peselx

defmodule Peselx do


    import Enum
    import String, only: [split: 3, to_integer: 1]
    import List, except: [to_integer: 1]

    @weigths [1,3,7,9,1,3,7,9,1,3]

    @doc """
       Validate PESEL number.

       ## Parameters
        - pesel: String represents PESEL number

       ## Examples

            iex> Peselx.validate("04231115629")
            {:ok, "Valid"}

            iex> Peselx.validate("04231115628")
            {:error, "Wrong checksum"}
    """
    @spec validate(String.t) :: {atom, String.t}
    def validate(pesel) when is_binary(pesel) do
      d = split(pesel, "", trim: true) |> map(&(to_integer &1))
      s = zip([d, @weigths]) |> map(&r_t_m/1)|> sum

      verify_cd(10 - rem(s, 10), last(d))
    end

    defp verify_cd(md, cd) when md == cd do
      {:ok, "Valid"}
    end

    defp verify_cd(md, cd) when md != cd do
      {:error, "Wrong checksum"}
    end

    defp r_t(tuple, f) when is_tuple(tuple) do
        Tuple.to_list(tuple) |> Enum.reduce(f)
    end

    defp r_t_m(tuple) when is_tuple(tuple) do
       r_t(tuple, &Kernel.*/2)
    end

end