//
   //  ========================================================================
   //  Copyright (c) 1995-2013 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  
  package org.eclipse.jetty.spdy.server.proxy;
  
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  import java.net.UnknownHostException;
  import java.util.HashSet;
  import java.util.Set;
  
  import org.eclipse.jetty.spdy.api.Stream;
  import org.eclipse.jetty.spdy.api.StreamFrameListener;
  import org.eclipse.jetty.spdy.api.SynInfo;
  import org.eclipse.jetty.spdy.server.http.HTTPSPDYHeader;
  import org.eclipse.jetty.util.Fields;
  
  /**
   * <p>{@link ProxyEngine} is the class for SPDY proxy functionalities that receives a SPDY request and converts it to
   * any protocol to its server side.</p>
   * <p>This class listens for SPDY events sent by clients; subclasses are responsible for translating
   * these SPDY client events into appropriate events to forward to the server, in the appropriate
   * protocol that is understood by the server.</p>
   */
  public abstract class ProxyEngine
  {
      private static final Set<String> HOP_HEADERS = new HashSet<>();
      static
      {
          HOP_HEADERS.add("proxy-connection");
          HOP_HEADERS.add("connection");
          HOP_HEADERS.add("keep-alive");
          HOP_HEADERS.add("transfer-encoding");
          HOP_HEADERS.add("te");
          HOP_HEADERS.add("trailer");
          HOP_HEADERS.add("proxy-authorization");
          HOP_HEADERS.add("proxy-authenticate");
          HOP_HEADERS.add("upgrade");
      }
  
      private final String name;
  
      protected ProxyEngine()
      {
          this(name());
      }
  
      private static String name()
      {
          try
          {
              return InetAddress.getLocalHost().getHostName();
          }
          catch (UnknownHostException x)
          {
              return "localhost";
          }
      }
  
      public abstract StreamFrameListener proxy(Stream clientStream, SynInfo clientSynInfo, ProxyEngineSelector.ProxyServerInfo proxyServerInfo);
  
      protected ProxyEngine(String name)
      {
          this.name = name;
      }
  
      public String getName()
      {
          return name;
      }
  
      protected void removeHopHeaders(Fields headers)
      {
          // Header names are case-insensitive (RFC2616) and oej.util.Fields.add converts the names to lowercase. So we
          // need to compare with the lowercase values only
          for (String hopHeader : HOP_HEADERS)
              headers.remove(hopHeader);
      }
  
      protected void addRequestProxyHeaders(Stream stream, Fields headers)
      {
          addViaHeader(headers);
          Fields.Field schemeField = headers.get(HTTPSPDYHeader.SCHEME.name(stream.getSession().getVersion()));
         if(schemeField != null)
             headers.add("X-Forwarded-Proto", schemeField.value());
         InetSocketAddress address = stream.getSession().getRemoteAddress();
         if (address != null)
         {
             headers.add("X-Forwarded-Host", address.getHostName());
             headers.add("X-Forwarded-For", address.toString());
         }
         headers.add("X-Forwarded-Server", name());
     }
 
     protected void addResponseProxyHeaders(Stream stream, Fields headers)
     {
         addViaHeader(headers);
     }
 
     private void addViaHeader(Fields headers)
     {
         headers.add("Via", "http/1.1 " + getName());
     }
 
     protected void customizeRequestHeaders(Stream stream, Fields headers)
     {
     }
 
     protected void customizeResponseHeaders(Stream stream, Fields headers)
     {
     }
 
 }