Add helper methods to create custom villager types. (#1076)

* Add helper methods to create custom villager types.

* Rename biome method

* Make it register and register the instance of the villager type.

* Javadoc 2

* Add texture javadoc

fabric-object-builder-api-v1/src/main/java/net/fabricmc/fabric/api/object/builder/v1/villager/VillagerTypeHelper.java

@@ -0,0 +1,75 @@
+/*
+ * 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.object.builder.v1.villager;
+
+import java.util.Objects;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import net.minecraft.util.Identifier;
+import net.minecraft.util.registry.RegistryKey;
+import net.minecraft.village.VillagerProfession;
+import net.minecraft.village.VillagerType;
+import net.minecraft.world.biome.Biome;
+
+import net.fabricmc.fabric.mixin.object.builder.VillagerTypeAccessor;
+
+/**
+ * Utilities related to the creation of {@link VillagerType}s.
+ * Not to be confused with a {@link VillagerProfession}, a villager type defines the appearance of a villager.
+ *
+ * <p>Creation and registration of custom villager types may be done by using {@link VillagerTypeHelper#register(Identifier)}.
+ *
+ * <p>Creation and registration of a villager type does not guarantee villagers of a specific type will be created in a world.
+ * Typically the villager type is bound to a specific group of biomes.
+ * To allow a villager type to be spawned in a specific biome, use {@link VillagerTypeHelper#addVillagerTypeToBiome(RegistryKey, VillagerType)}.
+ *
+ * <p>The texture used for the appearance of the villager is located at {@code assets/IDENTIFIER_NAMESPACE/textures/entity/villager/type/IDENTIFIER_PATH.png}.
+ */
+public final class VillagerTypeHelper {
+	private static final Logger LOGGER = LogManager.getLogger();
+
+	/**
+	 * Creates and registers a new villager type.
+	 *
+	 * @param id the id of the villager type
+	 * @return a new villager type
+	 */
+	public static VillagerType register(Identifier id) {
+		Objects.requireNonNull(id, "Id of villager type cannot be null");
+		return VillagerTypeAccessor.callRegister(id.toString());
+	}
+
+	/**
+	 * Sets the biome a villager type can spawn in.
+	 *
+	 * @param biomeKey the registry key of the biome
+	 * @param villagerType the villager type
+	 */
+	public static void addVillagerTypeToBiome(RegistryKey<Biome> biomeKey, VillagerType villagerType) {
+		Objects.requireNonNull(biomeKey, "Biome registry key cannot be null");
+		Objects.requireNonNull(villagerType, "Villager type cannot be null");
+
+		if (VillagerTypeAccessor.getBiomeTypeToIdMap().put(biomeKey, villagerType) != null) {
+			LOGGER.debug("Overriding existing Biome -> VillagerType registration for Biome {}", biomeKey.getValue().toString());
+		}
+	}
+
+	private VillagerTypeHelper() {
+	}
+}

fabric-object-builder-api-v1/src/main/java/net/fabricmc/fabric/mixin/object/builder/VillagerTypeAccessor.java

@@ -0,0 +1,41 @@
+/*
+ * 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.object.builder;
+
+import java.util.Map;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+import org.spongepowered.asm.mixin.gen.Invoker;
+
+import net.minecraft.util.registry.RegistryKey;
+import net.minecraft.village.VillagerType;
+import net.minecraft.world.biome.Biome;
+
+@Mixin(VillagerType.class)
+public interface VillagerTypeAccessor {
+	@Accessor("BIOME_TO_TYPE")
+	static Map<RegistryKey<Biome>, VillagerType> getBiomeTypeToIdMap() {
+		throw new AssertionError("Untransformed Accessor!");
+	}
+
+	// FIXME: This should be called `register` in yarn
+	@Invoker("create")
+	static VillagerType callRegister(String id) {
+		throw new AssertionError("Untransformed Accessor!");
+	}
+}

fabric-object-builder-api-v1/src/main/resources/fabric-object-builder-v1.mixins.json

@@ -16,7 +16,8 @@
     "TradeOffersAccessor",
     "TradeOffersMixin",
     "TypeAwareTradeMixin",
-    "VillagerProfessionAccessor"
+    "VillagerProfessionAccessor",
+    "VillagerTypeAccessor"
   ],
   "client": [
     "ModelPredicateProviderRegistryAccessor",