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/*
 * This is part of Geomajas, a GIS framework, http://www.geomajas.org/.
 *
 * Copyright 2008-2015 Geosparc nv, http://www.geosparc.com/, Belgium.
 *
 * The program is available in open source according to the GNU Affero
 * General Public License. All contributions in this program are covered
 * by the Geomajas Contributors License Agreement. For full licensing
 * details, see LICENSE.txt in the project root.
 */

package org.geomajas.service.pipeline;

import org.geomajas.annotation.Api;
import org.geomajas.global.GeomajasException;

/**
 * A pipeline interceptor allows to perform some action before and after a consecutive series of pipeline steps. It also
 * allows to optionally skip those steps and/or the after action by letting the before action returning different
 * execution modes.
 *
 * Do not implement this class, extend {@link AbstractPipelineInterceptor} instead.
 * 
 * @param 
 *            type of response object for the pipeline
 * 
 * @author Jan De Moerloose
 * @since 1.9.0
 */
@Api(allMethods = true)
public interface PipelineInterceptor {

	/**
	 * Execution mode. This allows to execute both steps and after action, nothing, just the steps or just the after
	 * action.
	 * 
	 * @author Jan De Moerloose
	 */
	enum ExecutionMode {
		/**
		 * Continue by executing everything, including the intercepted steps and
		 * {@link PipelineInterceptor#afterSteps(PipelineContext, Object)}.
		 */
		EXECUTE_ALL,
		/**
		 * Skip after the intercepted steps but do execute
		 * {@link PipelineInterceptor#afterSteps(PipelineContext, Object)}.
		 */
		EXECUTE_SKIP_STEPS,
		/**
		 * Continue by executing the steps, but do not execute
		 * {@link PipelineInterceptor#afterSteps(PipelineContext, Object)}..
		 */
		EXECUTE_STEPS_NOT_AFTER,
		/**
		 * Continue after the intercepted steps. {@link PipelineInterceptor#afterSteps(PipelineContext, Object)} is
		 * also not executed.
		 */
		EXECUTE_NONE
	}

	/**
	 * Get the id for the interceptor. This can be used to identify the interceptor step in the pipeline.
	 *
	 * @return interceptor id
	 */
	String getId();

	/**
	 * The id of the first step to intercept.
	 * 
	 * When this is not set, this pipeline will be intercepted from the beginning.
	 * 
	 * @return pipeline step id
	 */
	String getFromStepId();

	/**
	 * The id of the last step to intercept.
	 * 
	 * When this is not set, this pipeline will be intercepted till the end.
	 *
	 * @return pipeline step id
	 */
	String getToStepId();

	/**
	 * Perform some action before the steps are executed.
	 * 
	 * @param context
	 *            pipeline context
	 * @param response
	 *            pipeline response
	 * @return the execution mode
	 * @throws GeomajasException any exception which may have been thrown during the execution
	 */
	ExecutionMode beforeSteps(PipelineContext context, RESPONSE response) throws GeomajasException;

	/**
	 * Perform some action before the steps are executed.
	 * 
	 * @param context
	 *            pipeline context
	 * @param response
	 *            pipeline response
	 * @throws GeomajasException any exception which may have been thrown during the execution
	 */
	void afterSteps(PipelineContext context, RESPONSE response) throws GeomajasException;

}