module Roda::RodaPlugins::SinatraHelpers::ResponseMethods

def attachment(filename = nil, disposition='attachment')
  if filename
    param_filename = File.basename(filename)
    encoding = param_filename.encoding
    needs_encoding = param_filename.gsub!(/[^ 0-9a-zA-Z!\#$&\+\.\^_`\|~]+/, '-')
    params = "; filename=#{param_filename.inspect}"
    if needs_encoding && (encoding == UTF8_ENCODING || encoding == ISO88591_ENCODING)
      # File name contains non attr-char characters from RFC 5987 Section 3.2.1
      encoded_filename = File.basename(filename).force_encoding(BINARY_ENCODING)
      # Similar regexp as above, but treat each byte separately, and encode
      # space characters, since those aren't allowed in attr-char
      encoded_filename.gsub!(/[^0-9a-zA-Z!\#$&\+\.\^_`\|~]/) do |c|
        "%%%X" % c.ord
      end
      encoded_params = "; filename*=#{encoding.to_s}''#{encoded_filename}"
    end
    unless @headers[RodaResponseHeaders::CONTENT_TYPE]
      ext = File.extname(filename)
      unless ext.empty?
        content_type(ext)
      end
    end
  end
  @headers[RodaResponseHeaders::CONTENT_DISPOSITION] = "#{disposition}#{params}#{encoded_params}"
end