Reading stdin without buffering

readInput.hs

import qualified Turtle as T
import qualified System.IO as IO
import Control.DeepSeq

mergeUntilTwoBlankLines :: (() -> IO (Maybe String)) -> IO [String]
mergeUntilTwoBlankLines fn = do
    rd <- fn ()
    processFunc [] rd
  where processFunc ("" : existing) (Just "") = return existing
        processFunc existing (Just nxt) = do
          rd <- fn ()
          processFunc (nxt : existing) rd
        processFunc existing Nothing = return existing

readInput :: IO [String]
readInput = do
    IO.hSetBuffering IO.stdin IO.NoBuffering
    res <- mergeUntilTwoBlankLines (\_ -> readFn)
    res `deepseq` IO.hSetBuffering IO.stdin IO.LineBuffering
    return res
  where readFn = do
          readLineMaybe <- T.readline
          return $ fmap Text.unpack readLineMaybe