/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe 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 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe 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 MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.common;
  
  import java.io.Serializable;
  import java.util.Objects;
  import java.util.Optional;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  import org.mycore.frontend.servlets.MCRServlet;
  
  import jakarta.servlet.http.HttpSessionBindingEvent;
  import jakarta.servlet.http.HttpSessionBindingListener;
  
  /**
   * This Class will be stored in the a {@link jakarta.servlet.http.HttpSession} and can be used to resolve the
   * {@link MCRSession}. We can not store {@link MCRSession} directly in the {@link jakarta.servlet.http.HttpSession}
   * because values need to be {@link java.io.Serializable}.
   */
  public final class MCRSessionResolver implements Serializable, HttpSessionBindingListener {
  
      private static final Logger LOGGER = LogManager.getLogger();
  
      private final String sessionID;
  
      private MCRSessionResolver(final String sessionID) {
          this.sessionID = sessionID;
      }
  
      public MCRSessionResolver(final MCRSession session) {
          this(session.getID());
      }
  
      public String getSessionID() {
          return sessionID;
      }
  
      /**
       * Tries to resolve the {@link MCRSession} throught the {@link MCRSessionMgr}
       *
       * @return if is already closed it will return a {@link Optional#empty()}
       */
      public Optional<MCRSession> resolveSession() {
          return Optional.ofNullable(MCRSessionMgr.getSession(sessionID));
      }
  
      @Override
      public void valueBound(HttpSessionBindingEvent hsbe) {
          Object obj = hsbe.getValue();
          if (LOGGER.isDebugEnabled() && obj instanceof MCRSessionResolver) {
              LOGGER.debug("Bound MCRSession {} to HttpSession {}", ((MCRSessionResolver) obj).getSessionID(),
                  hsbe.getSession().getId());
          }
      }
  
      @Override
      public void valueUnbound(HttpSessionBindingEvent hsbe) {
          // hsbe.getValue() does not work right with tomcat
          Optional<MCRSessionResolver> newSessionResolver = Optional
              .ofNullable(hsbe.getSession().getAttribute(MCRServlet.ATTR_MYCORE_SESSION))
              .filter(o -> o instanceof MCRSessionResolver)
              .map(MCRSessionResolver.class::cast);
          MCRSessionResolver oldResolver = this;
          if (newSessionResolver.isPresent() && !oldResolver.equals(newSessionResolver.get())) {
              LOGGER.warn("Attribute {} is beeing unbound from session {} and replaced by {}!", hsbe.getName(),
                  oldResolver.getSessionID(), newSessionResolver.get());
              oldResolver.resolveSession().ifPresent(MCRSession::close);
          }
  
      }
  
      @Override
      public boolean equals(Object o) {
          if (this == o) {
              return true;
          }
          if (o == null || getClass() != o.getClass()) {
              return false;
          }
          MCRSessionResolver that = (MCRSessionResolver) o;
          return Objects.equals(getSessionID(), that.getSessionID());
      }
 
     @Override
     public int hashCode() {
         return Objects.hash(getSessionID());
     }
 
     @Override
     public String toString() {
         return "Resolver to " + getSessionID();
     }
 }