From da358531a943040a325275a457afe2a94571e7b1 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 14 Jan 2018 17:01:31 -0500
Subject: [PATCH] PreCreatureSpawnEvent

Adds an event to fire before an Entity is created, so that plugins that need to cancel
CreatureSpawnEvent can do so from this event instead.

Cancelling CreatureSpawnEvent rapidly causes a lot of garbage collection and CPU waste
as it's done after the Entity object has been fully created.

Mob Limiting plugins and blanket "ban this type of monster" plugins should use this event
instead and save a lot of server resources.

See: https://github.com/PaperMC/Paper/issues/917

diff --git a/src/main/java/net/minecraft/server/EntityTypes.java b/src/main/java/net/minecraft/server/EntityTypes.java
index 9aed0d6b8..dce9e2fc1 100644
--- a/src/main/java/net/minecraft/server/EntityTypes.java
+++ b/src/main/java/net/minecraft/server/EntityTypes.java
@@ -271,6 +271,7 @@ public class EntityTypes<T extends Entity> {
         return this.bf;
     }
 
+    public final MinecraftKey getKey() { return this.g(); } // Paper - OBFHELPER
     public MinecraftKey g() {
         if (this.bg == null) {
             MinecraftKey minecraftkey = IRegistry.ENTITY_TYPE.getKey(this);
diff --git a/src/main/java/net/minecraft/server/MobSpawnerAbstract.java b/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
index d8ae336e9..bca0e3a2e 100644
--- a/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
+++ b/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
@@ -103,6 +103,27 @@ public abstract class MobSpawnerAbstract {
                     double d4 = j >= 2 ? nbttaglist.h(1) : (double) (blockposition.getY() + world.random.nextInt(3) - 1);
                     double d5 = j >= 3 ? nbttaglist.h(2) : (double) blockposition.getZ() + (world.random.nextDouble() - world.random.nextDouble()) * (double) this.spawnRange + 0.5D;
 
+                    // Paper start
+                    EntityTypes entityType = optional.get();
+                    String key = entityType.getKey().getKey();
+                    org.bukkit.entity.EntityType type = org.bukkit.entity.EntityType.fromName(key);
+                    if (type != null) {
+                        com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
+                        event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                            MCUtil.toLocation(world, d3, d4, d5),
+                            type,
+                            org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER
+                        );
+                        if (!event.callEvent()) {
+                            flag = true;
+                            if (event.shouldAbortSpawn()) {
+                                break;
+                            }
+                            continue;
+                        }
+                    }
+                    // Paper end
+
                     if (world.c(((EntityTypes) optional.get()).a(d3, d4, d5))) {
                         Entity entity = EntityTypes.a(nbttagcompound, world, (entity1) -> {
                             entity1.setPositionRotation(d3, d4, d5, entity1.yaw, entity1.pitch);
diff --git a/src/main/java/net/minecraft/server/SpawnerCreature.java b/src/main/java/net/minecraft/server/SpawnerCreature.java
index 7e58e4714..e5695c760 100644
--- a/src/main/java/net/minecraft/server/SpawnerCreature.java
+++ b/src/main/java/net/minecraft/server/SpawnerCreature.java
@@ -38,7 +38,7 @@ public final class SpawnerCreature {
                     BiomeBase.BiomeMeta biomebase_biomemeta = null;
                     GroupDataEntity groupdataentity = null;
                     int l1 = MathHelper.f(Math.random() * 4.0D);
-                    int i2 = 0;
+                    int i2 = 0; // Paper - force diff on name change
                     int j2 = 0;
 
                     while (true) {
@@ -74,6 +74,25 @@ public final class SpawnerCreature {
                                                 if (entitypositiontypes_surface != null && a(entitypositiontypes_surface, (IWorldReader) world, (BlockPosition) blockposition_mutableblockposition, entitytypes) && world.c(entitytypes.a((double) f, (double) k, (double) f1))) {
                                                     EntityInsentient entityinsentient;
 
+                                                    // Paper start
+                                                    com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
+                                                    EntityTypes<?> cls = biomebase_biomemeta.b;
+                                                    org.bukkit.entity.EntityType type = org.bukkit.entity.EntityType.fromName(cls.getKey().getKey());
+                                                    if (type != null) {
+                                                        event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                                                            MCUtil.toLocation(world, blockposition_mutableblockposition),
+                                                            type, SpawnReason.NATURAL
+                                                        );
+                                                        if (!event.callEvent()) {
+                                                            if (event.shouldAbortSpawn()) {
+                                                                return;
+                                                            }
+                                                            ++i2;
+                                                            continue;
+                                                        }
+                                                    }
+                                                    // Paper end
+
                                                     try {
                                                         Entity entity = entitytypes.a(world);
 
-- 
2.21.0