Take game ID with turn into a GameState sub-structure shared between private and public parts to prevent replay-attack

src/Hanafuda/Message.hs

@@ -7,6 +7,7 @@
 module Hanafuda.Message (
       T(..)
     , FromClient(..)
+    , GameState(..)
     , PrivateState(..)
     , PublicGame(..)
     , PublicPlayer(..)
@@ -139,8 +140,18 @@ instance FromJSON Hanafuda.Flower
 instance ToJSON Hanafuda.Flower where
   toEncoding = genericToEncoding defaultOptions
 
+data GameState = GameState {
+      gameID :: GameID
+    , turns :: Int
+  } deriving (Eq, Generic, Show)
+
+instance FromJSON GameState
+instance ToJSON GameState where
+  toEncoding = genericToEncoding defaultOptions
+
 data PrivateState = PrivateState {
-      hands :: Map PlayerID Hanafuda.Pack
+      link :: GameState
+    , hands :: Map PlayerID Hanafuda.Pack
     , deck :: [Hanafuda.Card]
   } deriving Generic
 
@@ -158,7 +169,8 @@ instance ToJSON PublicPlayer where
   toEncoding = genericToEncoding defaultOptions
 
 data PublicState = PublicState {
-      mode :: KoiKoi.Mode
+      gameState :: GameState
+    , mode :: KoiKoi.Mode
     , scores :: KoiKoi.Scores
     , month :: Hanafuda.Flower
     , nextPlayer :: KoiKoi.PlayerTurn
@@ -169,7 +181,6 @@ data PublicState = PublicState {
     , river :: Hanafuda.Pack
     , step :: KoiKoi.Step
     , trick :: [Hanafuda.Card]
-    , turns :: Int
     , rounds :: [(PlayerID, KoiKoi.Score)]
   } deriving (Generic, Show)
 
@@ -184,8 +195,7 @@ instance ToJSON ByteString where
   toEncoding = toEncoding . decodeUtf8 . B64.encode
 
 data PublicGame = PublicGame {
-      gameID :: GameID
-    , nonce :: ByteString
+      nonce :: ByteString
     , playerHand :: Hanafuda.Pack
     , private :: ByteString
     , public :: PublicState