//
   //  ========================================================================
   //  Copyright (c) 1995-2016 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.Iterator;
  import java.util.Random;
  import java.util.Set;
  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.ConcurrentHashSet;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  import org.eclipse.jetty.util.thread.ScheduledExecutorScheduler;
  import org.eclipse.jetty.util.thread.Scheduler;
  
  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 JDBCSessionIdManager.
   * <p>
   * 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
   * <p>
   * This class has a timer that runs a periodic scavenger thread to query
   *  for all id's known to this node whose precalculated expiry time has passed.
   * <p>
   * 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 __defaultScavengePeriod = 30 * 60 * 1000; // every 30 minutes
     
      
      final DBCollection _sessions;
      protected Server _server;
      private Scheduler _scheduler;
      private boolean _ownScheduler;
      private Scheduler.Task _scavengerTask;
      private Scheduler.Task _purgerTask;
   
  
      
      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
      */
     protected final Set<String> _sessionsIds = new ConcurrentHashSet<>();
 
     /**
      * The maximum number of items to return from a purge query.
      */
     private int _purgeLimit = 0;
 
     private int _scavengeBlockSize;
     
     
     /**
      * Scavenger
      *
      */
     protected class Scavenger implements Runnable
     {
         @Override
         public void run()
         {
             try
             {
                 scavenge();
             }
             finally
             {
                 if (_scheduler != null && _scheduler.isRunning())
                     _scavengerTask = _scheduler.schedule(this, _scavengePeriod, TimeUnit.MILLISECONDS);
             }
         } 
     }
     
     
     /**
      * Purger
      *
      */
     protected class Purger implements Runnable
     {
         @Override
         public void run()
         {
             try
             {
                 purge();
             }
             finally
             {
                 if (_scheduler != null && _scheduler.isRunning())
                     _purgerTask = _scheduler.schedule(this, _purgeDelay, TimeUnit.MILLISECONDS);
             }
         }
     }
     
     
     
 
     /* ------------------------------------------------------------ */
     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());
 
         // index our accessed and valid fields so that purges are faster, note that the "valid" field is first
         // so that we can take advantage of index prefixes
         // http://docs.mongodb.org/manual/core/index-compound/#compound-index-prefix
         _sessions.ensureIndex(
                 BasicDBObjectBuilder.start().add(MongoSessionManager.__VALID, 1).add(MongoSessionManager.__ACCESSED, 1).get(),
                 BasicDBObjectBuilder.start().add("sparse", false).add("background", true).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);        
         /*
          * run a query returning results that:
          *  - are in the known list of sessionIds
          *  - the expiry time has passed
          *  
          *  we limit the query to return just the __ID so we are not sucking back full sessions
          *  
          *  break scavenge query into blocks for faster mongo queries
          */
         Set<String> block = new HashSet<String>();
             
         Iterator<String> itor = _sessionsIds.iterator();
         while (itor.hasNext())
         {
             block.add(itor.next());
             if ((_scavengeBlockSize > 0) && (block.size() == _scavengeBlockSize))
             {
                 //got a block
                 scavengeBlock (now, block);
                 //reset for next run
                 block.clear();
             }
         }
         
         //non evenly divisble block size, or doing it all at once
         if (!block.isEmpty())
             scavengeBlock(now, block);
     }
     
     
     /* ------------------------------------------------------------ */
     /**
      * Check a block of session ids for expiry and thus scavenge.
      * 
      * @param atTime purge at time
      * @param ids set of session ids
      */
     protected void scavengeBlock (long atTime, Set<String> ids)
     {
         if (ids == null)
             return;
         
         BasicDBObject query = new BasicDBObject();     
         query.put(MongoSessionManager.__ID,new BasicDBObject("$in", ids ));
         query.put(MongoSessionManager.__EXPIRY, new BasicDBObject("$gt", 0));
         query.put(MongoSessionManager.__EXPIRY, new BasicDBObject("$lt", atTime));   
             
         DBCursor checkSessions = _sessions.find(query, new BasicDBObject(MongoSessionManager.__ID, 1));
                         
         for ( DBObject session : checkSessions )
         {             
             __log.debug("SessionIdManager:scavenge: expiring session {}", (String)session.get(MongoSessionManager.__ID));
             expireAll((String)session.get(MongoSessionManager.__ID));
         }            
     }
     
     /* ------------------------------------------------------------ */
     /**
      * ScavengeFully will expire all sessions. In most circumstances
      * you should never need to call this method.
      * 
      * <b>USE WITH CAUTION</b>
      */
     protected void scavengeFully()
     {        
         __log.debug("SessionIdManager:scavengeFully");
 
         DBCursor checkSessions = _sessions.find();
 
         for (DBObject session : checkSessions)
         {
             expireAll((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 than 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()
     {
         __log.debug("PURGING");
         BasicDBObject invalidQuery = new BasicDBObject();
 
         invalidQuery.put(MongoSessionManager.__VALID, false);
         invalidQuery.put(MongoSessionManager.__ACCESSED, new BasicDBObject("$lt",System.currentTimeMillis() - _purgeInvalidAge));
         
         DBCursor oldSessions = _sessions.find(invalidQuery, new BasicDBObject(MongoSessionManager.__ID, 1));
 
         if (_purgeLimit > 0)
         {
             oldSessions.limit(_purgeLimit);
         }
 
         for (DBObject session : oldSessions)
         {
             String id = (String)session.get("id");
             
