module WeixinAuthorize::Api::Media

def download_media_url(media_id)
  download_media_url = WeixinAuthorize.endpoint_url("file", "#{media_base_url}/get")
  params = URI.encode_www_form("access_token" => get_access_token,
                               "media_id"     => media_id)
  download_media_url += "?#{params}"
  download_media_url
end