Add last adjustment check

README.md

@@ -0,0 +1,25 @@
+Minecraft doesn’t factor in network latency when determining a player's actions on the server.
+This causes the server to receive outdated information that doesn’t reflect the player's clientside position.
+As a result, players take negative velocity when they're on the ground clientside, but not serverside.
+
+This plugin handles knockback as if it were calculated clientside, ensuring that no player is at a disadvantage,
+regardless of their own or their opponent’s connection.
+
+## Frequently Asked Questions (FAQ)
+
+### Does this change put high ping players at a disadvantage?
+**It depends on the player.** Some may notice a difference if they're used to relying on high ping to reduce knockback. For others, it could actually be an advantage.
+
+### How does this change benefit high ping players?
+**Knockback control.** For example, it will be easier to escape crit chains and punish crit.
+
+### Why was the configurability of ping offset removed?
+**It promotes consistency across all servers.** Extensive testing with top players has shown that an offset of 20 provides a balanced experience for everyone.
+
+### How do I change the ping offset?
+**You must run a modified build of KnockbackSync.** The variable can be changed inside of the [PlayerData](src/main/java/me/caseload/knockbacksync/manager/PlayerData.java) class.
+
+## License
+GNU General Public License v3.0 or later
+
+See [COPYING](COPYING) to see the full text.

src/main/java/me/caseload/knockbacksync/listener/PlayerJoinQuitListener.java

@@ -8,7 +8,6 @@ import org.bukkit.entity.Player;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.Listener;
 import org.bukkit.event.player.PlayerJoinEvent;
-import org.bukkit.event.player.PlayerKickEvent;
 import org.bukkit.event.player.PlayerQuitEvent;
 
 import java.util.UUID;
@@ -37,15 +36,4 @@ public class PlayerJoinQuitListener implements Listener {
 
         PlayerDataManager.removePlayerData(uuid);
     }
-
-    @EventHandler
-    public void onPlayerKick(PlayerKickEvent event) {
-        UUID uuid = event.getPlayer().getUniqueId();
-        PlayerData playerData = PlayerDataManager.getPlayerData(uuid);
-
-        if (playerData.isInCombat())
-            playerData.quitCombat(true);
-
-        PlayerDataManager.removePlayerData(uuid);
-    }
 }

src/main/java/me/caseload/knockbacksync/listener/PlayerKnockbackListener.java

@@ -37,14 +37,18 @@ public class PlayerKnockbackListener implements Listener {
 
         Vector velocity = victim.getVelocity();
         Double verticalVelocity = playerData.getVerticalVelocity();
-
         if (verticalVelocity == null || !playerData.isOnGround(velocity.getY()))
             return;
 
+        Long lastAdjustment = playerData.getLastAdjustment();
+        if (lastAdjustment != null && System.currentTimeMillis() - lastAdjustment < 250)
+            return;
+
         Vector adjustedVelocity = velocity.clone().setY(
                 verticalVelocity
         );
 
         victim.setVelocity(adjustedVelocity);
+        playerData.setLastAdjustment(System.currentTimeMillis());
     }
 }

src/main/java/me/caseload/knockbacksync/manager/CombatManager.java

@@ -2,17 +2,16 @@ package me.caseload.knockbacksync.manager;
 
 import org.jetbrains.annotations.NotNull;
 
-import java.util.Collections;
-import java.util.HashSet;
 import java.util.Set;
 import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 
 public class CombatManager {
 
-    private static final Set<UUID> combatPlayers = new HashSet<>();
+    private static final Set<UUID> combatPlayers = ConcurrentHashMap.newKeySet();
 
     public static @NotNull Set<UUID> getPlayers() {
-        return Collections.unmodifiableSet(combatPlayers);
+        return combatPlayers;
     }
 
     public static void addPlayer(UUID uuid) {

src/main/java/me/caseload/knockbacksync/manager/PlayerData.java

@@ -8,6 +8,7 @@ import me.caseload.knockbacksync.KnockbackSync;
 import me.caseload.knockbacksync.util.MathUtil;
 import org.bukkit.*;
 import org.bukkit.attribute.Attribute;
+import org.bukkit.enchantments.Enchantment;
 import org.bukkit.entity.Player;
 import org.bukkit.potion.PotionEffect;
 import org.bukkit.potion.PotionEffectType;
@@ -40,7 +41,7 @@ public class PlayerData {
     private BukkitTask combatTask;
 
     @Nullable @Setter
-    private Long ping, previousPing;
+    private Long ping, previousPing, lastAdjustment;
 
     @Nullable @Setter
     private Double verticalVelocity;
@@ -74,14 +75,10 @@ public class PlayerData {
     }
 
     /**
-     * Determines if the Player is on the ground, either serverside or clientside.
+     * Determines if the Player is on the ground clientside, but not serverside
+     * <p>
+     * Returns <code>ping ≥ (tMax + tFall)</code> and <code>gDist ≤ 1.3</code>
      * <p>
-     * Returns <code>true</code> if:
-     * <ul>
-     *   <li>Clientside: <code>ping ≥ (tMax + tFall)</code> and <code>gDist ≤ 1.3</code></li>
-     *   <li>Serverside: <code>gDist ≤ 0</code></li>
-     * </ul>
-     *
      * Where:
      * <ul>
      *   <li><code>ping</code>: Estimated latency</li>
@@ -104,7 +101,7 @@ public class PlayerData {
 
         double gDist = getDistanceToGround();
         if (gDist <= 0)
-            return true;
+            return false; // prevent player from taking adjusted knockback when on ground serverside
 
         int tMax = verticalVelocity > 0 ? MathUtil.calculateTimeToMaxVelocity(verticalVelocity) : 0;
         double mH = verticalVelocity > 0 ? MathUtil.calculateDistanceTraveled(verticalVelocity, tMax) : 0;
@@ -172,6 +169,10 @@ public class PlayerData {
             yAxis -= resistanceFactor;
         }
 
+        // vertical velocity is always 0.4 when you have knockback level higher than 0
+        if (attacker.getInventory().getItemInMainHand().getEnchantmentLevel(Enchantment.KNOCKBACK) > 0)
+            yAxis = 0.4;
+
         return yAxis;
     }