SakuraMC/patches/server/0019-Merge-Cannon-Entities.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Samsuik <40902469+Samsuik@users.noreply.github.com>
Date: Sat, 9 Sep 2023 18:39:15 +0100
Subject: [PATCH] Merge Cannon Entities


diff --git a/src/main/java/me/samsuik/sakura/entity/merge/MergeHistory.java b/src/main/java/me/samsuik/sakura/entity/merge/MergeHistory.java
new file mode 100644
index 0000000000000000000000000000000000000000..90f36b2d3847e058cfa2b748838fc6ea3294c159
--- /dev/null
+++ b/src/main/java/me/samsuik/sakura/entity/merge/MergeHistory.java
@@ -0,0 +1,127 @@
+package me.samsuik.sakura.entity.merge;
+
+import it.unimi.dsi.fastutil.HashCommon;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.longs.LongOpenHashSet;
+import it.unimi.dsi.fastutil.longs.LongSet;
+import me.samsuik.sakura.utils.objects.Expiry;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.world.entity.Entity;
+
+import java.util.List;
+
+public class MergeHistory {
+
+    // packed position -> known merging information
+    private final Long2ObjectMap<MergeData> mergeDataMap = new Long2ObjectOpenHashMap<>();
+    private MergeData mergeData = null;
+
+    public MergeData retrievePositions(Entity entity) {
+        long origin = entity.getPackedOrigin();
+
+        if (mergeData != null && mergeData.knownPositions().contains(origin)) {
+            return mergeData;
+        }
+
+        return mergeData = mergeDataMap.get(origin);
+    }
+
+    public void markPositions(Entity entity) {
+        List<Entity> mergeList = entity.getMergeList();
+        long origin = entity.getPackedOrigin();
+
+        // I apologise for the lambda parameter name in advance
+        MergeData data = mergeDataMap.computeIfAbsent(origin, (OwO) -> new MergeData(
+            new LongOpenHashSet(), // Known entity positions
+            new LongOpenHashSet(), // Retained positions
+            new EntityTable(Math.min(mergeList.size() * 2, 512)),
+            new Expiry(MinecraftServer.currentTickLong, 200),
+            // Reasonable threshold to reduce abuse and breakage with on spawn merging.
+            new Threshold(MinecraftServer.currentTickLong, 12, 200)
+        ));
+
+        data.expiry().refresh(MinecraftServer.currentTickLong);
+
+        // Collect all merge positions
+        LongOpenHashSet positions = new LongOpenHashSet((mergeList.size() + 1) / 2);
+
+        positions.add(entity.getPackedOrigin());
+
+        for (Entity mergedEntity : mergeList) {
+            positions.add(mergedEntity.getPackedOrigin());
+        }
+
+        // Retain existing positions and insert new positions
+        if (!data.knownPositions().isEmpty()) {
+            data.retainedPositions().addAll(positions);
+        } else {
+            data.retainedPositions().retainAll(positions);
+        }
+
+        data.knownPositions().addAll(positions);
+    }
+
+    public void expire(long tick) {
+        mergeData = null; // clear this every tick
+
+        // only expire every 20 ticks
+        if (tick % 20 != 0) return;
+
+        mergeDataMap.values().removeIf(data -> data.expiry().isExpired(tick));
+    }
+
+    public record MergeData(LongSet knownPositions, LongSet retainedPositions, EntityTable table, Expiry expiry, Threshold threshold) {
+        public boolean hasPassed() {
+            return threshold.hasPassed(MinecraftServer.currentTickLong);
+        }
+
+        public Entity findFirstAtPosition(Entity entity) {
+            Entity found = table.locate(entity);
+
+            if (found != null && found.getId() < entity.getId() && knownPositions.contains(found.getPackedOrigin()) && !found.isRemoved() && entity.compareState(found)) {
+                return found;
+            }
+
+            return null;
+        }
+    }
+
+    private static class EntityTable {
+        private final Entity[] entities;
+        private final int mask;
+
+        EntityTable(int size) {
+            int n = HashCommon.nextPowerOfTwo(size - 1);
+            entities = new Entity[n];
+            mask = n - 1;
+        }
+
+        Entity locate(Entity entity) {
+            int pos = entity.blockPosition().hashCode();
+            int key = pos & mask;
+            Entity found = entities[key];
+            entities[key] = entity;
+            return found;
+        }
+    }
+
+    private static class Threshold {
+        private final long startingTick;
+        private final int thresholdAttempts;
+        private final long thresholdAge;
+        private int attempts;
+
+        Threshold(long tick, int attempts, long age) {
+            startingTick = tick;
+            thresholdAttempts = attempts;
+            thresholdAge = age;
+        }
+
+        boolean hasPassed(long tick) {
+            return ++attempts >= thresholdAttempts
+                || tick - startingTick >= thresholdAge;
+        }
+    }
+
+}
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 06af35cba1a7b9c11cade2bcd0cc72c4bc28e56f..f68da3e0168c9462aa05cce11e523b9cefefd7e7 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -1738,6 +1738,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             worldserver.explosionDensityCache.clear(); // Paper - Optimize explosions
             worldserver.localConfig().expire(currentTickLong); // Sakura
             worldserver.minimalTNT.clear(); // Sakura - visibility api
+            worldserver.mergeHistory.expire(currentTickLong); // Sakura - merge cannoning entities
         }
         this.isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked
 
