/*
    *  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.trinidad.bean.util;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.ObjectOutputStream;
  import java.io.Serializable;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  import java.util.concurrent.ConcurrentMap;
  
  import javax.faces.component.StateHolder;
  import javax.faces.context.ExternalContext;
  import javax.faces.context.FacesContext;
  
  import org.apache.myfaces.trinidad.bean.FacesBean;
  import org.apache.myfaces.trinidad.bean.PropertyKey;
  import org.apache.myfaces.trinidad.bean.PropertyMap;
  import org.apache.myfaces.trinidad.context.RequestContext;
  import org.apache.myfaces.trinidad.logging.TrinidadLogger;
  
  
  /**
   * Utilities for handling state persistance.
   */
  public final class StateUtils
  {
    static
    {
      // initialize checks for serialization verification
      boolean checkPropertyStateSerialization = false;
      boolean checkComponentStateSerialization = false;
      boolean checkComponentTreeStateSerialization = false;
      boolean checkSessionSerialization = false;
      boolean checkApplicationSerialization = false;
  
      String checkSerializationProperty;
  
      // determine if we need to aggressively check the serialization of components
      // we wrap the check in a try/catch in case of weird ecurity managers
      try
      {
        checkSerializationProperty = 
                         System.getProperty("org.apache.myfaces.trinidad.CHECK_STATE_SERIALIZATION");
      }
      catch (Throwable t)
      {
        checkSerializationProperty = null;
      }
  
      if (checkSerializationProperty != null)
      {
        checkSerializationProperty = checkSerializationProperty.toUpperCase();
        
        // comma-separated list with allowed whitespace
        String[] paramArray = checkSerializationProperty.split(",");
        
        Set<String> serializationFlags = new HashSet<String>(Arrays.asList(paramArray));
        
        if (!serializationFlags.contains("NONE"))
        {
          if (serializationFlags.contains("ALL"))
          {
            checkPropertyStateSerialization = true;
            checkComponentStateSerialization = true;
            checkComponentTreeStateSerialization = true;
            checkSessionSerialization = true;
            checkApplicationSerialization = true;
          }
          else
          {
            checkPropertyStateSerialization = serializationFlags.contains("PROPERTY");
            checkComponentStateSerialization = serializationFlags.contains("COMPONENT");
            checkComponentTreeStateSerialization = serializationFlags.contains("TREE");       
            checkSessionSerialization = serializationFlags.contains("SESSION");
           checkApplicationSerialization = serializationFlags.contains("APPLICATION");
         }
       }
     }
 
     _CHECK_PROPERTY_STATE_SERIALIZATION = checkPropertyStateSerialization;
     _CHECK_COMPONENT_STATE_SERIALIZATION = checkComponentStateSerialization;
     _CHECK_COMPONENT_TREE_STATE_SERIALIZATION = checkComponentTreeStateSerialization;
     _CHECK_SESSION_SERIALIZATION = checkSessionSerialization;
     _CHECK_APPLICATION_SERIALIZATION = checkApplicationSerialization;
   }
 
   private static final boolean _CHECK_COMPONENT_TREE_STATE_SERIALIZATION;
   private static final boolean _CHECK_COMPONENT_STATE_SERIALIZATION;
   private static final boolean _CHECK_PROPERTY_STATE_SERIALIZATION;
   private static final boolean _CHECK_SESSION_SERIALIZATION;
   private static final boolean _CHECK_APPLICATION_SERIALIZATION;
 
   /**
    * Returns <code>true</code> if properties should be checked for
    * serializability when when generating the view's state object.
    * <p>
    * By default property state serialization checking is off.  It can be
    * enabled by setting the system property
    * <code>org.apache.myfaces.trinidad.CHECK_STATE_SERIALIZATION</code>
    * to <code>all</code> or, more rately, adding <code>property</code> to the
    * comma-separated list of serialization checks to perform.
    * <p>
    * As property serialization checking is expensive, it is usually
    * only enabled after component tree serialization checking has detected
    * a problem
    * @return
    * @see #checkComponentStateSerialization
    * @see #checkComponentTreeStateSerialization
    */
   private static boolean _checkPropertyStateSerialization()
   {
     return _CHECK_PROPERTY_STATE_SERIALIZATION;
   }
 
