/*
 * Copyright 2017 Graz University of Technology EAAF-Core Components has been developed in a
 * cooperation between EGIZ, A-SIT Plus, 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 {

  @Override
  public IRequest execute(final IRequest pendingReq, final ExecutionContext executionContext)
      throws TaskExecutionException {
    final RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
    if (requestAttributes != null && requestAttributes instanceof ServletRequestAttributes) {
      final HttpServletRequest request =
          ((ServletRequestAttributes) requestAttributes).getRequest();
      final 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.");
    }
  }

  /**
   * 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}.
   *
   * <p>
   * This method sets the pending-request object of the task implementation and
   * starts the {@code execute} method of the task
   * </p>
   *
   * @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;

}