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 7a89e4f70195c62c51bbf1993a0988a9c5706449..2b49e60aba45f997143d6a575c5f39d6d5a26ef2 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -893,6 +893,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
             org.spigotmc.ActivationRange.activateEntities(this); // Spigot
             this.timings.entityTick.startTiming(); // Spigot
+            Entity[] previousEntity = new Entity[1]; // Sakura
             this.entityTickList.forEach((entity) -> {
                 if (!entity.isRemoved()) {
                     if (false && this.shouldDiscardEntity(entity)) { // CraftBukkit - We prevent spawning in general, so this butchering is not needed
@@ -912,6 +913,15 @@ public class ServerLevel extends Level implements WorldGenLevel {
                                 entity.stopRiding();
                             }
 
+                            // Sakura start
+                            Entity previous = previousEntity[0];
+                            if (entity.isMergeableType(previous) && entity.tryMergeInto(previous)) {
+                                return;
+                            } else {
+                                previousEntity[0] = entity;
+                            }
+                            // Sakura end
+
                             gameprofilerfiller.push("tick");
                             this.guardEntityTick(this::tickNonPassenger, entity);
                             gameprofilerfiller.pop();
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 88735691892aa19f30d4e686e88a3c09f565bb56..2320cbd0714294c078ec6e16c687713d28b0c174 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -611,6 +611,108 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         return BlockPos.asLong(v.getBlockX(), v.getBlockY(), v.getBlockZ());
     }
     // Sakura end - store entity data/state
+    // Sakura start - cannon entity merging
+    // List of merged entities, should be naturally sorted (oldest -> youngest)
+    private final List<Entity> mergeList = new java.util.ArrayList<>(1);
+    private @Nullable me.samsuik.sakura.entity.merge.MergeHistory.MergeData originData = null;
+    private me.samsuik.sakura.entity.merge.MergeLevel mergeLevel;
+    protected int stacked = 1; // default
+
+    public final me.samsuik.sakura.entity.merge.MergeLevel getMergeLevel() {
+        return mergeLevel;
+    }
+
+    public final void setMergeLevel(me.samsuik.sakura.entity.merge.MergeLevel level) {
+        mergeLevel = level;
+    }
+
+    public final int getStacked() {
+        return stacked;
+    }
+
+    public final void setStacked(int stack) {
+        stacked = stack;
+    }
+
+    public final List<Entity> getMergeList() {
+        return mergeList;
+    }
+
+    private boolean isSafeToSpawnMerge(Entity entity) {
+        return tickCount == 1 && originData != null
+            && originData.hasPassed() // on spawn safety delay has passed
+            && originData == entity.originData // make sure it's the same group
+            && originData.retainedPositions().contains(entity.getPackedOrigin());
+    }
+
+    public boolean isMergeableType(@Nullable Entity previous) {
+        return false;
+    }
+
+    public final boolean tryMergeInto(@Nullable Entity entity) {
+        if (mergeLevel.atLeast(me.samsuik.sakura.entity.merge.MergeLevel.NON_STRICT) && tickCount == 0) {
+            originData = level.mergeHistory.retrievePositions(this);
+        }
+
+        Entity mergeEntity = null;
+
+        if (entity == null || entity.getType() != getType()) {
+            // first entity in the tick loop, we have to let it into this method so that we can retrieve the originData
+            return false;
+        } else if (mergeLevel.atLeast(me.samsuik.sakura.entity.merge.MergeLevel.SPAWN) && entity.isSafeToSpawnMerge(this)) {
+            // On spawn merging, this merges entities immediately upon spawning after
+            // it is considered "safe". We try to make sure it is safe by only retaining
+            // positions that do not change when we're collecting information.
+            mergeEntity = entity;
+        } else {
+            // Strict, simple merging
+            // This merges entities that are in the exact same state and sequential.
+            // Sane for most use cases but as it is merging entities plugins may misbehave.
+            if (mergeLevel.atLeast(me.samsuik.sakura.entity.merge.MergeLevel.STRICT) && compareState(entity)) {
+                mergeEntity = entity;
+            }
+
+            // Non strict merging algorithm uses information collected after entities die
+            // to be able to perform more aggressive merging by already knowing the OOE.
+            if (mergeLevel.atLeast(me.samsuik.sakura.entity.merge.MergeLevel.NON_STRICT) && mergeEntity == null && originData != null) {
+                mergeEntity = originData.findFirstAtPosition(this);
+            }
+        }
+
+        if (mergeEntity != null && isSafeToMergeInto(mergeEntity)) {
+            mergeInto(mergeEntity);
+            return true;
+        }
+
+        return false;
+    }
+
+    protected boolean respawnMerged() {
+        return false;
+    }
+
+    protected boolean isSafeToMergeInto(Entity entity) {
+        return false;
+    }
+
+    private void mergeInto(Entity entity) {
+        entity.mergeList.add(this);
+        entity.mergeList.addAll(mergeList);
+        entity.stacked += stacked;
+
+        mergeList.clear(); // clear the list to stop our tracking when merging
+        stacked = 0; // prevent any possible duplication
+
+        discard();
+
+        // update api handle, this is so cannondebug can function
+        //noinspection ConstantValue
+        if (bukkitEntity != null) {
+            bukkitEntity.setHandle(entity);
+            bukkitEntity = entity.bukkitEntity;
+        }
+    }
+    // Sakura end - cannon entity merging
 
