// Copyright 2009 The Apache Software Foundation

 //

 // Licensed 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.tapestry5.ajax;

 import org.apache.tapestry5.ioc.internal.util.CollectionFactory;

 import org.apache.tapestry5.ioc.internal.util.Defense;

 import java.util.Map;

 /**

  * A mapping from <em>client-side zone ids</em> to objects that can render the content for that zone on the client. An

  * event handler method may instantiate an instance and chain together a series of calls to {@link #add(String,

  * Object)}, and return the final result.

  * <p/>

  * Remember that client-side element ids may not match server-side component ids, especially once Ajax is added to the

  * mix. Because of this, it is highly recommended that the client-side logic gather the actual component ids and include

  * those in the Ajax request, to ensure that the server generates updates that the client can process. Better yet, use

  * the Zone's id parameter to lock down the zone's id to a known, predictable value.

  *

  * @since 5.1.0.1

  */

 public class MultiZoneUpdate

 {

     private final MultiZoneUpdate parent;

     private final String zoneId;

     private final Object renderer;

     public MultiZoneUpdate(String zoneId, Object renderer)

     {

         this(zoneId, renderer, null);

     }

     private MultiZoneUpdate(String zoneId, Object renderer, MultiZoneUpdate parent)

     {

         this.zoneId = Defense.notBlank(zoneId, "zoneId");

         this.renderer = Defense.notNull(renderer, "renderer");

         this.parent = parent;

     }

     /**

      * Returns a <strong>new</strong> MultiZoneUpdate reflecting the mapping from the indicated zone to an object that

      * will render the content for that zone.

      *

      * @param zoneId   client id of zone to update

      * @param renderer object that can provide the content for the zone

      * @return new MultiZoneUpdate

      */

     public MultiZoneUpdate add(String zoneId, Object renderer)

     {

         return new MultiZoneUpdate(zoneId, renderer, this);

     }

     /**

      * Returns a mapping from client zone id to renderer object for that zone.

      *

      * @return string to renderer map

      */

     public Map<String, Object> getZoneToRenderMap()

     {

         Map<String, Object> result = CollectionFactory.newMap();

         MultiZoneUpdate cursor = this;

         while (cursor != null)

         {

             result.put(cursor.zoneId, cursor.renderer);

             cursor = cursor.parent;

         }

         return result;

     }

     @Override

     public String toString()

     {

         return String.format("MultiZoneUpdate[%s]", getZoneToRenderMap());

     }

 }