Add hooks to allow modification of structures spawn lists (#7344)

src/main/java/net/minecraftforge/common/extensions/IForgeStructure.java

@@ -0,0 +1,73 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2020.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.common.extensions;
+
+import java.util.Collections;
+import java.util.List;
+import net.minecraft.entity.EntityClassification;
+import net.minecraft.world.biome.MobSpawnInfo;
+import net.minecraft.world.gen.feature.structure.Structure;
+
+public interface IForgeStructure
+{
+    default Structure<?> getStructure()
+    {
+        return (Structure<?>) this;
+    }
+
+    /**
+     * Gets the default list of {@link EntityClassification#MONSTER} spawns for this structure.
+     *
+     * @apiNote Implement this over {@link Structure#getSpawnList()}
+     */
+    default List<MobSpawnInfo.Spawners> getDefaultSpawnList()
+    {
+        return Collections.emptyList();
+    }
+
+    /**
+     * Gets the default list of {@link EntityClassification#CREATURE} spawns for this structure.
+     *
+     * @apiNote Implement this over {@link Structure#getCreatureSpawnList()}
+     */
+    default List<MobSpawnInfo.Spawners> getDefaultCreatureSpawnList()
+    {
+        return Collections.emptyList();
+    }
+
+    /**
+     * Gets the default for if entity spawns are restricted to being inside of the pieces making up the structure or if being in the bounds of the overall structure
+     * is good enough.
+     * @return {@code true} if the location to check spawns for has to be inside of the pieces making up the structure, {@code false} otherwise.
+     */
+    default boolean getDefaultRestrictsSpawnsToInside()
+    {
+        //The Pillager Outpost and Ocean Monument check the full structure by default instead of limiting themselves to being within the structure's bounds
+        return getStructure() != Structure.field_236366_b_ && getStructure() != Structure.field_236376_l_;
+    }
+
+    /**
+     * Helper method to get the list of entity spawns for this structure for the given classification.
+     * @param classification The classification of entities.
+     * @apiNote This method is marked as final in {@link Structure} so as to not be overridden by modders and breaking support for
+     * {@link net.minecraftforge.event.world.StructureSpawnListGatherEvent}.
+     */
+    List<MobSpawnInfo.Spawners> getSpawnList(EntityClassification classification);
+}

