Paper-Old/patches/server-remapped/0376-implement-optional-per-player-mob-spawns.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: kickash32 <kickash32@gmail.com>
Date: Mon, 19 Aug 2019 01:27:58 +0500
Subject: [PATCH] implement optional per player mob spawns


diff --git a/src/main/java/co/aikar/timings/WorldTimingsHandler.java b/src/main/java/co/aikar/timings/WorldTimingsHandler.java
index 24eac9400fbf971742e89bbf47b0ba52b587c4eb..b818a7451d45d2ab7d4678f0065ada9017d8a631 100644
--- a/src/main/java/co/aikar/timings/WorldTimingsHandler.java
+++ b/src/main/java/co/aikar/timings/WorldTimingsHandler.java
@@ -58,6 +58,7 @@ public class WorldTimingsHandler {
 
 
     public final Timing miscMobSpawning;
+    public final Timing playerMobDistanceMapUpdate;
 
     public final Timing poiUnload;
     public final Timing chunkUnload;
@@ -123,6 +124,7 @@ public class WorldTimingsHandler {
 
 
         miscMobSpawning = Timings.ofSafe(name + "Mob spawning - Misc");
+        playerMobDistanceMapUpdate = Timings.ofSafe(name + "Per Player Mob Spawning - Distance Map Update");
 
