Apply End and Nether biome materials

src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java

@@ -11,7 +11,9 @@ import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.compat.ImmersivePortalsChunkLoaders;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.GlobalPos;
+import net.minecraft.core.Holder;
 import net.minecraft.core.HolderSet;
+import net.minecraft.data.worldgen.SurfaceRuleData;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
@@ -37,6 +39,7 @@ import net.minecraft.world.level.levelgen.FlatLevelSource;
 import net.minecraft.world.level.levelgen.Heightmap;
 import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
 import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.SurfaceRules;
 import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import net.neoforged.fml.ModList;
 
@@ -273,9 +276,47 @@ public final class AgeDimensionService {
         // Island/Skylands uses uniform floating-island density without the
         // End's central dragon island. Both use the Overworld environment.
         // random_vanilla is retained as a migration alias for existing Ages.
-        return new NoiseBasedChunkGenerator(
-                createBiomeSource(server, age, biomeParameters),
-                noiseSettings.getOrThrow(settingsKey)
+        BiomeSource biomeSource = createBiomeSource(server, age, biomeParameters);
+        NoiseGeneratorSettings baseSettings = noiseSettings.getOrThrow(settingsKey).value();
+        return new NoiseBasedChunkGenerator(biomeSource, Holder.direct(withBiomeMaterialRules(baseSettings)));
+    }
+
+    private static NoiseGeneratorSettings withBiomeMaterialRules(NoiseGeneratorSettings base) {
+        SurfaceRules.RuleSource biomeMaterials = SurfaceRules.sequence(
+                SurfaceRules.ifTrue(
+                        SurfaceRules.isBiome(
+                                Biomes.THE_END,
+                                Biomes.END_HIGHLANDS,
+                                Biomes.END_MIDLANDS,
+                                Biomes.SMALL_END_ISLANDS,
+                                Biomes.END_BARRENS
+                        ),
+                        SurfaceRuleData.end()
+                ),
+                SurfaceRules.ifTrue(
+                        SurfaceRules.isBiome(
+                                Biomes.NETHER_WASTES,
+                                Biomes.SOUL_SAND_VALLEY,
+                                Biomes.CRIMSON_FOREST,
+                                Biomes.WARPED_FOREST,
+                                Biomes.BASALT_DELTAS
+                        ),
+                        SurfaceRuleData.nether()
+                ),
+                base.surfaceRule()
+        );
+        return new NoiseGeneratorSettings(
+                base.noiseSettings(),
+                base.defaultBlock(),
+                base.defaultFluid(),
+                base.noiseRouter(),
+                biomeMaterials,
+                base.spawnTarget(),
+                base.seaLevel(),
+                base.disableMobGeneration(),
+                base.isAquifersEnabled(),
+                base.oreVeinsEnabled(),
+                base.useLegacyRandomSource()
         );
     }
 

src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java

@@ -22,6 +22,7 @@ import net.minecraft.gametest.framework.GameTestHelper;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.biome.Biomes;
 import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.phys.Vec3;
 import java.util.UUID;
@@ -347,9 +348,77 @@ public final class LinkingGameTests {
                     distribution + " Biome Distribution must use its Legacy scale"
             );
         }
+
+        assertSingleBiomeSurfaceMaterial(helper, Biomes.THE_END, Blocks.END_STONE);
+        assertSingleBiomeSurfaceMaterial(helper, Biomes.NETHER_WASTES, Blocks.NETHERRACK);
         helper.succeed();
     }
 
+    private static void assertSingleBiomeSurfaceMaterial(
+            GameTestHelper helper,
+            net.minecraft.resources.ResourceKey<net.minecraft.world.level.biome.Biome> biome,
+            net.minecraft.world.level.block.Block expectedBlock
+    ) {
+        var biomeRegistry = helper.getLevel().registryAccess().lookupOrThrow(net.minecraft.core.registries.Registries.BIOME);
+        var sortedBiomes = biomeRegistry.listElements()
+                .sorted(java.util.Comparator.comparing(holder -> holder.key().location().toString()))
+                .toList();
+        int targetIndex = -1;
+        for (int index = 0; index < sortedBiomes.size(); index++) {
+            if (sortedBiomes.get(index).is(biome)) {
+                targetIndex = index;
+                break;
+            }
+        }
+        helper.assertTrue(targetIndex >= 0, "The requested material-test biome must be registered");
+
+        long seed = 0L;
+        while (Math.floorMod(Long.hashCode(seed ^ 0x53494E474C454249L), sortedBiomes.size()) != targetIndex) {
+            seed++;
+        }
+        UUID id = UUID.randomUUID();
+        AgeDefinition definition = new AgeDefinition(
+                id,
+                "Material " + biome.location(),
+                seed,
+                AgeGenerationProfiles.STANDARD,
+                AgeDefinition.CURRENT_GENERATION_VERSION,
+                helper.getLevel().getGameTime(),
+                net.minecraft.resources.ResourceLocation.fromNamespaceAndPath(
+                        Rivencraft.MOD_ID, "gametest/material_" + biome.location().getPath() + "_" + id
+                ),
+                null,
+                new AgeTraits(
+                        AgeTraits.BiomeDistribution.SINGLE,
+                        AgeTraits.Lighting.NORMAL,
+                        AgeTraits.Weather.NORMAL,
+                        1.0D,
+                        0.0F,
+                        0.0F
+                )
+        );
+        var level = AgeDimensionService.ensureLoaded(helper.getLevel().getServer(), definition);
+        helper.assertTrue(level != null, biome.location() + " material test Age must load");
+        if (level == null) {
+            return;
+        }
+        helper.assertTrue(level.getChunkSource().getGenerator().getBiomeSource().possibleBiomes().stream().allMatch(holder -> holder.is(biome)),
+                "The material test Age must select " + biome.location());
+        // Sample away from the generated arrival platform around the Age spawn.
+        int sampleX = 64;
+        int sampleZ = 64;
+        level.getChunk(sampleX >> 4, sampleZ >> 4);
+        int surfaceY = level.getHeight(
+                net.minecraft.world.level.levelgen.Heightmap.Types.OCEAN_FLOOR_WG,
+                sampleX,
+                sampleZ
+        ) - 1;
+        var surfaceState = level.getBlockState(new BlockPos(sampleX, surfaceY, sampleZ));
+        helper.assertTrue(surfaceState.is(expectedBlock),
+                biome.location() + " terrain must expose " + expectedBlock.getDescriptionId()
+                        + " at the surface, found " + surfaceState);
+    }
+
     @GameTest(template = "empty")
     public static void travelUsesLeafyDestinationWithoutFloor(GameTestHelper helper) {
         helper.setBlock(ORIGIN.below(), Blocks.AIR);