src/main/java/net/minecraftforge/common/world/StructureSpawnManager.java

@@ -0,0 +1,134 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2020.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.common.world;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import javax.annotation.Nullable;
+import net.minecraft.entity.EntityClassification;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.biome.MobSpawnInfo;
+import net.minecraft.world.gen.feature.structure.Structure;
+import net.minecraft.world.gen.feature.structure.StructureManager;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.event.world.StructureSpawnListGatherEvent;
+import net.minecraftforge.registries.ForgeRegistries;
+
+/**
+ * Class to help manage entity spawns inside of structures
+ */
+public class StructureSpawnManager
+{
+    private static Map<Structure<?>, StructureSpawnInfo> structuresWithSpawns = Collections.emptyMap();
+
+    /**
+     * Gathers potential entity spawns for all the different registered structures.
+     * @apiNote Internal
+     */
+    public static void gatherEntitySpawns()
+    {
+        //We use a linked hash map to ensure that we check the structures in an order that if there are multiple structures a position satisfies
+        // then we have the same behavior as vanilla as vanilla checks, swamp huts, pillager outposts, ocean monuments, and nether fortresses in
+        // that order.
+        Map<Structure<?>, StructureSpawnInfo> structuresWithSpawns = new LinkedHashMap<>();
+        gatherEntitySpawns(structuresWithSpawns, Structure.field_236374_j_);
+        gatherEntitySpawns(structuresWithSpawns, Structure.field_236366_b_);
+        gatherEntitySpawns(structuresWithSpawns, Structure.field_236376_l_);
+        gatherEntitySpawns(structuresWithSpawns, Structure.field_236378_n_);
+        for (Structure<?> structure : ForgeRegistries.STRUCTURE_FEATURES.getValues())
+        {
+            if (structure != Structure.field_236374_j_ && structure != Structure.field_236366_b_ && structure != Structure.field_236376_l_ &&
+                structure != Structure.field_236378_n_)
+            {
+                //If we didn't already gather the spawns already to ensure we do vanilla ones already
+                // gather the spawns for this structure
+                gatherEntitySpawns(structuresWithSpawns, structure);
+            }
+        }
+        StructureSpawnManager.structuresWithSpawns = structuresWithSpawns;
+    }
+
+    private static void gatherEntitySpawns(Map<Structure<?>, StructureSpawnInfo> structuresWithSpawns, Structure<?> structure)
+    {
+        StructureSpawnListGatherEvent event = new StructureSpawnListGatherEvent(structure);
+        MinecraftForge.EVENT_BUS.post(event);
+        ImmutableMap.Builder<net.minecraft.entity.EntityClassification, List<MobSpawnInfo.Spawners>> builder = ImmutableMap.builder();
+        event.getEntitySpawns().forEach((classification, spawns) -> {
+            if (!spawns.isEmpty())
+                builder.put(classification, ImmutableList.copyOf(spawns));
+        });
+        Map<EntityClassification, List<MobSpawnInfo.Spawners>> entitySpawns = builder.build();
+        if (!entitySpawns.isEmpty())
+            structuresWithSpawns.put(structure, new StructureSpawnInfo(entitySpawns, event.isInsideOnly()));
+    }
+
+    /**
+     * Looks up if a given position is within a structure and returns any entity spawns that structure has for the given classification, or null if
+     * none are found.
+     * @param structureManager Structure Manager, used to check if a position is within a structure.
+     * @param classification   Entity classification
+     * @param pos              Position to get entity spawns of
+     */
+    @Nullable
+    public static List<MobSpawnInfo.Spawners> getStructureSpawns(StructureManager structureManager, EntityClassification classification, BlockPos pos)
+    {
+        for (Entry<Structure<?>, StructureSpawnInfo> entry : structuresWithSpawns.entrySet())
+        {
+            Structure<?> structure = entry.getKey();
+            StructureSpawnInfo spawnInfo = entry.getValue();
+            //Note: We check if the structure has spawns for a type first before looking at the world as it should be a cheaper check
+            if (spawnInfo.spawns.containsKey(classification) && structureManager.func_235010_a_(pos, spawnInfo.insideOnly, structure).isValid())
+                return spawnInfo.spawns.get(classification);
+        }
+        return null;
+    }
+
+    /**
+     * Gets the entity spawn lists for entities of a given classification for a given structure.
+     * @param structure      The Structure
+     * @param classification The classification to lookup
+     */
+    public static List<MobSpawnInfo.Spawners> getSpawnList(Structure<?> structure, EntityClassification classification)
+    {
+        if (structuresWithSpawns.containsKey(structure))
+            return structuresWithSpawns.get(structure).spawns.getOrDefault(classification, Collections.emptyList());
+        return Collections.emptyList();
+    }
+
+    /**
+     * Helper class to keep track of spawns and if the spawns should be restricted to inside the structure pieces.
+     */
+    private static class StructureSpawnInfo
+    {
+        private final Map<EntityClassification, List<MobSpawnInfo.Spawners>> spawns;
+        private final boolean insideOnly;
+
+        private StructureSpawnInfo(Map<EntityClassification, List<MobSpawnInfo.Spawners>> spawns, boolean insideOnly)
+        {
+            this.spawns = spawns;
+            this.insideOnly = insideOnly;
+        }
+    }
+}

