/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe 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 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe 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 General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.frontend.fileupload;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  import org.mycore.common.MCRCache;
  import org.mycore.common.MCRSession;
  import org.mycore.common.MCRSessionMgr;
  import org.mycore.common.MCRUsageException;
  import org.mycore.common.processing.MCRProcessableCollection;
  import org.mycore.common.processing.MCRProcessableDefaultCollection;
  import org.mycore.common.processing.MCRProcessableRegistry;
  
  /**
   * @author Frank Lützenkirchen
   * @author Harald Richter
   * @author Jens Kupferschmidt
   * 
   * @version $Revision$
   */
  public class MCRUploadHandlerManager {
  
      private static Logger LOGGER = LogManager.getLogger(MCRUploadHandlerManager.class);
  
      /** Cache of currently active upload handler sessions */
      protected static MCRCache<String, MCRUploadHandlerCacheEntry> HANDLERS;
  
      protected static MCRProcessableCollection COLLECTION;
  
      static {
          HANDLERS = new MCRCache<>(100, "UploadHandlerManager UploadHandlers");
          COLLECTION = new MCRProcessableDefaultCollection("Upload Manager");
          MCRProcessableRegistry registry = MCRProcessableRegistry.getSingleInstance();
          registry.register(COLLECTION);
      }
  
      static void register(MCRUploadHandler handler) {
          LOGGER.debug("Registering {} with upload ID {}", handler.getClass().getName(), handler.getID());
          String sessionID = MCRSessionMgr.getCurrentSession().getID();
          HANDLERS.put(handler.getID(), new MCRUploadHandlerCacheEntry(sessionID, handler));
          COLLECTION.add(handler);
      }
  
      public static MCRUploadHandler getHandler(String uploadID) {
  
          long yesterday = System.currentTimeMillis() - 86400000;
          MCRUploadHandlerCacheEntry entry = HANDLERS.getIfUpToDate(uploadID, yesterday);
  
          if (entry == null) {
              throw new MCRUsageException("Upload session " + uploadID + " timed out");
          }
  
          String sessionID = entry.getSessionID();
  
          if (!sessionID.equals(MCRSessionMgr.getCurrentSessionID())) {
              MCRSession session = MCRSessionMgr.getSession(sessionID);
              if (session != null) {
                  MCRSessionMgr.setCurrentSession(session);
              }
          }
  
          return entry.getUploadHandler();
      }
  
      public static void unregister(String uploadID) {
          MCRUploadHandlerCacheEntry cacheEntry = HANDLERS.get(uploadID);
          HANDLERS.remove(uploadID);
          COLLECTION.remove(cacheEntry.handler);
      }
  
      /** Represents a cache entry of currently active upload handler session */
      private static class MCRUploadHandlerCacheEntry {
  
          /** The ID of the MCRSession this upload is associated with */
          private String sessionID;
  
          /** The MCRUploadHander instance to be used */
          private MCRUploadHandler handler;
  
          MCRUploadHandlerCacheEntry(String sessionID, MCRUploadHandler handler) {
              this.sessionID = sessionID;
              this.handler = handler;
         }
 
         public String getSessionID() {
             return sessionID;
         }
 
         public MCRUploadHandler getUploadHandler() {
             return handler;
         }
     }
 }