From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Byteflux <byte@byteflux.net>
Date: Wed, 2 Mar 2016 02:17:54 -0600
Subject: [PATCH] Flat bedrock generator settings

== AT ==
public net.minecraft.world.level.levelgen.SurfaceRules$Condition
public net.minecraft.world.level.levelgen.SurfaceRules$Context
public net.minecraft.world.level.levelgen.SurfaceRules$Context blockX
public net.minecraft.world.level.levelgen.SurfaceRules$Context blockY
public net.minecraft.world.level.levelgen.SurfaceRules$Context blockZ
public net.minecraft.world.level.levelgen.SurfaceRules$Context context
public net.minecraft.world.level.levelgen.SurfaceRules$Context randomState
public net.minecraft.world.level.levelgen.SurfaceRules$LazyYCondition
public net.minecraft.world.level.levelgen.SurfaceRules$LazyCondition
public net.minecraft.world.level.levelgen.SurfaceRules$VerticalGradientConditionSource
public net.minecraft.world.level.levelgen.SurfaceRules$SurfaceRule

Co-authored-by: Noah van der Aa <ndvdaa@gmail.com>

diff --git a/src/main/java/io/papermc/paper/world/worldgen/OptionallyFlatBedrockConditionSource.java b/src/main/java/io/papermc/paper/world/worldgen/OptionallyFlatBedrockConditionSource.java
new file mode 100644
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000
--- /dev/null
+++ b/src/main/java/io/papermc/paper/world/worldgen/OptionallyFlatBedrockConditionSource.java
@@ -0,0 +0,0 @@
+package io.papermc.paper.world.worldgen;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.util.KeyDispatchDataCodec;
+import net.minecraft.util.Mth;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.levelgen.PositionalRandomFactory;
+import net.minecraft.world.level.levelgen.SurfaceRules;
+import net.minecraft.world.level.levelgen.VerticalAnchor;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+// Modelled off of SurfaceRules$VerticalGradientConditionSource
+@DefaultQualifier(NonNull.class)
+public record OptionallyFlatBedrockConditionSource(ResourceLocation randomName, VerticalAnchor trueAtAndBelow, VerticalAnchor falseAtAndAbove, boolean isRoof) implements SurfaceRules.ConditionSource {
+
+    private static final ResourceKey<MapCodec<? extends SurfaceRules.ConditionSource>> CODEC_RESOURCE_KEY = ResourceKey.create(
+        Registries.MATERIAL_CONDITION,
+        ResourceLocation.fromNamespaceAndPath(ResourceLocation.PAPER_NAMESPACE, "optionally_flat_bedrock_condition_source")
+    );
+    private static final KeyDispatchDataCodec<OptionallyFlatBedrockConditionSource> CODEC = KeyDispatchDataCodec.of(RecordCodecBuilder.mapCodec((instance) -> {
+        return instance.group(
+            ResourceLocation.CODEC.fieldOf("random_name").forGetter(OptionallyFlatBedrockConditionSource::randomName),
+            VerticalAnchor.CODEC.fieldOf("true_at_and_below").forGetter(OptionallyFlatBedrockConditionSource::trueAtAndBelow),
+            VerticalAnchor.CODEC.fieldOf("false_at_and_above").forGetter(OptionallyFlatBedrockConditionSource::falseAtAndAbove),
+            Codec.BOOL.fieldOf("is_roof").forGetter(OptionallyFlatBedrockConditionSource::isRoof)
+        ).apply(instance, OptionallyFlatBedrockConditionSource::new);
+    }));
+
+    public static void bootstrap() {
+        Registry.register(BuiltInRegistries.MATERIAL_CONDITION, CODEC_RESOURCE_KEY, CODEC.codec());
+    }
+
+    @Override
+    public KeyDispatchDataCodec<? extends SurfaceRules.ConditionSource> codec() {
+        return CODEC;
+    }
+
+    @Override
+    public SurfaceRules.Condition apply(final SurfaceRules.Context context) {
+        boolean hasFlatBedrock = context.context.getWorld().paperConfig().environment.generateFlatBedrock;
+        int tempTrueAtAndBelowY = this.trueAtAndBelow().resolveY(context.context);
+        int tempFalseAtAndAboveY = this.falseAtAndAbove().resolveY(context.context);
+
+        int flatYLevel = this.isRoof ? Math.max(tempFalseAtAndAboveY, tempTrueAtAndBelowY) - 1 : Math.min(tempFalseAtAndAboveY, tempTrueAtAndBelowY);
