Common.hs

{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE NoImplicitPrelude #-}

-- |
-- Module      : Authenticator.Common
-- Description : Utilty functions
-- Copyright   : (c) Justin Le 2017
-- License     : MIT
-- Maintainer  : justin@jle.im
-- Stability   : unstable
-- Portability : portable
--
-- Common utility functions and values used throughout the library.
module Authenticator.Common
  ( hlSettings,
    decodePad,
  )
where

import qualified Codec.Binary.Base32 as B32
import Control.Monad.IO.Class
import qualified Data.ByteString as BS
import Data.Char
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import Prelude.Compat
import qualified System.Console.Haskeline as L

-- | Default settings for haskeline.
hlSettings :: forall m. (MonadIO m) => L.Settings m
hlSettings =
  (L.defaultSettings @m)
    { L.complete = L.noCompletion,
      L.autoAddHistory = False
    }

-- | Pad and decode a base32-encoded value from its 'Text' prepresentation.
decodePad :: T.Text -> Maybe BS.ByteString
decodePad =
  either (const Nothing) Just
    . B32.decode
    . (\s' -> s' <> BS.replicate ((8 - BS.length s') `mod` 8) p)
    . T.encodeUtf8
    . T.map toUpper
    . T.filter isAlphaNum
  where
    p = fromIntegral $ ord '='