/*
    * 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.context.flash;
  
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;
  import org.apache.myfaces.shared.util.ExternalContextUtils;
  
  import javax.faces.application.FacesMessage;
  import javax.faces.context.ExternalContext;
  import javax.faces.context.FacesContext;
  import javax.faces.context.Flash;
  import javax.faces.event.PhaseId;
  import javax.servlet.http.Cookie;
  import javax.servlet.http.HttpServletResponse;
  import java.io.Serializable;
  import java.math.BigInteger;
  import java.security.NoSuchAlgorithmException;
  import java.security.SecureRandom;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.atomic.AtomicLong;
  import java.util.logging.Logger;
  
  /**
   * Implementation of Flash object
   * 
   * @author Leonardo Uribe (latest modification by $Author: lu4242 $)
   * @author Jakob Korherr
   * @version $Revision: 1200044 $ $Date: 2011-11-09 18:44:02 -0500 (Wed, 09 Nov 2011) $
   */
  public class FlashImpl extends Flash
  {
      
      // ~ static fields --------------------------------------------------------
      
      private static final Logger log = Logger.getLogger(FlashImpl.class.getName());
      
      /**
       * Defines whether flash scope is disabled, preventing add the Flash cookie to the response. 
       * 
       * <p>This is useful for applications that does not require to use flash scope, and instead uses other scopes.</p>
       */
      @JSFWebConfigParam(defaultValue="false",since="2.0.5")
      private static final String FLASH_SCOPE_DISABLED_PARAM = "org.apache.myfaces.FLASH_SCOPE_DISABLED";
  
      /**
       * Use this prefix instead of the whole class name, because
       * this makes the Cookies and the SubKeyMap operations (actually
       * every String based operation where this is used as a key) faster.
       */
      private static final String FLASH_PREFIX = "oam.Flash";
      
      /**
       * Key on application map to keep current instance
       */
      static final String FLASH_INSTANCE = FLASH_PREFIX + ".INSTANCE";
  
      /**
       * Key to store if this setRedirect(true) was called on this request,
       * and to store the redirect Cookie.
       */
      static final String FLASH_REDIRECT = FLASH_PREFIX + ".REDIRECT";
      
      /**
       * Key to store the value of the redirect cookie
       */
      static final String FLASH_PREVIOUS_REQUEST_REDIRECT 
              = FLASH_PREFIX + ".REDIRECT.PREVIOUSREQUEST";
      
      /**
       * Key used to check if this request should keep messages
       */
      static final String FLASH_KEEP_MESSAGES = FLASH_PREFIX + ".KEEP_MESSAGES";
  
      /**
       * Key used to store the messages list in the render FlashMap.
       */
      static final String FLASH_KEEP_MESSAGES_LIST = "KEEPMESSAGESLIST";
  
     /**
      * Session map prefix to flash maps
      */
     static final String FLASH_SESSION_MAP_SUBKEY_PREFIX = FLASH_PREFIX + ".SCOPE";
     
     /**
      * Key for the cached render FlashMap instance on the request map.
      */
     static final String FLASH_RENDER_MAP = FLASH_PREFIX + ".RENDERMAP";
     
     /**
      * Key for the current render FlashMap token.
      */
     static final String FLASH_RENDER_MAP_TOKEN = FLASH_PREFIX + ".RENDERMAP.TOKEN";
     
     /**
      * Key for the cached execute FlashMap instance on the request map.
      */
     static final String FLASH_EXECUTE_MAP = FLASH_PREFIX + ".EXECUTEMAP";
 
     /**
      * Key for the current execute FlashMap token.
      */
     static final String FLASH_EXECUTE_MAP_TOKEN = FLASH_PREFIX + ".EXECUTEMAP.TOKEN";
     
     /**
      * Token separator.
      */
     static final char SEPARATOR_CHAR = '.';
     
      // ~ static methods  -----------------------------------------------------
     
     /**
      * Return a Flash instance from the application map
      * 
      * @param context
      * @return
      */
     public static Flash getCurrentInstance(ExternalContext context)
     {
         Map<String, Object> applicationMap = context.getApplicationMap();
         