+        final int trueAtAndBelowY = hasFlatBedrock ? flatYLevel : tempTrueAtAndBelowY;
+        final int falseAtAndAboveY = hasFlatBedrock ? flatYLevel : tempFalseAtAndAboveY;
+
+        final PositionalRandomFactory positionalRandomFactory = context.randomState.getOrCreateRandomFactory(this.randomName());
+
+        class VerticalGradientCondition extends SurfaceRules.LazyYCondition {
+            VerticalGradientCondition(SurfaceRules.Context context) {
+                super(context);
+            }
+
+            @Override
+            protected boolean compute() {
+                int blockY = this.context.blockY;
+                if (blockY <= trueAtAndBelowY) {
+                    return true;
+                } else if (blockY >= falseAtAndAboveY) {
+                    return false;
+                } else {
+                    double d = Mth.map(blockY, trueAtAndBelowY, falseAtAndAboveY, 1.0D, 0.0D);
+                    RandomSource randomSource = positionalRandomFactory.at(this.context.blockX, blockY, this.context.blockZ);
+                    return (double)randomSource.nextFloat() < d;
+                }
+            }
+        }
+
+        return new VerticalGradientCondition(context);
+    }
+}
diff --git a/src/main/java/net/minecraft/server/Bootstrap.java b/src/main/java/net/minecraft/server/Bootstrap.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/Bootstrap.java
+++ b/src/main/java/net/minecraft/server/Bootstrap.java
@@ -0,0 +0,0 @@ public class Bootstrap {
                     CauldronInteraction.bootStrap();
                     // Paper start
                     BuiltInRegistries.bootStrap(() -> {
+                        io.papermc.paper.world.worldgen.OptionallyFlatBedrockConditionSource.bootstrap(); // Paper - Flat bedrock generator settings
                     });
                     // Paper end
                     CreativeModeTabs.validate();
diff --git a/src/main/java/net/minecraft/world/level/levelgen/NoiseBasedChunkGenerator.java b/src/main/java/net/minecraft/world/level/levelgen/NoiseBasedChunkGenerator.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/NoiseBasedChunkGenerator.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/NoiseBasedChunkGenerator.java
@@ -0,0 +0,0 @@ public final class NoiseBasedChunkGenerator extends ChunkGenerator {
     @Override
     public void buildSurface(WorldGenRegion region, StructureManager structures, RandomState noiseConfig, ChunkAccess chunk) {
         if (!SharedConstants.debugVoidTerrain(chunk.getPos())) {
-            WorldGenerationContext worldgenerationcontext = new WorldGenerationContext(this, region);
+            WorldGenerationContext worldgenerationcontext = new WorldGenerationContext(this, region, region.getMinecraftWorld()); // Paper - Flat bedrock generator settings
 
             this.buildSurface(chunk, worldgenerationcontext, noiseConfig, structures, region.getBiomeManager(), region.registryAccess().lookupOrThrow(Registries.BIOME), Blender.of(region));
         }
@@ -0,0 +0,0 @@ public final class NoiseBasedChunkGenerator extends ChunkGenerator {
             return this.createNoiseChunk(ichunkaccess1, structureAccessor, Blender.of(chunkRegion), noiseConfig);
         });
         Aquifer aquifer = noisechunk.aquifer();
-        CarvingContext carvingcontext = new CarvingContext(this, chunkRegion.registryAccess(), chunk.getHeightAccessorForGeneration(), noisechunk, noiseConfig, ((NoiseGeneratorSettings) this.settings.value()).surfaceRule());
+        CarvingContext carvingcontext = new CarvingContext(this, chunkRegion.registryAccess(), chunk.getHeightAccessorForGeneration(), noisechunk, noiseConfig, ((NoiseGeneratorSettings) this.settings.value()).surfaceRule(), chunkRegion.getMinecraftWorld()); // Paper - Flat bedrock generator settings
         CarvingMask carvingmask = ((ProtoChunk) chunk).getOrCreateCarvingMask();
 
