/*
    * Copyright 2002,2004 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.commons.jelly.tags.core;
  
  import java.lang.reflect.InvocationTargetException;
  import java.util.Map;
  
  import org.apache.commons.beanutils.BeanUtils;
  import org.apache.commons.jelly.JellyTagException;
  import org.apache.commons.jelly.TagSupport;
  import org.apache.commons.jelly.XMLOutput;
  import org.apache.commons.jelly.expression.Expression;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  
  /*** A tag which sets a variable from the result of an expression
    *
    * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
    * @version $Revision: 155420 $
    */
  public class SetTag extends TagSupport {
  
      /*** The Log to which logging calls will be made. */
      private static final Log log = LogFactory.getLog(SetTag.class);
  
      /*** The variable name to export. */
      private String var;
  
      /*** The variable scope to export */
      private String scope;
  
      /*** The expression to evaluate. */
      private Expression value;
  
      /*** The default value */
      private Expression defaultValue;
  
      /*** The target object on which to set a property. */
      private Object target;
  
      /*** The name of the property to set on the target object. */
      private String property;
  
      /*** Should we XML encode the body of this tag as text? */
      private boolean encode = true;
  
      public SetTag() {
      }
  
      // Tag interface
      //-------------------------------------------------------------------------
      public void doTag(XMLOutput output) throws JellyTagException {
          // perform validation up front to fail fast
          if ( var != null ) {
              if ( target != null || property != null ) {
                  throw new JellyTagException( "The 'target' and 'property' attributes cannot be used in combination with the 'var' attribute" );
              }
          }
          else {
              if ( target == null ) {
                  throw new JellyTagException( "Either a 'var' or a 'target' attribute must be defined for this tag" );
              }
              if ( property == null ) {
                  throw new JellyTagException( "The 'target' attribute requires the 'property' attribute" );
              }
          }
  
          Object answer = null;
          if ( value != null ) {
              answer = value.evaluate(context);
              if (defaultValue != null && isEmpty(answer)) {
                  answer = defaultValue.evaluate(context);
              }
          }
          else {
              answer = getBodyText(isEncode());
          }
  
          if ( var != null ) {
              if ( scope != null ) {
                  context.setVariable(var, scope, answer);
              }
              else {
                  context.setVariable(var, answer);
              }
         }
         else {
             setPropertyValue( target, property, answer );
         }
     }
 
     // Properties
     //-------------------------------------------------------------------------
     /*** Sets the variable name to define for this expression
      */
     public void setVar(String var) {
         this.var = var;
     }
 
     /***
      * Sets the variable scope for this variable. For example setting this value to 'parent' will
      * set this value in the parent scope. When Jelly is run from inside a Servlet environment
      * then other scopes will be available such as 'request', 'session' or 'application'.
      *
      * Other applications may implement their own custom scopes.
      */
     public void setScope(String scope) {
         this.scope = scope;
     }
 
     /*** Sets the expression to evaluate. */
     public void setValue(Expression value) {
         this.value = value;
     }
 
     /***
      * Sets the default value to be used if the value exprsesion results
      * in a null value or blank String
      */
     public void setDefaultValue(Expression defaultValue) {
         this.defaultValue = defaultValue;
     }
 
     /*** Sets the target object on which to set a property. */
     public void setTarget(Object target) {
         this.target = target;
     }
 
     /*** Sets the name of the property to set on the target object. */
     public void setProperty(String property) {
         this.property = property;
     }
 
     /***
      * Returns whether the body of this tag will be XML encoded or not.
      */
     public boolean isEncode() {
         return encode;
     }
 
     /***
      * Sets whether the body of the tag should be XML encoded as text (so that &lt; and &gt; are
      * encoded as &amp;lt; and &amp;gt;) or leave the text as XML which is the default.
      * This is only used if this tag is specified with no value so that the text body of this
      * tag is used as the body.
      */
     public void setEncode(boolean encode) {
         this.encode = encode;
     }
 
 
     // Implementation methods
     //-------------------------------------------------------------------------
     protected void setPropertyValue( Object target, String property, Object value ) {
         try {
             if ( target instanceof Map ) {
                 Map map = (Map) target;
                 map.put( property, value );
             }
             else {
                 BeanUtils.setProperty( target, property, value );
             }
         } catch (InvocationTargetException e) {
             log.error( "Failed to set the property: " + property + " on bean: " + target + " to value: " + value + " due to exception: " + e, e );
         } catch (IllegalAccessException e) {
             log.error( "Failed to set the property: " + property + " on bean: " + target + " to value: " + value + " due to exception: " + e, e );
         }
     }
 
     /***
      * @param value
      * @return true if the given value is null or an empty String
      */
     protected boolean isEmpty(Object value) {
         if (value == null) {
             return true;
         }
         if (value instanceof String) {
             String s = (String) value;
             return s.length() == 0;
         }
         return false;
     }
 
 }