From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sat, 23 Sep 2023 22:05:35 -0700
Subject: [PATCH] Lag compensation ticks

Areas affected by lag comepnsation:
 - Block breaking and destroying
 - Eating food items

diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 5caa39b529c6c0798d91e8e8468b40988f6fb987..09cf38a5d98fee1b73116d671c765ce17eb306d3 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -311,6 +311,9 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     public volatile Thread shutdownThread; // Paper
     public volatile boolean abnormalExit = false; // Paper
     public boolean isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked
+    // Paper start - lag compensation
+    public static final long SERVER_INIT = System.nanoTime();
+    // Paper end - lag compensation
 
     public static <S extends MinecraftServer> S spin(Function<Thread, S> serverFactory) {
         AtomicReference<S> atomicreference = new AtomicReference();
@@ -1685,6 +1688,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         Iterator iterator = this.getAllLevels().iterator(); // Paper - Throw exception on world create while being ticked; move down
         while (iterator.hasNext()) {
             ServerLevel worldserver = (ServerLevel) iterator.next();
+            worldserver.updateLagCompensationTick(); // Paper - lag compensation
             worldserver.hasPhysicsEvent =  org.bukkit.event.block.BlockPhysicsEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper
             net.minecraft.world.level.block.entity.HopperBlockEntity.skipHopperEvents = worldserver.paperConfig().hopper.disableMoveEvent || org.bukkit.event.inventory.InventoryMoveItemEvent.getHandlerList().getRegisteredListeners().length == 0; // Paper - Perf: Optimize Hoppers
             worldserver.hasEntityMoveEvent = io.papermc.paper.event.entity.EntityMoveEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - Add EntityMoveEvent
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 9d65f0558c7c4db75ed6337dc241c01746933315..3cef73da0ac4cbf8104fa5dff8321f605287a580 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -570,6 +570,17 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return player != null && player.level() == this ? player : null;
     }
     // Paper end - optimise getPlayerByUUID
+    // Paper start - lag compensation
+    private long lagCompensationTick = net.minecraft.server.MinecraftServer.SERVER_INIT;
+
+    public long getLagCompensationTick() {
+        return this.lagCompensationTick;
+    }
+
+    public void updateLagCompensationTick() {
+        this.lagCompensationTick = (System.nanoTime() - net.minecraft.server.MinecraftServer.SERVER_INIT) / (java.util.concurrent.TimeUnit.MILLISECONDS.toNanos(50L));
+    }
+    // Paper end - lag compensation
 
     // Add env and gen to constructor, IWorldDataServer -> WorldDataServer
     public ServerLevel(MinecraftServer minecraftserver, Executor executor, LevelStorageSource.LevelStorageAccess convertable_conversionsession, PrimaryLevelData iworlddataserver, ResourceKey<Level> resourcekey, LevelStem worlddimension, ChunkProgressListener worldloadlistener, boolean flag, long i, List<CustomSpawner> list, boolean flag1, @Nullable RandomSequences randomsequences, org.bukkit.World.Environment env, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider) {
diff --git a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
index 96dd68d55dbcb4f6bf3f3096802e48ca50ab766e..b8c0f11a29ebc738a935d78e7a1e19914d43b533 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
@@ -124,7 +124,7 @@ public class ServerPlayerGameMode {
     }
 
     public void tick() {
-        this.gameTicks = MinecraftServer.currentTick; // CraftBukkit;
+        this.gameTicks = (int)this.level.getLagCompensationTick(); // CraftBukkit; // Paper - lag compensation
         BlockState iblockdata;
 
         if (this.hasDelayedDestroy) {
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index a09ad0cdbc9f3eb2ac77836076292822991b3d08..3d8efaaeea5cf7582c23cbb48beecf8eaf98a03e 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -3819,6 +3819,10 @@ public abstract class LivingEntity extends Entity implements Attackable {
         this.getEntityData().resendPossiblyDesyncedDataValues(java.util.List.of(DATA_LIVING_ENTITY_FLAGS), serverPlayer);
     }
     // Paper end - Properly cancel usable items
+    // Paper start - lag compensate eating
+    protected long eatStartTime;
+    protected int totalEatTimeTicks;
+    // Paper end - lag compensate eating
     private void updatingUsingItem() {
         if (this.isUsingItem()) {
             if (ItemStack.isSameItem(this.getItemInHand(this.getUsedItemHand()), this.useItem)) {
@@ -3837,7 +3841,12 @@ public abstract class LivingEntity extends Entity implements Attackable {
             this.triggerItemUseEffects(stack, 5);
         }
 
-        if (--this.useItemRemaining == 0 && !this.level().isClientSide && !stack.useOnRelease()) {
+        // Paper start - lag compensate eating
+        // we add 1 to the expected time to avoid lag compensating when we should not
+        boolean shouldLagCompensate = this.useItem.getItem().isEdible() && this.eatStartTime != -1 && (System.nanoTime() - this.eatStartTime) > ((1 + this.totalEatTimeTicks) * 50 * (1000 * 1000));
+        if ((--this.useItemRemaining == 0 || shouldLagCompensate) && !this.level().isClientSide && !stack.useOnRelease()) {
+            this.useItemRemaining = 0;
+            // Paper end - lag compensate eating
             this.completeUsingItem();
         }
 
@@ -3885,7 +3894,10 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
         if (!itemstack.isEmpty() && !this.isUsingItem() || forceUpdate) { // Paper - Prevent consuming the wrong itemstack
             this.useItem = itemstack;
-            this.useItemRemaining = itemstack.getUseDuration();
+            // Paper start - lag compensate eating
+            this.useItemRemaining = this.totalEatTimeTicks = itemstack.getUseDuration();
+            this.eatStartTime = System.nanoTime();
+            // Paper end - lag compensate eating
             if (!this.level().isClientSide) {
                 this.setLivingEntityFlag(1, true);
                 this.setLivingEntityFlag(2, hand == InteractionHand.OFF_HAND);
@@ -3910,7 +3922,10 @@ public abstract class LivingEntity extends Entity implements Attackable {
                 }
             } else if (!this.isUsingItem() && !this.useItem.isEmpty()) {
                 this.useItem = ItemStack.EMPTY;
-                this.useItemRemaining = 0;
+                // Paper start - lag compensate eating
+                this.useItemRemaining = this.totalEatTimeTicks = 0;
+                this.eatStartTime = -1L;
+                // Paper end - lag compensate eating
             }
         }
 
@@ -4045,7 +4060,10 @@ public abstract class LivingEntity extends Entity implements Attackable {
         }
 
         this.useItem = ItemStack.EMPTY;
-        this.useItemRemaining = 0;
+        // Paper start - lag compensate eating
+        this.useItemRemaining = this.totalEatTimeTicks = 0;
+        this.eatStartTime = -1L;
+        // Paper end - lag compensate eating
     }
 
     public boolean isBlocking() {