/*
    * 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 javax.faces.component;
  
  import javax.el.ValueExpression;
  import javax.faces.FacesException;
  import javax.faces.context.FacesContext;
  import java.beans.BeanInfo;
  import java.beans.IntrospectionException;
  import java.beans.Introspector;
  import java.beans.PropertyDescriptor;
  import java.io.Serializable;
  import java.lang.reflect.Method;
  import java.util.*;
  
  /**
   * A custom implementation of the Map interface, where get and put calls
   * try to access getter/setter methods of an associated UIComponent before
   * falling back to accessing a real Map object.
   * <p/>
   * Some of the behaviours of this class don't really comply with the
   * definitions of the Map class; for example the key parameter to all
   * methods is required to be of type String only, and after clear(),
   * calls to get can return non-null values. However the JSF spec
   * requires that this class behave in the way implemented below. See
   * UIComponent.getAttributes for more details.
   * <p/>
   * The term "property" is used here to refer to real javabean properties
   * on the underlying UIComponent, while "attribute" refers to an entry
   * in the associated Map.
   *
   * @author Manfred Geiler (latest modification by $Author: lu4242 $)
   * @version $Revision: 1145322 $ $Date: 2011-07-11 15:06:13 -0500 (Mon, 11 Jul 2011) $
   */
  class _ComponentAttributesMap
          implements Map, Serializable
  {
      private static final long serialVersionUID = -9106832179394257866L;
  
      private static final Object[] EMPTY_ARGS = new Object[0];
  
      // The component that is read/written via this map.
      private UIComponent _component;
  
      // We delegate instead of derive from HashMap, so that we can later
      // optimize Serialization
      private Map<Object, Object> _attributes = null;
  
      // A cached hashmap of propertyName => PropertyDescriptor object for all
      // the javabean properties of the associated component. This is built by
      // introspection on the associated UIComponent. Don't serialize this as
      // it can always be recreated when needed.
      private transient Map<String, PropertyDescriptor> _propertyDescriptorMap = null;
  
      // Cache for component property descriptors
      private static Map<Class, Map<String, PropertyDescriptor>> _propertyDescriptorCache = new WeakHashMap<Class, Map<String, PropertyDescriptor>>();
  
      /**
       * Create a map backed by the specified component.
       * <p/>
       * This method is expected to be called when a component is first created.
       */
      _ComponentAttributesMap(UIComponent component)
      {
          _component = component;
          _attributes = new HashMap<Object, Object>();
      }
  
      /**
       * Create a map backed by the specified component. Attributes already
       * associated with the component are provided in the specified Map
       * class. A reference to the provided map is kept; this object's contents
       * are updated during put calls on this instance.
       * <p/>
       * This method is expected to be called during the "restore view" phase.
       */
      _ComponentAttributesMap(UIComponent component, Map<Object, Object> attributes)
      {
          _component = component;
          _attributes = new HashMap(attributes);
      }
  
      /**
      * Return the number of <i>attributes</i> in this map. Properties of the
      * underlying UIComponent are not counted.
      * <p/>
      * Note that because the get method can read properties of the
      * UIComponent and evaluate value-bindings, it is possible to have
      * size return zero while calls to the get method return non-null
      * values.
      */
     public int size()
     {
         return _attributes.size();
     }
 
     /**
      * Clear all the <i>attributes</i> in this map. Properties of the
      * underlying UIComponent are not modified.
      * <p/>
      * Note that because the get method can read properties of the
      * UIComponent and evaluate value-bindings, it is possible to have
      * calls to the get method return non-null values immediately after
      * a call to clear.
      */
     public void clear()
     {
         _attributes.clear();
     }
 
     /**
      * Return true if there are no <i>attributes</i> in this map. Properties
      * of the underlying UIComponent are not counted.
      * <p/>
      * Note that because the get method can read properties of the
      * UIComponent and evaluate value-bindings, it is possible to have
      * isEmpty return true, while calls to the get method return non-null
      * values.
      */
     public boolean isEmpty()
     {
         return _attributes.isEmpty();
     }
 
     /**
      * Return true if there is an <i>attribute</i> with the specified name,
      * but false if there is a javabean <i>property</i> of that name on the
      * associated UIComponent.
      * <p/>
      * Note that it should be impossible for the attributes map to contain
      * an entry with the same name as a javabean property on the associated
      * UIComponent.
      *
      * @param key <i>must</i> be a String. Anything else will cause a
      *            ClassCastException to be thrown.
      */
     public boolean containsKey(Object key)
     {
         checkKey(key);
 
         return getPropertyDescriptor((String) key) == null ? _attributes.containsKey(key) : false;
     }
 
