From 393045d4f2595a4e0291cc62e99f2365289c1445 Mon Sep 17 00:00:00 2001
From: Glease <4586901+Glease@users.noreply.github.com>
Date: Mon, 19 Jul 2021 17:45:18 +0800
Subject: [PATCH] Add utility method for lazy initialized structure elements

---
 .../structure/LazyStructureElement.java       | 38 +++++++++++++++++++
 .../structure/StructureUtility.java           | 23 +++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java

diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java b/src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java
new file mode 100644
index 00000000..b8c1e4a7
--- /dev/null
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java
@@ -0,0 +1,38 @@
+package com.gtnewhorizon.structurelib.structure;
+
+import net.minecraft.item.ItemStack;
+import net.minecraft.world.World;
+
+import java.util.function.Function;
+
+class LazyStructureElement<T> implements IStructureElementDeferred<T> {
+	private Function<T, IStructureElement<T>> to;
+	private IStructureElement<T> elem;
+
+	public LazyStructureElement(Function<T, IStructureElement<T>> to) {
+		this.to = to;
+	}
+
+	private IStructureElement<T> get(T t) {
+		if (to != null) {
+			elem = to.apply(t);
+			to = null;
+		}
+		return elem;
+	}
+
+	@Override
+	public boolean check(T t, World world, int x, int y, int z) {
+		return get(t).check(t, world, x, y, z);
+	}
+
+	@Override
+	public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
+		return get(t).placeBlock(t, world, x, y, z, trigger);
+	}
+
+	@Override
+	public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
+		return get(t).spawnHint(t, world, x, y, z, trigger);
+	}
+}
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java b/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java
index c09943ad..de2fca0a 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java
@@ -787,6 +787,28 @@ public class StructureUtility {
 
 	//region defer
 
+	/**
+	 * Similar to defer, but caches the first returned element returned and won't call it again.
+	 * Initialization is not thread safe.
+	 */
+	public static <T> IStructureElementDeferred<T> lazy(Supplier<IStructureElement<T>> to) {
+		if (to == null) {
+			throw new IllegalArgumentException();
+		}
+		return new LazyStructureElement<>(t -> to.get());
+	}
+
+	/**
+	 * Similar to defer, but caches the first returned element returned and won't call it again.
+	 * Initialization is not thread safe.
+	 */
+	public static <T> IStructureElementDeferred<T> lazy(Function<T, IStructureElement<T>> to) {
+		if (to == null) {
+			throw new IllegalArgumentException();
+		}
+		return new LazyStructureElement<>(to);
+	}
+
 	public static <T> IStructureElementDeferred<T> defer(Supplier<IStructureElement<T>> to) {
 		if (to == null) {
 			throw new IllegalArgumentException();
@@ -1414,4 +1436,5 @@ public class StructureUtility {
 		}
 		return shape;
 	}
+
 }