/*
    * 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.custom.autoscroll;
  
  import java.io.IOException;
  import java.util.List;
  
  import javax.faces.component.StateHolder;
  import javax.faces.component.UICommand;
  import javax.faces.component.UIComponent;
  import javax.faces.component.UIViewRoot;
  import javax.faces.component.behavior.ClientBehavior;
  import javax.faces.component.behavior.ClientBehaviorHolder;
  import javax.faces.context.FacesContext;
  import javax.faces.event.ComponentSystemEvent;
  import javax.faces.event.ComponentSystemEventListener;
  import javax.faces.event.PostAddToViewEvent;
  import javax.faces.event.PostRestoreStateEvent;
  import javax.faces.event.SystemEvent;
  import javax.faces.event.SystemEventListener;
  import javax.faces.view.facelets.FaceletContext;
  import javax.faces.view.facelets.TagAttribute;
  import javax.faces.view.facelets.TagConfig;
  import javax.faces.view.facelets.TagHandler;
  
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFFaceletAttribute;
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFFaceletTag;
  
  /**
   * Adds to UICommand components that implements ClientBehaviorHolder interface an
   * AutoscrollBehavior.
   * <p>
   * Use it in this way to ensure proper operation:
   * </p>
   * <code>
   * &lt;f:metadata&gt;
   *   &lt;t:autoScrollPage/&gt;
   * &lt;/f:metadata&gt;
   * </code>
   * <p>
   * Or in this way:
   * </p>
   * <code>
   * &lt;h:body&gt;
   *   &lt;t:autoScrollPage/&gt;
   * </code>
   * <p>
   * It is possible to use it at start of the page too, but note this tag attach a listener to
   * PostAddToViewEvent, so previous components added to the view before apply this TagHandler
   * will not be taken into account.
   * </p>
   * 
   * @since 1.1.10
   * @author Leonardo Uribe (latest modification by $Author: lu4242 $)
   * @version $Revision: 691856 $ $Date: 2008-09-03 21:40:30 -0500 (mié, 03 sep 2008) $
   */
  @JSFFaceletTag(name="t:autoScrollPage")
  public class AutoscrollPageTagHandler extends TagHandler
  {
  
      /**
       * 
       */
      @JSFFaceletAttribute(name="event",
              className="javax.el.ValueExpression",
              deferredValueType="java.lang.String")
      private TagAttribute _event;
      
      public AutoscrollPageTagHandler(TagConfig config)
      {
          super(config);
          _event = this.getAttribute("event");
      }
  
      public void apply(FaceletContext ctx, UIComponent parent)
              throws IOException
      {
          UIViewRoot root = getViewRoot(ctx, parent);
          
          if (!root.getAttributes().containsKey(AutoscrollBehaviorTagHandler.AUTOSCROLL_TAG_ON_PAGE))
          {
              root.getAttributes().put(AutoscrollBehaviorTagHandler.AUTOSCROLL_TAG_ON_PAGE, Boolean.TRUE);
          }
         
         String eventName = (_event == null) ? null : _event.getValue(ctx);
         
         root.subscribeToViewEvent(PostAddToViewEvent.class, 
                 new RegisterAutoscrollBehaviorOnCommandListener(eventName));
         root.subscribeToEvent(PostRestoreStateEvent.class, new RegisterAutoscrollListener(eventName));
     }
     
     private UIViewRoot getViewRoot(FaceletContext ctx, UIComponent parent)
     {
         UIComponent c = parent;
         do
         {
             if (c instanceof UIViewRoot)
             {
                 return (UIViewRoot) c;
             }
             else
             {
                 c = c.getParent();
             }
         } while (c != null);
 
         return ctx.getFacesContext().getViewRoot();
     }
 
     public static class RegisterAutoscrollListener implements ComponentSystemEventListener, StateHolder
     {
         private String eventName;
         
         public RegisterAutoscrollListener()
         {
             super();
         }
 
         public RegisterAutoscrollListener(String event)
         {
             super();
             eventName = event;
         }
 
         public void processEvent(ComponentSystemEvent event)
         {
             FacesContext.getCurrentInstance().getViewRoot().subscribeToViewEvent(PostAddToViewEvent.class, 
                     new RegisterAutoscrollBehaviorOnCommandListener(eventName));
         }
 
         public boolean isTransient()
         {
             return false;
         }
         
         public void setTransient(boolean newTransientValue)
         {
         }
 
         public void restoreState(FacesContext context, Object state)
         {
             eventName = (String)state;
         }
 
         public Object saveState(FacesContext context)
         {
             return eventName;
         }
     }
     
     public static class RegisterAutoscrollBehaviorOnCommandListener implements SystemEventListener
     {
         private String _eventName;
 
         public RegisterAutoscrollBehaviorOnCommandListener(String eventName)
         {
             super();
             _eventName = eventName;
         }
 
         public boolean isListenerForSource(Object source)
         {
             return (source instanceof UICommand && source instanceof ClientBehaviorHolder);
         }        
         
         public void processEvent(SystemEvent event)
         {
             ClientBehaviorHolder component = (ClientBehaviorHolder) event.getSource();
             
             String eventName = (_eventName == null) ? component.getDefaultEventName() : _eventName;
             
             boolean found = false;
             List<ClientBehavior> list = component.getClientBehaviors().get(eventName);
             if (list != null)
             {
                 for (ClientBehavior cb : list)
                 {
                     if (cb instanceof AutoscrollBehavior)
                     {
                         found = true;
                         break;
                     }
                 }
             }
             
             if (!found)
             {
                 ClientBehavior behavior = (ClientBehavior) FacesContext.getCurrentInstance().getApplication().createBehavior(AutoscrollBehavior.BEHAVIOR_ID);
                 component.addClientBehavior(eventName, behavior);
             }
         }
     }
 }