         Flash flash = (Flash) applicationMap.get(FLASH_INSTANCE);
         if (flash == null)
         {
             // synchronize the ApplicationMap to ensure that only
             // once instance of FlashImpl is created and stored in it.
             synchronized (applicationMap)
             {
                 // check again, because first try was un-synchronized
                 flash = (Flash) applicationMap.get(FLASH_INSTANCE);
                 if (flash == null)
                 {
                     flash = new FlashImpl(context);
                     applicationMap.put(FLASH_INSTANCE, flash);
                 }
             }
         }
 
         return flash;
     }
 
     /**
      * Returns a cryptographically secure random number to use as the _count seed
      */
     private static long _getSeed()
     {
         SecureRandom rng;
         try
         {
             // try SHA1 first
             rng = SecureRandom.getInstance("SHA1PRNG");
         }
         catch (NoSuchAlgorithmException e)
         {
             // SHA1 not present, so try the default (which could potentially not be
             // cryptographically secure)
             rng = new SecureRandom();
         }
 
         // use 48 bits for strength and fill them in
         byte[] randomBytes = new byte[6];
         rng.nextBytes(randomBytes);
 
         // convert to a long
         return new BigInteger(randomBytes).longValue();
     }
     
     // ~ private fields and constructor ---------------------------------------
     
     // the current token value
     private final AtomicLong _count;
     private boolean _flashScopeDisabled;
     
     public FlashImpl(ExternalContext externalContext)
     {
         _count = new AtomicLong(_getSeed());
 
         // Read whether flash scope is disabled.
         _flashScopeDisabled = "true".equalsIgnoreCase(externalContext.getInitParameter(FLASH_SCOPE_DISABLED_PARAM));
     }
     
     // ~ methods from javax.faces.context.Flash -------------------------------
 
     /**
      * Used to restore the redirect value and the FacesMessages of the previous 
      * request and to manage the flashMap tokens for this request before phase
      * restore view starts.
      */
     @Override
     public void doPrePhaseActions(FacesContext facesContext)
     {
         if (!_flashScopeDisabled)
         {
             final PhaseId currentPhaseId = facesContext.getCurrentPhaseId();
         
             if (PhaseId.RESTORE_VIEW.equals(currentPhaseId))
             {
                 // restore the redirect value
                 // note that the result of this method is used in many places, 
                 // thus it has to be the first thing to do
                 _restoreRedirectValue(facesContext);
             
                 // restore the FlashMap token from the previous request
                 // and create a new token for this request
                 _manageFlashMapTokens(facesContext);
             
                 // try to restore any saved messages
                 _restoreMessages(facesContext);
             }
         }
     }
     
     /**
      * Used to destroy the executeMap and to save all FacesMessages for the
      * next request, but only if this is the last invocation of this method
      * in the current lifecycle (if redirect phase 5, otherwise phase 6).
      */
     @Override
     public void doPostPhaseActions(FacesContext facesContext)
     {
         if (!_flashScopeDisabled)
         {
             // do the actions only if this is the last time
             // doPostPhaseActions() is called on this request
             if (_isLastPhaseInRequest(facesContext))
             {
                 if (_isRedirectTrueOnThisRequest(facesContext))
                 {
                     // copy entries from executeMap to renderMap, if they do not exist
                     Map<String, Object> renderMap = _getRenderFlashMap(facesContext);
 
                     for (Map.Entry<String, Object> entry 
                         : _getExecuteFlashMap(facesContext).entrySet())
                     {
                         if (!renderMap.containsKey(entry.getKey()))
                         {
                             renderMap.put(entry.getKey(), entry.getValue());
                         }
                     }
                 }
             
                 // remove execute Map entries from session (--> "destroy" executeMap)
                 _clearExecuteFlashMap(facesContext);
             
                 // save the current FacesMessages in the renderMap, if wanted
                 // Note that this also works on a redirect even though the redirect
                 // was already performed and the response has already been committed,
                 // because the renderMap is stored in the session.
                 _saveMessages(facesContext);
             }
         }
     }
     
