//
   //  ========================================================================
   //  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.nosql.mongodb;
  
  
  import java.net.UnknownHostException;
  import java.util.HashSet;
  import java.util.Random;
  import java.util.Set;
  import java.util.Timer;
  import java.util.TimerTask;
  import java.util.concurrent.TimeUnit;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpSession;
  
  import org.eclipse.jetty.server.Handler;
  import org.eclipse.jetty.server.Server;
  import org.eclipse.jetty.server.SessionManager;
  import org.eclipse.jetty.server.handler.ContextHandler;
  import org.eclipse.jetty.server.session.AbstractSessionIdManager;
  import org.eclipse.jetty.server.session.SessionHandler;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  import com.mongodb.BasicDBObject;
  import com.mongodb.BasicDBObjectBuilder;
  import com.mongodb.DBCollection;
  import com.mongodb.DBCursor;
  import com.mongodb.DBObject;
  import com.mongodb.Mongo;
  import com.mongodb.MongoException;
  
  /**
   * Based partially on the jdbc session id manager...
   *
   * Theory is that we really only need the session id manager for the local 
   * instance so we have something to scavenge on, namely the list of known ids
   * 
   * this class has a timer that runs at the scavenge delay that runs a query
   *  for all id's known to this node and that have and old accessed value greater
   *  then the scavengeDelay.
   *  
   * these found sessions are then run through the invalidateAll(id) method that 
   * is a bit hinky but is supposed to notify all handlers this id is now DOA and 
   * ought to be cleaned up.  this ought to result in a save operation on the session
   * that will change the valid field to false (this conjecture is unvalidated atm)
   */
  public class MongoSessionIdManager extends AbstractSessionIdManager
  {
      private final static Logger __log = Log.getLogger("org.eclipse.jetty.server.session");
  
      final static DBObject __version_1 = new BasicDBObject(MongoSessionManager.__VERSION,1);
      final static DBObject __valid_false = new BasicDBObject(MongoSessionManager.__VALID,false);
      final static DBObject __valid_true = new BasicDBObject(MongoSessionManager.__VALID,true);
  
      final static long __defaultScavengeDelay =  10 * 6 * 1000; // wait at least 10 minutes
      final static long __defaultScavengePeriod = 30 * 60 * 1000; // every 30 minutes
     
      
      final DBCollection _sessions;
      protected Server _server;
      private Timer _scavengeTimer;
      private Timer _purgeTimer;
      private TimerTask _scavengerTask;
      private TimerTask _purgeTask;
  
      
      
      private long _scavengeDelay = __defaultScavengeDelay;
      private long _scavengePeriod = __defaultScavengePeriod;
      
  
      /** 
       * purge process is enabled by default
       */
      private boolean _purge = true;
  
      /**
       * purge process would run daily by default
       */
      private long _purgeDelay = 24 * 60 * 60 * 1000; // every day
      
     /**
      * how long do you want to persist sessions that are no longer
      * valid before removing them completely
      */
     private long _purgeInvalidAge = 24 * 60 * 60 * 1000; // default 1 day
 
     /**
      * how long do you want to leave sessions that are still valid before
      * assuming they are dead and removing them
      */
     private long _purgeValidAge = 7 * 24 * 60 * 60 * 1000; // default 1 week
 
     
     /**
      * the collection of session ids known to this manager
      * 
      * TODO consider if this ought to be concurrent or not
      */
     protected final Set<String> _sessionsIds = new HashSet<String>();
     
 
     /* ------------------------------------------------------------ */
     public MongoSessionIdManager(Server server) throws UnknownHostException, MongoException
     {
         this(server, new Mongo().getDB("HttpSessions").getCollection("sessions"));
     }
 
     /* ------------------------------------------------------------ */
     public MongoSessionIdManager(Server server, DBCollection sessions)
     {
         super(new Random());
         
         _server = server;
         _sessions = sessions;
 
