{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE ViewPatterns #-}
import Data.Maybe (fromJust,isJust)
import Data.List.Split (chunksOf)
import Data.Tuple (swap)
import Data.Tuple.Extra (first,second,dupe)
import System.Environment (getArgs)
import qualified Data.ByteString.Lazy as BL
import qualified Data.ByteString as B
import qualified Data.Map.Strict as M
import Data.Char
import Data.Maybe
import Data.Word
import Data.Array
import Data.Bits
--import Data.ByteString.Base64.Lazy as B64
import Data.ByteString.Base64 as B64
import GHC.Int
import Control.Parallel
import Control.Parallel.Strategies

main :: IO()
main = BL.getContents >>= mapM_ BL.putStr . parMap rdeepseq (chunkBL 3 (fromNum 6 4.toNum 8)) . chunkB 100000

table64 :: Array Int Word8
table64 = array (0,63) $ zip [0..] $ map (fromIntegral.ord) $ 
          ['A'..'Z']++['a'..'z']++['0'..'9']++['+','/']

toNum :: Int->BL.ByteString->Int
toNum s  = BL.foldl' f 0 where f a v = a `shiftL` s + fromIntegral v

fromNum :: Int->Int->Int->BL.ByteString
fromNum s l x = BL.pack $ map f (reverse [0..l-1]) 
                where f v = table64 ! (x `shiftR` (v*s) .&. (2^s-1))

chunkBL :: Int64->(BL.ByteString->BL.ByteString)->BL.ByteString->BL.ByteString
chunkBL n f b | BL.null b  = b
              | otherwise = let l = f . BL.take n $ b
                                r = chunkBL n f . BL.drop n $ b
                            in  BL.append l r    

chunkB :: Int64->BL.ByteString->[BL.ByteString]
chunkB n b | BL.null b  = []
              | otherwise = let l = BL.take n $ b
                                r = chunkB n . BL.drop n $ b
                            in  l:r
{-
    let arr=reverse $ BL.foldr f (0,0:[]) b
             in arr --BL.unfoldr uf (0,snd arr)
             where uf (_,[])    = Nothing
                   uf (3,x:xs)  = Just (table64 ! x,(0,xs))
                   uf (c,x:xs)  = Just (table64 ! (x.&.63),(c+1,x `shiftR` 6:xs))
                   f :: (Int,[Int]) -> Word8 -> (Int,[Int])
                   f (_,[]) v = (0,[])
                   f (2,x:xs) v = (0,0:(x `shiftL` 8) + fromIntegral v:xs)
                   f (c,x:xs) v = (c+1,(x `shiftL` 8) + fromIntegral v:xs)

    -- BL.unfoldr uf . (,)3 . snd . BL.foldl' f (0,0:[])
    -- -}
{-
-}
    

--main = B.getContents >>= B.putStr . B64.encode
-- Example Usage: echo "hello world" | ./base64  | ./base64 -d

-- TODO
-- cleanup/simplify
-- unit testing (cross check with cli base64, different lengths)
-- flag for line widht / check flags / filename on command-line 
-- (see man base64)
-- compare performance . named map? array?

-- arg<-getArgs
{-
enc64 x = B.reverse $ B.unfoldr unf $ (4, (B.foldl' (\a b->a `shiftL` 8 + fromIntegral b) (0::Int) x))
unf (c,v) = if c==0 then Nothing else let r = v .&. 63  in Just (table64 ! r,(c-1,v`shiftR` 6))
          if length arg == 0 
             then putStr . (++"\n") . encode64 . map fromIntegral . B.unpack $ dat
             else B.putStr. B.pack . map fromIntegral . decode64 .  C.unpack $ dat
-}

--t1 = BL.getContents >>= BL.putStr . BL.fromChunks . map (B.map f) . BL.toChunks



--enc=B.map (\x->table64 ! (x `shiftR` 4))



-- -- reChunkIn :: Int -> [B.ByteString] -> [B.ByteString]
-- -- reChunkIn !n = go
-- --   where
-- --     go [] = []
-- --     go (y : ys) = case B.length y `divMod` n of
-- --                     (_, 0) -> y : go ys
-- --                     (d, _) -> case B.splitAt (d * n) y of
-- --                                 (prefix, suffix) -> prefix : fixup suffix ys
-- --     fixup acc [] = [acc]
-- --     fixup acc (z : zs) = case B.splitAt (n - B.length acc) z of
-- --                            (prefix, suffix) ->
-- --                              let acc' = acc `B.append` prefix
-- --                              in if B.length acc' == n
-- --                                 then let zs' = if B.null suffix
-- --                                                then          zs
-- --                                                else suffix : zs
-- --                                      in acc' : go zs'
-- --                                 else -- suffix must be null
-- --                                     fixup acc' zs
--
--dec64 k = M.lookup k mp where mp = M.fromList $ map swap table64

{-
encode64 :: [Int] -> [Char]
encode64 = map (fromJust.enc64.flip mod 64)  -- concat . map (pad . first enc . second length . dupe) . chunksOf 3
           where enc = map (fromJust . enc64) . sumC
                 sumC = map fst . reverse . take 4 . drop 1 .iterate to64 . (,) 0 . sum  . map (uncurry (*)) . zip mult
                 mult = map (256^) [2,1,0]
                 to64 (r,v) = let r' = v `mod` 64 in (r',(v-r')`div`64)
                 pad (v,l) =take 4 $ take (1+l) v ++ "==="

decode64 :: [Char]->[Int]
decode64 = map fst .  concat . map (rem . first (reverse . take 3 . drop 1 . iterate to256 . (,) 0 . dec. map (fromJust) . filter (isJust) . map dec64).second (length.filter(=='=')). dupe) . chunksOf 4 . filter (/='\n')
           where dec = sum . map (uncurry (*)) . zip (map (64^) [3,2..]) 
                 to256 (r,v) = let r' = v `mod` 256 in (r',(v-r')`div`256)
                 rem (v,l) = take (3-l) v
-}