A Very Small Program To Verify Iranian National Code.

code_verifier.ex

defmodule CodeVerifier do
  @moduledoc """
  A Very Small Program To Verify Iranian National Code
  """

  @doc """

  ## Examples
          
      Srting -> Boolean
      iex> CodeVerifier.is_a_valid_code?("7731689951")
      false

  """

  def is_a_valid_code?(code) do
    code_map = push_to_map(Map.new(), code, 0)

    sum =
      Enum.map(code_map, fn {index_number, item} ->
        {n, _} = Integer.parse(item)
        n * index_number
      end)
      |> Enum.sum()

    {n, _} = code_map[1] |> Integer.parse()
    remaining = rem(sum - n, 11)

    if (remaining < 2 && n == remaining) || n == 11 - remaining do
      true
    else
      false
    end
  end

  defp push_to_map(code_map, _code, 10), do: code_map

  defp push_to_map(code_map, code, i) do
    push_to_map(
      Map.put(code_map,
              10 - i,
              code |> String.codepoints() |> List.to_tuple() |> elem(i)
             ),
      code,
      i + 1
    )
  end
end