#619: Allow delegation of certain elements to Vanilla when using a custom ChunkGenerator

Allows delegation of caves, decorations, mobs and structures to the Vanilla generation algorithms.
Overriding these methods to return true enables that aspect of Vanilla generation, which is applied after the ChunkGenerator's custom generation.

src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java

@@ -8,25 +8,28 @@ import net.minecraft.server.BiomeManager;
 import net.minecraft.server.BiomeStorage;
 import net.minecraft.server.Block;
 import net.minecraft.server.BlockPosition;
+import net.minecraft.server.ChunkProviderGenerate;
+import net.minecraft.server.ChunkProviderHell;
+import net.minecraft.server.ChunkProviderTheEnd;
 import net.minecraft.server.ChunkSection;
+import net.minecraft.server.DefinedStructureManager;
 import net.minecraft.server.EnumCreatureType;
 import net.minecraft.server.GeneratorAccess;
 import net.minecraft.server.GeneratorSettingsDefault;
+import net.minecraft.server.GeneratorSettingsEnd;
+import net.minecraft.server.GeneratorSettingsNether;
+import net.minecraft.server.GeneratorSettingsOverworld;
 import net.minecraft.server.HeightMap;
 import net.minecraft.server.IChunkAccess;
 import net.minecraft.server.ITileEntity;
-import net.minecraft.server.MobSpawnerCat;
-import net.minecraft.server.MobSpawnerPatrol;
-import net.minecraft.server.MobSpawnerPhantom;
 import net.minecraft.server.ProtoChunk;
 import net.minecraft.server.RegionLimitedWorldAccess;
 import net.minecraft.server.StructureGenerator;
 import net.minecraft.server.TileEntity;
-import net.minecraft.server.VillageSiege;
 import net.minecraft.server.World;
+import net.minecraft.server.WorldChunkManager;
 import net.minecraft.server.WorldGenFeatureConfiguration;
 import net.minecraft.server.WorldGenStage;
-import net.minecraft.server.WorldGenerator;
 import net.minecraft.server.WorldServer;
 import org.bukkit.block.Biome;
 import org.bukkit.craftbukkit.block.CraftBlock;
@@ -35,15 +38,11 @@ import org.bukkit.generator.ChunkGenerator.BiomeGrid;
 import org.bukkit.generator.ChunkGenerator.ChunkData;
 
 public class CustomChunkGenerator extends InternalChunkGenerator<GeneratorSettingsDefault> {
+    private final net.minecraft.server.ChunkGenerator delegate;
     private final ChunkGenerator generator;
     private final WorldServer world;
     private final long seed;
     private final Random random;
-    private final StructureGenerator strongholdGen = WorldGenerator.STRONGHOLD;
-    private final MobSpawnerPhantom mobSpawnerPhantom = new MobSpawnerPhantom();
-    private final MobSpawnerPatrol mobSpawnerPatrol = new MobSpawnerPatrol();
-    private final MobSpawnerCat mobSpawnerCat = new MobSpawnerCat();
-    private final VillageSiege villageSiege = new VillageSiege();
 
     private class CustomBiomeGrid implements BiomeGrid {
 
@@ -78,6 +77,20 @@ public class CustomChunkGenerator extends InternalChunkGenerator<GeneratorSettin
 
     public CustomChunkGenerator(World world, long seed, ChunkGenerator generator) {
         super(world, world.worldProvider.getChunkGenerator().getWorldChunkManager(), new GeneratorSettingsDefault());
+        switch (world.getWorld().getEnvironment()) {
+            case NORMAL:
+                this.delegate = new ChunkProviderGenerate(world, world.worldProvider.getChunkGenerator().getWorldChunkManager(), new GeneratorSettingsOverworld());
+                break;
+            case NETHER:
+                this.delegate = new ChunkProviderHell(world, world.worldProvider.getChunkGenerator().getWorldChunkManager(), new GeneratorSettingsNether());
+                break;
+            case THE_END:
+                this.delegate = new ChunkProviderTheEnd(world, world.worldProvider.getChunkGenerator().getWorldChunkManager(), new GeneratorSettingsEnd());
+                break;
+            default:
+                throw new AssertionError("Unknown delegate for environment " + world.getWorld().getEnvironment());
+        }
+
         this.world = (WorldServer) world;
         this.generator = generator;
         this.seed = seed;
@@ -85,8 +98,39 @@ public class CustomChunkGenerator extends InternalChunkGenerator<GeneratorSettin
         this.random = new Random(seed);
     }
 
