day6.hs

#! /usr/bin/env stack
-- stack runghc --package parsec
import Data.Array.MArray
import Data.Ix (range)
import Data.Array.IO (IOArray)
import Control.Monad (liftM)
import Text.Parsec 
import Text.Parsec.String (Parser)
import Text.Parsec.Char (char, string, digit)

countLit :: IOArray (Int, Int) Bool -> IO Int
countLit = liftM (length . filter id) . getElems

toggle :: (Ix i) => i -> i -> IOArray i Bool -> IO ()
toggle x y a = mapM_ (($ True) . writeArray a) $ range (x, y)

turnOn :: (Ix i) => i -> i -> IOArray i Bool -> IO ()
turnOn x y a = mapM_ (($ True) . writeArray a) $ range (x, y)

turnOff :: (Ix i) => i -> i -> IOArray i Bool -> IO ()
turnOff x y a = mapM_ (($ False) . writeArray a) $ range (x, y)

getFn :: (Ix i) => String -> i -> i -> IOArray i Bool -> IO ()
getFn xs
  | xs == "turn on" = turnOn
  | xs == "turn off" = turnOff
  | xs == "toggle" = toggle
  | otherwise = undefined

tuplify :: [a] -> (a,a)
tuplify [x,y] = (x,y)

how2parse :: Parser ([IOArray (Int,Int) Bool -> IO ()])
how2parse = many1 $ do
    fnName <- (choice [try (string "toggle"),  try (string "turn off"), try (string "turn on"), fail "Well I guess it fucked up?"])
    char ' '
    pair1 <- sepBy1 ((read :: String -> Int) <$> many1 digit) (char ',')
    string " through "
    pair2 <- sepBy1 ((read :: String -> Int) <$> many1 digit) (char ',')
    optional $ char '\n'
    return $ (getFn fnName) (tuplify pair1) (tuplify pair2)

modifier :: String -> String -> [IOArray (Int, Int) Bool -> IO ()]
modifier name s = either (error . show) id . (parse how2parse name) $ s

main :: IO ()
main = do
  filename <- getLine
  contents <- readFile filename
  a <- newArray ((0, 0), (999, 999)) False
  mapM_ ($ a) . modifier filename $ contents
  countLit a >>= print