todo_shorter.exs

main = fn ->
  cmd = IO.gets("Enter a command: ") |> String.trim()

  case String.split(cmd) do
    ["show"] ->
      todos = Process.get(:todos) || []
      IO.puts(Enum.join(todos, "\n"))

    ["create" | rest] ->
      todos = Process.get(:todos) || []
      Process.put(:todos, [Enum.join(rest, " ") | todos])

    [action, idx] when action in ~w(complete delete)s ->
      # cheating
      todos = Process.get(:todos) || []
      {idx, _} = Integer.parse(idx)
      new_todos = List.delete_at(todos, idx)
      Process.put(:todos, new_todos)

    ["exit"] ->
      Process.exit(self(), :kill)

    _ ->
      IO.puts("Invalid command")
  end
end

Stream.repeatedly(fn -> main.() end) |> Stream.run()