sysadmin.ex

defmodule Username do
  def sanitize(username) do
    # ä becomes ae
    # ö becomes oe
    # ü becomes ue
    # ß becomes ss

    for u <- username do
      case u do


        # _
        ?_ -> '_'

        # \s
        # ?\s -> nil
        # ü
        ?ü -> 'ue'

        # ö
        ?ö -> 'oe'

        # ä
        ?ä ->  'ae'
        # ß
        ?ß -> 'ss'

        a when a <= ?z and a >= ?a -> [a]

        # a when  (a >= ?0 and a <= ?9) -> nil

        _ -> ''
      end
    end
    # |> Enum.filter(
    #   fn entry -> entry != nil end
    #   )
      |> List.flatten()

    # Please implement the sanitize/1 function
  end
end