From e2019e2d3b71394f853cc1ae92b37abff2e9c24f Mon Sep 17 00:00:00 2001
From: Tissevert <tissevert+devel@marvid.fr>
Date: Sat, 25 Jan 2020 11:13:56 +0100
Subject: [PATCH] Implement a partial ordering on game coordinates to allow
 implementing re-synchronization easily

---
 src/Hanafuda/Message.hs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/Hanafuda/Message.hs b/src/Hanafuda/Message.hs
index 4506a7f..ce33786 100644
--- a/src/Hanafuda/Message.hs
+++ b/src/Hanafuda/Message.hs
@@ -13,6 +13,7 @@ module Hanafuda.Message (
     , PublicPlayer(..)
     , PublicState(..)
     , Room
+    , orderCoordinates
   ) where
 
 import Data.Char (toLower)
@@ -153,6 +154,13 @@ instance FromJSON Coordinates
 instance ToJSON Coordinates where
   toEncoding = genericToEncoding defaultOptions
 
+orderCoordinates :: Coordinates -> Coordinates -> Maybe Ordering
+orderCoordinates coordinatesA coordinatesB
+  | gameID coordinatesA == gameID coordinatesB = Just $ compare
+    (month coordinatesA, turn coordinatesA)
+    (month coordinatesB, turn coordinatesB)
+  | otherwise = Nothing
+
 data PrivateState = PrivateState {
       link :: Coordinates
     , hands :: Map PlayerID Hanafuda.Pack