the tagless approach seems better

src/DesignSketch2.hs

@@ -0,0 +1,99 @@
+{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE RankNTypes #-}
+
+import Control.Monad.Random
+import Control.Monad.Reader
+import Data.IORef
+
+class (Monad m) => Avatar m where
+  queryTier :: m Int
+  makeRandom :: m Card
+
+newtype StateEffect = Summon String
+
+newtype Functionality = Deathrattle [StateEffect]
+
+data Card = Card
+  { cardName :: String,
+    functionality :: [Functionality]
+  }
+
+-- Example conversion of one of the cards
+randomSummoner :: (Avatar m) => m Card
+randomSummoner = do
+  c <- makeRandom
+  return $
+    Card
+      "randomSummoner"
+      [Deathrattle [Summon (cardName c)]]
+
+data GameState = GameState {gameTier :: Int}
+
+-- Real game instance
+newtype GameM a = GameM (ReaderT GameState (RandT StdGen IO) a)
+  deriving (Functor, Applicative, Monad, MonadRandom, MonadIO)
+
+instance Avatar GameM where
+  queryTier = GameM $ asks gameTier
+  makeRandom = do
+    tier <- queryTier
+    cards <- GameM $ asks (cardsInPool . filterByTier tier)
+    -- getRandomR from MonadRandom
+    i <- getRandomR (0, length cards - 1)
+    pure $ cards !! i
+
+filterByTier :: Int -> GameState -> b0
+filterByTier = _
+
+cardsInPool :: b0 -> [Card]
+cardsInPool = _
+
+-- Test instance
+data TestConfig = TestConfig
+  { mockTier :: Int,
+    mockCards :: [Card], -- Default sequence
+    mockCardGen :: Int -> Card -- Or generate based on context
+  }
+
+newtype TestM a = TestM (ReaderT TestConfig IO a)
+  deriving (Functor, Applicative, Monad, MonadIO)
+
+instance Avatar TestM where
+  queryTier = TestM $ asks mockTier
+  makeRandom =
+    TestM $
+      asks mockCards >>= \case
+        (c : cs) -> do
+          -- Update remaining cards for next call
+          liftIO $ modifyIORef' cardsRef (const cs)
+          pure c
+        [] -> asks mockCardGen <*> queryTier
+
+cardsRef :: IORef [Card]
+cardsRef = _
+
+-- Example usage:
+runGame :: GameM a -> GameState -> IO a
+runGame (GameM m) gs = do
+  gen <- newStdGen
+  evalRandT (runReaderT m gs) gen
+
+runTest :: TestM a -> TestConfig -> IO a
+runTest (TestM m) = runReaderT m
+
+-- Example test
+testRandomSummoner :: IO ()
+testRandomSummoner = do
+  let config =
+        TestConfig
+          { mockTier = 2,
+            mockCards = [Card "predetermined1" [], Card "predetermined2" []],
+            mockCardGen = \tier -> Card ("generated" ++ show tier) []
+          }
+
+  result <- runTest (functionality randomSummoner) config
+  _
+
+-- Assert on result