/*
 * The contents of this file are subject to the Mozilla Public License Version 1.1
 * (the "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
 * 
 * Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
 * WARRANTY OF ANY KIND, either express or implied. See the License for the specific
 * language governing rights and limitations under the License.
 * 
 * The Original Code is the Venice Web Communities System.
 * 
 * The Initial Developer of the Original Code is Eric J. Bowersox <erbo@silcom.com>,
 * for Silverwrist Design Studios.  Portions created by Eric J. Bowersox are
 * Copyright (C) 2002 Eric J. Bowersox/Silverwrist Design Studios.  All Rights Reserved.
 * 
 * Contributor(s): 
 */
package com.silverwrist.venice.ui;

import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.silverwrist.venice.core.*;
import com.silverwrist.venice.ui.config.RootConfig;

public class NullSession implements VeniceUISession, VeniceUISessionFactory
{
  /*--------------------------------------------------------------------------------
   * Static data members
   *--------------------------------------------------------------------------------
   */

  private static NullSession self = null;

  /*--------------------------------------------------------------------------------
   * Constructor
   *--------------------------------------------------------------------------------
   */

  private NullSession()
  { // do nothing
  } // end constructor

  /*--------------------------------------------------------------------------------
   * Internal operations
   *--------------------------------------------------------------------------------
   */

  private final void bogus()
  {
    throw new IllegalStateException("null session is not valid");

  } // end bogus

  /*--------------------------------------------------------------------------------
   * Implementations from interface VeniceUISession
   *--------------------------------------------------------------------------------
   */

  public long getCreationTime()
  {
    bogus();
    return 0;

  } // end getCreationTime

  public String getID()
  {
    return null;

  } // end getID

  public long getLastAccessedTime()
  {
    return 0;

  } // end getLastAccessedTime

  public void setMaxInactiveInterval(int interval)
  { // do nothing
  } // end setMaxInactiveInterval

  public int getMaxInactiveInterval()
  {
    return -1;

  } // end getMaxInactiveInterval

  public Object getAttribute(String name)
  {
    bogus();
    return null;

  } // end getAttribute

  public Enumeration getAttributeNames()
  {
    bogus();
    return null;

  } // end getAttributeNames

  public void setAttribute(String name, Object o)
  {
    bogus();

  } // end setAttribute

  public void removeAttribute(String name)
  {
    bogus();

  } // end removeAttribute

  public void invalidate()
  {
    bogus();

  } // end invalidate

  public UserContext getUser()
  {
    bogus();
    return null;

  } // end getUser

  public void setUser(UserContext user)
  {
    bogus();

  } // end setUser

  public void preprocess(RequestInput ri)
  { // do nothing
  } // end preprocess

  /*--------------------------------------------------------------------------------
   * Implementations from interface VeniceUISessionFactory
   *--------------------------------------------------------------------------------
   */

  public VeniceUISession createSession(ServletContext ctxt, HttpServletRequest request,
				       HttpServletResponse response, VeniceEngine engine,
				       RootConfig config)
  {
    return this;

  } // end createSession

  /*--------------------------------------------------------------------------------
   * External static operations
   *--------------------------------------------------------------------------------
   */

  public static final synchronized NullSession get()
  {
    if (self==null)
      self = new NullSession();
    return self;

  } // end get

} // end class NullSession