What.

what.exs

defmodule SecretHandshake do
  @doc """
  Determine the actions of a secret handshake based on the binary
  representation of the given `code`.

  If the following bits are set, include the corresponding action in your list
  of commands, in order from lowest to highest.

  1 = wink
  10 = double blink
  100 = close your eyes
  1000 = jump

  10000 = Reverse the order of the operations in the secret handshake
  """
  @spec commands(code :: integer) :: list(String.t())
  def commands(code) do
    seq = [32, 16, 8, 4, 2, 1]
    m(code, seq, [])
  end

  def m(val, [next | seq], sentence) do
    map = %{1 => ["wink"], 2 => "double blink", 4 => "close your eyes", 8 => "jump"}

    cond do
      # nothing left in the seq, just return the current sentence.
      next == nil ->
        sentence

      # No remainder, means its exactly that value.
      rem(val, next) == 0 ->
        {:ok, tmp} = Map.fetch(map, next)
        #      ** (FunctionClauseError) no function clause matching in SecretHandshake.m/3
        m(val - next, seq, sentence ++ tmp)

      # I think this means nothing was left over ?
      true ->
        m(val - next, seq, sentence)
    end
  end
end