package org.esigate.extension;
   
   import static org.apache.commons.lang3.StringUtils.containsIgnoreCase;
   
   import java.util.Properties;
   
   import org.esigate.Driver;
   import org.esigate.esi.EsiRenderer;
   import org.esigate.events.Event;
  import org.esigate.events.EventDefinition;
  import org.esigate.events.EventManager;
  import org.esigate.events.IEventListener;
  import org.esigate.events.impl.RenderEvent;
  import org.esigate.extension.surrogate.CapabilitiesEvent;
  import org.esigate.extension.surrogate.Surrogate;
  
  /**
   * This extension processes ESI directives. Ex:
   * <p>
   * &lt;esi:include src="$(PROVIDER{cms})/news" fragment="news_1"/&gt;
   * <p>
   * Surrogate-Control is supported, with the following behavior :
   * <ul>
   * <li>Exposed capabilities : "ESI/1.0", "ESI-Inline/1.0", "X-ESI-Fragment/1.0", "X-ESI-Replace/1.0", "X-ESI-XSLT/1.0",
   * "ESIGATE/4.0"</li>
   * <li>When one of these capabilities is requested, all are applied at once.</li>
   * </ul>
   * 
   * @author Nicolas Richeton
   */
  public class Esi implements Extension, IEventListener {
      private static final String[] CAPABILITIES = new String[] {"ESI/1.0", "ESI-Inline/1.0", "X-ESI-Fragment/1.0",
              "X-ESI-Replace/1.0", "X-ESI-XSLT/1.0", "ESIGATE/4.0"};
  
      @Override
      public boolean event(EventDefinition id, Event event) {
          RenderEvent renderEvent = (RenderEvent) event;
          boolean doEsi = true;
  
          // ensure we should process esi
          if (renderEvent.getHttpResponse() != null
                  && renderEvent.getHttpResponse().containsHeader(Surrogate.H_X_ENABLED_CAPABILITIES)) {
              String enabledCapabilities =
                      renderEvent.getHttpResponse().getFirstHeader(Surrogate.H_X_ENABLED_CAPABILITIES).getValue();
  
              doEsi = false;
              for (String capability : CAPABILITIES) {
                  if (containsIgnoreCase(enabledCapabilities, capability)) {
                      doEsi = true;
                      break;
                  }
              }
          }
  
          if (doEsi) {
              renderEvent.getRenderers().add(new EsiRenderer());
          }
  
          // Continue processing
          return true;
      }
  
      @Override
      public void init(Driver driver, Properties properties) {
          driver.getEventManager().register(EventManager.EVENT_RENDER_PRE, this);
  
          driver.getEventManager().register(Surrogate.EVENT_SURROGATE_CAPABILITIES, new IEventListener() {
              @Override
              public boolean event(EventDefinition id, Event event) {
                  CapabilitiesEvent capEvent = (CapabilitiesEvent) event;
                  for (String capability : CAPABILITIES) {
                      capEvent.getCapabilities().add(capability);
                  }
                  return true;
              }
          });
      }
  
  }