class WEBrick::HTTPProxyServer

def choose_header(src, dst)
  connections = split_field(src['connection'])
  src.each{|key, value|
    key = key.downcase
    if HopByHop.member?(key)          || # RFC2616: 13.5.1
       connections.member?(key)       || # RFC2616: 14.10
       ShouldNotTransfer.member?(key)    # pragmatics
      @logger.debug("choose_header: '#{key}: #{value}'")
      next
    end
    dst[key] = value
  }
end

def create_net_http(uri, upstream)
  Net::HTTP.new(uri.host, uri.port, upstream.host, upstream.port)
end

def do_CONNECT(req, res)
  # Proxy Authentication
  proxy_auth(req, res)
  ua = Thread.current[:WEBrickSocket]  # User-Agent
  raise HTTPStatus::InternalServerError,
    "[BUG] cannot get socket" unless ua
  host, port = req.unparsed_uri.split(":", 2)
  # Proxy authentication for upstream proxy server
  if proxy = proxy_uri(req, res)
    proxy_request_line = "CONNECT #{host}:#{port} HTTP/1.0"
    if proxy.userinfo
      credentials = "Basic " + [proxy.userinfo].pack("m0")
    end
    host, port = proxy.host, proxy.port
  end
  begin
    @logger.debug("CONNECT: upstream proxy is '#{host}:#{port}'.")
    os = TCPSocket.new(host, port)     # origin server
    if proxy
      @logger.debug("CONNECT: sending a Request-Line")
      os << proxy_request_line << CRLF
      @logger.debug("CONNECT: > #{proxy_request_line}")
      if credentials
        @logger.debug("CONNECT: sending credentials")
        os << "Proxy-Authorization: " << credentials << CRLF
      end
      os << CRLF
      proxy_status_line = os.gets(LF)
      @logger.debug("CONNECT: read Status-Line from the upstream server")
      @logger.debug("CONNECT: < #{proxy_status_line}")
      if %r{^HTTP/\d+\.\d+\s+200\s*} =~ proxy_status_line
        while line = os.gets(LF)
          break if /\A(#{CRLF}|#{LF})\z/om =~ line
        end
      else
        raise HTTPStatus::BadGateway
      end
    end
    @logger.debug("CONNECT #{host}:#{port}: succeeded")
    res.status = HTTPStatus::RC_OK
  rescue => ex
    @logger.debug("CONNECT #{host}:#{port}: failed '#{ex.message}'")
    res.set_error(ex)
    raise HTTPStatus::EOFError
  ensure
    if handler = @config[:ProxyContentHandler]
      handler.call(req, res)
    end
    res.send_response(ua)
    access_log(@config, req, res)
    # Should clear request-line not to send the response twice.
    # see: HTTPServer#run
    req.parse(NullReader) rescue nil
  end
  begin
    while fds = IO::select([ua, os])
      if fds[0].member?(ua)
        buf = ua.readpartial(1024);
        @logger.debug("CONNECT: #{buf.bytesize} byte from User-Agent")
        os.write(buf)
      elsif fds[0].member?(os)
        buf = os.readpartial(1024);
        @logger.debug("CONNECT: #{buf.bytesize} byte from #{host}:#{port}")
        ua.write(buf)
      end
    end
  rescue
    os.close
    @logger.debug("CONNECT #{host}:#{port}: closed")
  end
  raise HTTPStatus::EOFError
end

def do_GET(req, res)
  perform_proxy_request(req, res, Net::HTTP::Get)
end

def do_HEAD(req, res)
  perform_proxy_request(req, res, Net::HTTP::Head)
end

def do_OPTIONS(req, res)
  res['allow'] = "GET,HEAD,POST,OPTIONS,CONNECT"
end

def do_POST(req, res)
  perform_proxy_request(req, res, Net::HTTP::Post, req.body_reader)
end