     /**
      * Return the value of this property for the flash for this session.
      * 
      * This must be false unless:
      *   - setRedirect(boolean) was called for the current lifecycle traversal
      *     with true as the argument.
      *   - The current lifecycle traversal for this session is in the "execute"
      *     phase and the previous traversal had setRedirect(boolean) called with
      *     true as the argument.
      */
     @Override
     public boolean isRedirect()
     {
         FacesContext facesContext = FacesContext.getCurrentInstance();
         boolean thisRedirect = _isRedirectTrueOnThisRequest(facesContext);
         boolean prevRedirect = _isRedirectTrueOnPreviousRequest(facesContext);
         boolean executePhase = !PhaseId.RENDER_RESPONSE.equals(facesContext.getCurrentPhaseId());
         
         return thisRedirect || (executePhase && prevRedirect);
     }
     
     @Override
     public void setRedirect(boolean redirect)
     {
         // FIXME this method has a design flaw, because the only valid value
         // is true and it should only be called by the NavigationHandler
         // in a redirect case RIGHT BEFORE ExternalContext.redirect().
         // Maybe a PreRedirectEvent issued by the ExternalContext would be a good
         // choice for JSF 2.1.
         
         FacesContext facesContext = FacesContext.getCurrentInstance();
         ExternalContext externalContext = facesContext.getExternalContext();
         Map<String, Object> requestMap = externalContext.getRequestMap();
         
         // save the value on the requestMap for this request
         Boolean alreadySet = (Boolean) requestMap.get(FLASH_REDIRECT);
         alreadySet = (alreadySet == null ? Boolean.FALSE : Boolean.TRUE);
         
         // if true and not already set, store it for the following request
         if (!alreadySet && redirect)
         {
             requestMap.put(FLASH_REDIRECT, Boolean.TRUE);
             
             // save redirect=true for the next request
             _saveRedirectValue(facesContext);
         }
         else
         {
             if (alreadySet)
             {
                 log.warning("Multiple call to setRedirect() ignored.");
             }
             else // redirect = false
             {
                 log.warning("Ignored call to setRedirect(false), because this "
                         + "should only be set to true by the NavigationHandler. "
                         + "No one else should change it.");
             }
         }
     }
     
     /**
      * Take a value from the requestMap, or if it does not exist from the
      * execute FlashMap, and put it on the render FlashMap, so it is visible on
      * the next request.
      */
     @Override
     public void keep(String key)
     {
         _checkFlashScopeDisabled();
         FacesContext facesContext = FacesContext.getCurrentInstance();
         Map<String, Object> requestMap = facesContext.getExternalContext().getRequestMap();
         Object value = requestMap.get(key);
         
         // if the key does not exist in the requestMap,
         // try to get it from the execute FlashMap
         if (value == null)
         {
             Map<String, Object> executeMap = _getExecuteFlashMap(facesContext);
             // Null-check, because in the GET request of a POST-REDIRECT-GET 
             // pattern there is no execute map
             if (executeMap != null)
             {
                 value = executeMap.get(key);
                 // Store it on request map so we can get it later. For example, 
                 // this is used by org.apache.myfaces.el.FlashELResolver to return
                 // the value that has been promoted.
                 requestMap.put(key, value);
             }
         }
         
         // put it in the render FlashMap
         _getRenderFlashMap(facesContext).put(key, value);
     }
 
     /**
      * This is just an alias for the request scope map.
      */
     @Override
     public void putNow(String key, Object value)
     {
         _checkFlashScopeDisabled();
         FacesContext.getCurrentInstance().getExternalContext()
                 .getRequestMap().put(key, value);
     }
 
     /**
      * Returns the value of a previous call to setKeepMessages() from this
      * request. If there was no call yet, false is returned.
      */
     @Override
     public boolean isKeepMessages()
     {
         FacesContext facesContext = FacesContext.getCurrentInstance();
         ExternalContext externalContext = facesContext.getExternalContext();
         Map<String, Object> requestMap = externalContext.getRequestMap();
         Boolean keepMessages = (Boolean) requestMap.get(FLASH_KEEP_MESSAGES);
         
         return (keepMessages == null ? Boolean.FALSE : keepMessages);
     }
     
     /**
      * If this property is true, the messages should be kept for the next 
      * request, no matter if it is a normal postback case or a POST-
      * REDIRECT-GET case.
      * 
      * Note that we don't have to store this value for the next request
      * (like setRedirect()), because we will know if it was true on the 
      * next request, if we can find any stored messages in the FlashMap.
      * (also see _saveMessages() and _restoreMessages()).
      */
     @Override
     public void setKeepMessages(boolean keepMessages)
     {
         FacesContext facesContext = FacesContext.getCurrentInstance();
         ExternalContext externalContext = facesContext.getExternalContext();
         Map<String, Object> requestMap = externalContext.getRequestMap();
         requestMap.put(FLASH_KEEP_MESSAGES, keepMessages);
     }
     
