Add ability for Schematics to load chunks when applying

modules/schem/src/main/java/net/hollowcube/util/schem/Schematic.java

@@ -2,6 +2,8 @@
 
 import net.minestom.server.coordinate.Point;
 import net.minestom.server.coordinate.Vec;
+import net.minestom.server.instance.Chunk;
+import net.minestom.server.instance.Instance;
 import net.minestom.server.instance.batch.BatchOption;
 import net.minestom.server.instance.batch.RelativeBlockBatch;
 import net.minestom.server.instance.block.Block;
@@ -10,8 +12,10 @@
 import org.jetbrains.annotations.Nullable;
 
 import java.nio.ByteBuffer;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Map;
+import java.util.concurrent.CompletableFuture;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
 
@@ -50,6 +54,36 @@ public Point offset(Rotation rotation) {
         return rotatePos(offset, rotation);
     }
 
+    public @NotNull CompletableFuture<Void> applyToInstance(@NotNull Instance instance, @NotNull Point startPoint, boolean loadChunks, @NotNull Rotation rotation, @Nullable Function<Block, Block> blockModifier) {
+        RelativeBlockBatch batch = build(rotation, blockModifier);
+        if (loadChunks) {
+            Point min = startPoint.add(offset());
+            Point max = min.add(size());
+            int chunkXStart = min.chunkX();
+            int chunkXSize = max.chunkX() - min.chunkX() + 1;
+            int chunkZStart = min.chunkZ();
+            int chunkZSize = max.chunkZ() - min.chunkZ() + 1;
+            ArrayList<CompletableFuture<Chunk>> chunksToLoad = new ArrayList<>();
+            for (int i = chunkXStart; i < chunkXStart + chunkXSize; i++) {
+                for (int j = chunkZStart; j < chunkZStart + chunkZSize; j++) {
+                    chunksToLoad.add(instance.loadOptionalChunk(i, j));
+                }
+            }
+            return CompletableFuture.allOf(chunksToLoad.toArray(new CompletableFuture[0])).thenRun(() -> batch.apply(instance, startPoint, null)).thenRun(() -> {
+                for (int i = chunkXStart; i < chunkXStart + chunkXSize; i++) {
+                    for (int j = chunkZStart; j < chunkZStart + chunkZSize; j++) {
+                        Chunk chunk = instance.getChunk(i, j);
+                        if(chunk != null && chunk.isLoaded() && chunk.getViewers().isEmpty()) {
+                            instance.unloadChunk(chunk);
+                        }
+                    }
+                }
+            });
+        } else {
+            return CompletableFuture.runAsync(() -> batch.apply(instance, startPoint, null));
+        }
+    }
+
     /**
      * Convert the schematic into a {@link RelativeBlockBatch} which can be applied to an instance.
      * The schematic can be rotated around its {@link #offset()} before placement.

modules/schem/src/test/java/SchemPasterTest.java

@@ -0,0 +1,39 @@
+import net.hollowcube.util.schem.Rotation;
+import net.hollowcube.util.schem.Schematic;
+import net.hollowcube.util.schem.SchematicReader;
+import net.minestom.server.coordinate.Pos;
+import net.minestom.server.event.instance.InstanceChunkLoadEvent;
+import net.minestom.server.event.instance.InstanceChunkUnloadEvent;
+import net.minestom.server.instance.Instance;
+import net.minestom.server.test.Env;
+import net.minestom.server.test.EnvTest;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@EnvTest
+public class SchemPasterTest {
+
+    @Test
+    public void testSchemPaste(Env env) {
+        AtomicInteger chunksLoaded = new AtomicInteger();
+        AtomicInteger chunksUnloaded = new AtomicInteger();
+        Instance instance = env.createFlatInstance();
+        instance.eventNode().addListener(InstanceChunkLoadEvent.class, event -> chunksLoaded.getAndIncrement());
+        instance.eventNode().addListener(InstanceChunkUnloadEvent.class, event -> chunksUnloaded.getAndIncrement());
+        try {
+            Schematic big = SchematicReader.read(Path.of("src/test/resources/big.schem"));
+            CompletableFuture<Void> pasteProcess = big.applyToInstance(instance, new Pos(15, 40, 15), true, Rotation.NONE, null);
+            pasteProcess.join();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+        assertEquals(2, chunksLoaded.get());
+        assertEquals(chunksLoaded.get(), chunksUnloaded.get());
+    }
+}