         poiUnload = Timings.ofSafe(name + "Chunk unload - POI");
         chunkUnload = Timings.ofSafe(name + "Chunk unload - Chunk");
diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index b913cd2dd0cd1b369b3f7b5a9d8b1be73f6d7920..6aec502eb529d4090306e12e837117cde7e114eb 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -565,4 +565,9 @@ public class PaperWorldConfig {
             }
         }
     }
+
+    public boolean perPlayerMobSpawns = false;
+    private void perPlayerMobSpawns() {
+        perPlayerMobSpawns = getBoolean("per-player-mob-spawns", false);
+    }
 }
diff --git a/src/main/java/com/destroystokyo/paper/util/PlayerMobDistanceMap.java b/src/main/java/com/destroystokyo/paper/util/PlayerMobDistanceMap.java
new file mode 100644
index 0000000000000000000000000000000000000000..2a87599922d7075a9f888f48a2deb35ed3eb7c54
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/util/PlayerMobDistanceMap.java
@@ -0,0 +1,252 @@
+package com.destroystokyo.paper.util;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet;
+import java.util.List;
+import java.util.Map;
+import net.minecraft.core.SectionPos;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.level.ChunkPos;
+import org.spigotmc.AsyncCatcher;
+import java.util.HashMap;
+
+/** @author Spottedleaf */
+public final class PlayerMobDistanceMap {
+
+    private static final PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> EMPTY_SET = new PooledHashSets.PooledObjectLinkedOpenHashSet<>();
+
+    private final Map<ServerPlayer, SectionPos> players = new HashMap<>();
+    // we use linked for better iteration.
+    private final Long2ObjectOpenHashMap<PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer>> playerMap = new Long2ObjectOpenHashMap<>(32, 0.5f);
+    private int viewDistance;
+
+    private final PooledHashSets<ServerPlayer> pooledHashSets = new PooledHashSets<>();
+
+    public PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> getPlayersInRange(final ChunkPos chunkPos) {
+        return this.getPlayersInRange(chunkPos.x, chunkPos.z);
+    }
+
+    public PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> getPlayersInRange(final int chunkX, final int chunkZ) {
+        return this.playerMap.getOrDefault(ChunkPos.asLong(chunkX, chunkZ), EMPTY_SET);
+    }
+
+    public void update(final List<ServerPlayer> currentPlayers, final int newViewDistance) {
+        AsyncCatcher.catchOp("Distance map update");
+        final ObjectLinkedOpenHashSet<ServerPlayer> gone = new ObjectLinkedOpenHashSet<>(this.players.keySet());
+
+        final int oldViewDistance = this.viewDistance;
+        this.viewDistance = newViewDistance;
+
+        for (final ServerPlayer player : currentPlayers) {
+            if (player.isSpectator() || !player.affectsSpawning) {
+                continue; // will be left in 'gone' (or not added at all)
+            }
+
+            gone.remove(player);
+
+            final SectionPos newPosition = player.getPlayerMapSection();
+            final SectionPos oldPosition = this.players.put(player, newPosition);
+
+            if (oldPosition == null) {
+                this.addNewPlayer(player, newPosition, newViewDistance);
+            } else {
+                this.updatePlayer(player, oldPosition, newPosition, oldViewDistance, newViewDistance);
+            }
+            //this.validatePlayer(player, newViewDistance); // debug only
+        }
+
+        for (final ServerPlayer player : gone) {
+            final SectionPos oldPosition = this.players.remove(player);
+            if (oldPosition != null) {
+                this.removePlayer(player, oldPosition, oldViewDistance);
+            }
+        }
+    }
+
+    // expensive op, only for debug
+    private void validatePlayer(final ServerPlayer player, final int viewDistance) {
+        int entiesGot = 0;
+        int expectedEntries = (2 * viewDistance + 1);
+        expectedEntries *= expectedEntries;
+
+        final SectionPos currPosition = player.getPlayerMapSection();
+
+        final int centerX = currPosition.getX();
+        final int centerZ = currPosition.getZ();
+
+        for (final Long2ObjectLinkedOpenHashMap.Entry<PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer>> entry : this.playerMap.long2ObjectEntrySet()) {
+            final long key = entry.getLongKey();
+            final PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> map = entry.getValue();
+
+            if (map.referenceCount == 0) {
+                throw new IllegalStateException("Invalid map");
+            }
+
+            if (map.set.contains(player)) {
+                ++entiesGot;
+
+                final int chunkX = ChunkPos.getX(key);
+                final int chunkZ = ChunkPos.getZ(key);
+
+                final int dist = Math.max(Math.abs(chunkX - centerX), Math.abs(chunkZ - centerZ));
+
+                if (dist > viewDistance) {
+                    throw new IllegalStateException("Expected view distance " + viewDistance + ", got " + dist);
+                }
+            }
+        }
+
+        if (entiesGot != expectedEntries) {
+            throw new IllegalStateException("Expected " + expectedEntries + ", got " + entiesGot);
+        }
+    }
+
+    private void addPlayerTo(final ServerPlayer player, final int chunkX, final int chunkZ) {
+       this.playerMap.compute(ChunkPos.asLong(chunkX, chunkZ), (final Long key, final PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> players) -> {
+           if (players == null) {
+               return player.cachedSingleMobDistanceMap;
+           } else {
+               return PlayerMobDistanceMap.this.pooledHashSets.findMapWith(players, player);
+           }
+        });
+    }
+
+    private void removePlayerFrom(final ServerPlayer player, final int chunkX, final int chunkZ) {
+        this.playerMap.compute(ChunkPos.asLong(chunkX, chunkZ), (final Long keyInMap, final PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> players) -> {
+            return PlayerMobDistanceMap.this.pooledHashSets.findMapWithout(players, player); // rets null instead of an empty map
+        });
+    }
+
+    private void updatePlayer(final ServerPlayer player, final SectionPos oldPosition, final SectionPos newPosition, final int oldViewDistance, final int newViewDistance) {
+        final int toX = newPosition.getX();
+        final int toZ = newPosition.getZ();
+        final int fromX = oldPosition.getX();
+        final int fromZ = oldPosition.getZ();
+
+        final int dx = toX - fromX;
+        final int dz = toZ - fromZ;
+
+        final int totalX = Math.abs(fromX - toX);
+        final int totalZ = Math.abs(fromZ - toZ);
+
+        if (Math.max(totalX, totalZ) > (2 * oldViewDistance)) {
+            // teleported?
+            this.removePlayer(player, oldPosition, oldViewDistance);
+            this.addNewPlayer(player, newPosition, newViewDistance);
+            return;
+        }
+
+        // x axis is width
+        // z axis is height
+        // right refers to the x axis of where we moved
+        // top refers to the z axis of where we moved
+
+        if (oldViewDistance == newViewDistance) {
+            // same view distance
+
+            // used for relative positioning
+            final int up = 1 | (dz >> (Integer.SIZE - 1)); // 1 if dz >= 0, -1 otherwise
+            final int right = 1 | (dx >> (Integer.SIZE - 1)); // 1 if dx >= 0, -1 otherwise
+
+            // The area excluded by overlapping the two view distance squares creates four rectangles:
+            // Two on the left, and two on the right. The ones on the left we consider the "removed" section
+            // and on the right the "added" section.
+            // https://i.imgur.com/MrnOBgI.png is a reference image. Note that the outside border is not actually
+            // exclusive to the regions they surround.
+
+            // 4 points of the rectangle
+            int maxX; // exclusive
+            int minX; // inclusive
+            int maxZ; // exclusive
+            int minZ; // inclusive
+
+            if (dx != 0) {
+                // handle right addition
+
+                maxX = toX + (oldViewDistance * right) + right; // exclusive
+                minX = fromX + (oldViewDistance * right) + right; // inclusive
+                maxZ = fromZ + (oldViewDistance * up) + up; // exclusive
+                minZ = toZ - (oldViewDistance * up); // inclusive
+
+                for (int currX = minX; currX != maxX; currX += right) {
+                    for (int currZ = minZ; currZ != maxZ; currZ += up) {
+                        this.addPlayerTo(player, currX, currZ);
+                    }
+                }
+            }
+
+            if (dz != 0) {
+                // handle up addition
+
+                maxX = toX + (oldViewDistance * right) + right; // exclusive
+                minX = toX - (oldViewDistance * right); // inclusive
+                maxZ = toZ + (oldViewDistance * up) + up; // exclusive
+                minZ = fromZ + (oldViewDistance * up) + up; // inclusive
+
+                for (int currX = minX; currX != maxX; currX += right) {
+                    for (int currZ = minZ; currZ != maxZ; currZ += up) {
+                        this.addPlayerTo(player, currX, currZ);
+                    }
+                }
+            }
+
+            if (dx != 0) {
+                // handle left removal
+
+                maxX = toX - (oldViewDistance * right); // exclusive
+                minX = fromX - (oldViewDistance * right); // inclusive
+                maxZ = fromZ + (oldViewDistance * up) + up; // exclusive
+                minZ = toZ - (oldViewDistance * up); // inclusive
+
+                for (int currX = minX; currX != maxX; currX += right) {
+                    for (int currZ = minZ; currZ != maxZ; currZ += up) {
+                        this.removePlayerFrom(player, currX, currZ);
+                    }
+                }
+            }
+
+            if (dz != 0) {
+                // handle down removal
+
+                maxX = fromX + (oldViewDistance * right) + right; // exclusive
+                minX = fromX - (oldViewDistance * right); // inclusive
+                maxZ = toZ - (oldViewDistance * up); // exclusive
+                minZ = fromZ - (oldViewDistance * up); // inclusive
+
+                for (int currX = minX; currX != maxX; currX += right) {
+                    for (int currZ = minZ; currZ != maxZ; currZ += up) {
+                        this.removePlayerFrom(player, currX, currZ);
+                    }
+                }
+            }
+        } else {
+            // different view distance
+            // for now :)
+            this.removePlayer(player, oldPosition, oldViewDistance);
+            this.addNewPlayer(player, newPosition, newViewDistance);
+        }
+    }
+
+    private void removePlayer(final ServerPlayer player, final SectionPos position, final int viewDistance) {
+        final int x = position.getX();
+        final int z = position.getZ();
+
+        for (int xoff = -viewDistance; xoff <= viewDistance; ++xoff) {
+            for (int zoff = -viewDistance; zoff <= viewDistance; ++zoff) {
+                this.removePlayerFrom(player, x + xoff, z + zoff);
+            }
+        }
+    }
+
+    private void addNewPlayer(final ServerPlayer player, final SectionPos position, final int viewDistance) {
+        final int x = position.getX();
+        final int z = position.getZ();
+
+        for (int xoff = -viewDistance; xoff <= viewDistance; ++xoff) {
+            for (int zoff = -viewDistance; zoff <= viewDistance; ++zoff) {
+                this.addPlayerTo(player, x + xoff, z + zoff);
+            }
+        }
+    }
+}
diff --git a/src/main/java/com/destroystokyo/paper/util/PooledHashSets.java b/src/main/java/com/destroystokyo/paper/util/PooledHashSets.java
new file mode 100644
index 0000000000000000000000000000000000000000..4f13d3ff8391793a99f067189f854078334499c6
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/util/PooledHashSets.java
@@ -0,0 +1,241 @@
+package com.destroystokyo.paper.util;
+
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet;
+import java.lang.ref.WeakReference;
+import java.util.Iterator;
+
+/** @author Spottedleaf */
+public class PooledHashSets<E> {
+
+    // we really want to avoid that equals() check as much as possible...
+    protected final Object2ObjectOpenHashMap<PooledObjectLinkedOpenHashSet<E>, PooledObjectLinkedOpenHashSet<E>> mapPool = new Object2ObjectOpenHashMap<>(64, 0.25f);
+
+    protected void decrementReferenceCount(final PooledObjectLinkedOpenHashSet<E> current) {
+        if (current.referenceCount == 0) {
+            throw new IllegalStateException("Cannot decrement reference count for " + current);
+        }
+        if (current.referenceCount == -1 || --current.referenceCount > 0) {
+            return;
+        }
+
+        this.mapPool.remove(current);
+        return;
+    }
+
+    public PooledObjectLinkedOpenHashSet<E> findMapWith(final PooledObjectLinkedOpenHashSet<E> current, final E object) {
+        final PooledObjectLinkedOpenHashSet<E> cached = current.getAddCache(object);
+
+        if (cached != null) {
+            if (cached.referenceCount != -1) {
+                ++cached.referenceCount;
+            }
+
+            decrementReferenceCount(current);
+
+            return cached;
+        }
+
+        if (!current.add(object)) {
+            return current;
+        }
+
+        // we use get/put since we use a different key on put
+        PooledObjectLinkedOpenHashSet<E> ret = this.mapPool.get(current);
+
+        if (ret == null) {
+            ret = new PooledObjectLinkedOpenHashSet<>(current);
+            current.remove(object);
+            this.mapPool.put(ret, ret);
+            ret.referenceCount = 1;
+        } else {
+            if (ret.referenceCount != -1) {
+                ++ret.referenceCount;
+            }
+            current.remove(object);
+        }
+
+        current.updateAddCache(object, ret);
+
+        decrementReferenceCount(current);
+        return ret;
+    }
+
+    // rets null if current.size() == 1
+    public PooledObjectLinkedOpenHashSet<E> findMapWithout(final PooledObjectLinkedOpenHashSet<E> current, final E object) {
+        if (current.set.size() == 1) {
+            decrementReferenceCount(current);
+            return null;
+        }
+
+        final PooledObjectLinkedOpenHashSet<E> cached = current.getRemoveCache(object);
+
+        if (cached != null) {
+            if (cached.referenceCount != -1) {
+                ++cached.referenceCount;
+            }
+
+            decrementReferenceCount(current);
+
+            return cached;
+        }
+
+        if (!current.remove(object)) {
+            return current;
+        }
+
+        // we use get/put since we use a different key on put
+        PooledObjectLinkedOpenHashSet<E> ret = this.mapPool.get(current);
+
+        if (ret == null) {
+            ret = new PooledObjectLinkedOpenHashSet<>(current);
+            current.add(object);
+            this.mapPool.put(ret, ret);
+            ret.referenceCount = 1;
+        } else {
+            if (ret.referenceCount != -1) {
+                ++ret.referenceCount;
+            }
+            current.add(object);
+        }
+
+        current.updateRemoveCache(object, ret);
+
+        decrementReferenceCount(current);
+        return ret;
+    }
+
+    public static final class PooledObjectLinkedOpenHashSet<E> implements Iterable<E> {
+
+        private static final WeakReference NULL_REFERENCE = new WeakReference(null);
+
+        final ObjectLinkedOpenHashSet<E> set;
+        int referenceCount; // -1 if special
+        int hash; // optimize hashcode
+
+        // add cache
+        WeakReference<E> lastAddObject = NULL_REFERENCE;
+        WeakReference<PooledObjectLinkedOpenHashSet<E>> lastAddMap = NULL_REFERENCE;
+
+        // remove cache
+        WeakReference<E> lastRemoveObject = NULL_REFERENCE;
+        WeakReference<PooledObjectLinkedOpenHashSet<E>> lastRemoveMap = NULL_REFERENCE;
+
+        public PooledObjectLinkedOpenHashSet() {
+            this.set = new ObjectLinkedOpenHashSet<>(2, 0.6f);
+        }
+
+        public PooledObjectLinkedOpenHashSet(final E single) {
+            this();
+            this.referenceCount = -1;
+            this.add(single);
+        }
+
+        public PooledObjectLinkedOpenHashSet(final PooledObjectLinkedOpenHashSet<E> other) {
+            this.set = other.set.clone();
+            this.hash = other.hash;
+        }
+
+        // from https://github.com/Spottedleaf/ConcurrentUtil/blob/master/src/main/java/ca/spottedleaf/concurrentutil/util/IntegerUtil.java
+        // generated by https://github.com/skeeto/hash-prospector
+        static int hash0(int x) {
+            x *= 0x36935555;
+            x ^= x >>> 16;
+            return x;
+        }
+
+        public PooledObjectLinkedOpenHashSet<E> getAddCache(final E element) {
+            final E currentAdd = this.lastAddObject.get();
+
+            if (currentAdd == null || !(currentAdd == element || currentAdd.equals(element))) {
+                return null;
+            }
+
+            final PooledObjectLinkedOpenHashSet<E> map = this.lastAddMap.get();
+            if (map == null || map.referenceCount == 0) {
+                // we need to ret null if ref count is zero as calling code will assume the map is in use
+                return null;
+            }
+
+            return map;
+        }
+
+        public PooledObjectLinkedOpenHashSet<E> getRemoveCache(final E element) {
+            final E currentRemove = this.lastRemoveObject.get();
+
+            if (currentRemove == null || !(currentRemove == element || currentRemove.equals(element))) {
+                return null;
+            }
+
+            final PooledObjectLinkedOpenHashSet<E> map = this.lastRemoveMap.get();
+            if (map == null || map.referenceCount == 0) {
+                // we need to ret null if ref count is zero as calling code will assume the map is in use
+                return null;
+            }
+
+            return map;
+        }
+
+        public void updateAddCache(final E element, final PooledObjectLinkedOpenHashSet<E> map) {
+            this.lastAddObject = new WeakReference<>(element);
+            this.lastAddMap = new WeakReference<>(map);
+        }
+
+        public void updateRemoveCache(final E element, final PooledObjectLinkedOpenHashSet<E> map) {
+            this.lastRemoveObject = new WeakReference<>(element);
+            this.lastRemoveMap = new WeakReference<>(map);
+        }
+
+        boolean add(final E element) {
+            boolean added =  this.set.add(element);
+
+            if (added) {
+                this.hash += hash0(element.hashCode());
+            }
+
+            return added;
+        }
+
+        boolean remove(Object element) {
+            boolean removed = this.set.remove(element);
+
+            if (removed) {
+                this.hash -= hash0(element.hashCode());
+            }
+
+            return removed;
+        }
+
+        @Override
+        public Iterator<E> iterator() {
+            return this.set.iterator();
+        }
+
+        @Override
+        public int hashCode() {
+            return this.hash;
+        }
+
+        @Override
+        public boolean equals(final Object other) {
+            if (!(other instanceof PooledObjectLinkedOpenHashSet)) {
+                return false;
+            }
+            if (this.referenceCount == 0) {
+                return other == this;
+            } else {
+                if (other == this) {
+                    // Unfortunately we are never equal to our own instance while in use!
+                    return false;
+                }
+                return this.hash == ((PooledObjectLinkedOpenHashSet)other).hash && this.set.equals(((PooledObjectLinkedOpenHashSet)other).set);
+            }
+        }
+
+        @Override
+        public String toString() {
+            return "PooledHashSet: size: " + this.set.size() + ", reference count: " + this.referenceCount + ", hash: " +
+                this.hashCode() + ", identity: " + System.identityHashCode(this) + " map: " + this.set.toString();
+        }
+    }
+}
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index c00f7c60ce7b497d697d1abdf230f91f327e2113..190ddd4d9ef3472c33d46c2ead72fa0dc918054a 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -71,6 +71,7 @@ import net.minecraft.util.thread.ProcessorMailbox;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.EntityType;
 import net.minecraft.world.entity.Mob;
+import net.minecraft.world.entity.MobCategory;
 import net.minecraft.world.entity.ai.village.poi.PoiManager;
 import net.minecraft.world.entity.boss.EnderDragonPart;
 import net.minecraft.world.level.ChunkPos;
@@ -127,7 +128,8 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     public final Int2ObjectMap<ChunkMap.TrackedEntity> entityMap;
     private final Long2ByteMap chunkTypeCache;
     private final Queue<Runnable> unloadQueue; private final Queue<Runnable> getUnloadQueueTasks() { return this.unloadQueue; } // Paper - OBFHELPER
-    private int viewDistance;
+    int viewDistance; // Paper - private -> package private
+    public final com.destroystokyo.paper.util.PlayerMobDistanceMap playerMobDistanceMap; // Paper
 