     // ~ Methods from Map interface -------------------------------------------
     
     // NOTE that all these methods do not necessarily delegate to the same Map,
     // because we differentiate between reading and writing operations.
     
     public void clear()
     {
         _checkFlashScopeDisabled();
         _getFlashMapForWriting().clear();
     }
 
     public boolean containsKey(Object key)
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForReading().containsKey(key);
     }
 
     public boolean containsValue(Object value)
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForReading().containsValue(value);
     }
 
     public Set<java.util.Map.Entry<String, Object>> entrySet()
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForReading().entrySet();
     }
 
     public Object get(Object key)
     {
         _checkFlashScopeDisabled();
         if (key == null)
         {
             return null;
         }
         
         if ("keepMessages".equals(key))
         {
             return isKeepMessages();
         }
         else if ("redirect".equals(key))
         {
             return isRedirect();
         }
         
         return _getFlashMapForReading().get(key);
     }
     
     public boolean isEmpty()
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForReading().isEmpty();
     }
 
     public Set<String> keySet()
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForReading().keySet();
     }
 
     public Object put(String key, Object value)
     {
         _checkFlashScopeDisabled();
         if (key == null)
         {
             return null;
         }
         
         if ("keepMessages".equals(key))
         {
             Boolean booleanValue = _convertToBoolean(value);
             this.setKeepMessages(booleanValue);
             return booleanValue;
         }
         else if ("redirect".equals(key))
         {
             Boolean booleanValue = _convertToBoolean(value);
             this.setRedirect(booleanValue);
             return booleanValue;
         }
         else
         {
             return _getFlashMapForWriting().put(key, value); 
         }
     }
 
     public void putAll(Map<? extends String, ? extends Object> m)
     {
         _checkFlashScopeDisabled();
         _getFlashMapForWriting().putAll(m);
     }
 
     public Object remove(Object key)
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForWriting().remove(key);
     }
 
     public int size()
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForReading().size();
     }
 
     public Collection<Object> values()
     {
         _checkFlashScopeDisabled();
         return _getFlashMapForReading().values();
     }
     
     // ~ Implementation methods ----------------------------------------------- 
     
     /**
      * Returns true if the current phase is the last phase in the request
      * and thus if doPostPhaseActions() is called for the last time.
      * 
      * This will be true if either we are in phase 6 (render response)
      * or if setRedirect(true) was called on this request and we are
      * in phase 5 (invoke application).
      */
     private boolean _isLastPhaseInRequest(FacesContext facesContext)
     {
         final PhaseId currentPhaseId = facesContext.getCurrentPhaseId();
         
         boolean lastPhaseNormalRequest = PhaseId.RENDER_RESPONSE.equals(currentPhaseId);
         boolean lastPhaseIfRedirect = PhaseId.INVOKE_APPLICATION.equals(currentPhaseId) 
                 && _isRedirectTrueOnThisRequest(facesContext);
         
         return lastPhaseNormalRequest || lastPhaseIfRedirect;
     }
     
     /**
      * Return true if setRedirect(true) was called on this request.
      * @param facesContext
      * @return
      */
     private boolean _isRedirectTrueOnThisRequest(FacesContext facesContext)
     {
         ExternalContext externalContext = facesContext.getExternalContext();
         Map<String, Object> requestMap = externalContext.getRequestMap();
         Boolean redirect = (Boolean) requestMap.get(FLASH_REDIRECT);
         
         return Boolean.TRUE.equals(redirect);
     }
     
     /**
      * Return true if setRedirect(true) was called on the previous request.
      * Precondition: doPrePhaseActions() must have been called on restore view phase.
      * @param facesContext
      * @return
      */
     private boolean _isRedirectTrueOnPreviousRequest(FacesContext facesContext)
     {
         ExternalContext externalContext = facesContext.getExternalContext();
         Map<String, Object> requestMap = externalContext.getRequestMap();
         Boolean redirect = (Boolean) requestMap.get(FLASH_PREVIOUS_REQUEST_REDIRECT);
         
         return Boolean.TRUE.equals(redirect);
     }
     
     /**
      * Saves the value of setRedirect() for the next request, if it was true
      */
     private void _saveRedirectValue(FacesContext facesContext)
     {
         ExternalContext externalContext = facesContext.getExternalContext();
         