   /**
    * Returns <code>true</code> if components should be checked for
    * serializability when when generating the view's state object.
    * <p>
    * By default component state serialization checking is off.  It can be
    * enabled by setting the system property
    * <code>org.apache.myfaces.trinidad.CHECK_STATE_SERIALIZATION</code>
    * to <code>all</code> or, more rarely, adding <code>component</code> to the
    * comma-separated list of serialization checks to perform.
    * <p>
    * As property serialization checking is expensive, it is usually
    * only enabled after component tree serialization checking has detected
    * a problem.  In addition, since component serialization checking only
    * detects the problem component, it is usually combined with
    * property state serialization checking either by specifying <code>all</code>.
    * @return
    * @see #checkComponentTreeStateSerialization
    */
   public static boolean checkComponentStateSerialization(FacesContext context)
   {
     return _CHECK_COMPONENT_STATE_SERIALIZATION;
   }
 
   /**
    * Returns <code>true</code> if the component tree should be checked for
    * serializability when when generating the view's state object.
    * <p>
    * By default component tree state serialization checking is off.  It can be
    * enabled by setting the system property
    * <code>org.apache.myfaces.trinidad.CHECK_STATE_SERIALIZATION</code>
    * to <code>all</code> or, more commonly, adding <code>tree</code> to the
    * comma-separated list of serialization checks to perform.
    * <p>
    * Because unserializable objects defeat fail-over, it is important to
    * check for serializability when testing applications.  While component
    * tree state serializability checking isn't cheap, it is much faster to
    * initially only enable checking of the component tree and then switch
    * to <code>all</code> testing to determine the problem component and 
    * property when the component tree testing determines a problem.
    * @return
    * @see #checkComponentStateSerialization
    */
   public static boolean checkComponentTreeStateSerialization(FacesContext context)
   {
     return _CHECK_COMPONENT_TREE_STATE_SERIALIZATION;
   }
 
   /**
    * Returns <code>true</code> if Object written to the ExternalContext's Session Map should be
    * checked for Serializability when <code>put</code> is called.
    * <p>
    * Configuring this property allows this aspect of high-availability to be tested without
    * configuring the server to run in high-availability mode.
    * <p>
    * By default session serialization checking is off.  It can be
    * enabled by setting the system property
    * <code>org.apache.myfaces.trinidad.CHECK_STATE_SERIALIZATION</code>
    * to <code>all</code> or, more commonly, adding <code>session</code> to the
    * comma-separated list of serialization checks to perform.
    * @return
    * @see #checkComponentStateSerialization
    * @see #checkComponentTreeStateSerialization
    * @see #checkApplicationSerialization
    */
   public static boolean checkSessionSerialization(ExternalContext extContext)
   {
     return _CHECK_SESSION_SERIALIZATION;
   }
 
   /**
    * Returns <code>true</code> if Object written to the ExternalContext's Application Map should be
    * checked for Serializability when <code>put</code> is called.
    * <p>
    * Configuring this property allows this aspect of high-availability to be tested without
    * configuring the server to run in high-availability mode.
    * <p>
    * By default application serialization checking is off.  It can be
    * enabled by setting the system property
    * <code>org.apache.myfaces.trinidad.CHECK_STATE_SERIALIZATION</code>
    * to <code>all</code> or, more commonly, adding <code>application</code> to the
    * comma-separated list of serialization checks to perform.
    * @return
    * @see #checkComponentStateSerialization
    * @see #checkComponentTreeStateSerialization
    * @see #checkSessionSerialization
    */
   public static boolean checkApplicationSerialization(ExternalContext extContext)
   {
     return _CHECK_APPLICATION_SERIALIZATION;
   }
 
