/*
    * 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.application.viewstate;
  
  import javax.faces.context.ExternalContext;
  import javax.faces.context.FacesContext;
  
  import org.apache.myfaces.application.StateCache;
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;
  import org.apache.myfaces.shared.util.WebConfigParamUtils;
  
  class ClientSideStateCacheImpl extends StateCache<Object, Object>
  {
      
      /**
       * Define the time in minutes where the view state is valid when
       * client side state saving is used. By default it is set to 0
       * (infinite).
       */
      @JSFWebConfigParam(since="2.1.9, 2.0.15", defaultValue="0", group="state")
      public static final String INIT_PARAM_CLIENT_VIEW_STATE_TIMEOUT = 
              "org.apache.myfaces.CLIENT_VIEW_STATE_TIMEOUT";
      public static final Long INIT_PARAM_CLIENT_VIEW_STATE_TIMEOUT_DEFAULT = 0L;
      
      private static final int STATE_PARAM = 0;
      private static final int VIEWID_PARAM = 1;
      private static final int TIMESTAMP_PARAM = 2;
      
      private static final Object[] EMPTY_STATES = new Object[]{null, null};
      
      private Long _clientViewStateTimeout;
  
      @Override
      public Object saveSerializedView(FacesContext facesContext,
              Object serializedView)
      {
          // The state in this case the state is saved on the token sent to
          // the client (isWriteStateAfterRenderViewRequired() is set to true).
          // No additional operation is required here.
          return encodeSerializedState(facesContext, serializedView);
      }
  
      @Override
      public Object restoreSerializedView(FacesContext facesContext,
              String viewId, Object viewState)
      {
          Object[] state = (Object[]) viewState;
          long clientViewStateTimeout = getClientViewStateTimeout(facesContext.getExternalContext());
          
          if (clientViewStateTimeout > 0L)
          {
              Long timeStamp = (Long) state[TIMESTAMP_PARAM];
              if (timeStamp == null)
              {
                  //If no timestamp, state is invalid.
                  return null;
              }
              long passedTime = (System.currentTimeMillis() - timeStamp.longValue()) / 60000;
              
              if (passedTime > clientViewStateTimeout)
              {
                  //expire
                  return null;
              }
          }
          
          String restoredViewId = (String) state[VIEWID_PARAM];
          
          if (viewId != null && !viewId.equals(restoredViewId))
          {
              //invalid viewId, expire
              return null;
          }
          
          //return the state
          if (state[STATE_PARAM] == null)
          {
              return EMPTY_STATES;
          }
          else
          {
              Object serializedView = state[STATE_PARAM];
              if (serializedView instanceof Object[] &&
             ((Object[])serializedView).length == 2 &&
             ((Object[])serializedView)[0] == null &&
             ((Object[])serializedView)[1] == null)
             {
                 // Remember inside the state null is stored as an empty array.
                 return null;
             }
             
             return state[STATE_PARAM];
         }
     }
 
     @Override
     public Object encodeSerializedState(FacesContext facesContext,
             Object serializedView)
     {
         Object[] state = null;
         
         if (getClientViewStateTimeout(facesContext.getExternalContext()).longValue() > 0L)
         {
             state = new Object[3];
             state[TIMESTAMP_PARAM] = System.currentTimeMillis();
         }
         else
         {
             state = new Object[2];
         }
         
         if (serializedView == null)
         {
             state[STATE_PARAM] = EMPTY_STATES;
         }
         else if (serializedView instanceof Object[] &&
             ((Object[])serializedView).length == 2 &&
             ((Object[])serializedView)[0] == null &&
             ((Object[])serializedView)[1] == null)
         {
             // The generated state can be considered zero, set it as null
             // into the map.
             state[STATE_PARAM] = null;
         }
         else
         {
             state[STATE_PARAM] = serializedView;
         }
 
         state[VIEWID_PARAM] = facesContext.getViewRoot().getViewId();
         
         return state;
     }
 
     @Override
     public boolean isWriteStateAfterRenderViewRequired(FacesContext facesContext)
     {
         return true;
     }
 
     /**
      * @return the _clientViewStateTimeout
      */
     protected Long getClientViewStateTimeout(ExternalContext context)
     {
         if (_clientViewStateTimeout == null)
         {
             _clientViewStateTimeout = WebConfigParamUtils.getLongInitParameter(
                     context, INIT_PARAM_CLIENT_VIEW_STATE_TIMEOUT,
                     INIT_PARAM_CLIENT_VIEW_STATE_TIMEOUT_DEFAULT);
             if (_clientViewStateTimeout.longValue() < 0L)
             {
                 _clientViewStateTimeout = 0L;
             }
         }
         return _clientViewStateTimeout;
     }
 
 }