Fix save load race condition by event queue

ui/director.go

@@ -16,7 +16,7 @@ type Director struct {
 	inputChannel  chan int
 	closedChannel chan bool
 	roomID        string
-	hash		  string
+	hash          string
 }
 
 const FPS = 60
@@ -94,7 +94,8 @@ func (d *Director) PlayGame(path string) {
 
 func (d *Director) SaveGame() error {
 	if d.hash != "" {
-		return d.view.console.SaveState(savePath(d.hash))
+		d.view.Save(d.hash)
+		return nil
 	} else {
 		return nil
 	}
@@ -102,8 +103,9 @@ func (d *Director) SaveGame() error {
 
 func (d *Director) LoadGame() error {
 	if d.hash != "" {
-		return d.view.console.LoadState(savePath(d.hash))
+		d.view.Load(d.hash)
+		return nil
 	} else {
 		return nil
 	}
-}
+}

ui/gameview.go

@@ -36,6 +36,9 @@ type GameView struct {
 	// equivalent to the list key pressed const above
 	keyPressed [NumKeys * 2]bool
 
+	savingPath  string
+	loadingPath string
+
 	imageChannel chan *image.RGBA
 	inputChannel chan int
 }
@@ -108,12 +111,36 @@ func (view *GameView) Update(t, dt float64) {
 	}
 	console := view.console
 	view.updateControllers()
+	view.UpdateEvents()
 	console.StepSeconds(dt)
 
 	// fps to set frame
 	view.imageChannel <- console.Buffer()
 }
 
+func (view *GameView) Save(hash string) {
+	// put saving event to queue, process in updateEvent
+	view.savingPath = savePath(view.hash)
+}
+
+func (view *GameView) Load(path string) {
+	// put saving event to queue, process in updateEvent
+	view.loadingPath = savePath(view.hash)
+}
+
+func (view *GameView) UpdateEvents() {
+	// If there is saving event, save and discard the save event
+	if view.savingPath != "" {
+		view.console.SaveState(view.savingPath)
+		view.savingPath = ""
+	}
+	// If there is loading event, save and discard the load event
+	if view.loadingPath != "" {
+		view.console.LoadState(view.loadingPath)
+		view.loadingPath = ""
+	}
+}
+
 func (view *GameView) updateControllers() {
 	// Divide keyPressed to player 1 and player 2
 	// First 8 keys are player 1