/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.shiro.session.mgt;
  
  import org.apache.shiro.authz.AuthorizationException;
  import org.apache.shiro.session.ExpiredSessionException;
  import org.apache.shiro.session.InvalidSessionException;
  import org.apache.shiro.session.Session;
  import org.apache.shiro.session.UnknownSessionException;
  import org.apache.shiro.util.Destroyable;
  import org.apache.shiro.util.LifecycleUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Collection;
  
  
  /**
   * Default business-tier implementation of the {@link ValidatingSessionManager} interface.
   *
   * @since 0.1
   */
  public abstract class AbstractValidatingSessionManager extends AbstractNativeSessionManager
          implements ValidatingSessionManager, Destroyable {
  
      //TODO - complete JavaDoc
  
      private static final Logger log = LoggerFactory.getLogger(AbstractValidatingSessionManager.class);
  
      /**
       * The default interval at which sessions will be validated (1 hour);
       * This can be overridden by calling {@link #setSessionValidationInterval(long)}
       */
      public static final long DEFAULT_SESSION_VALIDATION_INTERVAL = MILLIS_PER_HOUR;
  
      protected boolean sessionValidationSchedulerEnabled;
  
      /**
       * Scheduler used to validate sessions on a regular basis.
       */
      protected SessionValidationScheduler sessionValidationScheduler;
  
      protected long sessionValidationInterval;
  
      public AbstractValidatingSessionManager() {
          this.sessionValidationSchedulerEnabled = true;
          this.sessionValidationInterval = DEFAULT_SESSION_VALIDATION_INTERVAL;
      }
  
      public boolean isSessionValidationSchedulerEnabled() {
          return sessionValidationSchedulerEnabled;
      }
  
      @SuppressWarnings({"UnusedDeclaration"})
      public void setSessionValidationSchedulerEnabled(boolean sessionValidationSchedulerEnabled) {
          this.sessionValidationSchedulerEnabled = sessionValidationSchedulerEnabled;
      }
  
      public void setSessionValidationScheduler(SessionValidationScheduler sessionValidationScheduler) {
          this.sessionValidationScheduler = sessionValidationScheduler;
      }
  
      public SessionValidationScheduler getSessionValidationScheduler() {
          return sessionValidationScheduler;
      }
  
      private void enableSessionValidationIfNecessary() {
          SessionValidationScheduler scheduler = getSessionValidationScheduler();
          if (isSessionValidationSchedulerEnabled() && (scheduler == null || !scheduler.isEnabled())) {
              enableSessionValidation();
          }
      }
  
      /**
       * If using the underlying default <tt>SessionValidationScheduler</tt> (that is, the
       * {@link #setSessionValidationScheduler(SessionValidationScheduler) setSessionValidationScheduler} method is
       * never called) , this method allows one to specify how
       * frequently session should be validated (to check for orphans).  The default value is
       * {@link #DEFAULT_SESSION_VALIDATION_INTERVAL}.
       * <p/>
       * If you override the default scheduler, it is assumed that overriding instance 'knows' how often to
       * validate sessions, and this attribute will be ignored.
       * <p/>
      * Unless this method is called, the default value is {@link #DEFAULT_SESSION_VALIDATION_INTERVAL}.
      *
      * @param sessionValidationInterval the time in milliseconds between checking for valid sessions to reap orphans.
      */
     public void setSessionValidationInterval(long sessionValidationInterval) {
         this.sessionValidationInterval = sessionValidationInterval;
     }
 
     public long getSessionValidationInterval() {
         return sessionValidationInterval;
     }
 
     @Override
     protected final Session doGetSession(final SessionKey key) throws InvalidSessionException {
         enableSessionValidationIfNecessary();
 
         log.trace("Attempting to retrieve session with key {}", key);
 
         Session s = retrieveSession(key);
         if (s != null) {
             validate(s, key);
         }
         return s;
     }
 
     /**
      * Looks up a session from the underlying data store based on the specified session key.
      *
      * @param key the session key to use to look up the target session.
      * @return the session identified by {@code sessionId}.
      * @throws UnknownSessionException if there is no session identified by {@code sessionId}.
      */
     protected abstract Session retrieveSession(SessionKey key) throws UnknownSessionException;
 
     protected Session createSession(SessionContext context) throws AuthorizationException {
         enableSessionValidationIfNecessary();
         return doCreateSession(context);
     }
 
     protected abstract Session doCreateSession(SessionContext initData) throws AuthorizationException;
 
     protected void validate(Session session, SessionKey key) throws InvalidSessionException {
         try {
             doValidate(session);
         } catch (ExpiredSessionException ese) {
             onExpiration(session, ese, key);
             throw ese;
         } catch (InvalidSessionException ise) {
             onInvalidation(session, ise, key);
             throw ise;
         }
     }
 
     protected void onExpiration(Session s, ExpiredSessionException ese, SessionKey key) {
         log.trace("Session with id [{}] has expired.", s.getId());
         try {
             onExpiration(s);
             notifyExpiration(s);
         } finally {
             afterExpired(s);
         }
     }
 