     // CraftBukkit start - recursion-safe executor for Chunk loadCallback() and unloadCallback()
     public final CallbackExecutor callbackExecutor = new CallbackExecutor();
@@ -206,6 +208,24 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         this.overworldDataStorage = supplier;
         this.poiManager = new PoiManager(new File(this.storageFolder, "poi"), dataFixer, flag, this.level); // Paper
         this.setViewDistance(i);
+        this.playerMobDistanceMap = this.level.paperConfig.perPlayerMobSpawns ? new com.destroystokyo.paper.util.PlayerMobDistanceMap() : null; // Paper
+    }
+
+    public void updatePlayerMobTypeMap(Entity entity) {
+        if (!this.level.paperConfig.perPlayerMobSpawns) {
+            return;
+        }
+        int chunkX = (int)Math.floor(entity.getX()) >> 4;
+        int chunkZ = (int)Math.floor(entity.getZ()) >> 4;
+        int index = entity.getType().getEnumCreatureType().ordinal();
+
+        for (ServerPlayer player : this.playerMobDistanceMap.getPlayersInRange(chunkX, chunkZ)) {
+            ++player.mobCounts[index];
+        }
+    }
+
+    public int getMobCountNear(ServerPlayer entityPlayer, MobCategory enumCreatureType) {
+        return entityPlayer.mobCounts[enumCreatureType.ordinal()];
     }
 
