Add locale change interval limit

src/main/java/cn/dreeam/caeruleum/config/Config.java

@@ -53,13 +53,30 @@ public interface Config {
     @AnnotationBasedSorter.Order(3)
     List<String> mainLocale();
 
+    @ConfKey("i18nPerm.locale-change-interval-limit")
+    @ConfComments({
+            "The maximum interval for locale change, to prevent using packet exploit to lag server, locale change between this interval will be discard.",
+            "(unit: ms)"
+    })
+    @ConfDefault.DefaultInteger(1000)
+    @AnnotationBasedSorter.Order(4)
+    int localeChangeIntervalLimit();
+
+    @ConfKey("i18nPerm.locale-change-interval-limit-message")
+    @ConfComments({
+            "The message sent to player when reached the interval limit."
+    })
+    @ConfDefault.DefaultString("<red>You can not change locale so fast!")
+    @AnnotationBasedSorter.Order(5)
+    String localeChangeIntervalLimitMessage();
+
     @ConfKey("i18nPerm.locale-list.fallback-locale")
     @ConfComments({
             "The fallback locale, if any unknown or unsupported locale found when player join/change locale,",
             "CaeruleumCore will assign lang permission based on the fallback locale here."
     })
     @ConfDefault.DefaultString("en_US")
-    @AnnotationBasedSorter.Order(4)
+    @AnnotationBasedSorter.Order(6)
     String localeBlackWhiteListFallback();
 
     @ConfKey("i18nPerm.locale-list.use-whitelist")
@@ -68,7 +85,7 @@ public interface Config {
             "Set to false to use blacklist mode."
     })
     @ConfDefault.DefaultBoolean(true)
-    @AnnotationBasedSorter.Order(5)
+    @AnnotationBasedSorter.Order(7)
     boolean localeBlackWhiteListUseWhitelist();
 
     @ConfKey("i18nPerm.locale-list.locales")
@@ -83,7 +100,7 @@ public interface Config {
             "lzh",
             "en_US"
     })
-    @AnnotationBasedSorter.Order(6)
+    @AnnotationBasedSorter.Order(8)
     List<String> localeBlackWhiteList();
 }
 

src/main/java/cn/dreeam/caeruleum/listener/LocaleChange.java

@@ -2,6 +2,9 @@
 
 import cn.dreeam.caeruleum.CaeruleumCore;
 import cn.dreeam.caeruleum.utils.PermUtil;
+import cn.dreeam.caeruleum.utils.Util;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.minimessage.MiniMessage;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.Listener;
 import org.bukkit.event.player.PlayerLocaleChangeEvent;
@@ -13,11 +16,18 @@ public class LocaleChange implements Listener {
 
     @EventHandler
     public void onLocaleChange(PlayerLocaleChangeEvent e) {
-        // Should add threshold to prevent lag Or use async queue to execute all logic.
+        // Use threshold limit to prevent lag using packets.
+        if (Util.reachThreshold()) {
+            final Component message = MiniMessage.miniMessage().deserialize(CaeruleumCore.config.localeChangeIntervalLimitMessage());
+            e.getPlayer().sendMessage(message);
+            return;
+        }
+
         String locale = e.locale().toString();
         UUID uuid = e.getPlayer().getUniqueId();
         List<String> langPerms = PermUtil.getLangPerm(uuid);
 
+        // Remove invalid perms
         if (langPerms.size() > 1) {
             PermUtil.clearLangPerm(uuid);
         }

src/main/java/cn/dreeam/caeruleum/utils/Util.java

@@ -0,0 +1,18 @@
+package cn.dreeam.caeruleum.utils;
+
+import cn.dreeam.caeruleum.CaeruleumCore;
+
+public class Util {
+
+    private static long lastTime = System.nanoTime();
+
+    public static boolean reachThreshold() {
+        long now = System.nanoTime();
+        if ((now - lastTime) / 1_000_000 > CaeruleumCore.config.localeChangeIntervalLimit()) {
+            lastTime = now;
+            return true;
+        }
+
+        return false;
+    }
+}