     protected void onExpiration(Session session) {
         onChange(session);
     }
 
     protected void afterExpired(Session session) {
     }
 
     protected void onInvalidation(Session s, InvalidSessionException ise, SessionKey key) {
         if (ise instanceof ExpiredSessionException) {
             onExpiration(s, (ExpiredSessionException) ise, key);
             return;
         }
         log.trace("Session with id [{}] is invalid.", s.getId());
         try {
             onStop(s);
             notifyStop(s);
         } finally {
             afterStopped(s);
         }
     }
 
     protected void doValidate(Session session) throws InvalidSessionException {
         if (session instanceof ValidatingSession) {
             ((ValidatingSession) session).validate();
         } else {
             String msg = "The " + getClass().getName() + " implementation only supports validating " +
                     "Session implementations of the " + ValidatingSession.class.getName() + " interface.  " +
                     "Please either implement this interface in your session implementation or override the " +
                     AbstractValidatingSessionManager.class.getName() + ".doValidate(Session) method to perform validation.";
             throw new IllegalStateException(msg);
         }
     }
 
     /**
      * Subclass template hook in case per-session timeout is not based on
      * {@link org.apache.shiro.session.Session#getTimeout()}.
      * <p/>
      * <p>This implementation merely returns {@link org.apache.shiro.session.Session#getTimeout()}</p>
      *
      * @param session the session for which to determine session timeout.
      * @return the time in milliseconds the specified session may remain idle before expiring.
      */
     protected long getTimeout(Session session) {
         return session.getTimeout();
     }
 
     protected SessionValidationScheduler createSessionValidationScheduler() {
         ExecutorServiceSessionValidationScheduler scheduler;
 
         if (log.isDebugEnabled()) {
             log.debug("No sessionValidationScheduler set.  Attempting to create default instance.");
         }
         scheduler = new ExecutorServiceSessionValidationScheduler(this);
         scheduler.setInterval(getSessionValidationInterval());
         if (log.isTraceEnabled()) {
             log.trace("Created default SessionValidationScheduler instance of type [" + scheduler.getClass().getName() + "].");
         }
         return scheduler;
     }
 
     protected synchronized void enableSessionValidation() {
         SessionValidationScheduler scheduler = getSessionValidationScheduler();
         if (scheduler == null) {
             scheduler = createSessionValidationScheduler();
             setSessionValidationScheduler(scheduler);
         }
         // it is possible that that a scheduler was already created and set via 'setSessionValidationScheduler()'
         // but would not have been enabled/started yet
         if (!scheduler.isEnabled()) {
             if (log.isInfoEnabled()) {
                 log.info("Enabling session validation scheduler...");
             }
             scheduler.enableSessionValidation();
             afterSessionValidationEnabled();
         }
     }
 
     protected void afterSessionValidationEnabled() {
     }
 
     protected synchronized void disableSessionValidation() {
         beforeSessionValidationDisabled();
         SessionValidationScheduler scheduler = getSessionValidationScheduler();
         if (scheduler != null) {
             try {
                 scheduler.disableSessionValidation();
                 if (log.isInfoEnabled()) {
                     log.info("Disabled session validation scheduler.");
                 }
             } catch (Exception e) {
                 if (log.isDebugEnabled()) {
                     String msg = "Unable to disable SessionValidationScheduler.  Ignoring (shutting down)...";
                     log.debug(msg, e);
                 }
             }
             LifecycleUtils.destroy(scheduler);
             setSessionValidationScheduler(null);
         }
     }
 
     protected void beforeSessionValidationDisabled() {
     }
 
     public void destroy() {
         disableSessionValidation();
     }
 
     /**
      * @see ValidatingSessionManager#validateSessions()
      */
     public void validateSessions() {
         if (log.isInfoEnabled()) {
             log.info("Validating all active sessions...");
         }
 
         int invalidCount = 0;
 
         Collection<Session> activeSessions = getActiveSessions();
 
         if (activeSessions != null && !activeSessions.isEmpty()) {
             for (Session s : activeSessions) {
                 try {
                     //simulate a lookup key to satisfy the method signature.
                     //this could probably stand to be cleaned up in future versions:
                     SessionKey key = new DefaultSessionKey(s.getId());
                     validate(s, key);
                 } catch (InvalidSessionException e) {
                     if (log.isDebugEnabled()) {
                         boolean expired = (e instanceof ExpiredSessionException);
                         String msg = "Invalidated session with id [" + s.getId() + "]" +
                                 (expired ? " (expired)" : " (stopped)");
                         log.debug(msg);
                     }
                     invalidCount++;
                 }
             }
         }
 
         if (log.isInfoEnabled()) {
             String msg = "Finished session validation.";
             if (invalidCount > 0) {
                 msg += "  [" + invalidCount + "] sessions were stopped.";
             } else {
                 msg += "  No sessions were stopped.";
             }
             log.info(msg);
         }
     }
 
     protected abstract Collection<Session> getActiveSessions();
 }