From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: MrPowerGamerBR <git@mrpowergamerbr.com>
Date: Thu, 23 Nov 2023 14:36:47 -0300
Subject: [PATCH] Optimize "canSee" checks

The "canSee" checks is in a hot path, invoked by each entity for each player on the server if they are in tracking range, so optimizing it is pretty nice

First, we change the original "HashMap" to fastutil's "Object2ObjectOpenHashMap", because the containsKey throughput is better

Then, we add a "isEmpty()" check before attempting to check if the map contains something

This seems stupid, but it does seem that it improves the performance a bit, and it makes sense, "containsKey(...)" does not attempt to check the map size before attempting to check if the map contains the key

We also create a "canSee" method tailored for "ChunkMap#updatePlayer()", a method without the equals check (the "updatePlayer()" already checks if the entity is the same entity) because the CraftPlayer's `equals()` check is a *bit* expensive compared to only checking the object's identity, and because the identity has already been check, we don't need to check it twice.

diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 5a7278b093e37b95fb005ad5cc3cac90ac36f8fb..6f886a44c4320df46c86f62ce2d6f070a9ca877f 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1425,7 +1425,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                 // Paper end - Configurable entity tracking range by Y
 
                 // CraftBukkit start - respect vanish API
-                if (flag && !player.getBukkitEntity().canSee(this.entity.getBukkitEntity())) { // Paper - only consider hits
+                if (flag && !player.getBukkitEntity().canSeeChunkMapUpdatePlayer(this.entity.getBukkitEntity())) { // Paper - only consider hits // SparklyPaper - optimize canSee checks
                     flag = false;
                 }
                 // CraftBukkit end
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index 206520f6f20b2e48b1eefdd4edb26510b88e4c92..715d9811a58a9224c72a923e4a74c76bd2b1e5f0 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -187,7 +187,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
     private boolean hasPlayedBefore = false;
     private final ConversationTracker conversationTracker = new ConversationTracker();
     private final Set<String> channels = new HashSet<String>();
-    private final Map<UUID, Set<WeakReference<Plugin>>> invertedVisibilityEntities = new HashMap<>();
+    private final Map<UUID, Set<WeakReference<Plugin>>> invertedVisibilityEntities = new it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap<>(); // SparklyPaper - optimize canSee checks
     private final Set<UUID> unlistedEntities = new HashSet<>(); // Paper - Add Listing API for Player
     private static final WeakHashMap<Plugin, WeakReference<Plugin>> pluginWeakReferences = new WeakHashMap<>();
     private int hash = 0;
@@ -2141,9 +2141,16 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
 
     @Override
     public boolean canSee(org.bukkit.entity.Entity entity) {
-        return this.equals(entity) || entity.isVisibleByDefault() ^ this.invertedVisibilityEntities.containsKey(entity.getUniqueId()); // SPIGOT-7312: Can always see self
+        return this.equals(entity) || entity.isVisibleByDefault() ^ (!invertedVisibilityEntities.isEmpty() && this.invertedVisibilityEntities.containsKey(entity.getUniqueId())); // SPIGOT-7312: Can always see self // SparklyPaper - optimize canSee checks
     }
 
+    // SparklyPaper - optimize canSee checks
+    // The check in ChunkMap#updatePlayer already rejects if it is the same entity, so we don't need to check it twice, especially because CraftPlayer's equals check is a bit expensive
+    public boolean canSeeChunkMapUpdatePlayer(org.bukkit.entity.Entity entity) {
+        return entity.isVisibleByDefault() ^ (!invertedVisibilityEntities.isEmpty() && this.invertedVisibilityEntities.containsKey(entity.getUniqueId())); // SPIGOT-7312: Can always see self // SparklyPaper - optimize canSee checks
+    }
+    // SparklyPaper end
+
     public boolean canSee(UUID uuid) {
         org.bukkit.entity.Entity entity = this.getServer().getPlayer(uuid);
         if (entity == null) {