/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Netscape Public License
 * Version 1.0 (the "NPL"); you may not use this file except in
 * compliance with the NPL.  You may obtain a copy of the NPL at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the NPL is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
 * for the specific language governing rights and limitations under the
 * NPL.
 *
 * The Initial Developer of this code under the NPL is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
 * Reserved.
 */

#ifndef nsITransactionManager_h__
#define nsITransactionManager_h__
#include "nsISupports.h"
#include "nsIOutputStream.h"
#include "nsITransaction.h"
// #include "nsITransactionListener.h"

/*
Transaction Manager interface to outside world
*/

#define NS_TRANSACTION_MANAGER_IID \
{ /* 58E330C2-7B48-11d2-98B9-00805F297D89 */ \
0x58e330c2, 0x7b48, 0x11d2, \
{ 0x98, 0xb9, 0x0, 0x80, 0x5f, 0x29, 0x7d, 0x89 } }; 


/**
 * A transaction manager specific interface. 
 * <P>
 * It's implemented by an object that tracks transactions.
 */
class nsITransactionManager  : public nsISupports{
public:

  /**
   * Execute() calls the transaction's Execute() method and  pushes it
   * on the undo queue. Execute() calls the transaction's AddRef() method.
   * The transaction's Release() method will be called when the undo or redo
   * stack is pruned or when the transaction manager is destroyed.
   *
   * @param nsITransaction *tx the transaction to execute.
   */
  virtual nsresult Execute(nsITransaction *tx) = 0;

  /**
   * Undo() pops the specified number of transactions off the undo stack,
   * calls their Undo() method, and pushes them onto the redo stack.
   *
   * @param PRInt32 n number of transactions to undo. n <= 0 means undo all
   * transactions.
   */
  virtual nsresult Undo(PRInt32 n) = 0;

  /**
   * Redo() pops the specified number of transactions off the redo stack,
   * calls their Redo() method, and pushes them onto the undo stack.
   *
   * @param PRInt32 n number of transactions to redo. n <= 0 means redo all
   * transactions previously undone.
   */
  virtual nsresult Redo(PRInt32 n) = 0;

  /**
   * Write() allows the transaction manager to output a stream representation
   * of itself, it then calls the Write() method of each transaction on the
   * undo and redo stacks.
   *
   * @param nsIOutputStream *os output stream for writing.
   */
  virtual nsresult Write(nsIOutputStream *os) = 0;

  /**
   * AddListener() adds the specified listener to the transaction manager's
   * list of listeners.  The listener is notified whenever a transaction is
   * executed, undone, or redone.  AddListener() calls the listener's AddRef()
   * method.
   *
   * @param nsITransactionListener *l the lister to add.
   */
  // virtual nsresult AddListener(nsITransactionListener *l) = 0;

  /**
   * RemoveListener() removes the specified listener from the transaction
   * manager's list of listeners.  Removing a listener that is not on the
   * transaction manager's list does nothing.  RemoveListener() calls the
   * listener's Release() method.
   *
   * @param nsITransactionListener *l the lister to add.
   */
  // virtual nsresult RemoveListener(nsITransactionListener *l) = 0;
};

#endif // nsITransactionManager