phon_number.exs

defmodule Phone do
  @doc """
  Remove formatting from a phone number.

  Returns "0000000000" if phone number is not valid
  (10 digits or "1" followed by 10 digits)

  ## Examples

  iex> Phone.number("123-456-7890")
  "1234567890"

  iex> Phone.number("+1 (303) 555-1212")
  "3035551212"

  iex> Phone.number("867.5309")
  "0000000000"
  """
  @spec number(String.t) :: String.t
	def number(raw) do
		raw
		|> to_char_list
		|> :phone_number_lexer.string
		|> check_length
		|> simple_number
  end

	defp check_length({:ok, [{:int, 1, '1'}|rest], _}) when length(rest) == 10, do: {:ok, rest, nil}
	defp check_length({:ok, tokens, _}) when length(tokens) == 10, do: {:ok, tokens, nil}
	defp check_length({:error, tokens, _}), do: {:error, tokens, nil}
	defp check_length({:ok, tokens, _}), do: {:error, tokens, nil}

	defp simple_number({:error, _, _}), do: "0000000000"
	defp simple_number({:ok, tokens, _}) do
		tokens 
		|> Enum.map(fn({:int, _, digit}) -> digit end)
		|> Enum.join("")
	end
end