         // This request contains a redirect. This condition is in general 
         // triggered by a NavigationHandler. After a redirect all request scope
         // values get lost, so in order to preserve this value we need to
         // pass it between request. One strategy is use a cookie that is never sent
         // to the client. Other alternative is use the session map.
         // See _restoreRedirectValue() for restoring this value.
         HttpServletResponse httpResponse = ExternalContextUtils
                 .getHttpServletResponse(externalContext);
         if (httpResponse != null)
         {
             Cookie cookie = _createFlashCookie(FLASH_REDIRECT, "true", externalContext);
             httpResponse.addCookie(cookie);
         }
         else
         {
             externalContext.getSessionMap().put(FLASH_REDIRECT, true);
         }
     }
 
     /**
      * Restores the redirect value of the previous request and saves
      * it in the RequestMap under the key FLASH_PREVIOUS_REQUEST_REDIRECT.
      * Must not be called more than once per request.
      * After this method was invoked, the requestMap will contain Boolean.TRUE
      * if setRedirect(true) was called on the previous request or Boolean.FALSE
      * or null otherwise.
      */
     private void _restoreRedirectValue(FacesContext facesContext)
     {
         ExternalContext externalContext = facesContext.getExternalContext();
         HttpServletResponse httpResponse = ExternalContextUtils
                 .getHttpServletResponse(externalContext);
         if (httpResponse != null)
         {
             // Request values are lost after a redirect. We can create a 
             // temporal cookie to pass the params between redirect calls.
             // It is better than use HttpSession object, because this cookie
             // is never sent by the server.
             Cookie cookie = (Cookie) externalContext
                     .getRequestCookieMap().get(FLASH_REDIRECT);
             if (cookie != null)
             {
                 // the cookie exists means there was a redirect, regardless of the value
                 externalContext.getRequestMap().put(
                         FLASH_PREVIOUS_REQUEST_REDIRECT, Boolean.TRUE);
                 
                 // A redirect happened, so it is safe to remove the cookie, setting
                 // the maxAge to 0 seconds. The effect is we passed FLASH_REDIRECT param 
                 // to this request object
                 cookie.setMaxAge(0);
                 cookie.setPath(_getCookiePath(externalContext));
                 //MYFACES-3354 jetty 6.1.5 does not allow this,
                 //call setMaxAge(0) is enough
                 //cookie.setValue(null);
                 httpResponse.addCookie(cookie);
             }
         }
         else
         {
             // Note that on portlet world we can't create cookies,
             // so we are forced to use the session map. Anyway, 
             // according to the Bridge implementation(for example see 
             // org.apache.myfaces.portlet.faces.bridge.BridgeImpl)
             // session object is created at start faces request
             Map<String, Object> sessionMap = externalContext.getSessionMap();
             
             // remove the value from the sessionMap
             Boolean redirect = (Boolean) sessionMap.remove(FLASH_REDIRECT);
             
             // put the value into the requestMap
             externalContext.getRequestMap().put(
                     FLASH_PREVIOUS_REQUEST_REDIRECT, redirect);
         }
     }
     
     /**
      * Saves the current FacesMessages as a List on the render FlashMap for the
      * next request if isKeepMessages() is true. Otherwise it removes any
      * existing FacesMessages-List from the renderFlashMap. 
      * @param facesContext
      */
     private void _saveMessages(FacesContext facesContext)
     {
         if (isKeepMessages()) 
         {
             // get all messages from the FacesContext and store
             // them on the renderMap
             List<MessageEntry> messageList = null;
                 
             Iterator<String> iterClientIds = facesContext.getClientIdsWithMessages();
             while (iterClientIds.hasNext())
             {
                 String clientId = (String) iterClientIds.next();
                 Iterator<FacesMessage> iterMessages = facesContext.getMessages(clientId);
                 
                 while (iterMessages.hasNext())
                 {
                     FacesMessage message = iterMessages.next();
     
                     if (messageList == null)
                     {
                         messageList = new ArrayList<MessageEntry>();
                     }
                     messageList.add(new MessageEntry(clientId, message));
                 }
             }
     
             _getRenderFlashMap(facesContext).put(FLASH_KEEP_MESSAGES_LIST, messageList);
         }
         else
         {
             // do not keep messages --> remove messagesList from renderMap
             _getRenderFlashMap(facesContext).remove(FLASH_KEEP_MESSAGES_LIST);
         }
     }
 
