/*

  * 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.view.impl;

 import java.math.BigInteger;

 import java.security.NoSuchAlgorithmException;

 import java.security.SecureRandom;

 import java.util.HashSet;

 import java.util.Map;

 import java.util.Set;

 import java.util.concurrent.atomic.AtomicLong;

 import javax.faces.context.ExternalContext;

 import javax.faces.context.FacesContext;

 import org.apache.myfaces.config.ManagedBeanDestroyer;

 import org.apache.myfaces.config.RuntimeConfig;

 import org.apache.myfaces.config.annotation.LifecycleProvider;

 import org.apache.myfaces.config.annotation.LifecycleProviderFactory;

 import org.apache.myfaces.shared.util.SubKeyMap;

 import org.apache.myfaces.spi.ViewScopeProvider;

 /**

  * Minimal implementation for view scope without CDI but always store

  * the beans into session.

  * 

  * @author Leonardo Uribe

  */

 public class DefaultViewScopeHandler extends ViewScopeProvider

 {

     private static final String VIEW_SCOPE_PREFIX = "oam.view.SCOPE";

     private static final String VIEW_SCOPE_PREFIX_KEY = VIEW_SCOPE_PREFIX+".KEY";

     private static final String VIEW_SCOPE_PREFIX_MAP = VIEW_SCOPE_PREFIX+".MAP";

     static final char SEPARATOR_CHAR = '.';

     private final AtomicLong _count;

     private ManagedBeanDestroyer _mbDestroyer;

     public DefaultViewScopeHandler()

     {

         _count = new AtomicLong(_getSeed());

     }

     /**

      * 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();

     }

     /**

      * 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);

     }

     public void onSessionDestroyed()

     {

         FacesContext facesContext = FacesContext.getCurrentInstance();

         if (facesContext.getExternalContext().getSession(false) != null)

         {

             ExternalContext external = facesContext.getExternalContext();

             Map<String, Object> sessionMap = external.getSessionMap();

             String prefix = VIEW_SCOPE_PREFIX_MAP + SEPARATOR_CHAR;

             Set<String> viewScopeIdSet = new HashSet<String>();

             for (Map.Entry<String,Object> entry: sessionMap.entrySet())

             {

                 if (entry.getKey() != null && 

                     entry.getKey().startsWith(prefix))

                 {

                     String viewScopeId = entry.getKey().substring(prefix.length(), 

                             entry.getKey().indexOf(SEPARATOR_CHAR, prefix.length()));

                     viewScopeIdSet.add(viewScopeId);

                 }

             }

             if (!viewScopeIdSet.isEmpty())

             {

                 for (String viewScopeId : viewScopeIdSet )

                 {

                     this.destroyViewScopeMap(facesContext, viewScopeId);

                 }

             }

         }

     }

     public Map<String, Object> createViewScopeMap(FacesContext facesContext, String viewScopeId)

     {

         String fullToken = VIEW_SCOPE_PREFIX_MAP + SEPARATOR_CHAR + viewScopeId + SEPARATOR_CHAR;

         Map<String, Object> map = _createSubKeyMap(facesContext, fullToken);

         return map;

     }

     public Map<String, Object> restoreViewScopeMap(FacesContext facesContext, String viewScopeId)

     {

         String fullToken = VIEW_SCOPE_PREFIX_MAP + SEPARATOR_CHAR + viewScopeId + SEPARATOR_CHAR;

         Map<String, Object> map = _createSubKeyMap(facesContext, fullToken);

         return map;

     }

     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);

     }

     public String generateViewScopeId(FacesContext facesContext)

     {

         // To ensure uniqueness in this part we use a counter that 

         // is stored into session and we add a random number to

         // make difficult to guess the next number.

         ExternalContext externalContext = facesContext.getExternalContext();

         Object sessionObj = externalContext.getSession(true);

         Integer sequence = null;

         // synchronized to increase sequence if multiple requests

         // are handled at the same time for the session

         synchronized (sessionObj) 

         {

             Map<String, Object> map = externalContext.getSessionMap();

             sequence = (Integer) map.get(VIEW_SCOPE_PREFIX_KEY);

             if (sequence == null || sequence.intValue() == Integer.MAX_VALUE)

             {

                 sequence = Integer.valueOf(1);

             }

             else

             {

                 sequence = Integer.valueOf(sequence.intValue());

             }

             map.put(VIEW_SCOPE_PREFIX_KEY, sequence);

         }

         return _getNextToken()+'_'+sequence.toString();

     }

     @Override

     public void destroyViewScopeMap(FacesContext facesContext, String viewScopeId)

     {

         if (facesContext.getExternalContext().getSession(false) != null)

         {        

             String fullToken = VIEW_SCOPE_PREFIX_MAP + SEPARATOR_CHAR + viewScopeId + SEPARATOR_CHAR;

             Map<String, Object> map = _createSubKeyMap(facesContext, fullToken);

             ManagedBeanDestroyer mbDestroyer = getManagedBeanDestroyer(facesContext.getExternalContext());

             for (Map.Entry<String,Object> entry : map.entrySet())

             {

                 mbDestroyer.destroy(entry.getKey(), entry.getValue());

             }

             map.clear();

         }

     }

     protected ManagedBeanDestroyer getManagedBeanDestroyer(ExternalContext externalContext)

     {

         if (_mbDestroyer == null)

         {

             RuntimeConfig runtimeConfig = RuntimeConfig.getCurrentInstance(externalContext);

             LifecycleProvider lifecycleProvider = LifecycleProviderFactory

                     .getLifecycleProviderFactory(externalContext).getLifecycleProvider(externalContext);

             _mbDestroyer = new ManagedBeanDestroyer(lifecycleProvider, runtimeConfig);

         }

         return _mbDestroyer;

     }

 }