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{-# LANGUAGE ViewPatterns #-}
module Codec.SafeBlob where
import qualified Data.ByteString.Char8 as B
import Data.Monoid
import Data.List (foldl')
import Data.Maybe
toSafe :: B.ByteString -> B.ByteString
toSafe blob = let as = zip [0..] (B.unpack blob)
bs = filter ((=='\n') . snd) as
is = map fst bs
in B.pack (show is) <> foldl' (replaceCharStrIndex '#') blob is
replaceCharStrIndex :: Char -> B.ByteString -> Int -> B.ByteString
replaceCharStrIndex c str i = a <> B.singleton c <> b
where (a,B.uncons -> Just (_,b)) = B.splitAt i str
fromSafe str = foldl' (replaceCharStrIndex '\n') (B.drop 1 str') is
where is = map fst . mapMaybe B.readInt $
B.groupBy (\c d -> (c/=',')&&(d/=',')) ls
(ls,str') = B.break (==']') (B.tail str)
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