     /**
      * Restore any saved FacesMessages from the previous request.
      * Note that we don't need to save the keepMessages value for this request,
      * because we just have to check if the value for FLASH_KEEP_MESSAGES_LIST exists.
      * @param facesContext
      */
     @SuppressWarnings("unchecked")
     private void _restoreMessages(FacesContext facesContext)
     {
         List<MessageEntry> messageList = (List<MessageEntry>) 
                 _getExecuteFlashMap(facesContext).get(FLASH_KEEP_MESSAGES_LIST);
 
         if (messageList != null)
         {
             Iterator<MessageEntry> iterMessages = messageList.iterator();
 
             while (iterMessages.hasNext())
             {
                 MessageEntry entry = iterMessages.next();
                 facesContext.addMessage(entry.clientId, entry.message);
             }
 
             // we can now remove the messagesList from the flashMap
             _getExecuteFlashMap(facesContext).remove(FLASH_KEEP_MESSAGES_LIST);
         }
     }
     
     /**
      * Take the render map key and store it as a key for the next request.
      * 
      * On the next request we can get it with _getRenderFlashMapTokenFromPreviousRequest().
      * @param externalContext
      */
     private void _saveRenderFlashMapTokenForNextRequest(ExternalContext externalContext)
     {
         String tokenValue = (String) externalContext.getRequestMap().get(FLASH_RENDER_MAP_TOKEN);
         
         HttpServletResponse httpResponse = ExternalContextUtils.getHttpServletResponse(externalContext);
         if (httpResponse != null)
         {
             Cookie cookie = _createFlashCookie(FLASH_RENDER_MAP_TOKEN, tokenValue, externalContext);
             httpResponse.addCookie(cookie);
         }
         else
         {
             //Use HttpSession or PortletSession object
             Map<String, Object> sessionMap = externalContext.getSessionMap();
             sessionMap.put(FLASH_RENDER_MAP_TOKEN, tokenValue);
         }
     }
     
     /**
      * Retrieve the map token of the render map from the previous request.
      * 
      * Returns the value of _saveRenderFlashMapTokenForNextRequest() from
      * the previous request.
      * @param externalContext
      * @return
      */
     private String _getRenderFlashMapTokenFromPreviousRequest(ExternalContext externalContext)
     {
         String tokenValue = null;
         HttpServletResponse httpResponse = ExternalContextUtils.getHttpServletResponse(externalContext);
         if (httpResponse != null)
         {
             //Use a cookie
             Cookie cookie = (Cookie) externalContext.getRequestCookieMap().get(FLASH_RENDER_MAP_TOKEN);
             if (cookie != null)
             {
                 tokenValue = cookie.getValue();
             }
         }
         else
         {
             //Use HttpSession or PortletSession object
             Map<String, Object> sessionMap = externalContext.getSessionMap();
             tokenValue = (String) sessionMap.get(FLASH_RENDER_MAP_TOKEN);
         }
         return tokenValue;
     }
     
     /**
      * Restores the render FlashMap token from the previous request.
      * This is the token of the executeMap for this request.
      * Furthermore it also creates a new token for this request's renderMap
      * (and thus implicitly a new renderMap).
      * @param facesContext
      */
     private void _manageFlashMapTokens(FacesContext facesContext)
     {
         ExternalContext externalContext = facesContext.getExternalContext();
         Map<String, Object> requestMap = externalContext.getRequestMap();
 
         final String previousRenderToken 
                 = _getRenderFlashMapTokenFromPreviousRequest(externalContext);
         if (previousRenderToken != null)
         {
             // "restore" the renderMap from the previous request
             // and put it as the executeMap for this request
             requestMap.put(FLASH_EXECUTE_MAP_TOKEN, previousRenderToken);
         }
         else
         {
             if (facesContext.isPostback())
             {
                 // on a postback, we should always have a previousToken
                 log.warning("Identifier for execute FlashMap was lost on " +
                         "the postback, thus FlashScope information is gone.");
             }
             
             // create a new token (and thus a new Map) for this request's 
             // executeMap so that we have an executeMap in any possible case.
             final String newExecuteToken = _getNextToken();
             requestMap.put(FLASH_EXECUTE_MAP_TOKEN, newExecuteToken);
         }
         
