{-# OPTIONS -fbang-patterns #-}

import System.Environment
import Control.Monad
import qualified Data.ByteString.Char8 as S
import qualified Data.ByteString.Unsafe as S
import qualified Data.IntMap as M

main = do
    [f] <- getArgs
    x <- loadToMap f
    print (M.size x)
    getChar -- wait

loadToMap :: String -> IO (M.IntMap S.ByteString)
loadToMap f = parseLines `fmap` S.readFile f

--
-- Build an IntMap as we traverse the NNN\tfoo\n lines of the file
--
parseLines :: S.ByteString -> M.IntMap S.ByteString
parseLines s = go s M.empty
  where
     go s m
        | S.null s  = m
        | otherwise = case S.readInt s of
            Nothing     -> error "No integer field"
            Just (n, y) -> go (S.tail rest) m'

                where (str,rest) = S.break ('\n'==) (S.unsafeTail y)
                      m'         = M.insert (fromIntegral n) str m