Add GameCoordinator logic for finding or creating games

apps/amethyst/lib/amethyst.ex

@@ -26,7 +26,8 @@ defmodule Amethyst.Application do
     children = [
       {Task.Supervisor, name: Amethyst.ConnectionSupervisor},
       {Amethyst.Keys, 1024},
-      {Amethyst.GameRegistry, []}
+      {Amethyst.GameRegistry, []},
+      {Amethyst.GameCoordinator, []}
     ]
 
     children = case Application.fetch_env!(:amethyst, :port) do

apps/amethyst/lib/api/game.ex

@@ -12,18 +12,18 @@ defmodule Amethyst.API.Game do
         def child_spec(state) do
           %{
             id: __MODULE__,
-            start: {__MODULE__, :start_link, []}
+            start: {__MODULE__, :register_self, []}
           }
         end
-        def start_link() do
-          register_self()
-          _loop()
-        end
-        defp _loop() do
-          _loop()
-        end
         def register_self() do
           Amethyst.GameRegistry.register(__MODULE__, unquote(meta))
+          Process.sleep(:infinity)
+        end
+        def start(state) do
+          loop(state)
+        end
+        defp loop(state) do
+          loop(state)
         end
     end
   end

apps/amethyst/lib/apps/game_coordinator.ex

@@ -6,31 +6,62 @@ defmodule Amethyst.GameCoordinator do
   instances of each game and can create new ones on demand.
   """
 
+  def start_link(initial) when is_list(initial) do
+    GenServer.start_link(__MODULE__, initial, name: {:global, __MODULE__})
+  end
+
   @impl true
   def init(initial) do
     {:ok, initial}
   end
 
   @impl true
-  def handle_call({:get, type}, _from, state) do
-    {:reply, find_or_create(type, state), state}
+  def handle_call({:find, type}, _from, state) do
+    {pid, state} = _find(type, state)
+    {:reply, pid, state}
   end
 
-  defp create(mod) do
-    state = mod.initialize()
-    spawn(mod, :listen, [state])
+  @impl true
+  def handle_call({:create, type}, _from, state) do
+    {pid, state} = _create(type, state)
+    {:reply, pid, state}
   end
 
-  defp find(type, games) do
-    existing = games |> Enum.filter(fn {mod, _pid, _opts} -> mod == type end)
+  @impl true
+  def handle_call({:find_or_create, type}, from, state) do
+    {pid, state} = _find(type, state)
+    case pid do
+      nil -> handle_call({:create, type}, from, state)
+      some -> {:reply, some, state}
+    end
+  end
+
+  defp _create(type, games) do
+    state = type.instantiate()
+    pid = spawn(type, :start, [state])
+    games = [{type, pid, []} | games]
+    {pid, games}
+  end
+
+  defp _find(type, games) do
+    alive_games = games |> Enum.filter(fn {_mod, pid, _opts} -> Process.alive?(pid) end)
+    # TODO: Here we should have some additional filtering for specifically joinable games
+    existing = alive_games |> Enum.filter(fn {mod, _pid, _opts} -> mod == type end)
+    if length(existing) > 0 do
       [{_mod, pid, _} | _] = existing
-    pid
+      {pid, alive_games}
+    else
+      {nil, alive_games}
+    end
   end
 
-  defp find_or_create(type, games) do
-    case find(type, games) do
-      nil -> create(type)
-      some -> some
-    end
+  def create(type) do
+    GenServer.call({:global, __MODULE__}, {:create, type})
+  end
+  def find(type) do
+    GenServer.call({:global, __MODULE__}, {:find, type})
+  end
+  def find_or_create(type) do
+    GenServer.call({:global, __MODULE__}, {:find_or_create, type})
   end
 end