     /**
      * Returns true if there is an <i>attribute</i> with the specified
      * value. Properties of the underlying UIComponent aren't examined,
      * nor value-bindings.
      *
      * @param value null is allowed
      */
     public boolean containsValue(Object value)
     {
         return _attributes.containsValue(value);
     }
 
     /**
      * Return a collection of the values of all <i>attributes</i>. Property
      * values are not included, nor value-bindings.
      */
     public Collection<Object> values()
     {
         return _attributes.values();
     }
 
     /**
      * Call put(key, value) for each entry in the provided map.
      */
     public void putAll(Map t)
     {
         for (Iterator it = t.entrySet().iterator(); it.hasNext();)
         {
             Map.Entry entry = (Entry) it.next();
             put(entry.getKey(), entry.getValue());
         }
     }
 
     /**
      * Return a set of all <i>attributes</i>. Properties of the underlying
      * UIComponent are not included, nor value-bindings.
      */
     public Set entrySet()
     {
         return _attributes.entrySet();
     }
 
     /**
      * Return a set of the keys for all <i>attributes</i>. Properties of the
      * underlying UIComponent are not included, nor value-bindings.
      */
     public Set<Object> keySet()
     {
         return _attributes.keySet();
     }
 
     /**
      * In order: get the value of a <i>property</i> of the underlying
      * UIComponent, read an <i>attribute</i> from this map, or evaluate
      * the component's value-binding of the specified name.
      *
      * @param key must be a String. Any other type will cause ClassCastException.
      */
     public Object get(Object key)
     {
         checkKey(key);
 
         // is there a javabean property to read?
         PropertyDescriptor propertyDescriptor
                 = getPropertyDescriptor((String) key);
         if (propertyDescriptor != null)
         {
             return getComponentProperty(propertyDescriptor);
         }
 
         // is there a literal value to read?
         Object mapValue = _attributes.get(key);
         if (mapValue != null)
         {
             return mapValue;
         }
 
         // is there a value-binding to read?
         ValueExpression ve = _component.getValueExpression((String) key);
         if (ve != null)
         {
             return ve.getValue(_component.getFacesContext().getELContext());
         }
 
         // no value found
         return null;
     }
 
     /**
      * Remove the attribute with the specified name. An attempt to
      * remove an entry whose name is that of a <i>property</i> on
      * the underlying UIComponent will cause an IllegalArgumentException.
      * Value-bindings for the underlying component are ignored.
      *
      * @param key must be a String. Any other type will cause ClassCastException.
      */
     public Object remove(Object key)
     {
         checkKey(key);
         PropertyDescriptor propertyDescriptor = getPropertyDescriptor((String) key);
         if (propertyDescriptor != null)
         {
             throw new IllegalArgumentException("Cannot remove component property attribute");
         }
         return _attributes.remove(key);
     }
 
     /**
      * Store the provided value as a <i>property</i> on the underlying
      * UIComponent, or as an <i>attribute</i> in a Map if no such property
      * exists. Value-bindings associated with the component are ignored; to
      * write to a value-binding, the value-binding must be explicitly
      * retrieved from the component and evaluated.
      * <p/>
      * Note that this method is different from the get method, which
      * does read from a value-binding if one exists. When a value-binding
      * exists for a non-property, putting a value here essentially "masks"
      * the value-binding until that attribute is removed.
      * <p/>
      * The put method is expected to return the previous value of the
      * property/attribute (if any). Because UIComponent property getter
      * methods typically try to evaluate any value-binding expression of
      * the same name this can cause an EL expression to be evaluated,
      * thus invoking a getter method on the user's model. This is fine
      * when the returned value will be used; Unfortunately this is quite
      * pointless when initialising a freshly created component with whatever
      * attributes were specified in the view definition (eg JSP tag
      * attributes). Because the UIComponent.getAttributes method
      * only returns a Map class and this class must be package-private,
      * there is no way of exposing a "putNoReturn" type method.
      *
      * @param key   String, null is not allowed
      * @param value null is allowed
      */
     public Object put(Object key, Object value)
     {
         checkKey(key);
 
         PropertyDescriptor propertyDescriptor = getPropertyDescriptor((String) key);
         if (propertyDescriptor == null)
         {
             if (value == null)
             {
                 throw new NullPointerException("value is null for a not available property: " + key);
             }
         }
         else
         {
             if (propertyDescriptor.getReadMethod() != null)
             {
                 Object oldValue = getComponentProperty(propertyDescriptor);
                 setComponentProperty(propertyDescriptor, value);
                 return oldValue;
             }
             setComponentProperty(propertyDescriptor, value);
             return null;
         }
         return _attributes.put(key, value);
     }
 
