/*
    * 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.convert;
  
  import javax.faces.component.PartialStateHolder;
  import javax.faces.component.UIComponent;
  import javax.faces.context.FacesContext;
  
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFConverter;
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;
  
  /**
   * see Javadoc of <a href="http://java.sun.com/j2ee/javaserverfaces/1.2/docs/api/index.html">JSF Specification</a>
   * 
   * @author Stan Silvert
   */
  @JSFConverter
  public class EnumConverter implements Converter, PartialStateHolder
  {
  
      public static final String CONVERTER_ID = "javax.faces.Enum";
      public static final String ENUM_ID = "javax.faces.converter.EnumConverter.ENUM";
      public static final String ENUM_NO_CLASS_ID = "javax.faces.converter.EnumConverter.ENUM_NO_CLASS";
  
      /**
       * If value is a String instance and this param is true, pass it directly without try any change.
       * 
       * See MYFACES-2739 for details.
       */
      @JSFWebConfigParam(name="org.apache.myfaces.ENUM_CONVERTER_ALLOW_STRING_PASSTROUGH", since="2.0.1",
                         expectedValues="true,false",defaultValue="false", group="validation")
      private static final String ALLOW_STRING_PASSTROUGH = "org.apache.myfaces.ENUM_CONVERTER_ALLOW_STRING_PASSTROUGH";
      
      // TODO: Find a valid generic usage -= Simon Lessard =-
      private Class targetClass;
  
      private boolean isTransient = false;
  
      /** Creates a new instance of EnumConverter */
      public EnumConverter()
      {
      }
  
      public EnumConverter(Class targetClass)
      {
          if (!targetClass.isEnum())
          {
              throw new IllegalArgumentException("targetClass for EnumConverter must be an Enum");
          }
          this.targetClass = targetClass;
      }
  
      public String getAsString(FacesContext facesContext, UIComponent uiComponent, Object value)
          throws ConverterException
      {
          if (facesContext == null)
          {
              throw new NullPointerException("facesContext can not be null");
          }
          if (uiComponent == null)
          {
              throw new NullPointerException("uiComponent can not be null");
          }
  
          checkTargetClass(facesContext, uiComponent, value);
  
          if (value == null)
          {
              return null;
          }
          
          if (value instanceof String
                  && _isPassThroughStringValues(facesContext))
          {
              // pass through the String value
              return (String) value;
          }
  
          // check if the value is an instance of the enum class
          if (targetClass.isInstance(value))
          {
              return ((Enum<?>) value).name();
         }
         
         Object[] params =
             new Object[] { value, firstConstantOfEnum(), _MessageUtils.getLabel(facesContext, uiComponent) };
 
         throw new ConverterException(_MessageUtils.getErrorMessage(facesContext, ENUM_ID, params));
     }
 
     public Object getAsObject(FacesContext facesContext, UIComponent uiComponent, String value)
         throws ConverterException
     {
         if (facesContext == null)
         {
             throw new NullPointerException("facesContext");
         }
         if (uiComponent == null)
         {
             throw new NullPointerException("uiComponent");
         }
         if (value == null)
         {
             return null;
         }
         value = value.trim();
         if (value.length() == 0)
         {
             return null;
         }
         checkTargetClass(facesContext, uiComponent, value);
 
         // we know targetClass and value can't be null, so we can use Enum.valueOf
         // instead of the hokey looping called for in the javadoc
         try
         {
             return Enum.valueOf(targetClass, value);
         }
         catch (IllegalArgumentException e)
         {
             Object[] params =
                     new Object[] { value, firstConstantOfEnum(), _MessageUtils.getLabel(facesContext, uiComponent) };
 
             throw new ConverterException(_MessageUtils.getErrorMessage(facesContext, ENUM_ID, params));
         }
     }
 
     private void checkTargetClass(FacesContext facesContext, UIComponent uiComponent, Object value)
     {
         if (targetClass == null)
         {
             Object[] params = new Object[] { value, _MessageUtils.getLabel(facesContext, uiComponent) };
             throw new ConverterException(_MessageUtils.getErrorMessage(facesContext, ENUM_NO_CLASS_ID, params));
         }
     }
 
     // find the first constant value of the targetClass and return as a String
     private String firstConstantOfEnum()
     {
         Object[] enumConstants = targetClass.getEnumConstants();
 
         if (enumConstants.length != 0)
         {
             return enumConstants[0].toString();
         }
 
         return ""; // if empty Enum
     }
 
     public void restoreState(FacesContext context, Object state)
     {
         if (state != null)
         {
             targetClass = (Class<?>)state;
         }
     }
 
     public Object saveState(FacesContext context)
     {
         if (!initialStateMarked())
         {
             return targetClass;
         }
         return null;
     }
 
     public void setTransient(boolean newTransientValue)
     {
         isTransient = newTransientValue;
     }
 
     public boolean isTransient()
     {
         return isTransient;
     }
     
     private boolean _initialStateMarked = false;
 
     public void clearInitialState()
     {
         _initialStateMarked = false;
     }
 
     public boolean initialStateMarked()
     {
         return _initialStateMarked;
     }
 
     public void markInitialState()
     {
         _initialStateMarked = true;
     }
     
     private boolean _isPassThroughStringValues(FacesContext facesContext)
     {
         String param = facesContext.getExternalContext().getInitParameter(ALLOW_STRING_PASSTROUGH);
         if (param != null)
         {
             return param.trim().equalsIgnoreCase("true");
         }
         // default: false
         return false;
     }
 
 }