package com.c2kernel.entity.proxy;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.StringTokenizer;

import com.c2kernel.common.ObjectNotFoundException;
import com.c2kernel.entity.C2KLocalObject;
import com.c2kernel.utils.Logger;

public class MemberSubscription implements Runnable {
    EntityProxy 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(EntityProxy subject, String interest, 
        EntityProxyObserver observer, boolean preLoad) {
        setObserver(observer);
        this.interest = interest;
        this.subject = subject;
        this.preLoad = preLoad;
    }

    public void run() {
        Thread.currentThread().setName("Member Subscription: "+subject.getSystemKey()+":"+interest);
        if (preLoad) loadChildren();
    }
    
    private void loadChildren() {
        C2KLocalObject newMember;
        EntityProxyObserver 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 (Iterator iter = newContents.iterator(); iter.hasNext();) {
                String newChild = (String)iter.next();
                
                // load child object
                try {
                    newMember = subject.getObject(interest+"/"+newChild);
                    contents.remove(newChild);
                } catch (ObjectNotFoundException ex) {
                    newMember = new MemberControl(MemberControl.ERROR, "Listed member "+newChild+" was not found.");
                }
                try {
                    observer.add(newMember);
                } catch (Throwable ex) {
                    Logger.error("Error publishing member to "+observer);
                    Logger.error(ex);
                }
            }
            // report what's left in old contents as deleted
            for (Iterator iter = contents.iterator(); iter.hasNext();) {
                String oldChild = (String)iter.next();
                observer.remove(interest+"/"+oldChild);
            }
            //replace contents arraylist
            contents = newContents;
            //report that we're done
            observer.add(MemberControl.theEND);
        } catch (Exception ex) {
            observer.add(new MemberControl(MemberControl.ERROR, "Query on "+interest+" failed with "+ex));
        }         
    }
    
    public boolean isRelevant(String path) {
        Logger.msg(7, "Checking relevance of "+path+" to "+interest);
        return (path.startsWith(interest));
    }
    
    public void update(String path, boolean deleted) {
        EntityProxyObserver observer = getObserver();
        if (observer == null) return; //reaped
        Logger.msg(7, "Processing proxy message 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());
            if (deleted) {
                Logger.msg(4, "Removing "+path);
                contents.remove(name);
                observer.remove(name);
            }
            else {                
                try {
                    C2KLocalObject newMember = subject.getObject(path);
                    Logger.msg(4, "Adding "+path);
                    contents.add(name);
                    observer.add(newMember);
                } catch (ObjectNotFoundException e) {
                    Logger.error("Member Subscription: could not load "+path);
                    Logger.error(e);
                }
            } 
        }
    }
    
    public void setObserver(EntityProxyObserver observer) {
        observerReference = new WeakReference(observer);
    }
    
    public EntityProxyObserver getObserver() {
        EntityProxyObserver observer = (EntityProxyObserver)observerReference.get();
        return observer;
    }
}