/*
 * Copyright 2006-2007 the original author or authors.
 *
 * 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.springframework.batch.repeat;


/**
 * Interface for batch completion policies, to enable batch operations to
 * strategise normal completion conditions. Stateful implementations of batch
 * iterators should <em>only</em> update state using the update method. If you
 * need custom behaviour consider extending an existing implementation or using
 * the composite provided.
 * 
 * @author Dave Syer
 * 
 */
public interface CompletionPolicy {

	/**
	 * Determine whether a batch is complete given the latest result from the
	 * callback. If this method returns true then
	 * {@link #isComplete(RepeatContext)} should also (but not necessarily vice
	 * versa, since the answer here depends on the result).
	 * 
	 * @param context the current batch context.
	 * @param result the result of the latest batch item processing.
	 * 
	 * @return true if the batch should terminate.
	 * 
	 * @see #isComplete(RepeatContext)
	 */
	boolean isComplete(RepeatContext context, RepeatStatus result);

	/**
	 * Allow policy to signal completion according to internal state, without
	 * having to wait for the callback to complete.
	 * 
	 * @param context the current batch context.
	 * 
	 * @return true if the batch should terminate.
	 */
	boolean isComplete(RepeatContext context);

	/**
	 * Create a new context for the execution of a batch. N.B. implementations
	 * should <em>not</em> return the parent from this method - they must
	 * create a new context to meet the specific needs of the policy. The best
	 * way to do this might be to override an existing implementation and use
	 * the {@link RepeatContext} to store state in its attributes.
	 * 
	 * @param parent the current context if one is already in progress.
	 * @return a context object that can be used by the implementation to store
	 * internal state for a batch.
	 */
	RepeatContext start(RepeatContext parent);

	/**
	 * Give implementations the opportunity to update the state of the current
	 * batch. Will be called <em>once</em> per callback, after it has been
	 * launched, but not necessarily after it completes (if the batch is
	 * asynchronous).
	 * 
	 * @param context the value returned by start.
	 */
	void update(RepeatContext context);

}