/*
 * Copyright (c) 1998-2008 Caucho Technology -- all rights reserved
 *
 * This file is part of Resin(R) Open Source
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Resin Open Source is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Resin Open Source is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Resin Open Source; if not, write to the
 *
 *   Free Software Foundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.quercus.env;

import java.io.Serializable;

import com.caucho.quercus.QuercusException;
import com.caucho.quercus.program.ClassDef;

/**
 * Represents a PHP null value, used for 
 */
public class NullThisValue extends NullValue
  implements Serializable
{
  public static final NullThisValue NULL = new NullThisValue();

  private ClassDef _classDef;
  
  protected NullThisValue()
  {
  }

  public NullThisValue(ClassDef classDef)
  {
    _classDef = classDef;
  }
  
  public NullThisValue(Env env, String clsName)
  {
    if (clsName != null)
      _classDef = env.findClassDef(clsName);
  }
  
  /**
   * Creates a null this context.
   */
  public static NullThisValue create()
  {
    return NULL;
  }

  /**
   * Returns true for an implementation of a class
   */
  @Override
  public boolean isA(String name)
  {
    if (_classDef != null)
      return _classDef.isA(name);
    else
      return false;
  }
  
  /*
   * Returns the object name of this value.
   */
  @Override
  public String getClassName()
  {
    if (_classDef != null)
      return _classDef.getName();
    else
      return null;
  }

  /**
   * Evaluates a method.
   */
  public Value callMethod(Env env, String methodName, Value []args)
  {
    throw new QuercusException(L.l("$this value of NULL cannot dispatch to method '{0}'.", methodName));
  }
  
  //
  // Java Serialization
  //
  
  private Object readResolve()
  {
    return NULL;
  }
}

