/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"
interface nsITransaction;

/*
 * The nsITransactionList interface.
 * <P>
 * The implementation for this interface is provided by the Transaction Manager.
 * This interface provides a mechanism for accessing the transactions on the
 * Undo or Redo stacks as well as any auto-aggregated children that a
 * transaction may have.
 */
[scriptable, uuid(97f863f3-f886-11d4-9d39-0060b0f8baff)]

interface nsITransactionList : nsISupports
{
  /**
   * The number of transactions contained in this list.
   */
  readonly attribute long numItems;

  /**
   * itemIsBatch() returns true if the item at aIndex is a batch. Note that
   * currently there is no requirement for a TransactionManager implementation
   * to associate a toplevel nsITransaction with a batch so it is possible for
   * itemIsBatch() to return true and getItem() to return null. However, you
   * can still access the transactions contained in the batch with a call to
   * getChildListForItem().
   * @param aIndex The index of the item in the list.
   */
  boolean itemIsBatch(in long aIndex);

  /**
   * getItem() returns the transaction at the given index in the list. Note that
   * a null can be returned here if the item is a batch. The transaction
   * returned is AddRef'd so it is up to the caller to Release the transaction
   * when it is done.
   * @param aIndex The index of the item in the list.
   */
  nsITransaction getItem(in long aIndex);

  /**
   * getNumChildrenForItem() returns the number of child (auto-aggreated)
   * transactions the item at aIndex has.
   * @param aIndex The index of the item in the list.
   */
  long getNumChildrenForItem(in long aIndex);

  /**
   * getChildListForItem() returns the list of children associated with the
   * item at aIndex. Implementations may return null if there are no children,
   * or an empty list. The list returned is AddRef'd so it is up to the caller
   * to Release the transaction when it is done.
   * @param aIndex The index of the item in the list.
   */
  nsITransactionList getChildListForItem(in long aIndex);
};