From 169856858c6d072c11feed68ff1354169a4d84cf Mon Sep 17 00:00:00 2001
From: Snownee <mjy523@126.com>
Date: Wed, 9 Dec 2020 20:04:57 +0800
Subject: [PATCH] Fix piston hitbox is directional (#453, #489)

---
 .../structureMovement/TranslatingContraption.java |  3 ++-
 .../piston/PistonContraption.java                 | 15 +++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/TranslatingContraption.java b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/TranslatingContraption.java
index 58d77be16..062be299c 100644
--- a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/TranslatingContraption.java
+++ b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/TranslatingContraption.java
@@ -1,5 +1,6 @@
 package com.simibubi.create.content.contraptions.components.structureMovement;
 
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -16,7 +17,7 @@ public abstract class TranslatingContraption extends Contraption {
 
 	public Set<BlockPos> getColliders(World world, Direction movementDirection) {
 		if (getBlocks() == null)
-			return null;
+			return Collections.EMPTY_SET;
 		if (cachedColliders == null || cachedColliderDirection != movementDirection) {
 			cachedColliders = new HashSet<>();
 			cachedColliderDirection = movementDirection;
diff --git a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/piston/PistonContraption.java b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/piston/PistonContraption.java
index 9c67056ee..33041f493 100644
--- a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/piston/PistonContraption.java
+++ b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/piston/PistonContraption.java
@@ -53,9 +53,14 @@ public class PistonContraption extends TranslatingContraption {
 	public boolean assemble(World world, BlockPos pos) {
 		if (!collectExtensions(world, pos, orientation))
 			return false;
+		int count = blocks.size();
 		if (!searchMovedStructure(world, anchor, retract ? orientation.getOpposite() : orientation))
 			return false;
-		bounds = bounds.union(pistonExtensionCollisionBox);
+		if (blocks.size() == count) { // no new blocks added
+			bounds = pistonExtensionCollisionBox;
+		} else {
+			bounds = bounds.union(pistonExtensionCollisionBox);
+		}
 		startMoving(world);
 		return true;
 	}
@@ -112,8 +117,10 @@ public class PistonContraption extends TranslatingContraption {
 		anchor = pos.offset(direction, initialExtensionProgress + 1);
 		extensionLength = extensionsInBack + extensionsInFront;
 		initialExtensionProgress = extensionsInFront;
-		pistonExtensionCollisionBox = new AxisAlignedBB(end.offset(direction, -extensionsInFront)
-			.subtract(anchor));
+		pistonExtensionCollisionBox = new AxisAlignedBB(
+				BlockPos.ZERO.offset(direction, -1),
+				BlockPos.ZERO.offset(direction, -extensionLength - 1)).expand(1,
+						1, 1);
 
 		if (extensionLength == 0)
 			return false;
@@ -124,7 +131,7 @@ public class PistonContraption extends TranslatingContraption {
 			BlockPos relPos = pole.pos.offset(direction, -extensionsInFront);
 			BlockPos localPos = relPos.subtract(anchor);
 			getBlocks().put(localPos, new BlockInfo(localPos, pole.state, null));
-			pistonExtensionCollisionBox = pistonExtensionCollisionBox.union(new AxisAlignedBB(localPos));
+			//pistonExtensionCollisionBox = pistonExtensionCollisionBox.union(new AxisAlignedBB(localPos));
 		}
 
 		return true;