+    @Override
+    public void createBiomes(IChunkAccess ichunkaccess) {
+        // Don't allow the server to override any custom biomes that have been set
+    }
+
     @Override
     public void buildBase(RegionLimitedWorldAccess regionlimitedworldaccess, IChunkAccess ichunkaccess) {
+        // Disable vanilla generation
+    }
+
+    @Override
+    public <C extends WorldGenFeatureConfiguration> C getFeatureConfiguration(BiomeBase biomebase, StructureGenerator<C> structuregenerator) {
+        return (C) delegate.getFeatureConfiguration(biomebase, structuregenerator);
+    }
+
+    @Override
+    public WorldChunkManager getWorldChunkManager() {
+        return delegate.getWorldChunkManager();
+    }
+
+    @Override
+    public void storeStructures(GeneratorAccess generatoraccess, IChunkAccess ichunkaccess) {
+        delegate.storeStructures(generatoraccess, ichunkaccess);
+    }
+
+    @Override
+    public int getSeaLevel() {
+        return delegate.getSeaLevel();
+    }
+
+    @Override
+    public void createStructures(BiomeManager biomemanager, IChunkAccess ichunkaccess, net.minecraft.server.ChunkGenerator<?> chunkgenerator, DefinedStructureManager definedstructuremanager) {
+        // Call the bukkit ChunkGenerator before structure generation so correct biome information is available.
         int x = ichunkaccess.getPos().x;
         int z = ichunkaccess.getPos().z;
         random.setSeed((long) x * 341873128712L + (long) z * 132897987541L);
@@ -136,73 +180,94 @@ public class CustomChunkGenerator extends InternalChunkGenerator<GeneratorSettin
                 }
             }
         }
+
+        if (generator.shouldGenerateStructures()) {
+            // Vanilla only uses biome at block 9 (see createStructures).
+            // We don't use BiomeGrid as another aspect of generation may try and get from a chunk somewhere else.
+            final BiomeBase biome = biomegrid.biome.getBiome(9 >> 2, 0, 9 >> 2);
+            delegate.createStructures(new BiomeManager(null, 0, null) {
+
+                @Override
+                public BiomeManager a(WorldChunkManager worldchunkmanager) {
+                    return this;
+                }
+
+                @Override
+                public BiomeBase a(BlockPosition blockposition) {
+                    return biome;
+                }
+            }, ichunkaccess, chunkgenerator, definedstructuremanager);
+        }
     }
 
     @Override
     public void doCarving(BiomeManager biomemanager, IChunkAccess ichunkaccess, WorldGenStage.Features worldgenstage_features) {
+        if (generator.shouldGenerateCaves()) {
+            delegate.doCarving(biomemanager, ichunkaccess, worldgenstage_features);
+        }
     }
 
     @Override
     public void buildNoise(GeneratorAccess generatoraccess, IChunkAccess ichunkaccess) {
+        // Disable vanilla generation
     }
 
     @Override
     public int getBaseHeight(int i, int j, HeightMap.Type heightmap_type) {
-        return 0;
+        return delegate.getBaseHeight(i, j, heightmap_type);
     }
 
     @Override
-    public List<BiomeBase.BiomeMeta> getMobsFor(EnumCreatureType type, BlockPosition position) {
-        BiomeBase biomebase = world.getBiome(position);
-
-        return biomebase == null ? null : biomebase.getMobs(type);
+    public List<BiomeBase.BiomeMeta> getMobsFor(EnumCreatureType enumcreaturetype, BlockPosition blockposition) {
+        return delegate.getMobsFor(enumcreaturetype, blockposition);
     }
 
     @Override
     public void addDecorations(RegionLimitedWorldAccess regionlimitedworldaccess) {
+        if (generator.shouldGenerateDecorations()) {
+            delegate.addDecorations(regionlimitedworldaccess);
+        }
     }
 
     @Override
     public void addMobs(RegionLimitedWorldAccess regionlimitedworldaccess) {
+        if (generator.shouldGenerateMobs()) {
+            delegate.addMobs(regionlimitedworldaccess);
+        }
     }
 
     @Override
-    public BlockPosition findNearestMapFeature(World world, String type, BlockPosition position, int i, boolean flag) {
-        return "Stronghold".equals(type) && this.strongholdGen != null ? this.strongholdGen.getNearestGeneratedFeature(world, this, position, i, flag) : null;
+    public BlockPosition findNearestMapFeature(World world, String s, BlockPosition blockposition, int i, boolean flag) {
+        return delegate.findNearestMapFeature(world, s, blockposition, i, flag);
     }
 
     @Override
     public GeneratorSettingsDefault getSettings() {
-        return settings;
+        return delegate.getSettings();
     }
 
     @Override
     public void doMobSpawning(WorldServer worldserver, boolean flag, boolean flag1) {
-        if (worldserver.getWorldProvider().isOverworld()) {
-            this.mobSpawnerPhantom.a(worldserver, flag, flag1);
-            this.mobSpawnerPatrol.a(worldserver, flag, flag1);
-            this.mobSpawnerCat.a(worldserver, flag, flag1);
-            this.villageSiege.a(worldserver, flag, flag1);
-        }
+        delegate.doMobSpawning(worldserver, flag, flag1);
     }
 
     @Override
     public boolean canSpawnStructure(BiomeBase biomebase, StructureGenerator<? extends WorldGenFeatureConfiguration> structuregenerator) {
-        return biomebase.a(structuregenerator);
+        return delegate.canSpawnStructure(biomebase, structuregenerator);
     }
 
     @Override
     public long getSeed() {
-        return seed;
+        return delegate.getSeed();
     }
 
     @Override
     public int getSpawnHeight() {
-        return world.getSeaLevel() + 1;
+        return delegate.getSpawnHeight();
     }
 
     @Override
     public int getGenerationDepth() {
-        return world.getHeight();
+        return delegate.getGenerationDepth();
     }
 }