package gnu.crypto.sasl.srp;

// ----------------------------------------------------------------------------
// $Id: ClientStore.java,v 1.4 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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 2, or (at your option)
// any later version.
//
// GNU Crypto 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 this program; see the file COPYING.  If not, write to the
//
//    Free Software Foundation Inc.,
//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
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// not derived from or based on this library.  If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so.  If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import java.util.HashMap;

/**
 * <p>The client-side implementation of the SRP security context store.</p>
 *
 * @version $Revision: 1.4 $
 */
public class ClientStore {

   // Constants and variables
   // -------------------------------------------------------------------------

   /** The underlying singleton. */
   private static ClientStore singleton = null;

   /** The map of uid --> SASL Security Context record. */
   private static final HashMap uid2ssc = new HashMap();

   /** The map of sid --> Session timing record. */
   private static final HashMap uid2ttl = new HashMap();

   /** A synchronisation lock. */
   private static final Object lock = new Object();

   // Constructor(s)
   // -------------------------------------------------------------------------

   /** Private constructor to enforce Singleton pattern. */
   private ClientStore() {
      super();

      // TODO: add a cleaning timer thread
   }

   // Class methods
   // -------------------------------------------------------------------------

   /**
    * <p>Returns the classloader Singleton.</p>
    *
    * @return the classloader Singleton instance.
    */
   static synchronized final ClientStore instance() {
      if (singleton == null) {
         singleton = new ClientStore();
      }
      return singleton;
   }

   // Instance methods
   // -------------------------------------------------------------------------

   /**
    * <p>Returns a boolean flag indicating if the designated client's session is
    * still alive or not.</p>
    *
    * @param uid the identifier of the client whose session to check.
    * @return <code>true</code> if the designated client's session is still
    * alive. <code>false</code> otherwise.
    */
   boolean isAlive(final String uid) {
      final boolean result;
      synchronized(lock) {
         final Object obj = uid2ssc.get(uid);
         result = (obj != null);
         if (result) { // is it still alive?
            final StoreEntry sto = (StoreEntry) uid2ttl.get(uid);
            if (!sto.isAlive()) { // invalidate it
               uid2ssc.remove(uid);
               uid2ttl.remove(uid);
            }
         }
      }
      return result;
   }

   /**
    * <p>Records a mapping between a client's unique identifier and its security
    * context.</p>
    *
    * @param uid the unique identifier of the SRP client for which the session
    * is to be cached.
    * @param ttl the session's Time-To-Live indicator (in seconds).
    * @param ctx the client's security context.
    */
   void cacheSession(final String uid, final int ttl, final SecurityContext ctx) {
      synchronized(lock) {
         uid2ssc.put(uid, ctx);
         uid2ttl.put(uid, new StoreEntry(ttl));
      }
   }

   /**
    * <p>Removes the mapping between the designated SRP client unique identifier
    * and the its session security context (and other timing information).</p>
    *
    * @param uid the identifier of the client whose session is to invalidate.
    */
   void invalidateSession(final String uid) {
      synchronized(lock) {
         uid2ssc.remove(uid);
         uid2ttl.remove(uid);
      }
   }

   /**
    * <p>Returns an SRP client's security context record mapped by that client's
    * unique identifier.</p>
    *
    * @param uid the identifier of the client whose session is to restore.
    * @return the SRP client's security context.
    */
   SecurityContext restoreSession(final String uid) {
      final SecurityContext result;
      synchronized(lock) {
         result = (SecurityContext) uid2ssc.remove(uid);
         uid2ttl.remove(uid);
      }
      return result;
   }
}