         for (int j = -8; j <= 8; ++j) {
diff --git a/src/main/java/net/minecraft/world/level/levelgen/WorldGenerationContext.java b/src/main/java/net/minecraft/world/level/levelgen/WorldGenerationContext.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/WorldGenerationContext.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/WorldGenerationContext.java
@@ -0,0 +0,0 @@ import net.minecraft.world.level.chunk.ChunkGenerator;
 public class WorldGenerationContext {
     private final int minY;
     private final int height;
+    private final @javax.annotation.Nullable net.minecraft.world.level.Level level; // Paper - Flat bedrock generator settings
 
-    public WorldGenerationContext(ChunkGenerator generator, LevelHeightAccessor world) {
+    public WorldGenerationContext(ChunkGenerator generator, LevelHeightAccessor world) { this(generator, world, null); } // Paper - Flat bedrock generator settings
+    public WorldGenerationContext(ChunkGenerator generator, LevelHeightAccessor world, @org.jetbrains.annotations.Nullable net.minecraft.world.level.Level level) { // Paper - Flat bedrock generator settings
         this.minY = Math.max(world.getMinY(), generator.getMinY());
         this.height = Math.min(world.getHeight(), generator.getGenDepth());
+        this.level = level; // Paper - Flat bedrock generator settings
     }
 
     public int getMinGenY() {
@@ -0,0 +0,0 @@ public class WorldGenerationContext {
     public int getGenDepth() {
         return this.height;
     }
+
+    // Paper start - Flat bedrock generator settings
+    public net.minecraft.world.level.Level getWorld() {
+        if (this.level == null) {
+            throw new NullPointerException("WorldGenerationContext was initialized without a Level, but WorldGenerationContext#getWorld was called");
+        }
+        return this.level;
+    }
+    // Paper end - Flat bedrock generator settings
 }
diff --git a/src/main/java/net/minecraft/world/level/levelgen/carver/CarvingContext.java b/src/main/java/net/minecraft/world/level/levelgen/carver/CarvingContext.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/carver/CarvingContext.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/carver/CarvingContext.java
@@ -0,0 +0,0 @@ public class CarvingContext extends WorldGenerationContext {
         LevelHeightAccessor heightLimitView,
         NoiseChunk chunkNoiseSampler,
         RandomState noiseConfig,
-        SurfaceRules.RuleSource materialRule
+        SurfaceRules.RuleSource materialRule, @javax.annotation.Nullable net.minecraft.world.level.Level level  // Paper - Flat bedrock generator settings
     ) {
-        super(noiseChunkGenerator, heightLimitView);
+        super(noiseChunkGenerator, heightLimitView, level); // Paper - Flat bedrock generator settings
         this.registryAccess = registryManager;
         this.noiseChunk = chunkNoiseSampler;
         this.randomState = noiseConfig;
diff --git a/src/main/java/net/minecraft/world/level/levelgen/placement/PlacementContext.java b/src/main/java/net/minecraft/world/level/levelgen/placement/PlacementContext.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/placement/PlacementContext.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/placement/PlacementContext.java
@@ -0,0 +0,0 @@ public class PlacementContext extends WorldGenerationContext {
     private final Optional<PlacedFeature> topFeature;
 
