From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Samsuik <kfian294ma4@gmail.com>
Date: Wed, 6 Oct 2021 17:25:27 +0100
Subject: [PATCH] Optimise New Liquid Level


diff --git a/src/main/java/net/minecraft/world/level/material/FlowingFluid.java b/src/main/java/net/minecraft/world/level/material/FlowingFluid.java
index 1c0712295695727ee9c4d430d4157b8e17cbd71f..67a7141328382ba75f7f66b46f0a423757babe56 100644
--- a/src/main/java/net/minecraft/world/level/material/FlowingFluid.java
+++ b/src/main/java/net/minecraft/world/level/material/FlowingFluid.java
@@ -137,7 +137,7 @@ public abstract class FlowingFluid extends Fluid {
             BlockState iblockdata = world.getBlockState(fluidPos);
             BlockPos blockposition1 = fluidPos.below();
             BlockState iblockdata1 = world.getBlockState(blockposition1);
-            FluidState fluid1 = this.getNewLiquid(world, blockposition1, iblockdata1);
+            FluidState fluid1 = this.getLiquidFlowingDown(world, blockposition1, iblockdata1); // Sakura - optimise new liquid level
 
             if (this.canSpreadTo(world, fluidPos, iblockdata, Direction.DOWN, blockposition1, iblockdata1, world.getFluidState(blockposition1), fluid1.getType())) {
                 // CraftBukkit start
@@ -196,7 +196,60 @@ public abstract class FlowingFluid extends Fluid {
         }
     }
 
+    // Sakura start - optimise new liquid level
+    private static final int FORM_LIQUID_SOURCE = 0xff;
+
+    private boolean canLiquidFlowDown(final Level level, final BlockPos pos, final BlockState state) {
+        final BlockPos abovePos = pos.above();
+        final BlockState stateAbove = level.getBlockState(abovePos);
+        final FluidState fluidStateAbove = stateAbove.getFluidState();
+
+        return !fluidStateAbove.isEmpty() && fluidStateAbove.getType().isSame(this)
+            && canPassThroughWall(Direction.UP, level, pos, state, abovePos, stateAbove);
+    }
+
+    @Deprecated
     protected FluidState getNewLiquid(Level world, BlockPos pos, BlockState state) {
+        return this.getLiquidFromSurroundings(world, pos, state, null, false);
+    }
+
+    private FluidState getLiquidFlowingDown(final Level level, final BlockPos pos, final BlockState state) {
+        final BlockState stateBelow = level.getBlockState(pos.below());
+        final FluidState fluidStateBelow = stateBelow.getFluidState();
+
+        // There's no point checking the surroundings if the liquid is unable to turn into a source.
+        if (!stateBelow.isSolid() || !this.isSourceBlockOfThisType(fluidStateBelow)) {
+            return this.getFlowing(8, true);
+        }
+
+        return this.getLiquidFromSurroundings(level, pos, state, Direction.DOWN, true);
+    }
+
+    @org.jspecify.annotations.NullUnmarked
+    private FluidState getLiquidFromSurroundings(final Level level, final BlockPos pos, final BlockState state,
+                                                 final Direction flowing, final boolean draining) {
+        final boolean flowingDown = flowing == Direction.DOWN || this.canLiquidFlowDown(level, pos, state);
+        if (draining && flowingDown) {
+            return this.getFlowing(8, true);
+        }
+
+        final Direction incoming = flowing != null ? flowing.getOpposite() : null;
+        final int liquidLevel = this.getLiquidLevelFromSurroundings(level, pos, state, incoming);
+        if (liquidLevel == FORM_LIQUID_SOURCE) {
+            return this.getSource(false);
+        }
+
+        if (flowingDown) {
+            return this.getFlowing(8, true);
+        } else {
+            final int newLiquidLevel = liquidLevel - this.getDropOff(level);
+            return newLiquidLevel <= 0 ? Fluids.EMPTY.defaultFluidState() : this.getFlowing(newLiquidLevel, false);
+        }
+    }
+
+    @org.jspecify.annotations.NullUnmarked
+    private int getLiquidLevelFromSurroundings(final Level world, final BlockPos pos, final BlockState state, final Direction incoming) {
+        // Sakura end - optimise new liquid level
         int i = 0;
         int j = 0;
         Iterator iterator = Direction.Plane.HORIZONTAL.iterator();
@@ -208,7 +261,7 @@ public abstract class FlowingFluid extends Fluid {
             if (iblockdata1 == null) continue; // Paper - Prevent chunk loading from fluid flowing
             FluidState fluid = iblockdata1.getFluidState();
 
-            if (fluid.getType().isSame(this) && this.canPassThroughWall(enumdirection, world, pos, state, blockposition1, iblockdata1)) {
+            if (fluid.getType().isSame(this) && (incoming == enumdirection || this.canPassThroughWall(enumdirection, world, pos, state, blockposition1, iblockdata1))) { // Sakura - optimise new liquid level
                 if (fluid.isSource()) {
                     ++j;
                 }
@@ -222,21 +275,11 @@ public abstract class FlowingFluid extends Fluid {
             FluidState fluid1 = iblockdata2.getFluidState();
 
             if (iblockdata2.isSolid() || this.isSourceBlockOfThisType(fluid1)) {
-                return this.getSource(false);
+                return FORM_LIQUID_SOURCE; // Sakura - optimise new liquid level
             }
         }
 
-        BlockPos blockposition2 = pos.above();
-        BlockState iblockdata3 = world.getBlockState(blockposition2);
-        FluidState fluid2 = iblockdata3.getFluidState();
-
-        if (!fluid2.isEmpty() && fluid2.getType().isSame(this) && this.canPassThroughWall(Direction.UP, world, pos, state, blockposition2, iblockdata3)) {
-            return this.getFlowing(8, true);
-        } else {
-            int k = i - this.getDropOff(world);
-
-            return k <= 0 ? Fluids.EMPTY.defaultFluidState() : this.getFlowing(k, false);
-        }
+        return i; // Sakura - optimise new liquid level
     }
 
     private boolean canPassThroughWall(Direction face, BlockGetter world, BlockPos pos, BlockState state, BlockPos fromPos, BlockState fromState) {
@@ -418,7 +461,7 @@ public abstract class FlowingFluid extends Fluid {
             // Paper end - Prevent chunk loading from fluid flowing
             BlockState iblockdata1 = (BlockState) pair.getFirst();
             FluidState fluid = (FluidState) pair.getSecond();
-            FluidState fluid1 = this.getNewLiquid(world, blockposition1, iblockdata1);
+            FluidState fluid1 = this.getLiquidFromSurroundings(world, blockposition1, iblockdata1, enumdirection, false); // Sakura - optimise new liquid level
 
             if (this.canPassThrough(world, fluid1.getType(), pos, state, enumdirection, blockposition1, iblockdata1, fluid)) {
                 BlockPos blockposition2 = blockposition1.below();
@@ -472,7 +515,7 @@ public abstract class FlowingFluid extends Fluid {
     @Override
     public void tick(Level world, BlockPos pos, FluidState state) {
         if (!state.isSource()) {
-            FluidState fluid1 = this.getNewLiquid(world, pos, world.getBlockState(pos));
+            FluidState fluid1 = this.getLiquidFromSurroundings(world, pos, world.getBlockState(pos), null, true); // Sakura - optimise new liquid level; liquid draining
             int i = this.getSpreadDelay(world, pos, state, fluid1);
 
             if (fluid1.isEmpty()) {