     public Entity(EntityType<?> type, Level world) {
         this.id = Entity.ENTITY_COUNTER.incrementAndGet();
@@ -659,6 +761,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         this.getEntityData().registrationLocked = true; // Spigot
         this.setPos(0.0D, 0.0D, 0.0D);
         this.eyeHeight = this.getEyeHeight(net.minecraft.world.entity.Pose.STANDING, this.dimensions);
+        this.mergeLevel = level.sakuraConfig().cannons.mergeLevel; // Sakura
     }
 
     public boolean isColliding(BlockPos pos, BlockState state) {
@@ -2526,6 +2629,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
                 nbttagcompound.putBoolean("Paper.FreezeLock", true);
             }
             // Paper end
+            // Sakura start
+            if (stacked > 0) {
+                nbttagcompound.putInt("Sakura.Stacked", stacked);
+            }
+            // Sakura end
             return nbttagcompound;
         } catch (Throwable throwable) {
             CrashReport crashreport = CrashReport.forThrowable(throwable, "Saving entity NBT");
@@ -2673,6 +2781,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
                 freezeLocked = nbt.getBoolean("Paper.FreezeLock");
             }
             // Paper end
+            // Sakura start
+            if (nbt.contains("Sakura.Stacked")) {
+                stacked = nbt.getInt("Sakura.Stacked");
+            }
+            // Sakura end
 
         } catch (Throwable throwable) {
             CrashReport crashreport = CrashReport.forThrowable(throwable, "Loading entity NBT");
@@ -4874,6 +4987,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
             return;
         }
         // Paper end - rewrite chunk system
+        // Sakura start
+        if (reason == RemovalReason.DISCARDED && !mergeList.isEmpty()) {
+            level.mergeHistory.markPositions(this);
+        }
+        // Sakura end
         final boolean alreadyRemoved = this.removalReason != null; // Paper - Folia schedulers
         if (this.removalReason == null) {
             this.removalReason = reason;
diff --git a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
index 85da566b151d6c9995b5c41333c4cd05235c1d70..ff6d82fe45dd9613faebed71f7936451100848df 100644
--- a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
@@ -132,6 +132,59 @@ public class FallingBlockEntity extends Entity {
         return !this.isRemoved();
     }
 
