/*
    * Copyright 2018 Hippo B.V. (http://www.onehippo.com)
    * 
    * Licensed 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.onehippo.forge.hst.spring.support.session.servlet;
  
  import java.io.Serializable;
  import java.time.Duration;
  import java.time.Instant;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpSession;
  
  import org.springframework.session.Session;
  
  /**
   * {@link Session} implementation simply by delegating call to the underlying container's {@link HttpSession}.
   */
  public class HttpSessionDelegatingSession implements Session, Serializable {
  
      private static final long serialVersionUID = 1L;
  
      static final String NAME = HttpSessionDelegatingSession.class.getName();
  
      private static final String SESSION_ATTRS_MAP_KEY = HttpSessionDelegatingSession.class.getName() + ".sessionAttrsMap";
  
      private transient HttpSession httpSession;
      private Instant lastAccessedTime;
  
      HttpSessionDelegatingSession(final HttpSession httpSession) {
          this.httpSession = httpSession;
      }
  
      @Override
      public String getId() {
          return httpSession.getId();
      }
  
      @Override
      public <T> T getAttribute(String attributeName) {
          final Map<String, Object> sessionAttrs = (Map<String, Object>) httpSession.getAttribute(SESSION_ATTRS_MAP_KEY);
          return (sessionAttrs != null) ? (T) sessionAttrs.get(attributeName) : null;
      }
  
      @Override
      public Set<String> getAttributeNames() {
          final Map<String, Object> sessionAttrs = (Map<String, Object>) httpSession.getAttribute(SESSION_ATTRS_MAP_KEY);
  
          if (sessionAttrs == null) {
              return Collections.emptySet();
          }
  
          Set<String> attrNames;
  
          synchronized (sessionAttrs) {
              attrNames = new HashSet<>(sessionAttrs.keySet());
          }
  
          return Collections.unmodifiableSet(attrNames);
      }
  
      @Override
      public void setAttribute(String attributeName, Object attributeValue) {
          Map<String, Object> sessionAttrs = (Map<String, Object>) httpSession.getAttribute(SESSION_ATTRS_MAP_KEY);
  
          if (sessionAttrs == null) {
              sessionAttrs = new ConcurrentHashMap<>();
              httpSession.setAttribute(SESSION_ATTRS_MAP_KEY, sessionAttrs);
          }
  
          sessionAttrs.put(attributeName, attributeValue);
      }
  
      @Override
      public void removeAttribute(String attributeName) {
          final Map<String, Object> sessionAttrs = (Map<String, Object>) httpSession.getAttribute(SESSION_ATTRS_MAP_KEY);
  
          if (sessionAttrs != null) {
              sessionAttrs.remove(attributeName);
          }
      }
  
      @Override
     public Instant getCreationTime() {
         return Instant.ofEpochMilli(httpSession.getCreationTime());
     }
 
     @Override
     public void setLastAccessedTime(Instant lastAccessedTime) {
         this.lastAccessedTime = lastAccessedTime;
     }
 
     @Override
     public Instant getLastAccessedTime() {
         if (lastAccessedTime != null) {
             return lastAccessedTime;
         }
 
         return Instant.ofEpochMilli(httpSession.getLastAccessedTime());
     }
 
     @Override
     public void setMaxInactiveInterval(Duration interval) {
         httpSession.setMaxInactiveInterval((int) interval.getSeconds());
     }
 
     @Override
     public Duration getMaxInactiveInterval() {
         return Duration.ofSeconds(httpSession.getMaxInactiveInterval());
     }
 
     @Override
     public boolean isExpired() {
         final long lastAccessedTimeMillis = getLastAccessedTime().toEpochMilli();
         final long maxInactiveIntervalSeconds = getMaxInactiveInterval().getSeconds();
 
         if (System.currentTimeMillis() - lastAccessedTimeMillis > 1000L * maxInactiveIntervalSeconds) {
             return true;
         }
 
         return false;
     }
 
     @Override
     public String changeSessionId() {
         final HttpServletRequest request = HttpSessionDelegatingContext.getCurrentServletRequest();
         httpSession.invalidate();
         httpSession = request.getSession(true);
         return httpSession.getId();
     }
 
 }