german-sysadmin

elixir/german-sysadmin/lib/username.ex

@@ -0,0 +1,17 @@
+defmodule Username do
+  def sanitize([]), do: []
+
+  def sanitize([first | other]) do
+    sanitized =
+      case first do
+        ?ä -> ~c"ae"
+        ?ö -> ~c"oe"
+        ?ü -> ~c"ue"
+        ?ß -> ~c"ss"
+        ok when ok in ?a..?z or ok == ?_ -> [ok]
+        _ -> []
+      end
+
+    sanitized ++ sanitize(other)
+  end
+end