src/main/java/net/minecraftforge/event/world/StructureSpawnListGatherEvent.java

@@ -0,0 +1,150 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2020.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.event.world;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import net.minecraft.entity.EntityClassification;
+import net.minecraft.world.biome.MobSpawnInfo;
+import net.minecraft.world.gen.feature.structure.Structure;
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.eventbus.api.EventPriority;
+
+/**
+ * This event fires when a Structure is gathering what mobs/creatures can spawn in it.
+ *
+ * In order to maintain the most compatibility possible with other mods' modifications to a structure,
+ * the event should be assigned a {@link net.minecraftforge.eventbus.api.EventPriority} as follows:
+ *
+ * - Additions : {@link EventPriority#HIGH}
+ * - Removals : {@link EventPriority#NORMAL}
+ * - Any other modification : {@link EventPriority#LOW}
+ *
+ * Be aware that another mod could have done an operation beforehand, so an expected value out of a vanilla structure might not
+ * always be the same, depending on other mods.
+ */
+public class StructureSpawnListGatherEvent extends Event
+{
+
+    private final Structure<?> structure;
+    private final Map<EntityClassification, List<MobSpawnInfo.Spawners>> entitySpawns = new HashMap<>();
+    private final Map<EntityClassification, List<MobSpawnInfo.Spawners>> entitySpawnsUnmodifiableLists = new HashMap<>();
+    private final Map<EntityClassification, List<MobSpawnInfo.Spawners>> entitySpawnsUnmodifiable = Collections.unmodifiableMap(entitySpawnsUnmodifiableLists);
+    private boolean insideOnly;
+
+    public StructureSpawnListGatherEvent(Structure<?> structure)
+    {
+        this.structure = structure;
+        this.insideOnly = this.structure.getDefaultRestrictsSpawnsToInside();
+        addEntitySpawns(EntityClassification.MONSTER, this.structure.getDefaultSpawnList());
+        addEntitySpawns(EntityClassification.CREATURE, this.structure.getDefaultCreatureSpawnList());
+    }
+
+    /**
+     * @return Structure to add or remove spawns to/from.
+     */
+    public Structure<?> getStructure()
+    {
+        return structure;
+    }
+
+    /**
+     * Change if entity spawn location checks are done against the entire bounds of the structure or only the inside the pieces of the structure.
+     * @param insideOnly {@code true} to restrict the spawn checks to inside the pieces of the structure, {@code false} to allow spawns outside
+     */
+    public void setInsideOnly(boolean insideOnly)
+    {
+        this.insideOnly = insideOnly;
+    }
+
+    /**
+     * Checks if spawns for the structure are restricted to being inside the individual pieces of the structure.
+     */
+    public boolean isInsideOnly()
+    {
+        return insideOnly;
+    }
+
+    /**
+     * Gets an unmodifiable view of the the list representing the entity spawns for the given classification.
+     * @param classification Entity Classification
+     * @return The list of spawns for the given classification.
+     */
+    public List<MobSpawnInfo.Spawners> getEntitySpawns(EntityClassification classification)
+    {
+        return this.entitySpawnsUnmodifiableLists.getOrDefault(classification, Collections.emptyList());
+    }
+
+    /**
+     * Gets the internal spawn list for a given entity classification, or adds one if needed. (This includes adding it to the unmodifiable view)
+     */
+    private List<MobSpawnInfo.Spawners> getOrCreateEntitySpawns(EntityClassification classification)
+    {
+        return this.entitySpawns.computeIfAbsent(classification, c -> {
+            List<MobSpawnInfo.Spawners> spawners = new ArrayList<>();
+            //If the classification isn't in entitySpawns yet, also add an unmodifiable view of the list to
+            // the unmodifiable list spawn map
+            this.entitySpawnsUnmodifiableLists.put(c, Collections.unmodifiableList(spawners));
+            return spawners;
+        });
+    }
+
+    /**
+     * Adds a spawn to the list of spawns for the given classification.
+     * @param classification Entity Classification
+     * @param spawner        Spawner
+     */
+    public void addEntitySpawn(EntityClassification classification, MobSpawnInfo.Spawners spawner)
+    {
+        getOrCreateEntitySpawns(classification).add(spawner);
+    }
+
+    /**
+     * Adds spawns to the list of spawns for the given classification.
+     * @param classification Entity Classification
+     * @param spawners       Spawners to add
+     */
+    public void addEntitySpawns(EntityClassification classification, List<MobSpawnInfo.Spawners> spawners)
+    {
+        getOrCreateEntitySpawns(classification).addAll(spawners);
+    }
+
+    /**
+     * Removes a spawn from the list of spawns for the given classification.
+     * @param classification Entity Classification
+     * @param spawner        Spawner
+     */
+    public void removeEntitySpawn(EntityClassification classification, MobSpawnInfo.Spawners spawner)
+    {
+        if (this.entitySpawns.containsKey(classification))
+            this.entitySpawns.get(classification).remove(spawner);
+    }
+
+    /**
+     * Gets an unmodifiable view of the map of spawns based on entity classification that is used to fill in the various spawn lists for the structure.
+     */
+    public Map<EntityClassification, List<MobSpawnInfo.Spawners>> getEntitySpawns()
+    {
+        return entitySpawnsUnmodifiable;
+    }
+}