def initialize(config={}, default=Config::HTTP)
  super(config, default)
  c = @config
  @via = "#{c[:HTTPVersion]} #{c[:ServerName]}:#{c[:Port]}"
end

def perform_proxy_request(req, res, req_class, body_stream = nil)
  uri = req.request_uri
  path = uri.path.dup
  path << "?" << uri.query if uri.query
  header = setup_proxy_header(req, res)
  upstream = setup_upstream_proxy_authentication(req, res, header)
  body_tmp = []
  http = create_net_http(uri, upstream)
  req_fib = Fiber.new do
    http.start do
      if @config[:ProxyTimeout]
        ##################################   these issues are
        http.open_timeout = 30   # secs  #   necessary (maybe because
        http.read_timeout = 60   # secs  #   Ruby's bug, but why?)
        ##################################
      end
      if body_stream && req['transfer-encoding'] =~ /\bchunked\b/i
        header['Transfer-Encoding'] = 'chunked'
      end
      http_req = req_class.new(path, header)
      http_req.body_stream = body_stream if body_stream
      http.request(http_req) do |response|
        # Persistent connection requirements are mysterious for me.
        # So I will close the connection in every response.
        res['proxy-connection'] = "close"
        res['connection'] = "close"
        # stream Net::HTTP::HTTPResponse to WEBrick::HTTPResponse
        res.status = response.code.to_i
        res.chunked = response.chunked?
        choose_header(response, res)
        set_cookie(response, res)
        set_via(res)
        response.read_body do |buf|
          body_tmp << buf
          Fiber.yield # wait for res.body Proc#call
        end
      end # http.request
    end
  end
  req_fib.resume # read HTTP response headers and first chunk of the body
  res.body = ->(socket) do
    while buf = body_tmp.shift
      socket.write(buf)
      buf.clear
      req_fib.resume # continue response.read_body
    end
  end
end

def proxy_auth(req, res)
  if proc = @config[:ProxyAuthProc]
    proc.call(req, res)
  end
  req.header.delete("proxy-authorization")
end

def proxy_service(req, res)
  # Proxy Authentication
  proxy_auth(req, res)
  begin
    public_send("do_#{req.request_method}", req, res)
  rescue NoMethodError
    raise HTTPStatus::MethodNotAllowed,
      "unsupported method '#{req.request_method}'."
  rescue => err
    logger.debug("#{err.class}: #{err.message}")
    raise HTTPStatus::ServiceUnavailable, err.message
  end
  # Process contents
  if handler = @config[:ProxyContentHandler]
    handler.call(req, res)
  end
end

def proxy_uri(req, res)
  # should return upstream proxy server's URI
  return @config[:ProxyURI]
end

def service(req, res)
  if req.request_method == "CONNECT"
    do_CONNECT(req, res)
  elsif req.unparsed_uri =~ %r!^http://!
    proxy_service(req, res)
  else
    super(req, res)
  end
end

def set_cookie(src, dst)
  if str = src['set-cookie']
    cookies = []
    str.split(/,\s*/).each{|token|
      if /^[^=]+;/o =~ token
        cookies[-1] << ", " << token
      elsif /=/o =~ token
        cookies << token
      else
        cookies[-1] << ", " << token
      end
    }
    dst.cookies.replace(cookies)
  end
end

def set_via(h)
  if @config[:ProxyVia]
    if  h['via']
      h['via'] << ", " << @via
    else
      h['via'] = @via
    end
  end
end

def setup_proxy_header(req, res)
  # Choose header fields to transfer
  header = Hash.new
  choose_header(req, header)
  set_via(header)
  return header
end

def setup_upstream_proxy_authentication(req, res, header)
  if upstream = proxy_uri(req, res)
    if upstream.userinfo
      header['proxy-authorization'] =
        "Basic " + [upstream.userinfo].pack("m0")
    end
    return upstream
  end
  return FakeProxyURI
end

def split_field(f) f ? f.split(/,\s+/).collect{|i| i.downcase } : [] end