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/net/minecraft/server/MinecraftServer.java b/net/minecraft/server/MinecraftServer.java
index 0c35921acebd88f3a9a37676e47e7482dfea6d9c..1ff57c17f7fe3af3fb7fc5fbc5148ca333b5e618 100644
--- a/net/minecraft/server/MinecraftServer.java
+++ b/net/minecraft/server/MinecraftServer.java
@@ -301,6 +301,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     public final io.papermc.paper.configuration.PaperConfigurations paperConfigurations; // Paper - add paper configuration files
     public boolean isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked
     private final Set<String> pluginsBlockingSleep = new java.util.HashSet<>(); // Paper - API to allow/disallow tick sleeping
+    public static final long SERVER_INIT = System.nanoTime(); // Paper - Lag compensation
 
     public static <S extends MinecraftServer> S spin(Function<Thread, S> threadFunction) {
         ca.spottedleaf.dataconverter.minecraft.datatypes.MCTypeRegistry.init(); // Paper - rewrite data converter system
@@ -1643,6 +1644,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         for (ServerLevel serverLevel : this.getAllLevels()) {
             serverLevel.hasPhysicsEvent = org.bukkit.event.block.BlockPhysicsEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - BlockPhysicsEvent
             serverLevel.hasEntityMoveEvent = io.papermc.paper.event.entity.EntityMoveEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - Add EntityMoveEvent
+            serverLevel.updateLagCompensationTick(); // Paper - lag compensation
             profilerFiller.push(() -> serverLevel + " " + serverLevel.dimension().location());
             /* Drop global time updates
             if (this.tickCount % 20 == 0) {
diff --git a/net/minecraft/server/level/ServerLevel.java b/net/minecraft/server/level/ServerLevel.java
index ffb5bfdd76a92bac61c7c352fdded4200d13b3ae..651a65aaa37f2cf26d54f75529cbda71e6fc2bc4 100644
--- a/net/minecraft/server/level/ServerLevel.java
+++ b/net/minecraft/server/level/ServerLevel.java
@@ -2678,4 +2678,16 @@ public class ServerLevel extends Level implements ServerEntityGetter, WorldGenLe
         return this.server.getPlayerList().getPlayer(uuid);
     }
     // Paper end - check global player list where appropriate
+
+    // Paper start - lag compensation
+    private long lagCompensationTick = MinecraftServer.SERVER_INIT;
+
+    public long getLagCompensationTick() {
+        return this.lagCompensationTick;
+    }
+
+    public void updateLagCompensationTick() {
+        this.lagCompensationTick = (System.nanoTime() - MinecraftServer.SERVER_INIT) / (java.util.concurrent.TimeUnit.MILLISECONDS.toNanos(50L));
+    }
+    // Paper end - lag compensation
 }
diff --git a/net/minecraft/server/level/ServerPlayerGameMode.java b/net/minecraft/server/level/ServerPlayerGameMode.java
index bf2a4c03afb73367a6d2530c78ff9f7c06f7f6a6..6207f45e7b84af4e6a2e4eb7b9fabf6b1e22a63a 100644
--- a/net/minecraft/server/level/ServerPlayerGameMode.java
+++ b/net/minecraft/server/level/ServerPlayerGameMode.java
@@ -111,7 +111,7 @@ public class ServerPlayerGameMode {
     }
 
     public void tick() {
-        this.gameTicks = net.minecraft.server.MinecraftServer.currentTick; // CraftBukkit
+        this.gameTicks = (int) this.level.getLagCompensationTick(); // Paper - lag compensation
         if (this.hasDelayedDestroy) {
             BlockState blockState = this.level.getBlockStateIfLoaded(this.delayedDestroyPos); // Paper - Don't allow digging into unloaded chunks
             if (blockState == null || blockState.isAir()) { // Paper - Don't allow digging into unloaded chunks
diff --git a/net/minecraft/world/entity/LivingEntity.java b/net/minecraft/world/entity/LivingEntity.java
index 635e6e49483194c43b0ab47b5e1bacfe84613c3a..195e1151f7b2a32d6c4eb67edd1952e38f58b266 100644
--- a/net/minecraft/world/entity/LivingEntity.java
+++ b/net/minecraft/world/entity/LivingEntity.java
@@ -3828,6 +3828,10 @@ public abstract class LivingEntity extends Entity implements Attackable {
         this.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)) {
@@ -3841,7 +3845,12 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
     protected void updateUsingItem(ItemStack usingItem) {
         usingItem.onUseTick(this.level(), this, this.getUseItemRemainingTicks());
-        if (--this.useItemRemaining == 0 && !this.level().isClientSide && !usingItem.useOnRelease()) {
+        // Paper start - lag compensate eating
+        // we add 1 to the expected time to avoid lag compensating when we should not
+        final boolean shouldLagCompensate = this.useItem.has(DataComponents.FOOD) && this.eatStartTime != -1 && (System.nanoTime() - this.eatStartTime) > ((1L + this.totalEatTimeTicks) * 50L * (1000L * 1000L));
+        if ((--this.useItemRemaining == 0 || shouldLagCompensate) && !this.level().isClientSide && !usingItem.useOnRelease()) {
+            this.useItemRemaining = 0;
+            // Paper end - lag compensate eating
             this.completeUsingItem();
         }
     }
@@ -3875,7 +3884,10 @@ public abstract class LivingEntity extends Entity implements Attackable {
         ItemStack itemInHand = this.getItemInHand(hand);
         if (!itemInHand.isEmpty() && !this.isUsingItem() || forceUpdate) { // Paper - Prevent consuming the wrong itemstack
             this.useItem = itemInHand;
-            this.useItemRemaining = itemInHand.getUseDuration(this);
+            // Paper start - lag compensate eating
+            this.useItemRemaining = this.totalEatTimeTicks = itemInHand.getUseDuration(this);
+            this.eatStartTime = System.nanoTime();
+            // Paper end - lag compensate eating
             if (!this.level().isClientSide) {
                 this.setLivingEntityFlag(1, true);
                 this.setLivingEntityFlag(2, hand == InteractionHand.OFF_HAND);
@@ -3899,7 +3911,10 @@ 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
             }
         }
     }
@@ -4023,7 +4038,10 @@ 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() {