// $Header: /home/cvs/jakarta-jmeter/src/core/org/apache/jmeter/control/Controller.java,v 1.8 2004/02/13 02:21:38 sebb Exp $
/*
 * Copyright 2001-2004 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.jmeter.control;

import org.apache.jmeter.engine.event.LoopIterationListener;
import org.apache.jmeter.samplers.Sampler;
import org.apache.jmeter.testelement.TestElement;

/**
 * This interface will typically be used in the following manner:
 *
 * Controller controller;  //gets initialized
 * while(!controller.isDone() && controller.hasNext())
 * {
 *    Sampler sampler = controller.next();
 *    return sampler;
 * }
 *
 * @author    Michael Stover
 * @author    Thad Smith
 * @version   $Revision: 1.8 $
 */
public interface Controller extends TestElement
{ 
    /**
     * Delivers the next Sampler.
     * @return org.apache.jmeter.samplers.Sampler
     */
    public Sampler next();

    /**
     * Indicates whether the Controller is done delivering Samplers for 
     * the rest of the test.
     * @return boolean
     */
    public boolean isDone();

    /**
     * Controllers have to notify listeners of when they begin an iteration
     * through their sub-elements.
     */
    public void addIterationListener(LoopIterationListener listener);

    /**
     * Called to initialize a controller at the beginning of a test
     * iteration.
     */
    public void initialize();
}