// Copyright 2006 Daniel Gredler

 //

 // 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 net.sf.beanform.binding;

 import java.util.Map;

 import java.util.Map.Entry;

 import org.apache.hivemind.Location;

 import org.apache.tapestry.IBinding;

 import org.apache.tapestry.IComponent;

 /**

  * A special binding type that allows us to simulate adding and removing

  * bindings to components. This binding behaves like a custom binding unless

  * there is no custom binding, in which case it behaves like the standard

  * (default) binding for a given binding name.

  *

  * @author Daniel Gredler

  */

 public class DualBinding implements IBinding {

     private IBinding custom;

     private IBinding standard;

     public DualBinding( IBinding custom, IBinding standard ) {

         this.custom = custom;

         this.standard = standard;

     }

     public void setCustom( IBinding custom ) {

         this.custom = custom;

     }

     public Object getObject() {

         if( this.custom != null ) return this.custom.getObject();

         else if( this.standard != null ) return this.standard.getObject();

         else return null;

     }

     public Object getObject( Class type ) {

         if( this.custom != null ) return this.custom.getObject( type );

         else if( this.standard != null ) return this.standard.getObject( type );

         else return null;

     }

     public boolean isInvariant() {

         return false;

     }

     public void setObject( Object value ) {

         if( this.custom != null ) this.custom.setObject( value );

         else if( this.standard != null ) this.standard.setObject( value );

     }

     public String getDescription() {

         if( this.custom != null ) return this.custom.getDescription();

         else if( this.standard != null ) return this.standard.getDescription();

         else return null;

     }

     public Location getLocation() {

         if( this.custom != null ) return this.custom.getLocation();

         else if( this.standard != null ) return this.standard.getLocation();

         else return null;

     }

     /**

      * Adds temporary custom bindings to a component by overriding the existing bindings

      * with {@link DualBinding} instances whose behavior can later be reverted.

      */

     public static void addCustomBindings( IComponent component, Map<String, IBinding> bindings, boolean clearFirst ) {

         if( clearFirst ) {

             DualBinding.removeCustomBindings( component );

         }

         for( Entry<String, IBinding> entry : bindings.entrySet() ) {

             String bindingName = entry.getKey();

             IBinding custom = entry.getValue();

             IBinding existing = component.getBinding( bindingName );

             DualBinding dual;

             if( existing instanceof DualBinding ) {

                 dual = (DualBinding) existing;

                 dual.setCustom( custom );

             }

             else {

                 dual = new DualBinding( custom, existing );

             }

             component.setBinding( bindingName, dual );

         }

     }

     /**

      * Reverts the behavior of the specified component's temporarily customized bindings to

      * whatever it was prior to customization.

      */

     @SuppressWarnings( "unchecked" )

     public static void removeCustomBindings( IComponent component ) {

         Map<String, IBinding> bindings = component.getBindings();

         for( IBinding binding : bindings.values() ) {

             if( binding instanceof DualBinding ) {

                 DualBinding dual = (DualBinding) binding;

                 dual.setCustom( null );

             }

         }

     }

 }