/*
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.apache.org/licenses/LICENSE-2.0
    *
    * Unless required by applicable law or agreed to in writing, software
    * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   */
  
  package org.esigate.extension.monitoring;
  
  import com.codahale.metrics.MetricRegistry;
  import com.codahale.metrics.ScheduledReporter;
  import com.codahale.metrics.Slf4jReporter;
  import org.apache.http.HttpStatus;
  import org.apache.http.client.cache.CacheResponseStatus;
  import org.apache.http.client.cache.HttpCacheContext;
  import org.esigate.Driver;
  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.FetchEvent;
  import org.esigate.events.impl.ProxyEvent;
  import org.esigate.extension.Extension;
  import org.esigate.util.Parameter;
  import org.esigate.util.ParameterInteger;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Properties;
  import java.util.concurrent.TimeUnit;
  
  /**
   * This extension will record proxy request, and backend request to generate statistics.
   * <p>
   * Result will be logged using SLF4J in INFO level every 60 seconds. Period can be configured in driver properties :
   * <p>
   * <code>metricPeriod=60</code>
   * <p>
   * <p>
   * Created by alexis on 20/03/14.
   */
  public class Metric implements Extension, IEventListener {
      private static final Logger LOG = LoggerFactory.getLogger(Metric.class);
      private static final Parameter<Integer> PARAM_METRIC_PERIOD = new ParameterInteger("metricPeriod", 60);
  
      private MetricRegistry metric = new MetricRegistry();
      private Driver driver;
  
      @Override
      public void init(Driver d, Properties properties) {
          this.driver = d;
          LOG.debug("Initialize Metric");
          driver.getEventManager().register(EventManager.EVENT_PROXY_POST, this);
          driver.getEventManager().register(EventManager.EVENT_FETCH_POST, this);
  
          ScheduledReporter reporter =
                  Slf4jReporter.forRegistry(this.metric).outputTo(LOG).convertRatesTo(TimeUnit.SECONDS)
                          .convertDurationsTo(TimeUnit.MILLISECONDS).build();
  
          reporter.start(PARAM_METRIC_PERIOD.getValue(properties), TimeUnit.SECONDS);
      }
  
      @Override
      public boolean event(EventDefinition id, Event event) {
  
          String timerName =
                  MetricRegistry.name(this.getClass().getSimpleName(), driver.getConfiguration().getInstanceName(),
                          id.getId());
  
          if (EventManager.EVENT_PROXY_POST.equals(id)) {
              if (((ProxyEvent) event).getErrorPage() != null) {
                  String statusCode =
                          String.valueOf(((ProxyEvent) event).getErrorPage().getHttpResponse().getStatusLine()
                                  .getStatusCode());
                  timerName = MetricRegistry.name(timerName, "error", statusCode);
              }
          } else if (EventManager.EVENT_FETCH_POST.equals(id)) {
              // Retrieve HTTP response status code and cache status
              FetchEvent e = (FetchEvent) event;
              int statusCode = e.getHttpResponse().getStatusLine().getStatusCode();
              CacheResponseStatus cacheResponseStatus =
                      (CacheResponseStatus) e.getHttpContext().getAttribute(HttpCacheContext.CACHE_RESPONSE_STATUS);
  
              // Adding status code when error
              if (statusCode >= HttpStatus.SC_BAD_REQUEST) {
                  timerName = MetricRegistry.name(timerName, "error", String.valueOf(statusCode));
              }
              // Adding cache if not MISS
              if (cacheResponseStatus != null && !cacheResponseStatus.equals(CacheResponseStatus.CACHE_MISS)) {
                  timerName = MetricRegistry.name(timerName, cacheResponseStatus.name().toLowerCase());
              }
         }
 
         metric.meter(timerName).mark();
 
         return true;
     }
 }