Add getHighestBlockYAt and spawnEntity to DecorationArea

worldgeneratorapi-impl/src/main/java/nl/rutgerkok/worldgeneratorapi/internal/DecorationAreaImpl.java

@@ -2,9 +2,11 @@
 
 import java.util.Objects;
 
+import org.bukkit.Location;
 import org.bukkit.Material;
 import org.bukkit.block.BlockState;
 import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_17_R1.CraftWorld;
 import org.bukkit.craftbukkit.v1_17_R1.block.CraftBanner;
 import org.bukkit.craftbukkit.v1_17_R1.block.CraftBarrel;
 import org.bukkit.craftbukkit.v1_17_R1.block.CraftBeacon;
@@ -38,12 +40,17 @@
 import org.bukkit.craftbukkit.v1_17_R1.block.CraftSmoker;
 import org.bukkit.craftbukkit.v1_17_R1.block.CraftStructureBlock;
 import org.bukkit.craftbukkit.v1_17_R1.block.data.CraftBlockData;
+import org.bukkit.entity.Entity;
+import org.bukkit.event.entity.CreatureSpawnEvent;
 
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.BlockPos.MutableBlockPos;
 import net.minecraft.core.Registry;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.world.entity.Mob;
+import net.minecraft.world.entity.MobSpawnType;
+import net.minecraft.world.entity.SpawnGroupData;
 import net.minecraft.world.level.ChunkPos;
 import net.minecraft.world.level.biome.Biome;
 import net.minecraft.world.level.block.entity.BannerBlockEntity;
@@ -77,6 +84,7 @@
 import net.minecraft.world.level.block.entity.StructureBlockEntity;
 import net.minecraft.world.level.block.entity.TheEndGatewayBlockEntity;
 import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
 import nl.rutgerkok.worldgeneratorapi.decoration.DecorationArea;
 
 class DecorationAreaImpl implements DecorationArea {
@@ -275,6 +283,11 @@ public int getCenterZ() {
         return chunkPos.getMinBlockZ();
     }
 
+    @Override
+    public int getHighestBlockYAt(int x, int z) {
+        return this.region.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z);
+    }
+
     @Override
     public void setBlock(int x, int y, int z, Material material) {
         setBlockData(x, y, z, material.createBlockData());
@@ -304,4 +317,30 @@ public void setBlockState(int x, int y, int z, BlockState blockState) {
         }
     }
 
-}
+    @Override
+    public <T extends Entity> T spawnEntity(Class<T> entityClass, double x, double y, double z)
+            throws IllegalArgumentException {
+        // Inspired on
+        // https://github.com/PaperMC/Paper/blob/c4c6e26c00665989d3c1c82fb115a8f7f8de659b/patches/server/0714-Add-Feature-Generation-API.patch
+        Objects.requireNonNull(entityClass, "entityClass");
+
+        CraftWorld world = this.region.getMinecraftWorld().getWorld();
+        net.minecraft.world.entity.Entity entity = world.createEntity(new Location(world, x, y, z), entityClass);
+        if (entity == null) {
+            throw new IllegalArgumentException("No entity for " + entityClass);
+        }
+        if (entity instanceof Mob) {
+            ((Mob) entity).finalizeSpawn(this.region, this.region
+                    .getCurrentDifficultyAt(entity.blockPosition()), MobSpawnType.COMMAND, (SpawnGroupData) null, null);
+        }
+
+        // SpawnReason is unused by WorldGenRegion
+        this.region.addEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM);
+
+        // Should be safe, see world.createEntity
+        @SuppressWarnings("unchecked")
+        T bukkitEntity = (T) entity.getBukkitEntity();
+        return bukkitEntity;
+    }
+
+}

worldgeneratorapi/src/main/java/nl/rutgerkok/worldgeneratorapi/decoration/DecorationArea.java

@@ -6,6 +6,8 @@
 import org.bukkit.block.Chest;
 import org.bukkit.block.Furnace;
 import org.bukkit.block.data.BlockData;
+import org.bukkit.entity.Creeper;
+import org.bukkit.entity.Entity;
 
 /**
  * Represents a square area of 32 x 32 blocks which should be populated. (So 2x2
@@ -131,6 +133,18 @@ public interface DecorationArea {
      */
     int getCenterZ();
 
+    /**
+     * Gets the highest non-empty coordinate at the given coordinates.
+     *
+     * @param x
+     *            The block x in the world.
+     * @param z
+     *            The block z in the world.
+     * @return The block y.
+     * @since 1.2
+     */
+    int getHighestBlockYAt(int x, int z);
+
     /**
      * Sets the material at the given position.
      *
@@ -182,4 +196,25 @@ public interface DecorationArea {
      * @since 0.3
      */
     void setBlockState(int x, int y, int z, BlockState blockState);
+
+    /**
+     * Spawns an entity in the world.
+     *
+     * @param <T>
+     *            Type of the entity.
+     * @param entityClass
+     *            Class of the entity, for example {@link Creeper}.class.
+     * @param x
+     *            Block x in the world.
+     * @param y
+     *            Block y in the world.
+     * @param z
+     *            Block z in the world.
+     * @return The entity, so that you can modify it further.
+     * @throws IllegalArgumentException
+     *             If spawning entities of this entity type is not possible.
+     * @since 1.2
+     */
+    <T extends Entity> T spawnEntity(Class<T> entityClass, double x, double y, double z)
+            throws IllegalArgumentException;
 }