/*******************************************************************************
 * Copyright 2017 Graz University of Technology
 * EAAF-Core Components has been developed in a cooperation between EGIZ,  
 * A-SIT+, A-SIT, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.2 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * https://joinup.ec.europa.eu/news/understanding-eupl-v12
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 *******************************************************************************/
/*******************************************************************************
 *******************************************************************************/
/*******************************************************************************
 *******************************************************************************/
package at.gv.egiz.eaaf.core.impl.idp.process.springweb;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.filter.RequestContextFilter;

import at.gv.egiz.eaaf.core.api.IRequest;
import at.gv.egiz.eaaf.core.api.idp.process.ExecutionContext;
import at.gv.egiz.eaaf.core.api.idp.process.Task;
import at.gv.egiz.eaaf.core.exceptions.TaskExecutionException;

/**
 * Abstract task implementation providing {@link HttpServletRequest} and {@link HttpServletResponse}.
 * <p/>
 * Note that this abstract task requires the Spring (web) framework including a {@link RequestContextFilter} to be set
 * within {@code web.xml}.
 * 
 * <pre>
 * ...
 * &lt;filter&gt;
 *   &lt;filter-name&gt;requestContextFilter&lt;/filter-name&gt;
 *   &lt;filter-class&gt;org.springframework.web.filter.RequestContextFilter&lt;/filter-class&gt;
 * &lt;/filter&gt;
 * &lt;filter-mapping&gt;
 *   &lt;filter-name&gt;requestContextFilter&lt;/filter-name&gt;
 *   &lt;url-pattern&gt;/*&lt;/url-pattern&gt;
 * &lt;/filter-mapping&gt;
 * ...
 * </pre>
 * 
 * @author tknall
 * @author tlenz
 * 
 */
public abstract class AbstractTask implements Task {

	/**
	 * Executes the task providing the underlying {@link ExecutionContext} {@code executionContext} as well as the
	 * respective {@link HttpServletRequest} and {@link HttpServletResponse}.
	 * 
	 * @param executionContext
	 *            The execution context (never {@code null}).
	 * @param request
	 *            The HttpServletRequest (never {@code null}).
	 * @param response
	 *            The HttpServletResponse (never {@code null}).
	 * @throws IllegalStateException
	 *             Thrown in case the task is nur being run within the required environment. Refer to javadoc for
	 *             further information.
	 * @throws Exception
	 *             Thrown in case of error executing the task.
	 */
	public abstract void execute(ExecutionContext executionContext, HttpServletRequest request,
			HttpServletResponse response) throws TaskExecutionException;

	/**
	 * Executes the task providing the underlying {@link ExecutionContext} {@code executionContext} 
	 * and the {@link IRequest} {@code pendingReq }as well as the
	 * respective {@link HttpServletRequest} and {@link HttpServletResponse}.
	 * 
	 * This method sets the pending-request object of the task implementation and starts the 
	 * {@code execute} method of the task
	 * 
	 * @param pendingReq The pending-request object (never {@code null}).
	 * @param executionContext The execution context (never {@code null}).
	 * @param request The HttpServletRequest (never {@code null}).
	 * @param response The HttpServletResponse (never {@code null}).
	 * @return The pending-request object, because Process-management works recursive
	 * 
	 * @throws IllegalStateException
	 *             Thrown in case the task is being run within the required environment. Refer to javadoc for
	 *             further information.
	 * @throws Exception
	 *             Thrown in case of error executing the task.
	 */
	protected abstract IRequest internalExecute(IRequest pendingReq, ExecutionContext executionContext, HttpServletRequest request,
			HttpServletResponse response) throws TaskExecutionException;
	
	@Override
	public IRequest execute(IRequest pendingReq, ExecutionContext executionContext) throws TaskExecutionException {
		RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
		if (requestAttributes != null && requestAttributes instanceof ServletRequestAttributes) {
			HttpServletRequest request = ((ServletRequestAttributes) requestAttributes).getRequest();
			HttpServletResponse response = ((ServletRequestAttributes) requestAttributes).getResponse();
			if (request == null || response == null) {
				throw new IllegalStateException(
						"Spring's RequestContextHolder did not provide HttpServletResponse. Did you forget to set the required org.springframework.web.filter.RequestContextFilter in your web.xml.");
			}
			return internalExecute(pendingReq, executionContext, request, response);
		} else {
			throw new IllegalStateException("Task needs to be executed within a Spring web environment.");
		}
	}

}