         // create a new token (and thus a new Map) for this request's renderMap
         final String newRenderToken = _getNextToken();
         requestMap.put(FLASH_RENDER_MAP_TOKEN, newRenderToken);
         
         // we now have the final render token for this request, thus we can
         // already save it for the next request, because it won't change
         _saveRenderFlashMapTokenForNextRequest(externalContext);
     }
     
     /**
      * Get the next token to be assigned to this request
      * 
      * @return
      */
     private String _getNextToken()
     {
         // atomically increment the value
         long nextToken = _count.incrementAndGet();
 
         // convert using base 36 because it is a fast efficient subset of base-64
         return Long.toString(nextToken, 36);
     }
 
     /**
      * Create a new subkey-wrapper of the session map with the given prefix.
      * This wrapper is used to implement the maps for the flash scope.
      * For more information see the SubKeyMap doc.
      */
     private Map<String, Object> _createSubKeyMap(FacesContext context, String prefix)
     {
         ExternalContext external = context.getExternalContext();
         Map<String, Object> sessionMap = external.getSessionMap();
 
         return new SubKeyMap<Object>(sessionMap, prefix);
     }
 
     /**
      * Return the flash map created on this traversal.
      * 
      * This FlashMap will be the execute FlashMap of the next traversal.
      * 
      * Note that it is supposed that FLASH_RENDER_MAP_TOKEN is initialized
      * before restore view phase (see doPrePhaseActions() for details).
      * 
      * @param context
      * @return
      */
     @SuppressWarnings("unchecked")
     private Map<String, Object> _getRenderFlashMap(FacesContext context)
     {
         // Note that we don't have to synchronize here, because it is no problem
         // if we create more SubKeyMaps with the same subkey, because they are
         // totally equal and point to the same entries in the SessionMap.
         
         Map<String, Object> requestMap = context.getExternalContext().getRequestMap();
         Map<String, Object> map = (Map<String, Object>) requestMap.get(FLASH_RENDER_MAP);
         if (map == null)
         {
             String token = (String) requestMap.get(FLASH_RENDER_MAP_TOKEN);
             String fullToken = FLASH_SESSION_MAP_SUBKEY_PREFIX + SEPARATOR_CHAR + token;
             map =  _createSubKeyMap(context, fullToken);
             requestMap.put(FLASH_RENDER_MAP, map);
         }
         return map;
     }
     
     /**
      * Return the execute Flash Map.
      * 
      * This FlashMap was the render FlashMap of the previous traversal. 
      * 
      * @param context
      * @return
      */
     @SuppressWarnings("unchecked")
     private Map<String, Object> _getExecuteFlashMap(FacesContext context)
     {
         // Note that we don't have to synchronize here, because it is no problem
         // if we create more SubKeyMaps with the same subkey, because they are
         // totally equal and point to the same entries in the SessionMap.
         
         Map<String, Object> requestMap = context.getExternalContext().getRequestMap();
         Map<String, Object> map = (Map<String, Object>) requestMap.get(FLASH_EXECUTE_MAP);
         if (map == null)
         {
             String token = (String) requestMap.get(FLASH_EXECUTE_MAP_TOKEN);
             String fullToken = FLASH_SESSION_MAP_SUBKEY_PREFIX + SEPARATOR_CHAR + token;
             map = _createSubKeyMap(context, fullToken);
             requestMap.put(FLASH_EXECUTE_MAP, map);
         }
         return map;
     }
     
