package com.atlassian.johnson.filters;
   
   import com.atlassian.johnson.JohnsonEventContainer;
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   import com.atlassian.johnson.event.Event;
   import com.atlassian.johnson.event.EventLevel;
   
   import javax.servlet.http.HttpServletResponse;
  import javax.servlet.http.HttpServletRequest;
  import java.io.IOException;
  import java.util.Collection;
  
  /**
   * A handler that returns a no-content temporarily unavailable response suitable for refusing responses when an
   * application is unable to handle normal requests. This is especially useful for cases where the normal response
   * is of an unknown, or dynamic content-type and sending actual content may confuse clients.
   * <p>
   * Example uses include AJAX requests, generated images, pdf, excel and word docs.
   */
  public class Johnson503Filter extends AbstractJohnsonFilter {
  
      private static final Logger log = LoggerFactory.getLogger(Johnson503Filter.class);
  
      protected void handleError(JohnsonEventContainer appEventContainer, HttpServletRequest servletRequest, HttpServletResponse servletResponse) throws IOException {
          log.info("The application is unavailable, or there are errors.  Returning a temporarily unavailable status.");
          servletResponse.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
          if (hasOnlyWarnings(appEventContainer)) {
              servletResponse.setHeader("Retry-After", "30");
          }
          // flushing the writer stops the app server from putting its html message into the otherwise empty response
          servletResponse.getWriter().flush();
      }
  
      protected void handleNotSetup(HttpServletRequest servletRequest, HttpServletResponse servletResponse) throws IOException {
          log.info("The application is not setup.  Returning a temporarily unavailable status.");
          servletResponse.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
          // flushing the writer stops the app server from putting its html message into the otherwise empty response
          servletResponse.getWriter().flush();
      }
  
      private boolean hasOnlyWarnings(final JohnsonEventContainer eventContainer) {
          if (eventContainer != null && eventContainer.hasEvents()) {
              final Collection events = eventContainer.getEvents();
              return allEventsAreWarnings(events);
          } else {
              return false;
          }
      }
  
      private boolean allEventsAreWarnings(final Collection events) {
          for (final Object eventObject : events) {
              if (eventObject instanceof Event) {
                  if (hasNonWarningLevel((Event) eventObject)) {
                      return false;
                  }
              } else {
                  return false;
              }
          }
          return true;
      }
  
      private boolean hasNonWarningLevel(final Event event) {
          return !EventLevel.WARNING.equals(event.getLevel().getLevel());
      }
  }