/**
 *    Copyright 2011 meltmedia
 *
 *    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.xchain.namespaces.core;

import org.apache.commons.jxpath.JXPathContext;
import org.xchain.annotations.Element;
import org.xchain.annotations.Attribute;
import org.xchain.annotations.AttributeType;

/**
 * The <code>if</code> command will execute its child commands if the <code>test</code> attribute evaluates to <code>true</code>.
 *
 * <code class="source">
 * <xchain:if xmlns:xchain="http://www.xchain.org/core/1.0" test="/some/xpath">
 *   ...
 * </xchain:if>
 * </code>
 *
 * @author Christian Trimble
 * @author Devon Tackett
 */
@Element(localName="if")
public abstract class IfCommand
  extends ChainCommand
{
  /**
   * The test for the <code>if</code> command.  This should evaluate to a boolean. 
   */  
  @Attribute(localName="test", type=AttributeType.JXPATH_VALUE)
  public abstract Boolean getTest( JXPathContext context );

  public boolean execute( JXPathContext context )
    throws Exception
  {
    Boolean result = getTest( context );

    // execute the nested chains.
    if( result != null && result.booleanValue() == true ) {
      return super.execute(context);
    }

    // if the test returned false, then return false and let the other chains execute.
    return false;
  }
}