/*
    * 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.taglib.core;
  
  import javax.el.ELContext;
  import javax.el.ValueExpression;
  import javax.faces.component.StateHolder;
  import javax.faces.component.UIComponent;
  import javax.faces.context.FacesContext;
  import javax.faces.convert.Converter;
  import javax.faces.convert.ConverterException;
  
  /**
   * This class is used in conjunction with ConverterImplTag. 
   * 
   * When a tag like this is in a jsp page:
   * <code>
   * &lt;f:converter binding="#{mybean}"/&gt;
   *  
   *  or
   *  
   * &lt;f:converter converterId="#{'anyid'}" binding="#{mybean}"/&gt;
   * </code>
   * The value of mybean could be already on the context, so this
   * converter avoid creating a new variable and use the previous one.
   * 
   * @author Leonardo Uribe (latest modification by $Author$)
   * @version $Revision$ $Date$ 
   */
  public class DelegateConverter implements Converter, StateHolder
  {
  
      private ValueExpression _converterId;
      private ValueExpression _binding;
      private String _converterIdString = null;
      
      public DelegateConverter()
      {
          
      }
      
      public DelegateConverter(ValueExpression id, ValueExpression binding, String converterIdString)
      {
          super();
          _converterId = id;
          _binding = binding;
          _converterIdString = converterIdString;
      }
  
      public boolean isTransient()
      {
          return false;
      }
  
      public void restoreState(FacesContext facesContext, Object state)
      {
          Object[] values = (Object[]) state;
          _converterId = (ValueExpression) values[0];
          _binding = (ValueExpression) values[1];
          _converterIdString = (String) values[2];
      }
  
      public Object saveState(FacesContext facesContext)
      {
          Object[] values = new Object[3];
          values[0] = _converterId;
          values[1] = _binding;
          values[2] = _converterIdString;
          return values;
      }
  
      public void setTransient(boolean arg0)
      {
          // Do nothing        
      }
  
      public Object getAsObject(FacesContext facesContext, UIComponent component,
              String value)
      {
          return _getDelegate().getAsObject(facesContext, component, value);
      }
  
      public String getAsString(FacesContext facesContext, UIComponent component,
             Object value)
     {
         return _getDelegate().getAsString(facesContext, component, value);
     }
 
     private Converter _getDelegate()
     {
         return _createConverter();
     }
 
     private Converter _createConverter()
     {
         Converter converter = null;
 
         FacesContext facesContext = FacesContext.getCurrentInstance();
         ELContext elContext = facesContext.getELContext();
 
         // try to create the converter from the binding expression first, and then from
         // the converterId
         if (_binding != null)
         {
             try
             {
                 converter = (Converter) _binding.getValue(elContext);
 
                 if (converter != null)
                 {
                     return converter;
                 }
             }
             catch (Exception e)
             {
                 throw new ConverterException("Exception creating converter using binding", e);
             }
         }
 
         if ((_converterId != null) || (_converterIdString != null))
         {
             try
             {
                 if (null != _converterIdString)
                 {
                     converter = facesContext.getApplication().createConverter(_converterIdString);
                 }
                 else
                 {
                     String converterId = (String) _converterId.getValue(elContext);
                     converter = facesContext.getApplication().createConverter(converterId);
                 }
 
                 // with binding no converter was created, set its value with the converter
                 // created using the converterId
                 if (converter != null && _binding != null)
                 {
                     _binding.setValue(elContext, converter);
                 }
             }
             catch (Exception e)
             {
                 throw new ConverterException("Exception creating converter with converterId: " + _converterId, e);
             }
         }
         
         if (converter == null)
         {
             throw new IllegalStateException("Could not create converter. Please specify a valid converterId" +
                     " or a non-null binding.");
         }
 
         return converter;
     }
 
 }