import System.Environment
import Text.Printf

--Code from the previous two exercises goes here

grepString :: Bool -> Maybe String -> [Chunk] -> String -> IO ()
grepString b p cs = mapM_ (printf "%s%s\n" $ maybe "" (++ ": ") p) .
                    filter ((== b) . match cs) . lines

grep :: Bool -> [String] -> IO ()
grep _ []     = error "Not enough arguments provided"
grep b (r:ps) = either print (f ps) $ parseRegex r where
    f [] cs = grepString b Nothing cs =<< getLine
    f _  cs = mapM_ (\p -> grepString b (Just p) cs =<< readFile p) ps

main :: IO ()
main = f =<< getArgs where
           f ("-v":args) = grep False args
           f args        = grep True  args