fix moveToSkat

src/Skat/Pile.hs

@@ -110,13 +110,18 @@ playCard :: HasCard c => Hand -> c -> Piles -> Piles
 playCard hand card' ps = (removeFromHand hand card ps) { _table = (CardS card (P hand)) : _table ps }
     where card = toCard card'
 
-moveToSkat :: HasCard c => Hand -> [c] -> Piles -> Piles
-moveToSkat hand cards' piles = removed { _skat = newSkat }
+moveToSkat :: HasCard c => Hand -> [c] -> Piles -> Maybe Piles
+moveToSkat hand cards' piles
+      | length cards' == 2 && all (`elem` possible) cards =
+            Just $ updated { _skat = newSkat }
+      | otherwise = Nothing
     where cards = map toCard cards'
-          skat = skatCards piles
-          notSkatYet = filter (not . (`elem` skat)) cards
-          newSkat = map (putAt S) $ skat ++ notSkatYet
+          oldSkat = skatCards piles
+          noLongerSkat = filter (not . (`elem` cards)) oldSkat
+          possible = map toCard (handCards hand piles) ++ oldSkat
+          newSkat = map (putAt S) cards
           removed = foldr (\card ps -> removeFromHand hand card ps) piles cards
+          updated = foldr (\card ps -> addToHand hand card ps) removed noLongerSkat
 
 unplayCard :: Hand -> Card -> Team -> Piles -> Piles
 unplayCard hand card winner ps