iorepro.hs

module Main where

import Data.IORef
  ( IORef
  , newIORef
  , readIORef
  , writeIORef
  )

import Control.Monad.Loops
  ( whileJust_
  )

main :: IO ()
main =
  upload "Hello world"

upload :: String -> IO ()
upload s =
  upload_shares =<< (make_share_maker s)
  where
    upload_shares :: IO (Maybe String) -> IO ()
    upload_shares shares =
      whileJust_ shares upload_one_share

    upload_one_share :: String -> IO ()
    upload_one_share = print

    make_share_maker :: String -> IO (IO (Maybe String))
    make_share_maker s = do
      state <- newIORef 0
      return $ make_shares state s

    make_shares :: IORef Int -> String -> IO (Maybe String)                                                                                                                                  
    make_shares state s = do                                                                                                                                                                 
      pos <- readIORef state
      writeIORef state (pos + 1)
      return $
        if pos < length s
        then Just $ drop pos s
        else Nothing