         _sessions.ensureIndex(
                 BasicDBObjectBuilder.start().add("id",1).get(),
                 BasicDBObjectBuilder.start().add("unique",true).add("sparse",false).get());
         _sessions.ensureIndex(
                 BasicDBObjectBuilder.start().add("id",1).add("version",1).get(),
                 BasicDBObjectBuilder.start().add("unique",true).add("sparse",false).get());
 
     }
  
     /* ------------------------------------------------------------ */
     /**
      * Scavenge is a process that periodically checks the tracked session
      * ids of this given instance of the session id manager to see if they 
      * are past the point of expiration.
      */
     protected void scavenge()
     {
         long now = System.currentTimeMillis();
         __log.debug("SessionIdManager:scavenge:at  " + now);        
         synchronized (_sessionsIds)
         {         
             /*
              * run a query returning results that:
              *  - are in the known list of sessionIds
              *  - have an accessed time less then current time - the scavenger period
              *  
              *  we limit the query to return just the __ID so we are not sucking back full sessions
              */
             BasicDBObject query = new BasicDBObject();     
             query.put(MongoSessionManager.__ID,new BasicDBObject("$in", _sessionsIds ));
          
             query.put(MongoSessionManager.__ACCESSED, new BasicDBObject("$lt",now - _scavengePeriod));
             
             DBCursor checkSessions = _sessions.find(query, new BasicDBObject(MongoSessionManager.__ID, 1));
                         
             for ( DBObject session : checkSessions )
             {             
                 __log.debug("SessionIdManager:scavenge: invalidating " + (String)session.get(MongoSessionManager.__ID));
                 invalidateAll((String)session.get(MongoSessionManager.__ID));
             }
         } 
         
     }
     
     /* ------------------------------------------------------------ */
     /**
      * ScavengeFully is a process that periodically checks the tracked session
      * ids of this given instance of the session id manager to see if they 
      * are past the point of expiration.
      * 
      * NOTE: this is potentially devastating and may lead to serious session
      * coherence issues, not to be used in a running cluster
      */
     protected void scavengeFully()
     {        
         __log.debug("SessionIdManager:scavengeFully");
 
         DBCursor checkSessions = _sessions.find();
 
         for (DBObject session : checkSessions)
         {
             invalidateAll((String)session.get(MongoSessionManager.__ID));
         }
 
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Purge is a process that cleans the mongodb cluster of old sessions that are no
      * longer valid.
      * 
      * There are two checks being done here:
      * 
      *  - if the accessed time is older then the current time minus the purge invalid age
      *    and it is no longer valid then remove that session
      *  - if the accessed time is older then the current time minus the purge valid age
      *    then we consider this a lost record and remove it
      *    
      *  NOTE: if your system supports long lived sessions then the purge valid age should be
      *  set to zero so the check is skipped.
      *  
      *  The second check was added to catch sessions that were being managed on machines 
      *  that might have crashed without marking their sessions as 'valid=false'
      */
     protected void purge()
     {
         BasicDBObject invalidQuery = new BasicDBObject();
 
         invalidQuery.put(MongoSessionManager.__ACCESSED, new BasicDBObject("$lt",System.currentTimeMillis() - _purgeInvalidAge));
         invalidQuery.put(MongoSessionManager.__VALID, false);
         
         DBCursor oldSessions = _sessions.find(invalidQuery, new BasicDBObject(MongoSessionManager.__ID, 1));
 
         for (DBObject session : oldSessions)
         {
             String id = (String)session.get("id");
             
             __log.debug("MongoSessionIdManager:purging invalid " + id);
             
             _sessions.remove(session);
         }
 
         if (_purgeValidAge != 0)
         {
             BasicDBObject validQuery = new BasicDBObject();
 
             validQuery.put(MongoSessionManager.__ACCESSED,new BasicDBObject("$lt",System.currentTimeMillis() - _purgeValidAge));
             validQuery.put(MongoSessionManager.__VALID, true);
 
             oldSessions = _sessions.find(validQuery,new BasicDBObject(MongoSessionManager.__ID,1));
 
             for (DBObject session : oldSessions)
             {
                 String id = (String)session.get(MongoSessionManager.__ID);
 
