WordCountModular.hs

-- To run this program:
--
-- cabal run --flag fusion-plugin WordCountModular test-data.txt
--
module Main (main) where

import Data.Char (chr, ord)
import Data.Function ((&))
import Data.Word (Word8)
import Streamly.Data.Fold (Fold, Tee(..))
import System.Environment (getArgs)

import qualified Streamly.Data.Fold as Fold
import qualified Streamly.Data.Stream as Stream
import qualified Streamly.FileSystem.File as File

{-# INLINE isSpace #-}
isSpace :: Char -> Bool
isSpace c = uc == 0x20 || uc - 0x9 <= 4
  where uc = fromIntegral (ord c) :: Word

-------------------------------------------------------------------------------
-- Fold the bytes from an input file
-------------------------------------------------------------------------------

-- The fold accepts a stream of `Word8` and returns a value of type "a".
foldWith :: Fold IO Word8 a -> String -> IO a
foldWith f file =
    File.read file    -- Stream IO Word8
  & Stream.fold f     -- IO a

-------------------------------------------------------------------------------
-- Count Lines
-------------------------------------------------------------------------------

-- ASCII character 10 is newline
countl :: Int -> Word8 -> Int
countl n ch = if ch == 10 then n + 1 else n

nlines :: Monad m => Fold m Word8 Int
nlines = Fold.foldl' countl 0

-------------------------------------------------------------------------------
-- Count Words
-------------------------------------------------------------------------------

countw :: (Int, Bool) -> Word8 -> (Int, Bool)
countw (n, wasSpace) ch =
    if isSpace $ chr $ fromIntegral ch
    then (n, True)
    else (if wasSpace then n + 1 else n, False)

-- The fold accepts a stream of `Word8` and returns a word count (`Int`)
nwords :: Monad m => Fold m Word8 Int
nwords = fst <$> Fold.foldl' countw (0, True)

-------------------------------------------------------------------------------
-- Count Bytes, Lines, Words
-------------------------------------------------------------------------------

-- The fold accepts a stream of `Word8` and returns the three counts
countAll :: Fold IO Word8 (Int, Int, Int)
countAll = unTee $ (,,) <$> Tee Fold.length <*> Tee nlines <*> Tee nwords

-------------------------------------------------------------------------------
-- Main
-------------------------------------------------------------------------------

main :: IO ()
main = do
    name <- fmap head getArgs
    -- foldWith Fold.length name >>= print -- count bytes only
    -- foldWith nlines name >>= print      -- count lines only
    -- foldWith nwords name >>= print      -- count words only
    (c, l, w) <- foldWith countAll name    -- count all at once
    putStrLn $ show l ++ " " ++ show w ++ " " ++ show c ++ " " ++ name