     private static double euclideanDistanceSquared(ChunkPos pos, Entity entity) {
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index 5e0d55c3821b1769d20514a8a6c5c74477019778..eac5e799c4d26e53286a27c54b56899ba0b9ffb2 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -768,7 +768,22 @@ public class ServerChunkCache extends ChunkSource {
             this.level.getProfiler().push("naturalSpawnCount");
             this.level.timings.countNaturalMobs.startTiming(); // Paper - timings
             int l = this.distanceManager.getNaturalSpawnChunkCount();
-            NaturalSpawner.SpawnState spawnercreature_d = NaturalSpawner.createState(l, this.level.getAllEntities(), this::getFullChunk);
+            // Paper start - per player mob spawning
+            NaturalSpawner.SpawnState spawnercreature_d; // moved down
+            if (this.chunkMap.playerMobDistanceMap != null) {
+                // update distance map
+                this.level.timings.playerMobDistanceMapUpdate.startTiming();
+                this.chunkMap.playerMobDistanceMap.update(this.level.players, this.chunkMap.viewDistance);
+                this.level.timings.playerMobDistanceMapUpdate.stopTiming();
+                // re-set mob counts
+                for (ServerPlayer player : this.level.players) {
+                    Arrays.fill(player.mobCounts, 0);
+                }
+                spawnercreature_d = NaturalSpawner.countMobs(l, this.level.getAllEntities(), this::getFullChunk, true);
+            } else {
+                spawnercreature_d = NaturalSpawner.countMobs(l, this.level.getAllEntities(), this::getFullChunk, false);
+            }
+            // Paper end
             this.level.timings.countNaturalMobs.stopTiming(); // Paper - timings
 
