Uno cards and shuffling

Cards.hs

module Cards where

   import System.Random
   import Data.Maybe
   import Data.List
   import Data.Function

   import Test.HUnit
   import Test.QuickCheck

   -- | Card values for uno cards
   data CardValue = Naught | One | Two | Three
      | Four | Five | Six | Seven | Eight | Nine
      | Skip | Reverse | DrawTwo | Wild | WildDrawFour
      deriving (Show, Eq, Enum)

   -- | Possible card colours
   data CardColour = Red | Blue | Green | Yellow
      deriving (Show, Eq, Enum)

   -- | Defines the attributes of a card
   data Card = Card CardValue (Maybe CardColour)
      deriving (Show)

   -- | Seeds a list of cards with a random value
   seedCards :: StdGen -> [Card] -> [(Card, Int)]
   seedCards g []     = []
   seedCards g (c:cs) = x:seedCards ng cs
      where (seed, ng) = randomR(1, 10000) g :: (Int, StdGen)
            x          = (c, seed)

   -- | Makes a randomly shuffled deck of cards
   makeShuffledDeck :: StdGen -> [Card]
   makeShuffledDeck g = [x | c <- sorted, let x = fst c]
      where cards  = seedCards g deck
            sorted = sortBy (compare `on` snd) cards
            deck   = val ++ take 10 (cycle spec)
            val    = [Card v (Just c) | v <- [Naught .. DrawTwo], c <- [Red .. Yellow]]
            spec   = [Card v Nothing | v <- [Wild .. WildDrawFour]]

   tests = TestList $ map TestCase
      [assertEqual "add tests here" 1 1]

   prop_empty c1 = (c1::Int) == c1

   runTests = do
      runTestTT tests
      quickCheck prop_empty

   -- | Main entry point
   main :: IO ()
   main = runTests