add an option to optimize chunks in anvil importer

Author: GliczDev

importer-anvil/src/main/java/net/roxymc/slime/importer/anvil/ChunkUtils.java

@@ -0,0 +1,35 @@
+package net.roxymc.slime.importer.anvil;
+
+import net.kyori.adventure.nbt.ListBinaryTag;
+import net.roxymc.slime.world.block.entity.BlockEntity;
+import net.roxymc.slime.world.block.state.BlockStates;
+import net.roxymc.slime.world.chunk.Section;
+import net.roxymc.slime.world.entity.Entity;
+
+import java.util.Arrays;
+
+final class ChunkUtils {
+    private static final String PALETTE_TAG = "palette";
+    private static final String NAME_TAG = "Name";
+    private static final String BLOCK_AIR = "minecraft:air";
+
+    private ChunkUtils() {
+    }
+
+    static boolean isEmpty(Section[] sections, BlockEntity[] blockEntities, Entity[] entities) {
+        if (Arrays.stream(sections).anyMatch(section -> !isOnlyAir(section.blockStates()))) {
+            return false;
+        }
+
+        return blockEntities.length == 0 && entities.length == 0;
+    }
+
+    static boolean isOnlyAir(BlockStates blockStates) {
+        ListBinaryTag palette = blockStates.tag().getList(PALETTE_TAG);
+        if (palette.isEmpty() || palette.size() > 1) {
+            return palette.isEmpty();
+        }
+
+        return palette.getCompound(0).getString(NAME_TAG).equals(BLOCK_AIR);
+    }
+}

importer-anvil/src/main/java/net/roxymc/slime/importer/anvil/SlimeAnvilImporter.java

@@ -74,11 +74,13 @@ public class SlimeAnvilImporter implements SlimeImporter {
     private final SlimeLoader slimeLoader;
     private final Set<String> preservedWorldTags;
     private final Set<String> preservedChunkTags;
+    private final boolean optimizeChunks;
 
     private SlimeAnvilImporter(Builder builder) {
         this.slimeLoader = builder.slimeLoader;
         this.preservedWorldTags = builder.preservedWorldTags;
         this.preservedChunkTags = builder.preservedChunkTags;
+        this.optimizeChunks = builder.optimizeChunks;
     }
 
     public static Builder builder(SlimeLoader slimeLoader) {
@@ -191,10 +193,6 @@ private Chunk[] readChunks(File root, Map<ChunkPos, EntityChunk> entityChunks) t
                 })
                 .toArray(Section[]::new);
 
-        Heightmaps heightmaps = slimeLoader.deserializers().heightmaps().deserialize(
-                tag.getCompound(HEIGHTMAPS_TAG)
-        );
-
         BlockEntity[] blockEntities = tag.getList(BLOCK_ENTITIES_TAG, BinaryTagTypes.COMPOUND).stream()
                 .map(CompoundBinaryTag.class::cast)
                 .map(slimeLoader.deserializers().blockEntity()::deserialize)
@@ -203,6 +201,14 @@ private Chunk[] readChunks(File root, Map<ChunkPos, EntityChunk> entityChunks) t
         ChunkPos chunkPos = new ChunkPos(x, z);
         Entity[] entities = entityChunks.containsKey(chunkPos) ? entityChunks.get(chunkPos).entities() : EMPTY_ENTITIES;
 
+        if (optimizeChunks && ChunkUtils.isEmpty(sections, blockEntities, entities)) {
+            return null;
+        }
+
+        Heightmaps heightmaps = slimeLoader.deserializers().heightmaps().deserialize(
+                tag.getCompound(HEIGHTMAPS_TAG)
+        );
+
         CompoundBinaryTag customDataTag = readCustomData(tag, preservedChunkTags);
 
         return slimeLoader.deserializers().chunk().deserialize(
@@ -302,6 +308,7 @@ public static class Builder {
         private final SlimeLoader slimeLoader;
         private Set<String> preservedWorldTags = Collections.emptySet();
         private Set<String> preservedChunkTags = Collections.emptySet();
+        private boolean optimizeChunks;
 
         private Builder(SlimeLoader slimeLoader) {
             this.slimeLoader = nonNull(slimeLoader, "slimeLoader");
@@ -317,6 +324,11 @@ public Builder preserveChunkTags(String... tags) {
             return this;
         }
 
+        public Builder optimizeChunks(boolean optimizeChunks) {
+            this.optimizeChunks = optimizeChunks;
+            return this;
+        }
+
         public SlimeAnvilImporter build() {
             return new SlimeAnvilImporter(this);
         }