             this.lastSpawnState = spawnercreature_d;
diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
index d6cfe68be1a944ff5d5780666467f5fd8e2794e3..b0eed4e18fc183856613c05f378576eb19985c46 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -93,6 +93,7 @@ import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.HumanoidArm;
 import net.minecraft.world.entity.LivingEntity;
 import net.minecraft.world.entity.Mob;
+import net.minecraft.world.entity.MobCategory;
 import net.minecraft.world.entity.NeutralMob;
 import net.minecraft.world.entity.animal.horse.AbstractHorse;
 import net.minecraft.world.entity.item.ItemEntity;
@@ -216,6 +217,11 @@ public class ServerPlayer extends Player implements ContainerListener {
     public boolean queueHealthUpdatePacket = false;
     public net.minecraft.network.protocol.game.ClientboundSetHealthPacket queuedHealthUpdatePacket;
     // Paper end
+    // Paper start - mob spawning rework
+    public static final int ENUMCREATURETYPE_TOTAL_ENUMS = MobCategory.values().length;
+    public final int[] mobCounts = new int[ENUMCREATURETYPE_TOTAL_ENUMS]; // Paper
+    public final com.destroystokyo.paper.util.PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> cachedSingleMobDistanceMap;
+    // Paper end
 
     // CraftBukkit start
     public String displayName;
@@ -254,6 +260,7 @@ public class ServerPlayer extends Player implements ContainerListener {
         this.adventure$displayName = net.kyori.adventure.text.Component.text(this.getScoreboardName()); // Paper
         this.canPickUpLoot = true;
         this.maxHealthCache = this.getMaxHealth();
+        this.cachedSingleMobDistanceMap = new com.destroystokyo.paper.util.PooledHashSets.PooledObjectLinkedOpenHashSet<>(this); // Paper
     }
 
     // Yes, this doesn't match Vanilla, but it's the best we can do for now.
@@ -2058,6 +2065,7 @@ public class ServerPlayer extends Player implements ContainerListener {
 
     }
 
+    public final SectionPos getPlayerMapSection() { return this.getLastSectionPos(); } // Paper - OBFHELPER
     public SectionPos getLastSectionPos() {
         return this.lastSectionPos;
     }
diff --git a/src/main/java/net/minecraft/world/entity/EntityType.java b/src/main/java/net/minecraft/world/entity/EntityType.java
index e39d950783599b01271bdb7e67fe68b46af0c49c..ae50030df7512c56c552e800b74ef4c69ec6d6d2 100644
--- a/src/main/java/net/minecraft/world/entity/EntityType.java
+++ b/src/main/java/net/minecraft/world/entity/EntityType.java
@@ -426,6 +426,7 @@ public class EntityType<T extends Entity> {
         return this.canSpawnFarFromPlayer;
     }
 
