secret_handshake

elixir/secret-handshake/lib/secret_handshake.ex

@@ -0,0 +1,35 @@
+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 1 = wink
+  2 10 = double blink
+  4 100 = close your eyes
+  8 1000 = jump
+
+  16 10000 = Reverse the order of the operations in the secret handshake
+  """
+
+  @coms %{
+    1 => "wink",
+    2 => "double blink",
+    4 => "close your eyes",
+    8 => "jump",
+    16 => "reverse"
+  }
+
+  @spec commands(code :: integer) :: list(String.t())
+  def commands(code) do
+    @coms
+    |> Map.keys()
+    |> Enum.reduce([], &if(Bitwise.band(code, &1) == &1, do: [@coms[&1] | &2], else: &2))
+    |> case do
+      ["reverse" | tail] -> tail
+      reversed_list -> Enum.reverse(reversed_list)
+    end
+  end
+end