{- This file is part of monad-hash.
 -
 - Written in 2016 by fr33domlover <fr33domlover@riseup.net>.
 -
 - ♡ Copying is an act of love. Please copy, reuse and share.
 -
 - The author(s) have dedicated all copyright and related and neighboring
 - rights to this software to the public domain worldwide. This software is
 - distributed without any warranty.
 -
 - You should have received a copy of the CC0 Public Domain Dedication along
 - with this software. If not, see
 - <http://creativecommons.org/publicdomain/zero/1.0/>.
 -}

import Control.Monad (unless)
import Control.Monad.IO.Class (liftIO)
import Control.Monad.Trans.Hash
import Crypto.Hash.Algorithms (SHA1)
import System.Exit (exitFailure)
import System.IO

import qualified Data.ByteString as B

incrementalHash :: Handle -> Int -> HashT SHA1 IO ()
incrementalHash h chunkSize = go
    where
    go = do
        b <- liftIO $ B.hGet h chunkSize
        unless (B.null b) $ do
            updateHash b
            go

main :: IO ()
main = do
    let file = "COPYING"
        sha1sum = "82da472f6d00dc5f0a651f33ebb320aa9c7b08d0"
        chunkSize = 1000
    (_, digest) <-
        withFile file ReadMode $ \ h -> runHashT $ incrementalHash h chunkSize
    let result = show digest
    putStrLn $ "Expecting: " ++ sha1sum
    putStrLn $ "Got:       " ++ result
    if sha1sum == result
        then putStrLn "Success!"
        else putStrLn "Failed!" >> exitFailure