+    public final MobCategory getEnumCreatureType() { return this.getCategory(); } // Paper - OBFHELPER
     public MobCategory getCategory() {
         return this.category;
     }
diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index 0fb69f9194078e5e05e36ed909eb48424b6465b4..df271598f6036c8cab8a8811151a376dda46e44d 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -17,6 +17,7 @@ import net.minecraft.core.Registry;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.server.MCUtil;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.tags.BlockTags;
 import net.minecraft.tags.FluidTags;
 import net.minecraft.tags.Tag;
@@ -60,9 +61,14 @@ public final class NaturalSpawner {
     });
 
     public static NaturalSpawner.SpawnState createState(int spawningChunkCount, Iterable<Entity> entities, NaturalSpawner.ChunkGetter chunkSource) {
+        // Paper start - add countMobs parameter
+        return countMobs(spawningChunkCount, entities, chunkSource, false);
+    }
+    public static NaturalSpawner.SpawnState countMobs(int i, Iterable<Entity> iterable, NaturalSpawner.ChunkGetter spawnercreature_b, boolean countMobs) {
+        // Paper end - add countMobs parameter
         PotentialCalculator spawnercreatureprobabilities = new PotentialCalculator();
         Object2IntOpenHashMap<MobCategory> object2intopenhashmap = new Object2IntOpenHashMap();
-        Iterator iterator = entities.iterator();
+        Iterator iterator = iterable.iterator();
 
         while (iterator.hasNext()) {
             Entity entity = (Entity) iterator.next();
@@ -89,7 +95,7 @@ public final class NaturalSpawner {
                 BlockPos blockposition = entity.blockPosition();
                 long j = ChunkPos.asLong(blockposition.getX() >> 4, blockposition.getZ() >> 4);
 
-                chunkSource.query(j, (chunk) -> {
+                spawnercreature_b.query(j, (chunk) -> {
                     MobSpawnSettings.MobSpawnCost biomesettingsmobs_b = getRoughBiome(blockposition, chunk).getMobSettings().getMobSpawnCost(entity.getType());
 
                     if (biomesettingsmobs_b != null) {
@@ -97,11 +103,16 @@ public final class NaturalSpawner {
                     }
 
                     object2intopenhashmap.addTo(enumcreaturetype, 1);
+                    // Paper start
+                    if (countMobs) {
+                        ((ServerLevel)chunk.world).getChunkSource().chunkMap.updatePlayerMobTypeMap(entity);
+                    }
+                    // Paper end
                 });
             }
         }
 
-        return new NaturalSpawner.SpawnState(spawningChunkCount, object2intopenhashmap, spawnercreatureprobabilities);
+        return new NaturalSpawner.SpawnState(i, object2intopenhashmap, spawnercreatureprobabilities);
     }
 
     private static Biome getRoughBiome(BlockPos pos, ChunkAccess chunk) {
@@ -155,13 +166,31 @@ public final class NaturalSpawner {
                 continue;
             }
 
-            if ((spawnAnimals || !enumcreaturetype.isFriendly()) && (spawnMonsters || enumcreaturetype.isFriendly()) && (shouldSpawnAnimals || !enumcreaturetype.isPersistent()) && info.a(enumcreaturetype, limit)) {
+            // Paper start - only allow spawns upto the limit per chunk and update count afterwards
+            int currEntityCount = info.getEntityCountsByType().getInt(enumcreaturetype);
+            int k1 = limit * info.getSpawnerChunks() / NaturalSpawner.MAGIC_NUMBER;
+            int difference = k1 - currEntityCount;
+
+            if (world.paperConfig.perPlayerMobSpawns) {
+                int minDiff = Integer.MAX_VALUE;
+                for (ServerPlayer entityplayer : world.getChunkSource().chunkMap.playerMobDistanceMap.getPlayersInRange(chunk.getPos())) {
+                    minDiff = Math.min(limit - world.getChunkSource().chunkMap.getMobCountNear(entityplayer, enumcreaturetype), minDiff);
+                }
+                difference = (minDiff == Integer.MAX_VALUE) ? 0 : minDiff;
+            }
+            // Paper end
+
+            // Paper start - per player mob spawning
+            if ((spawnAnimals || !enumcreaturetype.isFriendly()) && (spawnMonsters || enumcreaturetype.isFriendly()) && (shouldSpawnAnimals || !enumcreaturetype.isPersistent()) && difference > 0) {
                 // CraftBukkit end
-                spawnCategoryForChunk(enumcreaturetype, world, chunk, (entitytypes, blockposition, ichunkaccess) -> {
+                int spawnCount = spawnMobs(enumcreaturetype, world, chunk, (entitytypes, blockposition, ichunkaccess) -> {
                     return info.canSpawn(entitytypes, blockposition, ichunkaccess);
                 }, (entityinsentient, ichunkaccess) -> {
                     info.afterSpawn(entityinsentient, ichunkaccess);
-                });
+                },
+                difference, world.paperConfig.perPlayerMobSpawns ? world.getChunkSource().chunkMap::updatePlayerMobTypeMap : null);
+                info.getEntityCountsByType().mergeInt(enumcreaturetype, spawnCount, Integer::sum);
+                // Paper end - per player mob spawning
             }
         }
 