+    // Sakura start - cannon entity merging
+    @Override
+    public boolean isMergeableType(@Nullable Entity previous) {
+        return previous == null || !isRemoved() && !previous.isRemoved();
+    }
+
+    @Override
+    protected boolean isSafeToMergeInto(Entity entity) {
+        return entity instanceof FallingBlockEntity fbe
+            && fbe.blockState.equals(blockState)
+            && fbe.time - 1 == time; // todo: special case in case on spawn isn't used
+    }
+
+    @Override
+    protected boolean respawnMerged() {
+        if (stacked <= 1) return false;
+
+        while (stacked-- >= 1) {
+            // Unlike PrimedTnt we have to try respawn each stacked entity
+            FallingBlockEntity fallingBlock = new FallingBlockEntity(EntityType.FALLING_BLOCK, level());
+
+            // Try to stack the falling block
+            this.entityState().apply(fallingBlock);
+            fallingBlock.spawnReason = spawnReason;
+            fallingBlock.time = time - 1;
+            fallingBlock.tick();
+
+            // If you horizontal stack into a moving piston block this condition will be met.
+            if (!fallingBlock.isRemoved()) {
+                stacked++;
+                fallingBlock.storeEntityState();
+                fallingBlock.entityState().apply(this);
+                break;
+            } else if (stacked == 0) {
+                this.discard();
+            }
+        }
+
+        return true;
+    }
+
+    @Nullable
+    public ItemEntity spawnAtLocation(ItemLike item) {
+        ItemEntity itemEntity = null;
+
+        while (stacked-- >= 1) {
+            itemEntity = super.spawnAtLocation(item);
+        }
+
+        return itemEntity;
+    }
+    // Sakura end
+
     @Override
     public void tick() {
         // Paper start - fix sand duping
@@ -209,6 +262,7 @@ public class FallingBlockEntity extends Entity {
                                     return;
                                 }
                                 // CraftBukkit end
+                                if (this.respawnMerged()) return; // Sakura
                                 if (this.level().setBlock(blockposition, this.blockState, 3)) {
                                     ((ServerLevel) this.level()).getChunkSource().chunkMap.broadcast(this, new ClientboundBlockUpdatePacket(blockposition, this.level().getBlockState(blockposition)));
                                     this.discard();
diff --git a/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java b/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
index 46680f551f83b91581440d89a1c35c048db03638..72fb1690e6a0692b453b9c0997a6eb8544d1dbf5 100644
--- a/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
+++ b/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
@@ -71,6 +71,44 @@ public class PrimedTnt extends Entity implements TraceableEntity {
         return !this.isRemoved();
     }
 
+    // Sakura start - cannon entity merging
+    @Override
+    public boolean isMergeableType(@Nullable Entity previous) {
+        return previous == null || !isRemoved() && !previous.isRemoved();
+    }
+
+    @Override
+    protected boolean isSafeToMergeInto(Entity entity) {
+        return entity instanceof PrimedTnt tnt
+            && tnt.getFuse() + 1 == getFuse()
+            // required to prevent issues with powdered snow
+            && (tnt.entityState().fallDistance() == 0.0f && fallDistance == 0.0f
+              || tnt.entityState().fallDistance() > 2.5f && fallDistance > 2.5f);
+    }
+
+    @Override
+    protected boolean respawnMerged() {
+        if (stacked <= 1) return false;
+
+        PrimedTnt tnt = new PrimedTnt(EntityType.TNT, level());
+
+        while (stacked-- > 1) {
+            this.setFuse(100); // Prevent unwanted explosions while ticking
+
+            // Cause an explosion to affect this entity
+            tnt.setPos(this.position());
+            tnt.setDeltaMovement(this.getDeltaMovement());
+            this.entityState().apply(this);
+            tnt.explode();
+            this.storeEntityState();
+
+            this.tick();
+        }
+
+        return true;
+    }
+    // Sakura end
+
     @Override
     public void tick() {
         if (this.level().spigotConfig.maxTntTicksPerTick > 0 && ++this.level().spigotConfig.currentPrimedTnt > this.level().spigotConfig.maxTntTicksPerTick) { return; } // Spigot
@@ -96,6 +134,7 @@ public class PrimedTnt extends Entity implements TraceableEntity {
         if (i <= 0) {
             // CraftBukkit start - Need to reverse the order of the explosion and the entity death so we have a location for the event
             // this.discard();
+            this.respawnMerged(); // Sakura
             if (!this.level().isClientSide) {
                 this.explode();
             }
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 5927568271168548be5b2a2113764d8549ed2b17..1bc20269707a1c0a741666c0fb4b90ffc93560a7 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -231,6 +231,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         return slices.getSectionEntities(chunkY);
     }
     // Sakura end - add utility method for accessing ChunkEntitySlices
+    public final me.samsuik.sakura.entity.merge.MergeHistory mergeHistory = new me.samsuik.sakura.entity.merge.MergeHistory(); // Sakura - cannon entity merging
 
