Minimal uuid4 implementation

uuid4.ex

defmodule UUID4 do
  @moduledoc """
  Rough sketch of a uuid4 implementation
  """

  @doc false
  def uuid4 do
    <<u0::48, _::4, u1::12, _::2, u2::62>> = :crypto.strong_rand_bytes(16)
    <<u0::48, 4::4, u1::12, 2::2, u2::62>>
  end

  @doc false
  def to_string(<<u0::32, u1::16, u2::16, u3::16, u4::48>>) do
    cs = :io_lib.format("~8.16.0b-~4.16.0b-~4.16.0b-~4.16.0b-~12.16.0b", [u0, u1, u2, u3, u4])
    {:just, List.to_string(cs)}
  end

  def to_string(_) do
    {:nothing, nil}
  end
end