             __log.debug("MongoSessionIdManager:purging invalid session {}", id);
             
             _sessions.remove(session);
         }
 
         if (_purgeValidAge != 0)
         {
             BasicDBObject validQuery = new BasicDBObject();
 
             validQuery.put(MongoSessionManager.__VALID, true);
             validQuery.put(MongoSessionManager.__ACCESSED,new BasicDBObject("$lt",System.currentTimeMillis() - _purgeValidAge));
 
             oldSessions = _sessions.find(validQuery,new BasicDBObject(MongoSessionManager.__ID,1));
 
             if (_purgeLimit > 0)
             {
                 oldSessions.limit(_purgeLimit);
             }
 
             for (DBObject session : oldSessions)
             {
                 String id = (String)session.get(MongoSessionManager.__ID);
 
                 __log.debug("MongoSessionIdManager:purging valid session {}", 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 session {}", id);
             
             _sessions.remove(session);
         }
 
     }
     
     
     /* ------------------------------------------------------------ */
     public DBCollection getSessions()
     {
         return _sessions;
     }
     
     
     /* ------------------------------------------------------------ */
     public boolean isPurgeEnabled()
     {
         return _purge;
     }
     
     /* ------------------------------------------------------------ */
     public void setPurge(boolean purge)
     {
         this._purge = purge;
     }
 
 
     /* ------------------------------------------------------------ */
     /** 
      * The period in seconds between scavenge checks.
      * 
      * @param scavengePeriod the scavenge period in seconds
      */
     public void setScavengePeriod(long scavengePeriod)
     {
         if (scavengePeriod <= 0)
             _scavengePeriod = __defaultScavengePeriod;
         else
             _scavengePeriod = TimeUnit.SECONDS.toMillis(scavengePeriod);
     }
 
     /* ------------------------------------------------------------ */
     /** When scavenging, the max number of session ids in the query.
      * 
      * @param size the scavenge block size
      */
     public void setScavengeBlockSize (int size)
     {
         _scavengeBlockSize = size;
     }
 
     /* ------------------------------------------------------------ */
     public int getScavengeBlockSize ()
     {
         return _scavengeBlockSize;
     }
     
     
     /* ------------------------------------------------------------ */
     /**
      * The maximum number of items to return from a purge query. If &lt;= 0 there is no limit. Defaults to 0
      * 
      * @param purgeLimit the purge limit 
      */
     public void setPurgeLimit(int purgeLimit)
     {
         _purgeLimit = purgeLimit;
     }
 
     /* ------------------------------------------------------------ */
     public int getPurgeLimit()
     {
         return _purgeLimit;
     }
 
 
 
     /* ------------------------------------------------------------ */
     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
      * @param purgeValidAge the purge valid age
      */
     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
      * @param purgeValidAge the purge valid age
      */
     public void setPurgeValidAge(long purgeValidAge)
     {
         this._purgeValidAge = purgeValidAge;
     } 
 
     /* ------------------------------------------------------------ */
     @Override
     protected void doStart() throws Exception
     {
         __log.debug("MongoSessionIdManager:starting");
 
 
         synchronized (this)
         {
             //try and use a common scheduler, fallback to own
             _scheduler =_server.getBean(Scheduler.class);
             if (_scheduler == null)
             {
                 _scheduler = new ScheduledExecutorScheduler();
                 _ownScheduler = true;
                 _scheduler.start();
             }   
             else if (!_scheduler.isStarted())
                 throw new IllegalStateException("Shared scheduler not started");
             
 
             //setup the scavenger thread
             if (_scavengePeriod > 0)
             {
                 if (_scavengerTask != null)
                 {
                     _scavengerTask.cancel();
                     _scavengerTask = null;
                 }
 
                 _scavengerTask = _scheduler.schedule(new Scavenger(), _scavengePeriod, TimeUnit.MILLISECONDS);
             }
             else if (__log.isDebugEnabled())
                 __log.debug("Scavenger disabled");
 
 
             //if purging is enabled, setup the purge thread
             if ( _purge )
             { 
                 if (_purgerTask != null)
                 {
                     _purgerTask.cancel();
                     _purgerTask = null;
                 }
                 _purgerTask = _scheduler.schedule(new Purger(), _purgeDelay, TimeUnit.MILLISECONDS);
             }
             else if (__log.isDebugEnabled())
                 __log.debug("Purger disabled");
         }
     }
 
     /* ------------------------------------------------------------ */
     @Override
     protected void doStop() throws Exception
     {
         synchronized (this)
         {
             if (_scavengerTask != null)
             {
                 _scavengerTask.cancel();
                 _scavengerTask = null;
             }
  
             if (_purgerTask != null)
             {
                 _purgerTask.cancel();
                 _purgerTask = null;
             }
             
             if (_ownScheduler && _scheduler != null)
             {
                 _scheduler.stop();
                 _scheduler = null;
             }
         }
         super.doStop();
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Searches database to find if 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());
         
         _sessionsIds.add(session.getId());
         
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public void removeSession(HttpSession session)
     {
         if (session == null)
         {
             return;
         }
         
         _sessionsIds.remove(session.getId());
     }
 
     /* ------------------------------------------------------------ */
     /** Remove the session id from the list of in-use sessions.
      * Inform all other known contexts that sessions with the same id should be
      * invalidated.
      * @see org.eclipse.jetty.server.SessionIdManager#invalidateAll(java.lang.String)
      */
     @Override
     public void invalidateAll(String sessionId)
     {
         _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);
                 }
             }
         }
     }      
  
 
     /* ------------------------------------------------------------ */
     /**
      * Expire this session for all contexts that are sharing the session 
      * id.
      * @param sessionId the session id
      */
     public void expireAll (String sessionId)
     {
         _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).expire(sessionId);
                 }
             }
         }      
     }
     
     /* ------------------------------------------------------------ */
     @Override
     public void renewSessionId(String oldClusterId, String oldNodeId, HttpServletRequest request)
     {
         //generate a new id
         String newClusterId = newSessionId(request.hashCode());
 
         _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));
                 }
             }
         }
     }
 
 }