Extracting timestamp and randomness from ULID (using Ecto.ULID)

ulid_data.ex

defmodule ULID.Data do
  defstruct time: nil, random: nil

  def from_binary(<<time::integer-size(48), random::binary-size(10)>>) do
    time
    |> DateTime.from_unix(:millisecond)
    |> parse(random)
  end

  def from_string(ulid) do
    ulid
    |> Ecto.ULID.dump()
    |> parse
  end

  defp parse(%NaiveDateTime{} = time, random) do
    {:ok, %__MODULE__{time: time, random: random}}
  end

  defp parse({:ok, %DateTime{} = time}, random) do
    time
    |> DateTime.to_naive()
    |> parse(random)
  end

  defp parse({:ok, <<data::binary-size(16)>>}) do
    from_binary(data)
  end

  defp parse(:error), do: {:error, :invalid_ulid}
end