content: /*
   * This library is part of OpenCms -
   * the Open Source Content Management System
   *
   * Copyright (C) Alkacon Software (https://www.alkacon.com)
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library 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. See the GNU
   * Lesser General Public License for more details.
   *
   * For further information about Alkacon Software, please see the
   * company website: https://www.alkacon.com
   *
   * For further information about OpenCms, please see the
   * project website: https://www.opencms.org
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  package org.opencms.ade.sitemap;
  
  import org.opencms.file.CmsObject;
  import org.opencms.file.CmsUser;
  
  import java.util.concurrent.TimeUnit;
  
  import com.google.common.cache.Cache;
  import com.google.common.cache.CacheBuilder;
  
  /**
   * A class used to keep track of which user is editing the alias table from which sites.<p>
   *
   * It consists of a table from site roots to users. The entries of the table will be removed
   * if they haven't been updated in a given interval of time, but can also be removed manually.<p>
   *
   */
  public class CmsAliasEditorLockTable {
  
      /**
       * The interval after which a lock which has not been updated will be removed.<p>
       */
      public static final long TIMEOUT_INTERVAL = 60 * 1000;
  
      /**
       * Internal map from site roots to users.
       */
      private Cache<String, CmsUser> m_map;
  
      /**
       * Creates a new lock table instance.<p>
       */
      public CmsAliasEditorLockTable() {
  
          CacheBuilder<Object, Object> mm = CacheBuilder.newBuilder().expireAfterWrite(
              TIMEOUT_INTERVAL,
              TimeUnit.MILLISECONDS);
          m_map = mm.build();
      }
  
      /**
       * Clears the entry for a given site root, but only if the user from the given CMS context matches the user in the entry.<p>
       *
       * @param cms the current CMS context
       * @param siteRoot the site root for which the entry should be cleared
       */
      public void clear(CmsObject cms, String siteRoot) {
  
          CmsUser originalUser = m_map.getIfPresent(siteRoot);
          if ((originalUser == null) || !originalUser.equals(cms.getRequestContext().getCurrentUser())) {
              return;
          }
          m_map.invalidate(siteRoot);
      }
  
      /**
       * Tries to update or create an entry for the given user/site root combination.<p>
       *
       * If this method succeeds, it will return null, but if another user has created an entry for the site root,
       * it will return that user.<p>
       *
       * @param cms the current CMS context
       * @param siteRoot the site root
       *
       * @return null of the user who has already created an entry
       */
      public CmsUser update(CmsObject cms, String siteRoot) {
  
          CmsUser originalUser = m_map.getIfPresent(siteRoot);
          if ((originalUser == null) || originalUser.equals(cms.getRequestContext().getCurrentUser())) {
              m_map.put(siteRoot, cms.getRequestContext().getCurrentUser());
              return null;
          }
          return originalUser;
      }
  }
  