//
   //  ========================================================================
   //  Copyright (c) 1995-2013 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.server.session;
  
  import java.security.SecureRandom;
  import java.util.Random;
  
  import javax.servlet.http.HttpServletRequest;
  
  import org.eclipse.jetty.server.SessionIdManager;
  import org.eclipse.jetty.util.component.AbstractLifeCycle;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  public abstract class AbstractSessionIdManager extends AbstractLifeCycle implements SessionIdManager
  {
      private static final Logger LOG = Log.getLogger(AbstractSessionIdManager.class);
  
      private final static String __NEW_SESSION_ID="org.eclipse.jetty.server.newSessionId";  
      
      protected Random _random;
      protected boolean _weakRandom;
      protected String _workerName;
      protected long _reseed=100000L;
      
      /* ------------------------------------------------------------ */
      public AbstractSessionIdManager()
      {
      }
      
      /* ------------------------------------------------------------ */
      public AbstractSessionIdManager(Random random)
      {
          _random=random;
      }
  
  
      /* ------------------------------------------------------------ */
      /**
       * @return the reseed probability
       */
      public long getReseed()
      {
          return _reseed;
      }
  
      /* ------------------------------------------------------------ */
      /** Set the reseed probability.
       * @param reseed  If non zero then when a random long modulo the reseed value == 1, the {@link SecureRandom} will be reseeded.
       */
      public void setReseed(long reseed)
      {
          _reseed = reseed;
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Get the workname. If set, the workername is dot appended to the session
       * ID and can be used to assist session affinity in a load balancer.
       * 
       * @return String or null
       */
      public String getWorkerName()
      {
          return _workerName;
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Set the workname. If set, the workername is dot appended to the session
       * ID and can be used to assist session affinity in a load balancer.
       * 
       * @param workerName
       */
      public void setWorkerName(String workerName)
      {
          if (workerName.contains("."))
              throw new IllegalArgumentException("Name cannot contain '.'");
          _workerName=workerName;
      }
  
      /* ------------------------------------------------------------ */
      public Random getRandom()
     {
         return _random;
     }
 
     /* ------------------------------------------------------------ */
     public synchronized void setRandom(Random random)
     {
         _random=random;
         _weakRandom=false;
     }
     
     /* ------------------------------------------------------------ */
     /** 
      * Create a new session id if necessary.
      * 
      * @see org.eclipse.jetty.server.SessionIdManager#newSessionId(javax.servlet.http.HttpServletRequest, long)
      */
     public String newSessionId(HttpServletRequest request, long created)
     {
         synchronized (this)
         {
             if (request!=null)
             {
                 // A requested session ID can only be used if it is in use already.
                 String requested_id=request.getRequestedSessionId();
                 if (requested_id!=null)
                 {
                     String cluster_id=getClusterId(requested_id);
                     if (idInUse(cluster_id))
                         return cluster_id;
                 }
 
                 // Else reuse any new session ID already defined for this request.
                 String new_id=(String)request.getAttribute(__NEW_SESSION_ID);
                 if (new_id!=null&&idInUse(new_id))
                     return new_id;
             }
             
             // pick a new unique ID!
             String id=null;
             while (id==null||id.length()==0||idInUse(id))
             {
                 long r0=_weakRandom
                 ?(hashCode()^Runtime.getRuntime().freeMemory()^_random.nextInt()^(((long)request.hashCode())<<32))
                 :_random.nextLong();
                 if (r0<0)
                     r0=-r0;
 
 		// random chance to reseed
 		if (_reseed>0 && (r0%_reseed)== 1L)
 		{
 		    LOG.debug("Reseeding {}",this);
 		    if (_random instanceof SecureRandom)
 		    {
 			SecureRandom secure = (SecureRandom)_random;
 			secure.setSeed(secure.generateSeed(8));
 		    }
 		    else
 		    {
 			_random.setSeed(_random.nextLong()^System.currentTimeMillis()^request.hashCode()^Runtime.getRuntime().freeMemory());
 		    }
 		}
 
                 long r1=_weakRandom
                 ?(hashCode()^Runtime.getRuntime().freeMemory()^_random.nextInt()^(((long)request.hashCode())<<32))
                 :_random.nextLong();
                 if (r1<0)
                     r1=-r1;
                 id=Long.toString(r0,36)+Long.toString(r1,36);
                 
                 //add in the id of the node to ensure unique id across cluster
                 //NOTE this is different to the node suffix which denotes which node the request was received on
                 if (_workerName!=null)
                     id=_workerName + id;
             }
 
             request.setAttribute(__NEW_SESSION_ID,id);
             return id;
         }
     }
 
     /* ------------------------------------------------------------ */
     @Override
     protected void doStart() throws Exception
     {
        initRandom();
     }
     
     /* ------------------------------------------------------------ */
     @Override
     protected void doStop() throws Exception
     {
     }
     
     /* ------------------------------------------------------------ */
     /**
      * Set up a random number generator for the sessionids.
      * 
      * By preference, use a SecureRandom but allow to be injected.
      */
     public void initRandom ()
     {
         if (_random==null)
         {
             try
             {
                 _random=new SecureRandom();
             }
             catch (Exception e)
             {
                 LOG.warn("Could not generate SecureRandom for session-id randomness",e);
                 _random=new Random();
                 _weakRandom=true;
             }
         }
         else
             _random.setSeed(_random.nextLong()^System.currentTimeMillis()^hashCode()^Runtime.getRuntime().freeMemory()); 
     }
     
     
 }