{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleInstances #-}
#if __GLASGOW_HASKELL__ >= 800
{-# OPTIONS_GHC -Wno-orphans #-}
#endif
-- compile with:
-- ghc -O2 -fspec-constr-recursive=10 -fmax-worker-args=16 word-classifier.hs
--
import qualified Data.Char as Char
import           Data.Foldable
import           Data.Function ((&))
import           Data.Functor.Identity (Identity(..))
import qualified Data.HashMap.Strict as Map
import           Data.Hashable
import           Data.IORef
import qualified Data.List as List
import qualified Data.Ord as Ord
import           Foreign.Storable (Storable(..))
import qualified Streamly.Data.Unicode.Stream as S
import qualified Streamly.Internal.Data.Unicode.Stream as S
import qualified Streamly.Data.Fold as FL
import qualified Streamly.Internal.Data.Fold as IFL
import qualified Streamly.Internal.Data.Unfold as IUF
import qualified Streamly.Internal.FileSystem.File as File
import qualified Streamly.Memory.Array as A
import qualified Streamly.Prelude as S
import           System.Environment (getArgs)

instance (Enum a, Storable a) => Hashable (A.Array a) where
    hash arr = runIdentity $ IUF.fold A.read IFL.rollingHash arr
    hashWithSalt salt arr = runIdentity $
        IUF.fold A.read (IFL.rollingHashWithSalt salt) arr

{-# INLINE toLower #-}
toLower :: Char -> Char
toLower c
  | uc >= 0x61 && uc <= 0x7a = c
  | otherwise = Char.toLower c
  where
    uc = fromIntegral (Char.ord c) :: Word

{-# INLINE isAlpha #-}
isAlpha :: Char -> Bool
isAlpha c
  | uc >= 0x61 && uc <= 0x7a = True
  | otherwise = Char.isAlpha c
  where
    uc = fromIntegral (Char.ord c) :: Word

main :: IO ()
main = do
    inFile <- fmap head getArgs

    -- Write the stream to a hashmap consisting of word counts
    mp <-
        let
            alter Nothing    = fmap Just $ newIORef (1 :: Int)
            alter (Just ref) = modifyIORef' ref (+ 1) >> return (Just ref)
        in File.toBytes inFile    -- SerialT IO Word8
         & S.decodeLatin1         -- SerialT IO Char
         & S.map toLower          -- SerialT IO Char
         & S.words FL.toList      -- SerialT IO String
         & S.filter (all isAlpha) -- SerialT IO String
         & S.foldlM' (flip (Map.alterF alter)) Map.empty -- IO (Map String (IORef Int))

    -- Print the top hashmap entries
    counts <-
        let readRef (w, ref) = do
                cnt <- readIORef ref
                return (w, cnt)
         in Map.toList mp
          & mapM readRef

    traverse_ print $ List.sortOn (Ord.Down . snd) counts
                    & List.take 25