@@ -170,31 +199,43 @@ public final class NaturalSpawner {
     }
 
     public static void spawnCategoryForChunk(MobCategory group, ServerLevel world, LevelChunk chunk, NaturalSpawner.SpawnPredicate checker, NaturalSpawner.AfterSpawnCallback runner) {
-        BlockPos blockposition = getRandomPosWithin(world, chunk);
+        // Paper start - add parameters and int ret type
+        spawnMobs(group, world, chunk, checker, runner, Integer.MAX_VALUE, null);
+    }
+    public static int spawnMobs(MobCategory enumcreaturetype, ServerLevel worldserver, LevelChunk chunk, NaturalSpawner.SpawnPredicate spawnercreature_c, NaturalSpawner.AfterSpawnCallback spawnercreature_a, int maxSpawns, Consumer<Entity> trackEntity) {
+        // Paper end - add parameters and int ret type
+        BlockPos blockposition = getRandomPosWithin(worldserver, chunk);
 
         if (blockposition.getY() >= 1) {
-            spawnCategoryForPosition(group, world, (ChunkAccess) chunk, blockposition, checker, runner);
+            return spawnMobsInternal(enumcreaturetype, worldserver, (ChunkAccess) chunk, blockposition, spawnercreature_c, spawnercreature_a, maxSpawns, trackEntity);
         }
+        return 0; // Paper
     }
 
     public static void spawnCategoryForPosition(MobCategory group, ServerLevel world, ChunkAccess chunk, BlockPos pos, NaturalSpawner.SpawnPredicate checker, NaturalSpawner.AfterSpawnCallback runner) {
-        StructureFeatureManager structuremanager = world.structureFeatureManager();
-        ChunkGenerator chunkgenerator = world.getChunkSource().getGenerator();
-        int i = pos.getY();
-        BlockState iblockdata = world.getTypeIfLoadedAndInBounds(pos); // Paper - don't load chunks for mob spawn
-
-        if (iblockdata != null && !iblockdata.isRedstoneConductor(chunk, pos)) { // Paper - don't load chunks for mob spawn
+        // Paper start - add maxSpawns parameter and return spawned mobs
+        spawnMobsInternal(group, world, chunk, pos, checker, runner, Integer.MAX_VALUE, null);
+    }
+    public static int spawnMobsInternal(MobCategory enumcreaturetype, ServerLevel worldserver, ChunkAccess ichunkaccess, BlockPos blockposition, NaturalSpawner.SpawnPredicate spawnercreature_c, NaturalSpawner.AfterSpawnCallback spawnercreature_a, int maxSpawns, Consumer<Entity> trackEntity) {
+        // Paper end - add maxSpawns parameter and return spawned mobs
+        StructureFeatureManager structuremanager = worldserver.structureFeatureManager();
+        ChunkGenerator chunkgenerator = worldserver.getChunkSource().getGenerator();
+        int i = blockposition.getY();
+        BlockState iblockdata = worldserver.getTypeIfLoadedAndInBounds(blockposition); // Paper - don't load chunks for mob spawn
+        int j = 0; // Paper - moved up
+
+        if (iblockdata != null && !iblockdata.isRedstoneConductor(ichunkaccess, blockposition)) { // Paper - don't load chunks for mob spawn
             BlockPos.MutableBlockPos blockposition_mutableblockposition = new BlockPos.MutableBlockPos();
-            int j = 0;
+            // Paper - moved up
             int k = 0;
 
             while (k < 3) {
-                int l = pos.getX();
-                int i1 = pos.getZ();
+                int l = blockposition.getX();
+                int i1 = blockposition.getZ();
                 boolean flag = true;
                 MobSpawnSettings.SpawnerData biomesettingsmobs_c = null;
                 SpawnGroupData groupdataentity = null;
-                int j1 = Mth.ceil(world.random.nextFloat() * 4.0F);
+                int j1 = Mth.ceil(worldserver.random.nextFloat() * 4.0F);
                 int k1 = 0;
                 int l1 = 0;
 
@@ -202,53 +243,58 @@ public final class NaturalSpawner {
                     if (l1 < j1) {
                         label53:
                         {
-                            l += world.random.nextInt(6) - world.random.nextInt(6);
-                            i1 += world.random.nextInt(6) - world.random.nextInt(6);
+                            l += worldserver.random.nextInt(6) - worldserver.random.nextInt(6);
+                            i1 += worldserver.random.nextInt(6) - worldserver.random.nextInt(6);
                             blockposition_mutableblockposition.set(l, i, i1);
                             double d0 = (double) l + 0.5D;
                             double d1 = (double) i1 + 0.5D;
-                            Player entityhuman = world.getNearestPlayer(d0, (double) i, d1, -1.0D, false);
+                            Player entityhuman = worldserver.getNearestPlayer(d0, (double) i, d1, -1.0D, false);
 
                             if (entityhuman != null) {
                                 double d2 = entityhuman.distanceToSqr(d0, (double) i, d1);
 
-                                if (isRightDistanceToPlayerAndSpawnPoint(world, chunk, blockposition_mutableblockposition, d2) && world.isLoadedAndInBounds(blockposition_mutableblockposition)) { // Paper - don't load chunks for mob spawn
+                                if (isRightDistanceToPlayerAndSpawnPoint(worldserver, ichunkaccess, blockposition_mutableblockposition, d2) && worldserver.isLoadedAndInBounds(blockposition_mutableblockposition)) { // Paper - don't load chunks for mob spawn
                                     if (biomesettingsmobs_c == null) {
-                                        biomesettingsmobs_c = getRandomSpawnMobAt(world, structuremanager, chunkgenerator, group, world.random, (BlockPos) blockposition_mutableblockposition);
+                                        biomesettingsmobs_c = getRandomSpawnMobAt(worldserver, structuremanager, chunkgenerator, enumcreaturetype, worldserver.random, (BlockPos) blockposition_mutableblockposition);
                                         if (biomesettingsmobs_c == null) {
                                             break label53;
                                         }
 
