# -*- encoding: binary -*-
require "digest/md5"
module HTTP_Spew::ContentMD5
  class MismatchError < HTTP_Spew::Error
  end
  class LengthError < HTTP_Spew::Error
  end

  def self.input(env)
    if trailer = env["HTTP_TRAILER"]
      have_md5 = trailer.split(/\s*,\s*/).grep(/\AContent-MD5\z/i)[0]
      return env["rack.input"] if have_md5 && env["HTTP_CONTENT_MD5"]
    end
    if trailer
      unless have_md5
        trailer << (trailer.empty? ? "Content-MD5" : ",Content-MD5")
      end
    else
      env["HTTP_TRAILER"] = "Content-MD5"
    end
    env["HTTP_TRANSFER_ENCODING"] = "chunked"
    rd, wr = HTTP_Spew::ChunkyPipe.new
    md5 = env.delete("HTTP_CONTENT_MD5")
    len = env.delete("CONTENT_LENGTH")
    start_write_driver(env["rack.input"], rd, wr, md5, len)
    rd
  end

  def self.start_write_driver(input, rd, wr, expect_md5, expect_len)
    Thread.new do
      begin
        digest, buf, bytes = Digest::MD5.new, "", 0
        while input.read(0x4000, buf)
          n = buf.size
          bytes += n
          wr.kgio_write("#{n.to_s(16)}\r\n")
          digest.update(buf)
          wr.kgio_write(buf << "\r\n")
        end
        if expect_len && expect_len.to_i != bytes
          raise LengthError, "expect=#{expect_len} != got=#{bytes}"
        end
        digest = [ digest.digest ].pack("m").strip!
        if expect_md5 && expect_md5.strip != digest
          raise MismatchError, "expect=#{expect_md5} != got=#{digest}"
        end
        wr.write "0\r\nContent-MD5: #{digest}\r\n\r\n"
      rescue => e
        rd.error = e
      ensure
        wr.close
      end
    end
  end
end