ex_aws_s3_sign.ex

defp prepare_signed_url({region, bucket, object}, friendly_name) do
  config = ExAws.Config.new(:s3, %{region: region})
  encoded_name = URI.encode(friendly_name, fn
    x when ?0 <= x <= ?9 -> true
    x when ?A <= x <= ?Z -> true
    x when ?a <= x <= ?z -> true
    _ -> false
  end)
  
  options = [
    expires_in: 1800,
    query_params: [{
      "response-content-disposition",
      "attachment; filename*=UTF-8''#{encoded_name}"
    }]
  ]
  ExAws.S3.presigned_url(config, :get, bucket, object, options)
end