/*
    * 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.http;
  
  import java.net.InetAddress;
  import java.net.UnknownHostException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.Properties;
  
  import org.apache.http.HttpHost;
  import org.apache.http.conn.DnsResolver;
  import org.apache.http.impl.client.HttpClientBuilder;
  import org.esigate.Driver;
  import org.esigate.Parameters;
  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.HttpClientBuilderEvent;
  import org.esigate.extension.Extension;
  import org.esigate.util.Parameter;
  import org.esigate.util.ParameterCollection;
  import org.esigate.util.UriUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * DNS extension that allow to associates IP addresses to the given host in a DNS overrider. The IP addresses are
   * assumed to be already resolved.
   * 
   * @author Alexis Thaveau on 26/01/16.
   */
  public class DNS implements Extension, IEventListener {
      private static final Logger LOG = LoggerFactory.getLogger(DNS.class);
  
      // Core parameters
      public static final Parameter<Collection<String>> REMOTE_IP = new ParameterCollection("remoteIP");
  
      private DnsResolver dnsResolver;
  
      public DnsResolver getDnsResolver() {
          return dnsResolver;
      }
  
      @Override
      public void init(Driver driver, Properties properties) {
          Collection<String> ips = REMOTE_IP.getValue(properties);
  
          if (ips.isEmpty()) {
              LOG.error("Missing configuration properties for driver {}. Property {}", driver.getConfiguration()
                      .getInstanceName(), REMOTE_IP.getName());
          } else {
              String[] remoteURLS = Parameters.REMOTE_URL_BASE.getValue(properties);
              List<InetAddress> inetAddresses = new ArrayList<>();
              CustomizableDNSResolver customizableDNSResolver = new CustomizableDNSResolver();
              dnsResolver = customizableDNSResolver;
              for (String ip : ips) {
                  try {
                      inetAddresses.add(InetAddress.getByName(ip));
                  } catch (UnknownHostException e) {
                      LOG.error("Unable to resolve InetAddress [{}]", ip, e);
                  }
              }
  
              for (String remoteURL : remoteURLS) {
  
                  HttpHost host = UriUtils.extractHost(remoteURL);
                  customizableDNSResolver.add(host.getHostName(), inetAddresses.toArray(new InetAddress[] {}));
              }
  
              driver.getEventManager().register(EventManager.EVENT_HTTP_BUILDER_INITIALIZATION, this);
          }
      }
  
      @Override
      public boolean event(EventDefinition id, Event event) {
          HttpClientBuilderEvent httpClientBuilderEvent = (HttpClientBuilderEvent) event;
          HttpClientBuilder httpClientBuilder = httpClientBuilderEvent.getHttpClientBuilder();
          httpClientBuilder.setDnsResolver(dnsResolver);
          return false;
      }
  }