@spec data_version() :: Date.t()

Returns the date of the Japan Post data bundled with this version.

@spec lookup(term()) ::
  {:ok, [Yubin.Address.t(), ...]} | {:error, :not_found | :invalid}

Returns the addresses of a postal code.

Accepts the input forms of normalize/1. {:error, :not_found} can mean a code newer than the bundled data, see data_version/0.

@spec normalize(term()) :: {:ok, String.t()} | {:error, :invalid}

Returns the postal code in the form "NNN-NNNN", or {:error, :invalid} when the input is not one.

The input is 7 digits with an optional hyphen after the third. Full-width characters, any hyphen or dash, a leading 〒 and spaces are accepted.

iex> Yubin.normalize("〒５３０ー０００１")
{:ok, "530-0001"}

iex> Yubin.normalize("530-001")
{:error, :invalid}

@spec prefectures() :: [Yubin.Prefecture.t()]

Returns the 47 prefectures in JIS order.