-                                        j1 = biomesettingsmobs_c.minCount + world.random.nextInt(1 + biomesettingsmobs_c.maxCount - biomesettingsmobs_c.minCount);
+                                        j1 = biomesettingsmobs_c.minCount + worldserver.random.nextInt(1 + biomesettingsmobs_c.maxCount - biomesettingsmobs_c.minCount);
                                     }
 
                                     // Paper start
-                                    Boolean doSpawning = a(world, group, structuremanager, chunkgenerator, biomesettingsmobs_c, blockposition_mutableblockposition, d2);
+                                    Boolean doSpawning = a(worldserver, enumcreaturetype, structuremanager, chunkgenerator, biomesettingsmobs_c, blockposition_mutableblockposition, d2);
                                     if (doSpawning == null) {
-                                        return;
+                                        return j; // Paper
                                     }
-                                    if (doSpawning && checker.test(biomesettingsmobs_c.type, blockposition_mutableblockposition, chunk)) {
+                                    if (doSpawning && spawnercreature_c.test(biomesettingsmobs_c.type, blockposition_mutableblockposition, ichunkaccess)) {
                                         // Paper end
-                                        Mob entityinsentient = getMobForSpawn(world, biomesettingsmobs_c.type);
+                                        Mob entityinsentient = getMobForSpawn(worldserver, biomesettingsmobs_c.type);
 
 
                                         if (entityinsentient == null) {
-                                            return;
+                                            return j; // Paper
                                         }
 
-                                        entityinsentient.moveTo(d0, (double) i, d1, world.random.nextFloat() * 360.0F, 0.0F);
-                                        if (isValidPositionForMob(world, entityinsentient, d2)) {
-                                            groupdataentity = entityinsentient.finalizeSpawn(world, world.getCurrentDifficultyAt(entityinsentient.blockPosition()), MobSpawnType.NATURAL, groupdataentity, (CompoundTag) null);
+                                        entityinsentient.moveTo(d0, (double) i, d1, worldserver.random.nextFloat() * 360.0F, 0.0F);
+                                        if (isValidPositionForMob(worldserver, entityinsentient, d2)) {
+                                            groupdataentity = entityinsentient.finalizeSpawn(worldserver, worldserver.getCurrentDifficultyAt(entityinsentient.blockPosition()), MobSpawnType.NATURAL, groupdataentity, (CompoundTag) null);
                                             // CraftBukkit start
-                                            world.addAllEntities(entityinsentient, SpawnReason.NATURAL);
+                                            worldserver.addAllEntities(entityinsentient, SpawnReason.NATURAL);
                                             if (!entityinsentient.removed) {
-                                                ++j;
+                                                ++j; // Paper - force diff on name change - we expect this to be the total amount spawned
                                                 ++k1;
-                                                runner.run(entityinsentient, chunk);
+                                                spawnercreature_a.run(entityinsentient, ichunkaccess);
+                                                // Paper start
+                                                if (trackEntity != null) {
+                                                    trackEntity.accept(entityinsentient);
+                                                }
+                                                // Paper end
                                             }
                                             // CraftBukkit end
-                                            if (j >= entityinsentient.getMaxSpawnClusterSize()) {
-                                                return;
+                                            if (j >= entityinsentient.getMaxSpawnClusterSize() || j >= maxSpawns) { // Paper
+                                                return j; // Paper
                                             }
 
                                             if (entityinsentient.isMaxGroupSizeReached(k1)) {
@@ -270,6 +316,7 @@ public final class NaturalSpawner {
             }
 
         }
+        return j; // Paper
     }
 
     private static boolean isRightDistanceToPlayerAndSpawnPoint(ServerLevel world, ChunkAccess chunk, BlockPos.MutableBlockPos pos, double squaredDistance) {
@@ -510,8 +557,8 @@ public final class NaturalSpawner {
 
     public static class SpawnState {
 
-        private final int spawnableChunkCount;
-        private final Object2IntOpenHashMap<MobCategory> mobCategoryCounts;
+        private final int spawnableChunkCount; final int getSpawnerChunks() { return this.spawnableChunkCount; } // Paper - OBFHELPER
+        private final Object2IntOpenHashMap<MobCategory> mobCategoryCounts; final Object2IntMap<MobCategory> getEntityCountsByType() { return this.mobCategoryCounts; } // Paper - OBFHELPER
         private final PotentialCalculator spawnPotential;
         private final Object2IntMap<MobCategory> unmodifiableMobCategoryCounts;
         @Nullable
@@ -572,7 +619,7 @@ public final class NaturalSpawner {
 
         // CraftBukkit start
         private boolean a(MobCategory enumcreaturetype, int limit) {
-            int i = limit * this.spawnableChunkCount / NaturalSpawner.MAGIC_NUMBER;
+            int i = limit * this.spawnableChunkCount / NaturalSpawner.MAGIC_NUMBER; // Paper - diff on change, needed in the spawn method
             // CraftBukkit end
 
             return this.mobCategoryCounts.getInt(enumcreaturetype) < i;