refactor: spawn and terminate bots

internal/core/core.go

@@ -218,37 +218,41 @@ func stateBotsNumber(state map[int]int) (number int) {
 }
 
 func (c *Core) unsafeApplyDiff(ctx context.Context, d map[int]int) {
-	// TODO: Refactor this disaster method.
-
 	for gameId, bots := range d {
 		if bots > 0 {
-			c.wg.Add(bots)
+			c.unsafeSpawn(ctx, gameId, bots)
+		} else {
+			c.unsafeTerminate(ctx, gameId, -bots)
+		}
+	}
+}
 
-			for i := 0; i < bots; i++ {
-				// Initialize new bot
-				bot := c.factory.New(gameId)
+func (c *Core) unsafeSpawn(ctx context.Context, gameId, bots int) {
+	c.wg.Add(bots)
 
-				// Start bot
-				go func(gameId int) {
-					defer c.wg.Done()
+	for i := 0; i < bots; i++ {
+		// Initialize new bot
+		bot := c.factory.New(gameId)
 
-					bot.Run(utils.WithField(ctx, "game", gameId))
-				}(gameId)
+		// Start bot
+		go func(gameId int) {
+			defer c.wg.Done()
 
-				// This is only okay because we are in the mutex lock:
-				// bot termination will not be called simultaneously.
-				c.bots[gameId] = append(c.bots[gameId], bot)
-			}
-		} else {
-			for i := 0; i < -bots; i++ {
-				c.bots[gameId][0].Stop()
-				c.bots[gameId] = c.bots[gameId][1:]
+			bot.Run(utils.WithField(ctx, "game", gameId))
+		}(gameId)
 
-				if len(c.bots[gameId]) == 0 {
-					delete(c.bots, gameId)
-				}
-			}
-		}
+		c.bots[gameId] = append(c.bots[gameId], bot)
+	}
+}
+
+func (c *Core) unsafeTerminate(ctx context.Context, gameId, bots int) {
+	for i := 0; i < bots && len(c.bots[gameId]) > 0; i++ {
+		c.bots[gameId][0].Stop()
+		c.bots[gameId] = c.bots[gameId][1:]
+	}
+
+	if len(c.bots[gameId]) == 0 {
+		delete(c.bots, gameId)
 	}
 }