/*
    * 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.myfaces.shared.application;
  
  import java.util.logging.Level;
  import java.util.logging.Logger;
  import javax.faces.application.ProjectStage;
  import javax.faces.context.FacesContext;
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;
  import org.apache.myfaces.shared.util.ConcurrentLRUCache;
  import org.apache.myfaces.shared.util.WebConfigParamUtils;
  
  public class CheckedViewIdsCache
  {
      private static final Logger LOG = Logger.getLogger(CheckedViewIdsCache.class.getName());
      private static final String INSTANCE_KEY = CheckedViewIdsCache.class.getName();
      
      /**
       * Controls the size of the cache used to "remember" if a view exists or not.
       */
      @JSFWebConfigParam(defaultValue = "500", since = "2.0.2", group="viewhandler", tags="performance", 
              classType="java.lang.Integer",
              desc="Controls the size of the cache used to 'remember' if a view exists or not.")
      private static final String CHECKED_VIEWID_CACHE_SIZE_ATTRIBUTE = "org.apache.myfaces.CHECKED_VIEWID_CACHE_SIZE";
  
      /**
       * Enable or disable a cache used to "remember" if a view exists or not and reduce the impact of
       * sucesive calls to ExternalContext.getResource().
       */
      @JSFWebConfigParam(defaultValue = "true", since = "2.0.2", expectedValues="true, false", group="viewhandler", 
              tags="performance",
              desc="Enable or disable a cache used to 'remember' if a view exists or not and reduce the impact " +
                   "of sucesive calls to ExternalContext.getResource().")
      private static final String CHECKED_VIEWID_CACHE_ENABLED_ATTRIBUTE = 
          "org.apache.myfaces.CHECKED_VIEWID_CACHE_ENABLED";
  
      private volatile ConcurrentLRUCache<String, Boolean> cache = null;
      private boolean enabled;
      private int size;
      
      private CheckedViewIdsCache()
      {
      }
      
      public void init(FacesContext facesContext)
      {
          // first, check if the ProjectStage is development and skip caching in this case
          if (facesContext.isProjectStage(ProjectStage.Development))
          {
              enabled = false;
          }
          else
          {
              // in all ohter cases, make sure that the cache is not explicitly disabled via context param
              enabled = WebConfigParamUtils.getBooleanInitParameter(facesContext.getExternalContext(),
                      CHECKED_VIEWID_CACHE_ENABLED_ATTRIBUTE,
                      true);
          }
          
          size = WebConfigParamUtils.getIntegerInitParameter(facesContext.getExternalContext(),
                  CHECKED_VIEWID_CACHE_SIZE_ATTRIBUTE,
                  500);
  
          cache = new ConcurrentLRUCache<>((size * 4 + 3) / 3, size);
          
          if (LOG.isLoggable(Level.FINE))
          {
              LOG.log(Level.FINE, "MyFaces CheckedViewIdsCache enabled=" + enabled + ", size=" + size);
          }
      }
      
      public boolean isEnabled()
      {
          return enabled;
      }
      
      public ConcurrentLRUCache<String, Boolean> getCache()
      {
          return cache;
      }
      
      public static CheckedViewIdsCache getInstance(FacesContext facesContext)
      {
         CheckedViewIdsCache instance = (CheckedViewIdsCache)
                 facesContext.getExternalContext().getApplicationMap().get(INSTANCE_KEY);
         if (instance == null)
         {
             instance = new CheckedViewIdsCache();
             instance.init(facesContext);
             facesContext.getExternalContext().getApplicationMap().put(INSTANCE_KEY, instance);
         }
         
         return instance;
     }
 }