/*
    * 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.servlet.jsp.tagext.TagSupport;
  import javax.servlet.jsp.JspException;
  import javax.faces.webapp.UIComponentClassicTagBase;
  import javax.faces.webapp.UIComponentELTag;
  import javax.faces.component.UIComponent;
  import javax.faces.context.FacesContext;
  import javax.el.ValueExpression;
  import javax.el.ELContext;
  
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFJspAttribute;
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFJspTag;
  
  /**
   * This tag associates an attribute with the nearest parent UIComponent.
   * <p>
   * When the value is not an EL expression, this tag has the same effect as calling component.getAttributes.put(name,
   * value). When the attribute name specified matches a standard property of the component, that property is set. However
   * it is also valid to assign attributes to components using any arbitrary name; the component itself won't make any use
   * of these but other objects such as custom renderers, validators or action listeners can later retrieve the attribute
   * from the component by name.
   * </p>
   * <p>
   * When the value is an EL expression, this tag has the same effect as calling component.setValueBinding. A call to
   * method component.getAttributes().get(name) will then cause that expression to be evaluated and the result of the
   * expression is returned, not the original EL expression string.
   * </p>
   * <p>
   * See the javadoc for UIComponent.getAttributes for more details.
   * </p>
   * <p>
   * Unless otherwise specified, all attributes accept static values or EL expressions.
   * </p>
   * 
   * @author Manfred Geiler (latest modification by $Author$)
   * @author Bruno Aranda (JSR-252)
   * @version $Revision$ $Date$
   */
  @JSFJspTag(name = "f:attribute", bodyContent = "empty")
  public class AttributeTag extends TagSupport
  {
      private static final long serialVersionUID = 31476300171678632L;
      private ValueExpression _nameExpression;
      private ValueExpression _valueExpression;
  
      /**
       * The name of the attribute.
       * 
       * @param nameExpression
       */
      @JSFJspAttribute(className="javax.el.ValueExpression",
              deferredValueType="java.lang.String")
      public void setName(ValueExpression nameExpression)
      {
          _nameExpression = nameExpression;
      }
  
      /**
       * The attribute's value.
       * 
       * @param valueExpression
       */
      @JSFJspAttribute(className="javax.el.ValueExpression",
              deferredValueType="java.lang.Object")
      public void setValue(ValueExpression valueExpression)
      {
          _valueExpression = valueExpression;
      }
  
      @Override
      public int doStartTag() throws JspException
      {
          UIComponentClassicTagBase componentTag = UIComponentELTag.getParentUIComponentClassicTagBase(pageContext);
          if (componentTag == null)
          {
              throw new JspException("no parent UIComponentTag found");
          }
          UIComponent component = componentTag.getComponentInstance();
          if (component == null)
          {
             throw new JspException("parent UIComponentTag has no UIComponent");
         }
 
         FacesContext facesContext = FacesContext.getCurrentInstance();
         ELContext elContext = facesContext.getELContext();
 
         String name = null;
         Object value = null;
         boolean isLiteral = false;
 
         if (_nameExpression != null)
         {
             name = (String)_nameExpression.getValue(elContext);
         }
 
         if (_valueExpression != null)
         {
             isLiteral = _valueExpression.isLiteralText();
             value = _valueExpression.getValue(elContext);
         }
 
         if (name != null)
         {
             if (component.getAttributes().get(name) == null)
             {
                 if (isLiteral)
                 {
                     component.getAttributes().put(name, value);
                 }
                 else
                 {
                     component.setValueExpression(name, _valueExpression);
                 }
             }
         }
 
         return SKIP_BODY;
     }
     
     @Override
     public void release()
     {
         super.release();
         _nameExpression = null;
         _valueExpression = null;
     }
 }