/*
    * 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.context;
  
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import javax.el.ELContext;
  import javax.faces.application.Application;
  import javax.faces.application.FacesMessage;
  import javax.faces.application.ProjectStage;
  import javax.faces.component.UINamingContainer;
  import javax.faces.component.UIViewRoot;
  import javax.faces.event.PhaseId;
  import javax.faces.render.RenderKit;
  
  /**
   * see Javadoc of <a href="http://java.sun.com/javaee/javaserverfaces/1.2/docs/api/index.html">JSF Specification</a>
   */
  public abstract class FacesContext
  {
      private static ThreadLocal<FacesContext> currentInstance = new ThreadLocal<FacesContext>();
  
      private static ThreadLocal<FacesContext> firstInstance = new ThreadLocal<FacesContext>();
  
      public abstract void addMessage(String clientId, FacesMessage message);
  
      public abstract Application getApplication();
  
      /**
       * 
       * @return
       * 
       * @since 2.0
       */
      public Map<Object, Object> getAttributes()
      {
          FacesContext ctx = firstInstance.get();
          
          if (ctx == null)
          {
              throw new UnsupportedOperationException();
          }
          
          return ctx.getAttributes();
      }
  
      public abstract Iterator<String> getClientIdsWithMessages();
  
      public static FacesContext getCurrentInstance()
      {
          return currentInstance.get();
      }
  
      /**
       * 
       * @return
       * 
       * @since 2.0
       */
      public PhaseId getCurrentPhaseId()
      {
          FacesContext ctx = firstInstance.get();
          
          if (ctx == null)
          {
              throw new UnsupportedOperationException();
          }
          
          return ctx.getCurrentPhaseId();
      }
      
      /**
       * Return the context within which all EL-expressions are evaluated.
       * <p>
       * A JSF implementation is expected to provide a full implementation of this class. However JSF also explicitly
       * allows user code to apply the "decorator" pattern to this type, by overriding the FacesContextFactory class. In
       * that pattern, the decorating class has a reference to an "underlying" implementation and forward calls to it,
       * possibly after taking other related actions.
       * <p>
       * The decorator pattern does have difficulties with backwards-compatibility when new methods are added to the class
      * being decorated, as with this method which was added in JSF1.2. Decorator classes that were written for JSF1.1
      * will subclass this class, but will not override this method to pass the call on to the "underlying" instance.
      * This base implementation therefore must do that for it.
      * <p>
      * Unfortunately the JSF designers stuffed up the design; this base class has no way of knowing what the
      * "underlying" instance is! The current implementation here is therefore to delegate directly to the very
      * <i>first</i> FacesContext instance registered within this request (via setCurrentInstance). This instance should
      * be the "full" implementation provided by the JSF framework. The drawback is that when any decorator class is
      * present which defaults to this base implementation, then any following decorator instances that do override this
      * method do not get it invoked.
      * <p>
      * It is believed that the Sun JSF implementation (Mojarra) does something similar.
      * 
      * @since 1.2
      */
     public ELContext getELContext()
     {
         // Do NOT use getCurrentInstance here. For FacesContext decorators that
         // register themselves as "the current instance" that will cause an
         // infinite loop. For FacesContext decorators that do not register
         // themselves as "the current instance", if they are themselves wrapped
         // by a decorator that *does* register itself, then an infinite loop
         // also occurs.
         //
         // As noted above, we really want to do something like
         // ctx = getWrappedInstance();
         // where the subclass can return the object it is delegating to.
         // As there is no such method, however, the best we can do is pass the
         // method call on to the first-registered FacesContext instance. That
         // instance will never be "this", as the real original FacesContext
         // object will provide a proper implementation of this method.
         FacesContext ctx = firstInstance.get();
 
         if (ctx == null)
         {
             throw new NullPointerException(FacesContext.class.getName());
         }
 
         ELContext elctx = ctx.getELContext();
         if (elctx == null)
         {
             throw new UnsupportedOperationException();
         }
 
         return elctx;
     }
 
     /**
      * 
      * @return
      * 
      * @since 2.0
      */
     public ExceptionHandler getExceptionHandler()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         return ctx.getExceptionHandler();
     }
 
     public abstract ExternalContext getExternalContext();
 
     public abstract FacesMessage.Severity getMaximumSeverity();
 