     /**
      * Get the proper map according to the current phase:
      * 
      * Normal case:
      * 
      * - First request, restore view phase (create a new one): render map n
      * - First request, execute phase: Skipped
      * - First request, render  phase: render map n
      * 
      *   Render map n saved and put as execute map n
      * 
      * - Second request, execute phase: execute map n
      * - Second request, render  phase: render map n+1
      * 
      * Post Redirect Get case: Redirect is triggered by a call to setRedirect(true) from NavigationHandler
      * or earlier using c:set tag.
      * 
      * - First request, restore view phase (create a new one): render map n
      * - First request, execute phase: Skipped
      * - First request, render  phase: render map n
      * 
      *   Render map n saved and put as execute map n
      * 
      * POST
      * 
      * - Second request, execute phase: execute map n
      *   Note that render map n+1 is also created here to perform keep().
      * 
      * REDIRECT
      * 
      * - NavigationHandler do the redirect, requestMap data lost, called Flash.setRedirect(true)
      * 
      *   Render map n+1 saved and put as render map n+1 on GET request.
      * 
      * GET
      * 
      * - Third  request, restore view phase (create a new one): render map n+1 (restorred)
      *   (isRedirect() should return true as javadoc says)
      * - Third  request, execute phase: skipped
      * - Third  request, render  phase: render map n+1
      * 
      * In this way proper behavior is preserved even in the case of redirect, since the GET part is handled as
      * the "render" part of the current traversal, keeping the semantic of flash object.
      * 
      * @return
      */
     private Map<String, Object> _getActiveFlashMap()
     {
         FacesContext facesContext = FacesContext.getCurrentInstance();
         if (PhaseId.RENDER_RESPONSE.equals(facesContext.getCurrentPhaseId()) 
                 || !facesContext.isPostback())
         {
             return _getRenderFlashMap(facesContext);
         }
         else
         {
             return _getExecuteFlashMap(facesContext);
         }
     }
     
     /**
      * Returns the FlashMap used in the reading methods of java.util.Map
      * like e.g. get() or values().
      * @return
      */
     private Map<String, Object> _getFlashMapForReading()
     {
         return _getExecuteFlashMap(FacesContext.getCurrentInstance());
     }
     
     /**
      * Returns the FlashMap used in the writing methods of java.util.Map
      * like e.g. put() or clear().
      * @return
      */
     private Map<String, Object> _getFlashMapForWriting()
     {
         return _getActiveFlashMap();
     }
 
     /**
      * Destroy the execute FlashMap, because it is not needed anymore.
      * @param facesContext
      */
     private void _clearExecuteFlashMap(FacesContext facesContext)
     {
         Map<String, Object> map = _getExecuteFlashMap(facesContext);
 
         // Clear everything - note that because of naming conventions,
         // this will in fact automatically recurse through all children
         // grandchildren etc. - which is kind of a design flaw of SubKeyMap,
         // but one we're relying on
         
         // NOTE that we do not need a null check here, because there will
         // always be an execute Map, however sometimes an empty one!
         map.clear();
     }
 
     /**
      * Creates a Cookie with the given name and value.
      * In addition, it will be configured with maxAge=-1, the current request path and secure value.
      *
      * @param name
      * @param value
      * @param externalContext
      * @return
      */
     private Cookie _createFlashCookie(String name, String value, ExternalContext externalContext)
     {
         Cookie cookie = new Cookie(name, value);
 
         cookie.setMaxAge(-1);
         cookie.setPath(_getCookiePath(externalContext));
         cookie.setSecure(externalContext.isSecure());
 
         return cookie;
     }
 
     /**
      * Returns the path for the Flash-Cookies.
      * @param externalContext
      * @return
      */
     private String _getCookiePath(ExternalContext externalContext)
     {
         String contextPath = externalContext.getRequestContextPath();
 
         if (contextPath == null || "".equals(contextPath))
         {
             contextPath = "/";
         }
 
         return contextPath;
     }
     
     /**
      * Convert the Object to a Boolean.
      * @param value
      * @return
      */
     private Boolean _convertToBoolean(Object value)
     {
         Boolean booleanValue;
         if (value instanceof Boolean)
         {
             booleanValue = (Boolean) value;
         }
         else
         {
             booleanValue = Boolean.parseBoolean(value.toString());
         }
         return booleanValue;
     }
     
     /**
      * Checks whether flash scope is disabled.
      * @throws FlashScopeDisabledException if flash scope is disabled
      */
     private void _checkFlashScopeDisabled()
     {
         if (_flashScopeDisabled)
         {
             throw new FlashScopeDisabledException("Flash scope was disabled by context param " 
                 + FLASH_SCOPE_DISABLED_PARAM + " but erroneously accessed");
         }
     }
     
     // ~ Inner classes --------------------------------------------------------
     
     /**
      * Class used to store a FacesMessage with its clientId.
      */
     private static class MessageEntry implements Serializable
     {
         private static final long serialVersionUID = -690264660230199234L;
         private final String clientId;
         private final FacesMessage message;
 
         public MessageEntry(String clientId, FacesMessage message)
         {
             this.clientId = clientId;
             this.message = message;
         }
     }
     
 }