     public PlacementContext(WorldGenLevel world, ChunkGenerator generator, Optional<PlacedFeature> placedFeature) {
-        super(generator, world);
+        super(generator, world, world.getLevel()); // Paper - Flat bedrock generator settings
         this.level = world;
         this.generator = generator;
         this.topFeature = placedFeature;
diff --git a/src/main/resources/data/minecraft/worldgen/noise_settings/amplified.json b/src/main/resources/data/minecraft/worldgen/noise_settings/amplified.json
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/resources/data/minecraft/worldgen/noise_settings/amplified.json
+++ b/src/main/resources/data/minecraft/worldgen/noise_settings/amplified.json
@@ -0,0 +0,0 @@
       {
         "type": "minecraft:condition",
         "if_true": {
-          "type": "minecraft:vertical_gradient",
+          "type": "paper:optionally_flat_bedrock_condition_source",
+          "is_roof": false,
           "false_at_and_above": {
             "above_bottom": 5
           },
diff --git a/src/main/resources/data/minecraft/worldgen/noise_settings/caves.json b/src/main/resources/data/minecraft/worldgen/noise_settings/caves.json
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/resources/data/minecraft/worldgen/noise_settings/caves.json
+++ b/src/main/resources/data/minecraft/worldgen/noise_settings/caves.json
@@ -0,0 +0,0 @@
         "if_true": {
           "type": "minecraft:not",
           "invert": {
-            "type": "minecraft:vertical_gradient",
+            "type": "paper:optionally_flat_bedrock_condition_source",
+            "is_roof": true,
             "false_at_and_above": {
               "below_top": 0
             },
@@ -0,0 +0,0 @@
       {
         "type": "minecraft:condition",
         "if_true": {
-          "type": "minecraft:vertical_gradient",
+          "type": "paper:optionally_flat_bedrock_condition_source",
+          "is_roof": false,
           "false_at_and_above": {
             "above_bottom": 5
           },
diff --git a/src/main/resources/data/minecraft/worldgen/noise_settings/large_biomes.json b/src/main/resources/data/minecraft/worldgen/noise_settings/large_biomes.json
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/resources/data/minecraft/worldgen/noise_settings/large_biomes.json
+++ b/src/main/resources/data/minecraft/worldgen/noise_settings/large_biomes.json
@@ -0,0 +0,0 @@
       {
         "type": "minecraft:condition",
         "if_true": {
-          "type": "minecraft:vertical_gradient",
+          "type": "paper:optionally_flat_bedrock_condition_source",
+          "is_roof": false,
           "false_at_and_above": {
             "above_bottom": 5
           },
diff --git a/src/main/resources/data/minecraft/worldgen/noise_settings/nether.json b/src/main/resources/data/minecraft/worldgen/noise_settings/nether.json
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/resources/data/minecraft/worldgen/noise_settings/nether.json
+++ b/src/main/resources/data/minecraft/worldgen/noise_settings/nether.json
@@ -0,0 +0,0 @@
       {
         "type": "minecraft:condition",
         "if_true": {
-          "type": "minecraft:vertical_gradient",
+          "type": "paper:optionally_flat_bedrock_condition_source",
+          "is_roof": false,
           "false_at_and_above": {
             "above_bottom": 5
           },
@@ -0,0 +0,0 @@
         "if_true": {
           "type": "minecraft:not",
           "invert": {
-            "type": "minecraft:vertical_gradient",
+            "type": "paper:optionally_flat_bedrock_condition_source",
+            "is_roof": true,
             "false_at_and_above": {
               "below_top": 0
             },
diff --git a/src/main/resources/data/minecraft/worldgen/noise_settings/overworld.json b/src/main/resources/data/minecraft/worldgen/noise_settings/overworld.json
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/resources/data/minecraft/worldgen/noise_settings/overworld.json
+++ b/src/main/resources/data/minecraft/worldgen/noise_settings/overworld.json
@@ -0,0 +0,0 @@
       {
         "type": "minecraft:condition",
         "if_true": {
-          "type": "minecraft:vertical_gradient",
+          "type": "paper:optionally_flat_bedrock_condition_source",
+          "is_roof": false,
           "false_at_and_above": {
             "above_bottom": 5
           },
