From 308147db14435f9fb362fb3b80771aa35f145d33 Mon Sep 17 00:00:00 2001
From: "exercism-solutions-syncer[bot]"
 <211797793+exercism-solutions-syncer[bot]@users.noreply.github.com>
Date: Thu, 14 Aug 2025 10:08:07 +0000
Subject: [PATCH] [Sync Iteration] elixir/atbash-cipher/2

---
 .../elixir/atbash-cipher/2/lib/atbash.ex      | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 solutions/elixir/atbash-cipher/2/lib/atbash.ex

diff --git a/solutions/elixir/atbash-cipher/2/lib/atbash.ex b/solutions/elixir/atbash-cipher/2/lib/atbash.ex
new file mode 100644
index 0000000..462420f
--- /dev/null
+++ b/solutions/elixir/atbash-cipher/2/lib/atbash.ex
@@ -0,0 +1,29 @@
+defmodule Atbash do  
+  @doc """
+  Encode a given plaintext to the corresponding ciphertext
+
+  ## Examples
+
+  iex> Atbash.encode("completely insecure")
+  "xlnko vgvob rmhvx fiv"
+  """
+  @spec encode(String.t()) :: String.t()
+  def encode(plaintext) do
+    plaintext
+    |> String.downcase()
+    |> String.to_charlist()
+    |> Enum.map_join(&transpose/1)
+    |> String.replace(~r/(.{5})\B/, "\\1 ")
+  end
+  
+  @spec decode(String.t()) :: String.t()
+  def decode(cipher) do
+    cipher
+    |> String.to_charlist()
+    |> Enum.map_join(&transpose/1)
+  end
+
+  defp transpose(char) when char in ?0..?9, do: <<char>>
+  defp transpose(char) when char in ?a..?z, do: <<?a + ?z - char>>
+  defp transpose(_), do: ""
+end