Prune empty game if removing its only player

Signed-off-by: Sebastian Crane <seabass-labrax@gmx.com>

src/game.clj

@@ -1,7 +1,8 @@
 ;; SPDX-License-Identifier: Apache-2.0
 ;; SPDX-FileCopyrightText: 2021 Sebastian Crane <seabass-labrax@gmx.com>
 
-(ns game)
+(ns game
+  (:require [clojure.set :refer [superset?]]))
 
 (defn get-players-of-game [state game]
   (get-in state [:games game]))
@@ -10,7 +11,10 @@
   (update-in state [:games game] #(set (conj % player))))
 
 (defn remove-player-of-game [state game player]
-  (update-in state [:games game] #(disj % player)))
+  (update state :games
+          #(if (superset? (set [player]) (% game))
+             (dissoc % game)
+             (update % game disj player))))
 
 (defn get-games [state]
   (keys (:games state)))