     /**
      * Retrieve info about getter/setter methods for the javabean property
      * of the specified name on the underlying UIComponent object.
      * <p/>
      * This method optimises access to javabean properties of the underlying
      * UIComponent by maintaining a cache of ProperyDescriptor objects for
      * that class.
      * <p/>
      * TODO: Consider making the cache shared between component instances;
      * currently 100 UIInputText components means performing introspection
      * on the UIInputText component 100 times.
      */
     private PropertyDescriptor getPropertyDescriptor(String key)
     {
         if (_propertyDescriptorMap == null)
         {
             // Try to get descriptor map from cache
             _propertyDescriptorMap = _propertyDescriptorCache.get(_component.getClass());
             // Cache miss: create descriptor map and put it in cache
             if (_propertyDescriptorMap == null)
             {
                 // Create descriptor map...
                 BeanInfo beanInfo;
                 try
                 {
                     beanInfo = Introspector.getBeanInfo(_component.getClass());
                 }
                 catch (IntrospectionException e)
                 {
                     throw new FacesException(e);
                 }
                 PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
                 _propertyDescriptorMap = new HashMap<String, PropertyDescriptor>();
                 for (int i = 0; i < propertyDescriptors.length; i++)
                 {
                     PropertyDescriptor propertyDescriptor = propertyDescriptors[i];
                     if (propertyDescriptor.getReadMethod() != null)
                     {
                         _propertyDescriptorMap.put(propertyDescriptor.getName(),
                                 propertyDescriptor);
                     }
                 }
                 // ... and put it in cache
                 synchronized(_propertyDescriptorCache)
                 {
                     // Use a synchronized block to ensure proper operation on concurrent use cases.
                     // This is a racy single check, because initialization over the same class could happen
                     // multiple times, but the same result is always calculated. The synchronized block 
                     // just ensure thread-safety, because only one thread will modify the cache map
                     // at the same time.
                     _propertyDescriptorCache.put(_component.getClass(), _propertyDescriptorMap);
                 }
             }
         }
         return _propertyDescriptorMap.get(key);
     }
 
 
     /**
      * Execute the getter method of the specified property on the underlying
      * component.
      *
      * @param propertyDescriptor specifies which property to read.
      * @return the value returned by the getter method.
      * @throws IllegalArgumentException if the property is not readable.
      * @throws FacesException           if any other problem occurs while invoking
      *                                  the getter method.
      */
     private Object getComponentProperty(PropertyDescriptor propertyDescriptor)
     {
         Method readMethod = propertyDescriptor.getReadMethod();
         if (readMethod == null)
         {
             throw new IllegalArgumentException("Component property " + propertyDescriptor.getName() + " is not readable");
         }
         try
         {
             return readMethod.invoke(_component, EMPTY_ARGS);
         }
         catch (Exception e)
         {
             FacesContext facesContext = _component.getFacesContext();
             throw new FacesException("Could not get property " + propertyDescriptor.getName() + " of component " + _component.getClientId(facesContext), e);
         }
     }
 
     /**
      * Execute the setter method of the specified property on the underlying
      * component.
      *
      * @param propertyDescriptor specifies which property to write.
      * @throws IllegalArgumentException if the property is not writable.
      * @throws FacesException           if any other problem occurs while invoking
      *                                  the getter method.
      */
     private void setComponentProperty(PropertyDescriptor propertyDescriptor, Object value)
     {
         Method writeMethod = propertyDescriptor.getWriteMethod();
         if (writeMethod == null)
         {
             throw new IllegalArgumentException("Component property " + propertyDescriptor.getName() + " is not writable");
         }
         try
         {
             writeMethod.invoke(_component, new Object[]{value});
         }
         catch (Exception e)
         {
             FacesContext facesContext = _component.getFacesContext();
             throw new FacesException("Could not set property " + propertyDescriptor.getName() +
                     " of component " + _component.getClientId(facesContext) + " to value : " + value + " with type : " +
                     (value == null ? "null" : value.getClass().getName()), e);
         }
     }
 
     private void checkKey(Object key)
     {
         if (key == null)
         {
             throw new NullPointerException("key");
         }
         if (!(key instanceof String))
         {
             throw new ClassCastException("key is not a String");
         }
     }
 
     /**
      * Return the map containing the attributes.
      * <p/>
      * This method is package-scope so that the UIComponentBase class can access it
      * directly when serializing the component.
      */
     Map<Object, Object> getUnderlyingMap()
     {
         return _attributes;
     }
 
     /**
      * TODO: Document why this method is necessary, and why it doesn't try to
      * compare the _component field.
      */
     public boolean equals(Object obj)
     {
         return _attributes.equals(obj);
     }
 
     public int hashCode()
     {
         return _attributes.hashCode();
     }
 }