                 __log.debug("MongoSessionIdManager:purging valid " + id);
 
                 _sessions.remove(session);
             }
         }
 
     }
     
     /* ------------------------------------------------------------ */
     /**
      * Purge is a process that cleans the mongodb cluster of old sessions that are no
      * longer valid.
      * 
      */
     protected void purgeFully()
     {
         BasicDBObject invalidQuery = new BasicDBObject();
 
         invalidQuery.put(MongoSessionManager.__VALID, false);
         
         DBCursor oldSessions = _sessions.find(invalidQuery, new BasicDBObject(MongoSessionManager.__ID, 1));
         
         for (DBObject session : oldSessions)
         {
             String id = (String)session.get(MongoSessionManager.__ID);
             
             __log.debug("MongoSessionIdManager:purging invalid " + id);
             
             _sessions.remove(session);
         }
 
     }
     
     
     /* ------------------------------------------------------------ */
     public DBCollection getSessions()
     {
         return _sessions;
     }
     
     
     /* ------------------------------------------------------------ */
     public boolean isPurgeEnabled()
     {
         return _purge;
     }
     
     /* ------------------------------------------------------------ */
     public void setPurge(boolean purge)
     {
         this._purge = purge;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * sets the scavengeDelay
      */
     public void setScavengeDelay(long scavengeDelay)
     {
         if (scavengeDelay <= 0)
             this._scavengeDelay = __defaultScavengeDelay;
         else
             this._scavengeDelay = TimeUnit.SECONDS.toMillis(scavengeDelay);  
     }
 
 
     /* ------------------------------------------------------------ */
     public void setScavengePeriod(long scavengePeriod)
     {
         if (scavengePeriod <= 0)
             _scavengePeriod = __defaultScavengePeriod;
         else
             _scavengePeriod = TimeUnit.SECONDS.toMillis(scavengePeriod);
     }
 
     /* ------------------------------------------------------------ */
     public void setPurgeDelay(long purgeDelay)
     {
         if ( isRunning() )
         {
             throw new IllegalStateException();
         }
         
         this._purgeDelay = purgeDelay;
     }
  
     /* ------------------------------------------------------------ */
     public long getPurgeInvalidAge()
     {
         return _purgeInvalidAge;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * sets how old a session is to be persisted past the point it is
      * no longer valid
      */
     public void setPurgeInvalidAge(long purgeValidAge)
     {
         this._purgeInvalidAge = purgeValidAge;
     } 
     
     /* ------------------------------------------------------------ */
     public long getPurgeValidAge()
     {
         return _purgeValidAge;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * sets how old a session is to be persist past the point it is 
      * considered no longer viable and should be removed
      * 
      * NOTE: set this value to 0 to disable purging of valid sessions
      */
     public void setPurgeValidAge(long purgeValidAge)
     {
         this._purgeValidAge = purgeValidAge;
     } 
 
     /* ------------------------------------------------------------ */
     @Override
     protected void doStart() throws Exception
     {
         __log.debug("MongoSessionIdManager:starting");
      
         /*
          * setup the scavenger thread
          */
         if (_scavengeDelay > 0)
         {
             _scavengeTimer = new Timer("MongoSessionIdScavenger",true);
 
             synchronized (this)
             {
                 if (_scavengerTask != null)
                 {
                     _scavengerTask.cancel();
                 }
                 
                 _scavengerTask = new TimerTask()
                 {
                     @Override
                     public void run()
                     {
                         scavenge();
                     }
                 };
                 
                 _scavengeTimer.schedule(_scavengerTask,_scavengeDelay,_scavengePeriod);
             }
         }
         
