Make save game and backup game

lib/memory/application.ex

@@ -12,6 +12,7 @@ defmodule Memory.Application do
       supervisor(MemoryWeb.Endpoint, []),
       # Start your own worker by calling: Memory.Worker.start_link(arg1, arg2, arg3)
       # worker(Memory.Worker, [arg1, arg2, arg3]),
+      worker(Memory.GameBackup, [])
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html

lib/memory/game_backup.ex

@@ -0,0 +1,19 @@
+defmodule Memory.GameBackup do
+  use Agent
+
+  def start_link do
+    Agent.start_link(fn -> %{} end, name: __MODULE__)
+  end
+
+  def save(name, game) do
+    Agent.update(__MODULE__, fn state ->
+      Map.put(state, name, game)
+    end)
+  end
+
+  def load(name) do
+    Agent.get(__MODULE__, fn state ->
+      Map.get(state, name)
+    end)
+  end
+end

lib/memory_web/channels/games_channel.ex

@@ -5,7 +5,7 @@ defmodule MemoryWeb.GamesChannel do
 
   def join("games:" <> name, payload, socket) do
     if authorized?(payload) do
-      game = Game.new()
+      game = Memory.GameBackup.load(name) || Game.new()
 
       socket =
         socket
@@ -22,6 +22,7 @@ defmodule MemoryWeb.GamesChannel do
   # by sending replies to requests from the client
   def handle_in("click", %{"clickedIndex" => cardIndex}, socket) do
     game = Game.handleClick(socket.assigns[:game], cardIndex)
+    Memory.GameBackup.save(socket.assigns[:name], game)
     socket = assign(socket, :game, game)
     {:reply, {:ok, %{"game" => game}}, socket}
   end