From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 17 Apr 2016 17:27:09 -0400
Subject: [PATCH] Prevent Fire from loading chunks & wrongly spread

This causes the nether to spam unload/reload chunks, plus overall
bad behavior.

This also stops fire from spreading to illegal locations.

diff --git a/src/main/java/net/minecraft/world/level/block/FireBlock.java b/src/main/java/net/minecraft/world/level/block/FireBlock.java
index 700078c2fd536cc22351eadf51503efb9acd9df9..85170008de6e77cfb8e4f55ae440a8428d868af4 100644
--- a/src/main/java/net/minecraft/world/level/block/FireBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/FireBlock.java
@@ -134,7 +134,7 @@ public class FireBlock extends BaseFireBlock {
                 BooleanProperty blockstateboolean = (BooleanProperty) FireBlock.PROPERTY_BY_DIRECTION.get(enumdirection);
 
                 if (blockstateboolean != null) {
-                    iblockdata1 = (BlockState) iblockdata1.setValue(blockstateboolean, this.canBurn(world.getBlockState(pos.relative(enumdirection))));
+                    iblockdata1 = (BlockState) iblockdata1.setValue(blockstateboolean, this.canBurn(world.getTypeIfLoaded(pos.relative(enumdirection)))); // Paper - prevent chunk loads
                 }
             }
 
@@ -214,6 +214,7 @@ public class FireBlock extends BaseFireBlock {
                                 }
 
                                 blockposition_mutableblockposition.setWithOffset((Vec3i) pos, l, j1, i1);
+                                if (blockposition_mutableblockposition.isInvalidYLocation() || !world.hasChunkAt(blockposition_mutableblockposition)) continue; // Paper
                                 int l1 = this.getFireOdds((LevelReader) world, (BlockPos) blockposition_mutableblockposition);
 
                                 if (l1 > 0) {
@@ -259,10 +260,16 @@ public class FireBlock extends BaseFireBlock {
     }
 
     private void trySpread(Level world, BlockPos blockposition, int i, Random random, int j, BlockPos sourceposition) { // CraftBukkit add sourceposition
-        int k = this.getBurnOdd(world.getBlockState(blockposition));
+        // Paper start
+        final BlockState iblockdata = world.getTypeIfLoaded(blockposition);
+        if (iblockdata == null) {
+            return;
+        }
+        int k = this.getBurnOdd(iblockdata);
+        // Paper end
 
         if (random.nextInt(i) < k) {
-            BlockState iblockdata = world.getBlockState(blockposition);
+            //IBlockData iblockdata = world.getType(blockposition); // Paper
 
             // CraftBukkit start
             org.bukkit.block.Block theBlock = world.getWorld().getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ());
@@ -308,7 +315,7 @@ public class FireBlock extends BaseFireBlock {
         for (int j = 0; j < i; ++j) {
             Direction enumdirection = aenumdirection[j];
 
-            if (this.canBurn(world.getBlockState(pos.relative(enumdirection)))) {
+            if (this.canBurn(world.getTypeIfLoaded(pos.relative(enumdirection)))) { // Paper - prevent chunk loads
                 return true;
             }
         }
@@ -326,7 +333,12 @@ public class FireBlock extends BaseFireBlock {
 
             for (int k = 0; k < j; ++k) {
                 Direction enumdirection = aenumdirection[k];
-                BlockState iblockdata = iworldreader.getBlockState(pos.relative(enumdirection));
+                // Paper start
+                BlockState iblockdata = iworldreader.getTypeIfLoaded(pos.relative(enumdirection));
+                if (iblockdata == null) {
+                    continue;
+                }
+                // Paper end
 
                 i = Math.max(this.getFlameOdds(iblockdata), i);
             }
@@ -337,7 +349,7 @@ public class FireBlock extends BaseFireBlock {
 
     @Override
     protected boolean canBurn(BlockState state) {
-        return this.getFlameOdds(state) > 0;
+        return state != null && this.getFlameOdds(state) > 0;  // Paper - iblockdata can be nullable if chunk is unloaded now
     }
 
     @Override