{-#LANGUAGE BangPatterns #-}
import Control.Foldl (Fold(..))
import qualified Control.Foldl as L
import qualified Data.Vector.Unboxed as V
import qualified Data.Sequence as Seq
import Control.Applicative
import Criterion.Main
import System.Environment
a >< b = fmap (,) a <*> b

main = do
  f:n:_ <- getArgs
  case f of
    "v" -> do
       let folder = L.purely_ (\a b -> V.foldl a b (V.enumFromTo 1 (10^6::Int)))
       case n of
              "1" -> print $ folder $ index (10^4+1)
              "2" -> print $ folder $ index (10^4) >< index (10^4+1)
              "3" -> print $ folder $ index (10^4-1) >< index (10^4) >< index (10^4+1)
    "s" -> do
      let folder = flip L.fold (Seq.replicate (10^6) (1::Int))
      case n of
             "1" -> print $ folder $ index (10^4+1)
             "2" -> print $ folder $ index (10^4) >< index (10^4+1)
             "3" -> print $ folder $ index (10^4-1) >< index (10^4) >< index (10^4+1)

    "l" -> do
      let folder = flip L.fold (enumFromTo 1 (10^6::Int))
      case n of
             "1" -> print $ folder $ index (10^4+1)
             "2" -> print $ folder $ index (10^4) >< index (10^4+1)
             "3" -> print $ folder $ index (10^4-1) >< index (10^4) >< index (10^4+1)


   -- L.fold folds $ Seq.replicate (10^4) (1::Int) where
-- --   folds =  (index (10^6+1))
--    folds = liftA2 (,) (index (10^2-1)) $ liftA2 (,) (index (10^2)) (index (10^2+1))

data IndexSt a = NotYet !Int | Yet !a

index :: Int -> Fold a (Maybe a)
index n = Fold step (NotYet n) done where
  step (Yet a) _ = Yet a
  step (NotYet 0) a = Yet a
  step (NotYet n) a = NotYet (n-1)
  done (NotYet _) = Nothing
  done (Yet a) = Just a