PreCreatureSpawnEvent - Closes #917

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

Spigot-API-Patches/PreCreatureSpawnEvent.patch

@@ -0,0 +1,120 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Sun, 14 Jan 2018 16:59:43 -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/com/destroystokyo/paper/event/entity/PreCreatureSpawnEvent.java b/src/main/java/com/destroystokyo/paper/event/entity/PreCreatureSpawnEvent.java
+new file mode 100644
+index 00000000..c4751b61
+--- /dev/null
++++ b/src/main/java/com/destroystokyo/paper/event/entity/PreCreatureSpawnEvent.java
+@@ -0,0 +0,0 @@
++package com.destroystokyo.paper.event.entity;
++
++import com.google.common.base.Preconditions;
++import org.bukkit.Location;
++import org.bukkit.entity.EntityType;
++import org.bukkit.event.Cancellable;
++import org.bukkit.event.Event;
++import org.bukkit.event.HandlerList;
++import org.bukkit.event.entity.CreatureSpawnEvent;
++
++/**
++ * WARNING: This event only fires for a limited number of cases, and not for every case that CreatureSpawnEvent does.
++ *
++ * You should still listen to CreatureSpawnEvent as a backup, and only use this event as an "enhancement".
++ * The intent of this event is to improve server performance, so limited use cases.
++ * 
++ * Currently: NATURAL and SPAWNER based reasons. Please submit a Pull Request for future additions.
++ */
++public class PreCreatureSpawnEvent extends Event implements Cancellable {
++    private final Location location;
++    private final EntityType type;
++    private final CreatureSpawnEvent.SpawnReason reason;
++    private boolean shouldAbortSpawn;
++
++    public PreCreatureSpawnEvent(Location location, EntityType type, CreatureSpawnEvent.SpawnReason reason) {
++        this.location = Preconditions.checkNotNull(location, "Location may not be null").clone();
++        this.type = Preconditions.checkNotNull(type, "Type may not be null");
++        this.reason = Preconditions.checkNotNull(reason, "Reason may not be null");
++    }
++
++    /**
++     * @return The location this creature is being spawned at
++     */
++    public Location getSpawnLocation() {
++        return location;
++    }
++
++    /**
++     * @return The type of creature being spawned
++     */
++    public EntityType getType() {
++        return type;
++    }
++
++    /**
++     * @return Reason this creature is spawning (ie, NATURAL vs SPAWNER)
++     */
++    public CreatureSpawnEvent.SpawnReason getReason() {
++        return reason;
++    }
++
++    /**
++     * @return If the spawn process should be aborted vs trying more attempts
++     */
++    public boolean shouldAbortSpawn() {
++        return shouldAbortSpawn;
++    }
++
++    /**
++     * Set this if you are more blanket blocking all types of these spawns, and wish to abort the spawn process from
++     * trying more attempts after this cancellation.
++     *
++     * @param shouldAbortSpawn Set if the spawn process should be aborted vs trying more attempts
++     */
++    public void setShouldAbortSpawn(boolean shouldAbortSpawn) {
++        this.shouldAbortSpawn = shouldAbortSpawn;
++    }
++
++    private static final HandlerList handlers = new HandlerList();
++
++    public HandlerList getHandlers() {
++        return handlers;
++    }
++
++    public static HandlerList getHandlerList() {
++        return handlers;
++    }
++
++    private boolean cancelled = false;
++
++    /**
++     * @return If the spawn of this creature is cancelled or not
++     */
++    @Override
++    public boolean isCancelled() {
++        return cancelled;
++    }
++
++    /**
++     * Cancelling this event is more effecient than cancelling CreatureSpawnEvent
++     * @param cancel true if you wish to cancel this event, and abort the spawn of this creature
++     */
++    @Override
++    public void setCancelled(boolean cancel) {
++        cancelled = cancel;
++    }
++}
+--

Spigot-Server-Patches/MC-Utils.patch

@@ -51,9 +51,33 @@ index 1f2fe87b6..2cb462b8e 100644
      protected DataBits b;
      protected DataPalette c;
      private int e;
+diff --git a/src/main/java/net/minecraft/server/EntityTypes.java b/src/main/java/net/minecraft/server/EntityTypes.java
+index ba461ad48..66c270493 100644
+--- a/src/main/java/net/minecraft/server/EntityTypes.java
++++ b/src/main/java/net/minecraft/server/EntityTypes.java
+@@ -0,0 +0,0 @@ public class EntityTypes {
+         a("zombie_villager", 5651507, 7969893);
+         EntityTypes.d.add(EntityTypes.a);
+     }
++    // Paper start
++    public static Map<Class<? extends Entity>, MinecraftKey> clsToKeyMap = new java.util.HashMap<>();
++    public static Map<Class<? extends Entity>, org.bukkit.entity.EntityType> clsToTypeMap = new java.util.HashMap<>();
++    // Paper end
+ 
+     private static void a(int i, String s, Class<? extends Entity> oclass, String s1) {
+         try {
+@@ -0,0 +0,0 @@ public class EntityTypes {
+ 
+             EntityTypes.b.a(i, minecraftkey, oclass);
+             EntityTypes.d.add(minecraftkey);
++            clsToKeyMap.put(oclass, minecraftkey); // Paper
++            clsToTypeMap.put(oclass, org.bukkit.entity.EntityType.fromName(s)); // Paper
+ 
+             while (EntityTypes.g.size() <= i) {
+                 EntityTypes.g.add(null); // Paper - Decompile fix
 diff --git a/src/main/java/net/minecraft/server/MCUtil.java b/src/main/java/net/minecraft/server/MCUtil.java
 new file mode 100644
-index 000000000..1159eea1a
+index 000000000..a4b0901cf
 --- /dev/null
 +++ b/src/main/java/net/minecraft/server/MCUtil.java
 @@ -0,0 +0,0 @@
@@ -176,6 +200,18 @@ index 000000000..1159eea1a
 +    /**
 +     * Converts a NMS World/BlockPosition to Bukkit Location
 +     * @param world
++     * @param x
++     * @param y
++     * @param z
++     * @return
++     */
++    public static Location toLocation(World world, double x, double y, double z) {
++        return new Location(world.getWorld(), x, y, z);
++    }
++
++    /**
++     * Converts a NMS World/BlockPosition to Bukkit Location
++     * @param world
 +     * @param pos
 +     * @return
 +     */