         /*
          * if purging is enabled, setup the purge thread
          */
         if ( _purge )
         {
             _purgeTimer = new Timer("MongoSessionPurger", true);
             
             synchronized (this)
             {
                 if (_purgeTask != null)
                 {
                     _purgeTask.cancel();
                 }
                 _purgeTask = new TimerTask()
                 {
                     @Override
                     public void run()
                     {
                         purge();
                     }
                 };
                
                 _purgeTimer.schedule(_purgeTask,0,_purgeDelay);
             }
         }
     }
     
     /* ------------------------------------------------------------ */
     @Override
     protected void doStop() throws Exception
     {
         if (_scavengeTimer != null)
         {
             _scavengeTimer.cancel();
             _scavengeTimer = null;
         }
         
         if (_purgeTimer != null)
         {
             _purgeTimer.cancel();
             _purgeTimer = null;
         }
         
         super.doStop();
     }
 
     /* ------------------------------------------------------------ */
     /**
      * is the session id known to mongo, and is it valid
      */
     @Override
     public boolean idInUse(String sessionId)
     {        
         /*
          * optimize this query to only return the valid variable
          */
         DBObject o = _sessions.findOne(new BasicDBObject("id",sessionId), __valid_true);
         
         if ( o != null )
         {                    
             Boolean valid = (Boolean)o.get(MongoSessionManager.__VALID);
             
             if ( valid == null )
             {
                 return false;
             }
             
             return valid;
         }
         
         return false;
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public void addSession(HttpSession session)
     {
         if (session == null)
         {
             return;
         }
         
         /*
          * already a part of the index in mongo...
          */
         
         __log.debug("MongoSessionIdManager:addSession:" + session.getId());
         
         synchronized (_sessionsIds)
         {
             _sessionsIds.add(session.getId());
         }
         
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public void removeSession(HttpSession session)
     {
         if (session == null)
         {
             return;
         }
         
         synchronized (_sessionsIds)
         {
             _sessionsIds.remove(session.getId());
         }
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public void invalidateAll(String sessionId)
     {
         synchronized (_sessionsIds)
         {
             _sessionsIds.remove(sessionId);
             
             
             //tell all contexts that may have a session object with this id to
             //get rid of them
             Handler[] contexts = _server.getChildHandlersByClass(ContextHandler.class);
             for (int i=0; contexts!=null && i<contexts.length; i++)
             {
                 SessionHandler sessionHandler = ((ContextHandler)contexts[i]).getChildHandlerByClass(SessionHandler.class);
                 if (sessionHandler != null) 
                 {
                     SessionManager manager = sessionHandler.getSessionManager();
 
                     if (manager != null && manager instanceof MongoSessionManager)
                     {
                         ((MongoSessionManager)manager).invalidateSession(sessionId);
                     }
                 }
             }
         }      
     } 
     
     /* ------------------------------------------------------------ */
     @Override
     public void renewSessionId(String oldClusterId, String oldNodeId, HttpServletRequest request)
     {
         //generate a new id
         String newClusterId = newSessionId(request.hashCode());
 
         synchronized (_sessionsIds)
         {
             _sessionsIds.remove(oldClusterId);//remove the old one from the list
             _sessionsIds.add(newClusterId); //add in the new session id to the list
 
             //tell all contexts to update the id 
             Handler[] contexts = _server.getChildHandlersByClass(ContextHandler.class);
             for (int i=0; contexts!=null && i<contexts.length; i++)
             {
                 SessionHandler sessionHandler = ((ContextHandler)contexts[i]).getChildHandlerByClass(SessionHandler.class);
                 if (sessionHandler != null) 
                 {
                     SessionManager manager = sessionHandler.getSessionManager();
 
                     if (manager != null && manager instanceof MongoSessionManager)
                     {
                         ((MongoSessionManager)manager).renewSessionId(oldClusterId, oldNodeId, newClusterId, getNodeId(newClusterId, request));
                     }
                 }
             }
         }
     }
 
 }