     /**
      * 
      * @return
      * 
      * @since 2.0
      */
     public List<FacesMessage> getMessageList()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         return ctx.getMessageList();
     }
     
     /**
      * 
      * @param clientId
      * @return
      * 
      * @since 2.0
      */
     public List<FacesMessage> getMessageList(String clientId)
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         return ctx.getMessageList(clientId);
     }
 
     public abstract Iterator<FacesMessage> getMessages();
 
     public abstract Iterator<FacesMessage> getMessages(String clientId);
 
     /**
      * <p>
      * Return the PartialViewContext for this request. The PartialViewContext is used to control the processing of
      * specified components during the execute portion of the request processing lifecycle (known as partial processing)
      * and the rendering of specified components (known as partial rendering). This method must return a new
      * PartialViewContext if one does not already exist.
      * </p>
      * 
      * @return The PartialViewContext
      * @throws IllegalStateException
      *             if this method is called after this instance has been released
      * 
      * @since 2.0
      */
     public PartialViewContext getPartialViewContext()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         return ctx.getPartialViewContext();
     }
 
     public abstract RenderKit getRenderKit();
 
     public abstract boolean getRenderResponse();
 
     public abstract boolean getResponseComplete();
 
     public abstract ResponseStream getResponseStream();
 
     public abstract ResponseWriter getResponseWriter();
     
     /**
      * 
      * @return
      * 
      * @since 2.0
      */
     public boolean isValidationFailed()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         return ctx.isValidationFailed();
     }
 
     public abstract UIViewRoot getViewRoot();
 
     /**
      * 
      * @return
      * 
      * @since 2.0
      */
     public boolean isPostback()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         return ctx.isPostback();
     }
     
     /**
      * 
      * @return
      * 
      * @since 2.0
      */
     public boolean isProcessingEvents()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         return ctx.isProcessingEvents();
     }
 
     public abstract void release();
 
     public abstract void renderResponse();
 
     public abstract void responseComplete();
 
     protected static void setCurrentInstance(FacesContext context)
     {
         if (context == null)
         {
             currentInstance.remove();
             firstInstance.remove();
         }
         else
         {
             currentInstance.set(context);
 
             if (firstInstance.get() == null)
             {
                 firstInstance.set(context);
             }
         }
     }
 
     /**
      * 
      * @param currentPhaseId 
      * @since 2.0
      */
     public void setCurrentPhaseId(PhaseId currentPhaseId)
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         ctx.setCurrentPhaseId(currentPhaseId);
     }
 
     /**
      * 
      * @param exceptionHandler 
      * @since 2.0
      */
     public void setExceptionHandler(ExceptionHandler exceptionHandler)
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         ctx.setExceptionHandler(exceptionHandler);
     }
     
     /**
      * 
      * @param processingEvents
      * @since 2.0
      */
     public void setProcessingEvents(boolean processingEvents)
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         ctx.setProcessingEvents(processingEvents);
     }
 
     public abstract void setResponseStream(ResponseStream responseStream);
 
     public abstract void setResponseWriter(ResponseWriter responseWriter);
 
     public abstract void setViewRoot(UIViewRoot root);
     
     /**
      * 
      * 
      * @since 2.0
      */
     public void validationFailed()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
         
         ctx.validationFailed();
     }
     
     public boolean isProjectStage(ProjectStage stage)
     {
         if (stage == null)
         {
             throw new NullPointerException();
         }
         
         if (stage.equals(getApplication().getProjectStage()))
         {
             return true;
         }
         return false;
     }
     
     /**
      * 
      * @since 2.1
      * @return
      */
     public boolean isReleased()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             throw new UnsupportedOperationException();
         }
 
         return ctx.isReleased();
     }
     
     /**
      * @since 2.2
      * @return 
      */
     public List<String> getResourceLibraryContracts()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             return Collections.emptyList();
         }        
         
         return ctx.getResourceLibraryContracts();
     }
     
     /**
      * @since 2.2
      * @param contracts 
      */
     public void setResourceLibraryContracts(List<String> contracts)
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             return;
         }
         ctx.setResourceLibraryContracts(contracts);
     }
     
     /**
      * @since 2.2
      * @return 
      */
     public char getNamingContainerSeparatorChar()
     {
         FacesContext ctx = firstInstance.get();
         
         if (ctx == null)
         {
             return UINamingContainer.getSeparatorChar(this);
         }
         return ctx.getNamingContainerSeparatorChar();
     }
 }