Spigot-Server-Patches/PreCreatureSpawnEvent.patch

@@ -0,0 +1,80 @@
+From 0000000000000000000000000000000000000000 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/MobSpawnerAbstract.java b/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
+index c29df55fa..d6c73a5a0 100644
+--- a/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
++++ b/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
+@@ -0,0 +0,0 @@
+ package net.minecraft.server;
+ 
+ import com.google.common.collect.Lists;
++
+ import java.util.Iterator;
+ import java.util.List;
+ import javax.annotation.Nullable;
+@@ -0,0 +0,0 @@ public abstract class MobSpawnerAbstract {
+                     double d3 = j >= 1 ? nbttaglist.f(0) : (double) blockposition.getX() + (world.random.nextDouble() - world.random.nextDouble()) * (double) this.spawnRange + 0.5D;
+                     double d4 = j >= 2 ? nbttaglist.f(1) : (double) (blockposition.getY() + world.random.nextInt(3) - 1);
+                     double d5 = j >= 3 ? nbttaglist.f(2) : (double) blockposition.getZ() + (world.random.nextDouble() - world.random.nextDouble()) * (double) this.spawnRange + 0.5D;
++                    // Paper start
++                    if (this.getMobName() == null) {
++                        return;
++                    }
++                    com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
++                    event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
++                            MCUtil.toLocation(world, d3, d4, d5),
++                            org.bukkit.entity.EntityType.fromName(this.getMobName().getKey()),
++                            org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER
++                    );
++                    if (!event.callEvent()) {
++                        if (event.shouldAbortSpawn()) {
++                            break;
++                        }
++                        continue;
++                    }
++                    // Paper end
+                     Entity entity = ChunkRegionLoader.a(nbttagcompound, world, d3, d4, d5, false);
+ 
+                     if (entity == null) {
+diff --git a/src/main/java/net/minecraft/server/SpawnerCreature.java b/src/main/java/net/minecraft/server/SpawnerCreature.java
+index 2cd063829..1137dda86 100644
+--- a/src/main/java/net/minecraft/server/SpawnerCreature.java
++++ b/src/main/java/net/minecraft/server/SpawnerCreature.java
+@@ -0,0 +0,0 @@ public final class SpawnerCreature {
+                                                     }
+ 
+                                                     if (worldserver.a(enumcreaturetype, biomebase_biomemeta, (BlockPosition) blockposition_mutableblockposition) && a(EntityPositionTypes.a(biomebase_biomemeta.b), worldserver, blockposition_mutableblockposition)) {
++                                                        // Paper start
++                                                        com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
++                                                        event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
++                                                                MCUtil.toLocation(worldserver,  blockposition_mutableblockposition),
++                                                                EntityTypes.clsToTypeMap.get(biomebase_biomemeta.b),
++                                                                SpawnReason.NATURAL
++                                                                );
++                                                        if (!event.callEvent()) {
++                                                            if (event.shouldAbortSpawn()) {
++                                                                continue label120;
++                                                            }
++                                                            j1 += l2;
++                                                            ++j4;
++                                                            continue;
++                                                        }
++                                                        // Paper end
+                                                         EntityInsentient entityinsentient;
+ 
+                                                         try {
+--

Spigot-Server-Patches/String-based-Action-Bar-API.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] String based Action Bar API
 
 
 diff --git a/src/main/java/net/minecraft/server/MCUtil.java b/src/main/java/net/minecraft/server/MCUtil.java
-index 1159eea1..38359517 100644
+index a4b0901cf..02940d697 100644
 --- a/src/main/java/net/minecraft/server/MCUtil.java
 +++ b/src/main/java/net/minecraft/server/MCUtil.java
 @@ -0,0 +0,0 @@
@@ -62,7 +62,7 @@ index 1159eea1..38359517 100644
 +    }
  }
 diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
-index ef873c17..b17f2c06 100644
+index ef873c17d..b17f2c067 100644
 --- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
 +++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
 @@ -0,0 +0,0 @@ public class CraftPlayer extends CraftHumanEntity implements Player {