Structure Pool Callback (#1540)

* Structure Pool Callback

* Update build.gradle

* Update fabric-structure-api-v1/src/main/java/net/fabricmc/fabric/api/structure/v1/FabricStructurePool.java

Co-authored-by: liach <7806504+liach@users.noreply.github.com>

* Update fabric-structure-api-v1/src/main/java/net/fabricmc/fabric/api/structure/v1/FabricStructurePool.java

Co-authored-by: liach <7806504+liach@users.noreply.github.com>

* Fix certain concerns

* Expose identifier for easier access

* Final test mod thing

* fix access widener

* Fix a few things

* Fix a few things

* Fix license

* haha lets see if this works

* checkstyle was working after I did checkstyleMain so u bettar work

* i take too much time to do checkstyle fixes

* checkstyle fix testmod ugh amirite

* Fix a few concerns brought up <3

* Oops, forgot to add a mutanle there

* Let's test this one more time?

* Remove Access Widener woop woop

* rename to poolAccessor

* Simplify the pool modification a bit

Co-authored-by: liach <7806504+liach@users.noreply.github.com>

fabric-structure-api-v1/src/main/java/net/fabricmc/fabric/api/structure/v1/FabricStructurePool.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.api.structure.v1;
+
+import net.minecraft.structure.pool.StructurePool;
+import net.minecraft.structure.pool.StructurePoolElement;
+import net.minecraft.util.Identifier;
+
+/**
+ * Represents a modifiable structure pool that has several helper methods for modders.
+ */
+public interface FabricStructurePool {
+	/**
+	 * Adds a new {@link StructurePoolElement} to the {@link StructurePool}.
+	 * See the alternative {@link #addStructurePoolElement(StructurePoolElement, int)} for details.
+	 *
+	 * @param element the element to add
+	 */
+	void addStructurePoolElement(StructurePoolElement element);
+
+	/**
+	 * Adds a new {@link StructurePoolElement} to the {@link StructurePool}.
+	 * Its weight determines the amount of times an element is added to a list used for sampling during structure generation.
+	 *
+	 * @param element the element to add
+	 * @param weight  the weight of the element
+	 */
+	void addStructurePoolElement(StructurePoolElement element, int weight);
+
+	/**
+	 * Gets the underlying structure pool.
+	 */
+	StructurePool getUnderlyingPool();
+
+	/**
+	 * Gets the identifier for the pool.
+	 */
+	default Identifier getId() {
+		return getUnderlyingPool().getId();
+	}
+}

fabric-structure-api-v1/src/main/java/net/fabricmc/fabric/api/structure/v1/StructurePoolAddCallback.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.api.structure.v1;
+
+import net.fabricmc.fabric.api.event.Event;
+import net.fabricmc.fabric.api.event.EventFactory;
+
+/**
+ * A callback for newly added structure pools.
+ *
+ * <p><strong>Word of warning</strong>: Mods may be editing on the structure pool from user configured data packs
+ * instead of the builtin Minecraft or mod resources.
+ *
+ * <p>Example usage:
+ * <pre>{@code
+ * StructurePoolAddCallback.EVENT.register(structurePool -> {
+ * 			if (structurePool.getId().equals(new Identifier("minecraft:village/desert/houses"))) {
+ * 				structurePool.addStructurePoolElement(StructurePoolElement.ofProcessedLegacySingle("fabric:cactus_farm", StructureProcessorLists.FARM_PLAINS).apply(StructurePool.Projection.RIGID));
+ *          }
+ * });}
+ * </pre>
+ */
+public interface StructurePoolAddCallback {
+	/**
+	 * Called when structure pools are reloaded at data pack reload time.
+	 */
+	Event<StructurePoolAddCallback> EVENT = EventFactory.createArrayBacked(StructurePoolAddCallback.class,
+			listeners -> initialPool -> {
+				for (StructurePoolAddCallback listener : listeners) {
+					listener.onAdd(initialPool);
+				}
+			}
+	);
+
+	void onAdd(FabricStructurePool initialPool);
+}

fabric-structure-api-v1/src/main/java/net/fabricmc/fabric/impl/structure/FabricStructurePoolImpl.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.impl.structure;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.google.common.collect.ImmutableList;
+import com.mojang.datafixers.util.Pair;
+
+import net.minecraft.structure.pool.StructurePool;
+import net.minecraft.structure.pool.StructurePoolElement;
+
+import net.fabricmc.fabric.api.structure.v1.FabricStructurePool;
+import net.fabricmc.fabric.mixin.structure.StructurePoolAccessor;
+
+public class FabricStructurePoolImpl implements FabricStructurePool {
+	private final StructurePool pool;
+
+	public FabricStructurePoolImpl(StructurePool pool) {
+		this.pool = pool;
+	}
+
+	@Override
+	public void addStructurePoolElement(StructurePoolElement element) {
+		addStructurePoolElement(element, 1);
+	}
+
+	@Override
+	public void addStructurePoolElement(StructurePoolElement element, int weight) {
+		if (weight <= 0) {
+			throw new IllegalArgumentException("weight must be positive");
+		}
+
+		//adds to elementCounts list; minecraft makes these immutable lists, so we temporarily replace them with an array list
+		StructurePoolAccessor poolAccessor = (StructurePoolAccessor) getUnderlyingPool();
+
+		List<Pair<StructurePoolElement, Integer>> list = new ArrayList<>(poolAccessor.getElementCounts());
+		list.add(Pair.of(element, weight));
+		poolAccessor.setElementCounts(ImmutableList.copyOf(list));
+
+		//adds to elements list
+		for (int i = 0; i < weight; i++) {
+			poolAccessor.getElements().add(element);
+		}
+	}
+
+	@Override
+	public StructurePool getUnderlyingPool() {
+		return pool;
+	}
+}

