defmodule IbanEx.Parser do
  @moduledoc false

  alias IbanEx.{Country, Iban, Validator}
  import IbanEx.Commons, only: [normalize_and_slice: 2]

  @type iban_string() :: String.t()
  @type country_code_string() :: <<_::16>>
  @type check_digits_string() :: <<_::16>>
  @type iban_or_error() :: IbanEx.Iban.t() | {:error, atom()}

  @spec parse({:ok, String.t()} | String.t()) :: iban_or_error()
  def parse({:ok, iban_string}), do: parse(iban_string)

  def parse(iban_string) do
    case Validator.validate(iban_string) do
      {:ok, valid_iban} ->
        iban_map = %{
          country_code: country_code(valid_iban),
          check_digits: check_digits(valid_iban)
        }

        regex = Country.country_module(iban_map.country_code).rule()
        bban = bban(iban_string)

        bban_map =
          for {key, val} <- Regex.named_captures(regex, bban),
              into: %{},
              do: {String.to_atom(key), val}

        {:ok, struct(Iban, Map.merge(iban_map, bban_map))}

      {:error, error_type} ->
        {:error, error_type}
    end
  end

  @spec country_code(iban_string()) :: country_code_string()
  def country_code(iban_string), do: normalize_and_slice(iban_string, 0..1)

  @spec check_digits(binary()) :: check_digits_string()
  def check_digits(iban_string), do: normalize_and_slice(iban_string, 2..3)

  @spec bban(binary()) :: binary()
  def bban(iban_string), do: normalize_and_slice(iban_string, 4..-1//1)
end