import Data.List (isPrefixOf)
import System.Environment (getArgs)
import System.IO (hPrint, stderr)

main = do
  args <- getArgs
  mapM_ identify args

identify f = do
  g <- isInteresting f
  case g of
    Right h -> putStrLn (f ++ ": " ++ if h then "interesting" else "boring")
    Left e  -> hPrint stderr e

isInteresting f = catch action handler
    where
      action = do
        x <- readFile f
        return (Right (x `contains` "Haskell"))
      handler e = return (Left e)

[] `contains` _ = False
(x:xs) `contains` y = y `isPrefixOf` (x:xs) || xs `contains` y