/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: NPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Netscape 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/NPL/
 *
 * 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 mozilla.org code.
 *
 * The Initial Developer of the Original Code is 
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *          Radha Kulkarni (radha@netscape.com)
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or 
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
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 * use your version of this file under the terms of the NPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the NPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "nsISupports.idl"

interface nsIHistoryEntry;
interface nsISHistoryListener;
interface nsISimpleEnumerator;
/**
 * An interface to the primary properties of the Session History
 * component. In an embedded browser environment, the nsIWebBrowser
 * object creates an instance of session history for each open window.
 * A handle to the session history object can be obtained from
 * nsIWebNavigation. In a non-embedded situation, the  owner of the
 * session history component must create a instance of it and set
 * it in the nsIWebNavigation object.
 * This interface is accessible from javascript. 
 *
 * @status FROZEN
 */
 

%{C++
#define NS_SHISTORY_CID \
{0x7294fe9c, 0x14d8, 0x11d5, {0x98, 0x82, 0x00, 0xC0, 0x4f, 0xa0, 0x2f, 0x40}}

#define NS_SHISTORY_CONTRACTID "@mozilla.org/browser/shistory;1"
%}

[scriptable, uuid(7294FE9B-14D8-11D5-9882-00C04FA02F40)]
interface nsISHistory: nsISupports
{
  /**
   * A readonly property of the interface that returns 
   * the number of toplevel documents currently available
   * in session history.
   */
   readonly attribute long count;

  /**
   * A readonly property of the interface that returns 
   * the index of the current document in session history.
   */
   readonly attribute long index;

  /**
   * A read/write property of the interface, used to Get/Set
   * the maximum number of toplevel documents, session history 
   * can hold for each instance. 
   */
   attribute long maxLength;

  /**
   * Called to obtain handle to the history entry at a
   * given index.
   *
   * @param index             The index value whose entry is requested.
   * @param modifyIndex       A boolean flag that indicates if the current
   *                          index of session history should be modified 
   *                          to the parameter index.
   *
   * @return                  <code>NS_OK</code> history entry for 
   *                          the index is obtained successfully.
   *                          <code>NS_ERROR_FAILURE</code> Error in obtaining
   *                          history entry for the given index.
   */
   nsIHistoryEntry getEntryAtIndex(in long index, in boolean modifyIndex);


  /**
   * Called to purge older documents from history.
   * Documents can be removed from session history for various 
   * reasons. For example to  control memory usage of the browser, to 
   * prevent users from loading documents from history, to erase evidence of
   * prior page loads etc...
   *
   * @param numEntries        The number of toplevel documents to be
   *                          purged from history. During purge operation,
   *                          the latest documents are maintained and older 
   *                          'numEntries' documents are removed from history.
   * @return                  <code>NS_OK</code> Purging was successfull
   *                          <code>NS_ERROR_FAILURE</code> numEntries is
   *                          invalid or out of bounds with the size of history.
   *                          
   */
   void PurgeHistory(in long numEntries);

  /**
   * Called to register a listener for the session history component.
   * Listeners are notified when pages are loaded or purged from history.
   * 
   * @param aListener         Listener object to be notified for all
   *                          page loads that initiate in session history.
   *
   * @note                    A listener object must implement 
   *                          nsISHistoryListener and nsSupportsWeakReference
   *
   * @see nsISHistoryListener
   * @see nsSupportsWeakReference
   */
   void addSHistoryListener(in nsISHistoryListener aListener);

  /**
   * Called to remove a listener for the session history component.
   * Listeners are notified when pages are loaded from history.
   * 
   * @param aListener         Listener object to be removed from 
   *                          session history.
   *
   * @note                    A listener object must implement 
   *                          nsISHistoryListener and nsSupportsWeakReference
   * @see nsISHistoryListener
   * @see nsSupportsWeakReference
   */ 
   void removeSHistoryListener(in nsISHistoryListener aListener);

  /**
   * Called to obtain a enumerator for all the  documents stored in 
   * session history. The enumerator object thus returned by this method
   * can be traversed using nsISimpleEnumerator. 
   *
   * @note  To access individual history entries of the enumerator, perform the
   *        following steps:
   *        1) Call nsISHistory->GetSHistoryEnumerator() to obtain handle 
   *           the nsISimpleEnumerator object.
   *        2) Use nsISimpleEnumerator->GetNext() on the object returned
   *           by step #1 to obtain handle to the next object in the list. 
   *           The object returned by this step is of type nsISupports.
   *        3) Perform a QueryInterface on the object returned by step #2 
   *           to nsIHistoryEntry.
   *        4) Use nsIHistoryEntry to access properties of each history entry. 
   *
   * @see nsISimpleEnumerator
   * @see nsIHistoryEntry
   * @see QueryInterface()
   * @see do_QueryInterface()
   */
   readonly attribute nsISimpleEnumerator SHistoryEnumerator;
};