fabric-structure-api-v1/src/main/java/net/fabricmc/fabric/mixin/structure/DynamicRegistryManagerMixin.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.mixin.structure;
+
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Coerce;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import org.spongepowered.asm.mixin.injection.callback.LocalCapture;
+import org.spongepowered.asm.mixin.Mixin;
+
+import net.minecraft.structure.pool.StructurePool;
+import net.minecraft.util.dynamic.RegistryOps;
+import net.minecraft.util.registry.DynamicRegistryManager;
+import net.minecraft.util.registry.Registry;
+import net.minecraft.util.registry.RegistryKey;
+
+import net.fabricmc.fabric.api.structure.v1.StructurePoolAddCallback;
+import net.fabricmc.fabric.impl.structure.FabricStructurePoolImpl;
+
+@Mixin(DynamicRegistryManager.class)
+public abstract class DynamicRegistryManagerMixin {
+	@Inject(method = "load(Lnet/minecraft/util/dynamic/RegistryOps;Lnet/minecraft/util/registry/DynamicRegistryManager;Lnet/minecraft/util/registry/DynamicRegistryManager$Info;)V", at = @At("TAIL"), locals = LocalCapture.CAPTURE_FAILHARD)
+	private static <E> void load(RegistryOps<?> ops, DynamicRegistryManager manager, @Coerce Object info, CallbackInfo ci, RegistryKey<? extends Registry<E>> registryKey) {
+		if (registryKey.equals(Registry.STRUCTURE_POOL_KEY)) {
+			for (E registryEntry : manager.get(registryKey)) {
+				if (registryEntry instanceof StructurePool pool) {
+					StructurePoolAddCallback.EVENT.invoker().onAdd(new FabricStructurePoolImpl(pool));
+				}
+			}
+		}
+	}
+}

fabric-structure-api-v1/src/main/java/net/fabricmc/fabric/mixin/structure/StructurePoolAccessor.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.mixin.structure;
+
+import java.util.List;
+
+import com.mojang.datafixers.util.Pair;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Mutable;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+import net.minecraft.structure.pool.StructurePool;
+import net.minecraft.structure.pool.StructurePoolElement;
+
+@Mixin(StructurePool.class)
+public interface StructurePoolAccessor {
+	@Accessor(value = "elements")
+	List<StructurePoolElement> getElements();
+
+	@Accessor(value = "elementCounts")
+	List<Pair<StructurePoolElement, Integer>> getElementCounts();
+
+	@Mutable
+	@Accessor(value = "elementCounts")
+	void setElementCounts(List<Pair<StructurePoolElement, Integer>> list);
+}

fabric-structure-api-v1/src/main/resources/fabric-structure-api-v1.mixins.json

@@ -4,8 +4,10 @@
   "compatibilityLevel": "JAVA_16",
   "mixins": [
     "ChunkSerializerMixin",
+    "DynamicRegistryManagerMixin",
     "FlatChunkGeneratorConfigAccessor",
     "StructureFeatureAccessor",
+    "StructurePoolAccessor",
     "StructuresConfigAccessor"
   ],
   "client": [

fabric-structure-api-v1/src/testmod/java/net/fabricmc/fabric/test/structure/StructureTest.java

@@ -24,6 +24,9 @@ import org.apache.logging.log4j.Logger;
 
 import net.minecraft.block.Blocks;
 import net.minecraft.nbt.NbtCompound;
+import net.minecraft.structure.pool.StructurePool;
+import net.minecraft.structure.pool.StructurePoolElement;
+import net.minecraft.structure.processor.StructureProcessorLists;
 import net.minecraft.structure.StructureManager;
 import net.minecraft.structure.StructurePieceType;
 import net.minecraft.structure.StructurePieceWithDimensions;
@@ -47,6 +50,7 @@ import net.minecraft.world.gen.feature.DefaultFeatureConfig;
 import net.minecraft.world.gen.feature.StructureFeature;
 
 import net.fabricmc.fabric.api.structure.v1.FabricStructureBuilder;
+import net.fabricmc.fabric.api.structure.v1.StructurePoolAddCallback;
 
 public class StructureTest {
 	private static final Logger LOGGER = LogManager.getLogger();
@@ -64,6 +68,16 @@ public class StructureTest {
 				.adjustsSurface()
 				.register();
 		Registry.register(Registry.STRUCTURE_PIECE, new Identifier("fabric", "test_structure_piece"), PIECE);
+
+		//Basic Test of Callback
+		StructurePoolAddCallback.EVENT.register(structurePool -> LOGGER.info("Structure pool {} added", structurePool.getId()));
+
+		//The ideal usage of this callback is to add structures to a Village. Here, I constructed a Cactus Farm, which will be added to the house pool for deserts. For testing purposes, we will make it very common, and use a plains-style log outline so it is clear that it doesn't belong.
+		StructurePoolAddCallback.EVENT.register(structurePool -> {
+			if (structurePool.getId().equals(new Identifier("minecraft:village/desert/houses"))) {
+				structurePool.addStructurePoolElement(StructurePoolElement.ofProcessedLegacySingle("fabric:cactus_farm", StructureProcessorLists.FARM_PLAINS).apply(StructurePool.Projection.RIGID));
+			}
+		});
 	}
 
 	public static class TestStructureFeature extends StructureFeature<DefaultFeatureConfig> {