From 3a602518368debf6c8527a47807a9f05010d1659 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 98eb0d24cc..77d4bbce19 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 93fad14d3f..55764deec4 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 f4f842b863..5da0f2211b 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