   /**
    * Persists a property key.
    */
   static public Object saveKey(PropertyKey key)
   {
     int index = key.getIndex();
     if (index < 0)
       return key.getName();
 
     if (index < 128)
       return Byte.valueOf((byte) index);
 
     return Integer.valueOf(index);
   }
 
 
   /**
    * Restores a persisted PropertyKey.
    */
   static public PropertyKey restoreKey(FacesBean.Type type, Object value)
   {
     PropertyKey key;
     if (value instanceof Number)
     {
       key = type.findKey(((Number) value).intValue());
       if (key == null)
         throw new IllegalStateException(_LOG.getMessage(
           "INVALID_INDEX"));
     }
     else
     {
       key = type.findKey((String) value);
       if (key == null)
         key = PropertyKey.createPropertyKey((String) value);
     }
 
     return key;
   }
 
   /**
    * Generic (unoptimized) version of PropertyMap state saving.
    */
   static public Object saveState(
     PropertyMap    map,
     FacesContext   context,
     boolean        useStateHolder)
   {
     int size = map.size();
     if (size == 0)
       return null;
 
     Object[] values = new Object[2 * size];
     int i = 0;
     for(Map.Entry<PropertyKey, Object> entry : map.entrySet())
     {
       PropertyKey key = entry.getKey();
       if (key.isTransient())
         continue;
 
       Object value = entry.getValue();
 
       values[i] = saveKey(key);
       if (_LOG.isFinest())
       {
         _LOG.finest("SAVE {" + key + "=" + value + "}");
       }
 
       Object saveValue;
       
       if (useStateHolder)
         saveValue = saveStateHolder(context, value);
       else
         saveValue = key.saveValue(context, value);
 
       // aggressively check the serializability of the value
       if (_checkPropertyStateSerialization())
       {
         try
         {
           new ObjectOutputStream(new ByteArrayOutputStream()).writeObject(saveValue);
         }
         catch (IOException e)
         {          
           throw new RuntimeException(_LOG.getMessage("UNSERIALIZABLE_PROPERTY_VALUE",
                                                      new Object[]{saveValue, key, map}),
                                      e);
         }
       }
       
       values[i + 1] = saveValue;
       
       i+=2;
     }
 
     return values;
   }
 
 
   /**
    * Generic (unoptimized) version of PropertyMap state restoring.
    */
   static public void restoreState(
     PropertyMap    map,
     FacesContext   context,
     FacesBean.Type type,
     Object         state,
     boolean        useStateHolder)
   {
     if (state == null)
       return;
 
     Object[] values = (Object[]) state;
     int size = values.length / 2;
     for (int i = 0; i < size; i++)
     {
       Object savedKey = values[i * 2];
       if (savedKey == null)
         continue;
 
       Object savedValue = values[i * 2 + 1];
       PropertyKey key = restoreKey(type, savedKey);
       Object value;
 
       if (useStateHolder)
         value = restoreStateHolder(context, savedValue);
       else
         value = key.restoreValue(context, savedValue);
 
       if (_LOG.isFinest())
       {
         _LOG.finest("RESTORE {" + key + "=" + value + "}");
       }
 
       map.put(key, value);
     }
   }
 
   /**
    * Saves an object that may implement StateHolder.
    */
   static public Object saveStateHolder(
     FacesContext context,
     Object       value)
   {
     if (value == null)
       return null;
 
     Saver saver = null;
     if (value instanceof StateHolder)
     {
       if (((StateHolder) value).isTransient())
         return null;
 
       saver = new SHSaver();
     }
     else if (value instanceof Serializable)
     {
       return value;
     }
     else
     {
       saver = new Saver();
     }
 
     if (saver != null)
       saver.saveState(context, value);
 
     return saver;
   }
 
   /**
    * Restores an object that was saved using saveStateHolder()
    */
   static public Object restoreStateHolder(
     FacesContext context,
     Object       savedValue)
   {
     if (!(savedValue instanceof Saver))
       return savedValue;
 
     return ((Saver) savedValue).restoreState(context);
   }
 
 
 
   /**
    * Saves a List whose elements may implement StateHolder.
    */
   @SuppressWarnings("unchecked")
   static public Object saveList(
     FacesContext context,
     Object       value)
   {
     if (value == null)
       return null;
 
