{-# LANGUAGE Safe #-}

-----------------------------------------------------------------------------
-- |
-- Module      : Passman.Core.Internal.BFEncoding
-- Copyright   : Matthew Harm Bekkema 2016
-- License     : GPL-2
-- Maintainer  : mbekkema97@gmail.com
-- Stability   : experimental
-- Portability : POSIX
-----------------------------------------------------------------------------

module Passman.Core.Internal.BFEncoding
( decode
, encode
, toB64
, fromB64
) where

import qualified Data.ByteString as BS
import qualified Data.ByteString.Base64 as B64
import Data.Word

toB64 :: Word8 -> Word8
toB64 46  = 65
toB64 47  = 66
toB64 89  = 97
toB64 90  = 98
toB64 121 = 48
toB64 122 = 49
toB64 56  = 43
toB64 57  = 47
toB64 c   = c + 2

fromB64 :: Word8 -> Word8
fromB64 65 = 46
fromB64 66 = 47
fromB64 97 = 89
fromB64 98 = 90
fromB64 48 = 121
fromB64 49 = 122
fromB64 43 = 56
fromB64 47 = 57
fromB64 c  = c - 2

decode :: BS.ByteString -> BS.ByteString
decode = B64.decodeLenient . BS.map toB64

encode :: BS.ByteString -> BS.ByteString
encode = BS.map fromB64 . BS.takeWhile (61 /=) . B64.encode