     protected Level(WritableLevelData worlddatamutable, ResourceKey<Level> resourcekey, RegistryAccess iregistrycustom, Holder<DimensionType> holder, Supplier<ProfilerFiller> supplier, boolean flag, boolean flag1, long i, int j, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider, org.bukkit.World.Environment env, java.util.function.Function<org.spigotmc.SpigotWorldConfig, io.papermc.paper.configuration.WorldConfiguration> paperWorldConfigCreator, Supplier<me.samsuik.sakura.configuration.WorldConfiguration> sakuraWorldConfigCreator, java.util.concurrent.Executor executor) { // Sakura // Paper - create paper world config; Async-Anti-Xray: Pass executor
         this.spigotConfig = new org.spigotmc.SpigotWorldConfig(((net.minecraft.world.level.storage.PrimaryLevelData) worlddatamutable).getLevelName()); // Spigot
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftFallingBlock.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftFallingBlock.java
index 1359d25a32b4a5d5e8e68ce737bd19f7b5afaf69..0afa2cfb04b5097788927076669e85fe24041df9 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftFallingBlock.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftFallingBlock.java
@@ -14,6 +14,28 @@ public class CraftFallingBlock extends CraftEntity implements FallingBlock {
         super(server, entity);
     }
 
+    // Sakura start
+    @Override
+    public @org.jetbrains.annotations.NotNull me.samsuik.sakura.entity.merge.MergeLevel getMergeLevel() {
+        return getHandle().getMergeLevel();
+    }
+
+    @Override
+    public void setMergeLevel(@org.jetbrains.annotations.NotNull me.samsuik.sakura.entity.merge.MergeLevel level) {
+        getHandle().setMergeLevel(level);
+    }
+
+    @Override
+    public int getStacked() {
+        return getHandle().getStacked();
+    }
+
+    @Override
+    public void setStacked(int stacked) {
+        getHandle().setStacked(stacked);
+    }
+    // Sakura end
+
     @Override
     public FallingBlockEntity getHandle() {
         return (FallingBlockEntity) this.entity;
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftTNTPrimed.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftTNTPrimed.java
index dac3d34677688ac560bc1be2087a08479ef71b87..3e80513263236d56019e3402c52f4a3677c83c76 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftTNTPrimed.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftTNTPrimed.java
@@ -12,6 +12,28 @@ public class CraftTNTPrimed extends CraftEntity implements TNTPrimed {
         super(server, entity);
     }
 
+    // Sakura start
+    @Override
+    public @org.jetbrains.annotations.NotNull me.samsuik.sakura.entity.merge.MergeLevel getMergeLevel() {
+        return getHandle().getMergeLevel();
+    }
+
+    @Override
+    public void setMergeLevel(@org.jetbrains.annotations.NotNull me.samsuik.sakura.entity.merge.MergeLevel level) {
+        getHandle().setMergeLevel(level);
+    }
+
+    @Override
+    public int getStacked() {
+        return getHandle().getStacked();
+    }
+
+    @Override
+    public void setStacked(int stacked) {
+        getHandle().setStacked(stacked);
+    }
+    // Sakura end
+
     @Override
     public float getYield() {
         return this.getHandle().yield;