# -*- encoding: binary -*-

module Kcar

# This may be used to generate a Rack response
#
class Response < Struct.new(:sock, :hdr, :unchunk, :buf, :parser)

  # :stopdoc:
  LAST_CHUNK = "0\r\n"
  CRLF = "\r\n"
  # :startdoc:

  # By default we readpartial at most 16K off a socket at once
  READ_SIZE = 0x4000

  # initializes a socket, +sock+ must respond to the "readpartial"
  # method.  +unchunk+ may be set to disable transparent unchunking
  # +hdr+ may be a Hash, Array, or Rack::Utils::HeaderHash
  def initialize(sock, hdr = {}, unchunk = true)
    super(sock, hdr, unchunk, "", Parser.new)
  end

  # returns a 3-element array that resembles a Rack response, but is
  # more useful for additional processing by other code.
  #
  #    [ status, headers, body ]
  #
  # Use Kcar::Response#rack if you want to guaranteee a proper Rack response.
  #
  # this method will not return until the response headers are fully parsed,
  # but the body returned will be this Kcar::Response handler itself.
  # +unchunk+ must be true to guarantee trailers will be stored in the
  # returned +header+ object
  def read
    buf << sock.readpartial(READ_SIZE) if buf.empty?
    while (response = parser.headers(hdr, buf)).nil?
      buf << sock.readpartial(READ_SIZE)
    end
    response << self
  end

  # returns a 3-element array suitable for use as a Rack response:
  #    [ status, headers, body ]
  #
  # this method will not return until the response headers are fully parsed,
  # but the body returned will be this Kcar::Response handler itself.
  # It is not guaranteed that trailers will be stored in the returned +header+
  def rack
    self.unchunk = false
    read
  end

  # this is expected to be called by our Rack server, it will close
  # our given +sock+ object if keepalive is not used otherwise it
  # will just reset the parser and clear the header object
  def close
    parser.keepalive? ? reset : sock.close
  end

  # this method allows our Kcar::Response object to be used as a Rack response
  # body.  It may only be called once (usually by a Rack server) as it streams
  # the response body off the our socket object.
  def each(&block)
    return if parser.body_eof?
    if unchunk
      parser.chunked? ? each_unchunk(&block) : each_identity(&block)
    else
      if parser.keepalive?
        parser.chunked? ? each_rechunk(&block) : each_identity(&block)
      else
        each_until_eof(&block) # fastest path
      end
    end
    rescue EOFError
  end

  # :stopdoc:
  def reset
    parser.reset
    hdr.clear
  end

  def each_rechunk(&block)
    # We have to filter_body to keep track of parser state
    # (which sucks).  Also, as a benefit to clients we'll rechunk
    # to increase the likelyhood of network transfers being on
    # chunk boundaries so we're less likely to trigger bugs in
    # other people's code :)
    dst = ""
    begin
      parser.filter_body(dst, buf) and break
      size = dst.size
      if size > 0
        yield("#{size.to_s(16)}\r\n")
        yield(dst << CRLF)
      end
      break if parser.body_eof?
    end while buf << sock.readpartial(READ_SIZE, dst)

    yield LAST_CHUNK

    while parser.trailers(hdr, buf).nil?
      buf << sock.readpartial(READ_SIZE, dst)
    end

    # since Rack does not provide a way to explicitly send trailers
    # in the response, we'll just yield a stringified version to our
    # server and pretend it's part of the body.
    trailers = parser.extract_trailers(hdr)
    yield(trailers.map! { |k,v| "#{k}: #{v}\r\n" }.join("") << CRLF)
  end

  def each_until_eof(&block)
    yield buf unless buf.empty?
    # easy, just read and write everything until EOFError
    dst = sock.readpartial(READ_SIZE)
    begin
      yield dst
    end while sock.readpartial(READ_SIZE, dst)
  end

  def each_identity(&block)
    len = parser.body_bytes_left
    if len.nil?
      each_until_eof(&block)
    else
      dst = buf
      if dst.size > 0
        # in case of keepalive we need to read the second response,
        # so modify buf so that the second response is at the front
        # of the buffer
        if dst.size >= len
          tmp = dst[len, dst.size]
          dst = dst[0, len]
          buf.replace(tmp)
        end

        len -= dst.size
        yield dst
      end

      if len > 0
        begin
          len -= sock.readpartial(len > READ_SIZE ? READ_SIZE : len, dst).size
          yield dst
        end while len > 0
        dst.respond_to?(:clear) ? dst.clear : self.buf = ''
      end
    end
  end

  def each_unchunk(&block)
    dst = ""
    begin
      parser.filter_body(dst, buf) and break
      yield dst if dst.size > 0
      parser.body_eof? and break
    end while buf << sock.readpartial(READ_SIZE, dst)

    # we can't pass trailers to the client since we unchunk
    # the response, so just read them off the socket and
    # stash them in hdr just in case...
    while parser.headers(hdr, buf).nil?
      buf << sock.readpartial(READ_SIZE, dst)
    end
  end
  # :startdoc:

end # class Response
end # module Kcar