        return (path.startsWith(interest));
    }

    public void update(String path, boolean deleted) {
        ProxyObserver observer = getObserver();
        if (observer == null) return; //reaped
        Logger.msg(7, "MemberSubscription.update() - path "+path +" for "+observer+". Interest: "+interest+" Was Deleted:"+deleted);

        if (!path.startsWith(interest)) // doesn't concern us
            return;

        if (path.equals(interest)) // refresh contents
            loadChildren();
        else {
            String name = path.substring(interest.length()+1);
            if (deleted) {
                Logger.msg(7, "MemberSubscription.update() - Removing path:"+path+" name:"+name);
                contents.remove(name);
                observer.remove(name);
            }
            else {
                try {
                    C newMember = (C)subject.getObject(path);
                    Logger.msg(7, "MemberSubscription.update() - Adding path:"+path+" name:"+name);
                    contents.add(name);
                    observer.add(newMember);
                }
                catch (ObjectNotFoundException e) {
                    Logger.error("MemberSubscription could not load path:"+path);
                    Logger.error(e);
                }
            }
        }
    }

    public void setObserver(ProxyObserver observer) {
        observerReference = new WeakReference>(observer);
    }

    public void setSubject(ItemProxy subject) {
        this.subject = subject;
    }

    public ProxyObserver getObserver() {
        return observerReference.get();
    }
}