     List<Object> list = (List<Object>) value;
     int size = list.size();
     if (size == 0)
       return null;
 
     Object[] array = new Object[size];
     // 2006-08-01: -= Simon Lessard =-
     //             Inefficient loop if the list implementation
     //             ever change to a linked data structure. Use
     //             iterators instead
     //for (int i = 0; i < size; i++)
     //  array[i] = saveStateHolder(context, list.get(i));
     int index = 0;
     for(Object object : list)
     {
       array[index++] = saveStateHolder(context, object);
     }
 
     return array;
   }
 
   /**
    * Restores a List whose elements may implement StateHolder.
    */
   static public Object restoreList(
     FacesContext context,
     Object       savedValue)
   {
     if (savedValue == null)
       return null;
 
     Object[] array = (Object[]) savedValue;
     int length = array.length;
     if (length == 0)
       return null;
 
     List<Object> list = new ArrayList<Object>(length);
     for(Object state : array)
     {
       Object restored = restoreStateHolder(context, state);
       if (restored != null)
       {
         list.add(restored);
       }
     }
 
     return list;
   }
 
 
 
   /**
    * Instance used to save generic instances;  simply saves
    * the class name.
    */
   static private class Saver implements Serializable
   {
     public void saveState(FacesContext context, Object saved)
     {
       _name = saved.getClass().getName();
     }
 
     public Object restoreState(FacesContext context)
     {
       // we don't need to use concurrent map methods like putIfAbsent. If someone happens to
       // add a name/value pair again it's fine because as the doc for put in HashMap says
       // "If the map previously contained a mapping for this key, the old value is replaced."
       ConcurrentMap<String, Object> appMap = 
                            RequestContext.getCurrentInstance().getApplicationScopedConcurrentMap();
       
 
       Map<String, Class> classMap = (Map<String, Class>) appMap.get(_CLASS_MAP_KEY);
       
       if (classMap == null)
       {    
         // the classMap doesn't need to worry about synchronization, 
         // if the Class is loaded twice that's fine. 
         Map<String, Class> newClassMap = new HashMap<String, Class>();
         Map<String, Class> oldClassMap = 
                               (Map<String, Class>) appMap.putIfAbsent(_CLASS_MAP_KEY, newClassMap);
         
         if (oldClassMap != null)
           classMap = oldClassMap;
         else
           classMap = newClassMap;
       }
             
       Class clazz = classMap.get(_name);
 
       if (clazz == null)
       {
         try
         {
           ClassLoader cl = _getClassLoader();
           clazz = cl.loadClass(_name);
           classMap.put(_name, clazz);
         }
         catch (Throwable t)
         {
           _LOG.severe(t);
           return null;
         }
       }
 
       try
       {
         return clazz.newInstance();
       }
       catch (Throwable t)
       {
         _LOG.severe(t);
         return null;
       }
     }
 
     private String _name;
     private static final long serialVersionUID = 1L;
   }
 
 
   /**
    * Instance used to save StateHolder objects.
    */
   static private class SHSaver extends Saver
   {
     @Override
     public void saveState(FacesContext context, Object value)
     {
       super.saveState(context, value);
       _save = ((StateHolder) value).saveState(context);
     }
 
     @Override
     public Object restoreState(FacesContext context)
     {
       Object o = super.restoreState(context);
       if (o != null)
         ((StateHolder) o).restoreState(context, _save);
 
       return o;
     }
 
     private Object _save;
     private static final long serialVersionUID = 1L;
   }
 
 
   //
   // Pick a ClassLoader
   //
   static private ClassLoader _getClassLoader()
   {
     ClassLoader cl = Thread.currentThread().getContextClassLoader();
     if (cl == null)
       cl = StateUtils.class.getClassLoader();
 
     return cl;
   }
 
   static private final TrinidadLogger _LOG = TrinidadLogger.createTrinidadLogger(StateUtils.class);
 
   private static final String _CLASS_MAP_KEY = 
                                            "org.apache.myfaces.trinidad.bean.util.CLASS_MAP_KEY";
 
 
 }