antl_utils

defmodule AntlUtils.Elixir.Integer do
  @alphabets %{
    62 => "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",
    64 => "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
  }

  @doc """
  Returns a binary which corresponds to the text representation of integer in the given base

  base can be an integer between 2 and 36, 62 or 64

  ## Examples

    iex> Integer.to_string(0, 62)
    "0"
    iex> Integer.to_string(1, 62)
    "1"

  """
  @spec to_string(integer, 1..255) :: binary
  def to_string(integer, base)
      when is_integer(integer) and is_integer(base) and base >= 2 and base <= 32 do
    Integer.to_string(integer, base)
  end

  def to_string(integer, base) when is_integer(integer) and base in [62, 64] do
    to_string(integer, "", base)
  end

  defp to_string(integer, "", _base) when is_integer(integer) and integer <= 0 do
    "0"
  end

  defp to_string(integer, acc, _base) when is_integer(integer) and integer <= 0 do
    acc
  end

  defp to_string(integer, acc, base)
       when is_number(integer) and integer > 0 and is_binary(acc) and is_integer(base) do
    remainder = rem(integer, base)

    to_string(
      div(integer - remainder, base),
      "#{String.at(Map.get(@alphabets, base), remainder)}#{acc}",
      base
    )
  end
end