{-|
Module      : Verismith
Description : Verismith
Copyright   : (c) 2020, Yann Herklotz
License     : GPL-3
Maintainer  : yann [at] yannherklotz [dot] com
Stability   : experimental
Portability : POSIX
-}

module Verismith.Utils
  (generateByteString)
where

import System.Random (mkStdGen, newStdGen, randoms)
import Data.ByteString (ByteString, pack)

generateByteString :: (Maybe Int) -> Int -> Int -> IO [ByteString]
generateByteString mseed size n = do
    fmap pack . chunksOf size . take (size * n) . randoms <$>
      case mseed of
        Just seed' -> return $ mkStdGen seed'
        Nothing    -> newStdGen
  where
    chunksOf i _ | i <= 0 = error $ "chunksOf, number must be positive, got " ++ show i
    chunksOf i xs = repeatedly (splitAt i) xs
    repeatedly _ [] = []
    repeatedly f as = b : repeatedly f as'
      where (b, as') = f as