class W3CPoster
  def self.post_file_to_w3c_validator(file_path, doc_type)
    query = MultipartPost.build_form_data(
          :uploaded_file  => File.new(file_path, 'r'),
          :charset        => '(detect automatically)',
          :doctype        => doc_type,   
          :group          => '1'
          )

    Net::HTTP.start('validator.w3.org') do |http|
      http.post2("/check", query, MultipartPost::REQ_HEADER)
    end
  end

  def self.valid_response?(w3c_response)
    html = w3c_response.read_body
    html.include? "[Valid]"
  end

  def self.w3c_valid?(file_path)
    resp = post_file_to_w3c_validator(file_path, 'HTML 4.01 Strict')
    valid_response?(resp)
  end
end