defmodule Hull.Time.Progress do
  def print(enum, total \\ 0) do
    enum
    |> Stream.scan({nil, {now(), now(), 0}}, fn item, {_, {start, last, count}} ->
      next = count + 1
      now = now()

      cond do
        now - last >= 1 ->
          diff = now - start

          IO.puts(
            "#{progress(count, total)} | Elapsed Time: #{diff}s #{remaining(count, total, diff)}"
          )

          {item, {start, now, next}}

        true ->
          {item, {start, last, next}}
      end
    end)
    |> Stream.map(fn {item, _} -> item end)
  end

  defp progress(count, 0), do: "#{count} done"
  defp progress(count, total), do: "#{count} of #{total}"

  defp remaining(count, total, diff) when total != 0 and count != 0,
    do: "| #{round(diff / count * total - diff)}s remaining"

  defp remaining(_count, _total, _diff), do: ""

  defp now(), do: :os.system_time(:second)
end