/**
 * ServletList.java  1.00 11.13.97 Michael Shoffner
 *
 * Copyright (c) 1997 Shoffner/Hughes. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * for non-commercial purposes and without fee is hereby granted
 * provided that this copyright notice appears in all copies.
 *
 * shoffner@prominence.com
 */

package shoffner.step.jan;

import java.io.*;
import java.util.*;
import java.net.*;

import org.merlin.step.dec.*;
import org.merlin.step.dec.socket.*;

public class ServletList extends ObservableList implements Runnable {
  public static final int UPDATE_DELAY = 10 * 1000;
  
  URL server;
  IDList list;
  Thread processor;

  public ServletList (String host, String loc) {
    try {
      server = new URL ("http://" + host + "/" + loc);
    } catch (MalformedURLException ex) {
      ex.printStackTrace ();
    }
    list = new IDList ();
    update ();
    processor = new Thread (this);
    processor.start ();
  }

  public Enumeration elements () {
    return list.elements ();
  }
  
  public void addElement (Object element) {
    Object id = queryServer (new AddElementMsg (element));
    list.addElementWithID (id, element);
  }
  
  public void replaceElementAtEnd (Object oldE, Object newE) {
    Object oldID = list.getIDOfElement (oldE);
    Object id = queryServer (new ReplaceElementMsg (oldID, newE));
    if (id != null)
      list.replaceElementWithID (oldID, id, newE);
    else
      System.out.println ("Unknown id:" + oldID);
  }

  public void run () {
    while (true) {
      try {
        Thread.sleep (UPDATE_DELAY);
        update ();
      }
      catch (Exception ignored) {
        ignored.printStackTrace ();
      }
    }
  }

  public void stop () {
    if (processor != null) {
      processor.stop ();
      processor = null;
    }
  }

  void update () {
    InitMsg i = (InitMsg) queryServer (new UpdateMsg (list.getUpdateCount ()));
    System.err.println ("ServletList.update (): i == " + i);
    IDList initList = i.getList ();
    if (initList != null) {
      list = initList;
      fireUpdate ();
    }
  }

  Object queryServer (Object arg) {
    URLConnection con;
    ObjectOutputStream req = null;
    ObjectInputStream res = null;
    Object result = null;
    try {
      con = server.openConnection ();
      con.setDoOutput (true);
      req = new ObjectOutputStream (new BufferedOutputStream
                                    (con.getOutputStream ()));
      req.writeObject (arg);
      req.flush ();
      req.close ();

      res = new ObjectInputStream (new BufferedInputStream
                                   (con.getInputStream ()));
      result = res.readObject ();
    } catch (IOException ignored) {
      ignored.printStackTrace ();
    } catch (ClassNotFoundException ex) {
      ex.printStackTrace ();      
    } finally {
      try {
        res.close ();
      } catch (IOException ex) {}
    }
    return result;
  }
}