From 7b21c85d3312a1ed431692988f99e8f8b2a4f273 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Sun, 24 Mar 2024 20:28:58 +0100
Subject: [PATCH 01/15] Add slot validation at inventory level Each inventory
 can provide any validator for their transaction

---
 src/inventory/ArmorInventory.php              |  9 +++-
 src/inventory/SlotSafeInventory.php           | 33 ++++++++++++++
 .../transaction/action/SlotChangeAction.php   | 13 ++++++
 .../validator/ArmorInventoryValidator.php     | 44 +++++++++++++++++++
 .../InventoryTransactionValidator.php         | 31 +++++++++++++
 5 files changed, 129 insertions(+), 1 deletion(-)
 create mode 100644 src/inventory/SlotSafeInventory.php
 create mode 100644 src/inventory/transaction/validator/ArmorInventoryValidator.php
 create mode 100644 src/inventory/transaction/validator/InventoryTransactionValidator.php

diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index dcb3c04cb2e..cf4988f6b0c 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -24,9 +24,10 @@
 namespace pocketmine\inventory;
 
 use pocketmine\entity\Living;
+use pocketmine\inventory\transaction\validator\ArmorInventoryValidator;
 use pocketmine\item\Item;
 
-class ArmorInventory extends SimpleInventory{
+class ArmorInventory extends SimpleInventory implements SlotSafeInventory{
 	public const SLOT_HEAD = 0;
 	public const SLOT_CHEST = 1;
 	public const SLOT_LEGS = 2;
@@ -73,4 +74,10 @@ public function setLeggings(Item $leggings) : void{
 	public function setBoots(Item $boots) : void{
 		$this->setItem(self::SLOT_FEET, $boots);
 	}
+
+	public static function getSlotValidators() : array{
+		return [
+			new ArmorInventoryValidator()
+		];
+	}
 }
diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
new file mode 100644
index 00000000000..897fad08b46
--- /dev/null
+++ b/src/inventory/SlotSafeInventory.php
@@ -0,0 +1,33 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory;
+
+use pocketmine\inventory\transaction\validator\InventoryTransactionValidator;
+
+interface SlotSafeInventory{
+	/**
+	 * @phpstan-return InventoryTransactionValidator[]
+	 */
+	public static function getSlotValidators() : array;
+}
diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index 453f0c4d228..8467e7b2577 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -24,9 +24,11 @@
 namespace pocketmine\inventory\transaction\action;
 
 use pocketmine\inventory\Inventory;
+use pocketmine\inventory\SlotSafeInventory;
 use pocketmine\inventory\transaction\InventoryTransaction;
 use pocketmine\inventory\transaction\TransactionValidationException;
 use pocketmine\item\Item;
+use pocketmine\item\VanillaItems;
 use pocketmine\player\Player;
 
 /**
@@ -74,6 +76,17 @@ public function validate(Player $source) : void{
 		if($this->targetItem->getCount() > $this->inventory->getMaxStackSize()){
 			throw new TransactionValidationException("Target item exceeds inventory max stack size");
 		}
+		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->equals(VanillaItems::AIR())){
+			$result = false;
+			foreach($this->inventory::getSlotValidators() as $validator){
+				if(($result = $validator->validate($this->inventory, $this->targetItem, $this->inventorySlot))){
+					break;
+				}
+			}
+			if(!$result){
+				throw new TransactionValidationException("Target item is not accepted by the inventory");
+			}
+		}
 	}
 
 	/**
diff --git a/src/inventory/transaction/validator/ArmorInventoryValidator.php b/src/inventory/transaction/validator/ArmorInventoryValidator.php
new file mode 100644
index 00000000000..41fccac423f
--- /dev/null
+++ b/src/inventory/transaction/validator/ArmorInventoryValidator.php
@@ -0,0 +1,44 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory\transaction\validator;
+
+use pocketmine\block\BlockTypeIds;
+use pocketmine\block\MobHead;
+use pocketmine\inventory\ArmorInventory;
+use pocketmine\inventory\Inventory;
+use pocketmine\item\Armor;
+use pocketmine\item\Item;
+use pocketmine\item\ItemBlock;
+
+class ArmorInventoryValidator implements InventoryTransactionValidator{
+	public function validate(Inventory $inventory, Item $item, int $slot) : bool{
+		return $inventory instanceof ArmorInventory && (
+				($item instanceof Armor && $item->getArmorSlot() === $slot) ||
+				($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
+						$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||
+						$item->getBlock() instanceof MobHead
+					))
+			);
+	}
+}
diff --git a/src/inventory/transaction/validator/InventoryTransactionValidator.php b/src/inventory/transaction/validator/InventoryTransactionValidator.php
new file mode 100644
index 00000000000..e3923caf004
--- /dev/null
+++ b/src/inventory/transaction/validator/InventoryTransactionValidator.php
@@ -0,0 +1,31 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory\transaction\validator;
+
+use pocketmine\inventory\Inventory;
+use pocketmine\item\Item;
+
+interface InventoryTransactionValidator{
+	public function validate(Inventory $inventory, Item $item, int $slot) : bool;
+}

From 388a7699fb7a94ef0c765e8c11f3de8bf189ecfd Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Sun, 24 Mar 2024 20:49:54 +0100
Subject: [PATCH 02/15] add some docs

---
 src/inventory/SlotSafeInventory.php                  | 12 ++++++++++++
 .../validator/InventoryTransactionValidator.php      | 10 ++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index 897fad08b46..c1d5989c920 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -25,8 +25,20 @@
 
 use pocketmine\inventory\transaction\validator\InventoryTransactionValidator;
 
+/**
+ * A "slot safe inventory" is an inventory that has a set of rules that determine whether or not an item can be placed in a
+ * particular slot. This ensures that the inventory's internal state is always valid and consistent.
+ */
 interface SlotSafeInventory{
 	/**
+	 * Return a list of validators that will be used to determine whether or not an item can be placed in a particular slot.
+	 * All validators need to return true for the transaction to be allowed.
+	 * If one of the validators returns false, the transaction will be cancelled.
+	 *
+	 * There is no guarantee that the validators will be called in any particular order. All validators need to be stateless
+	 * and not depend on the order in which they are called.
+	 *
+	 * @return InventoryTransactionValidator[]
 	 * @phpstan-return InventoryTransactionValidator[]
 	 */
 	public static function getSlotValidators() : array;
diff --git a/src/inventory/transaction/validator/InventoryTransactionValidator.php b/src/inventory/transaction/validator/InventoryTransactionValidator.php
index e3923caf004..afc6e976c99 100644
--- a/src/inventory/transaction/validator/InventoryTransactionValidator.php
+++ b/src/inventory/transaction/validator/InventoryTransactionValidator.php
@@ -24,8 +24,18 @@
 namespace pocketmine\inventory\transaction\validator;
 
 use pocketmine\inventory\Inventory;
+use pocketmine\inventory\SlotSafeInventory;
 use pocketmine\item\Item;
 
+/**
+ * This interface is used to validate the transactions of a "safe" inventory. {@see SlotSafeInventory}
+ *
+ * In this way, each inventory can determine whether or not an item has the right to be placed in a particular slot.
+ */
 interface InventoryTransactionValidator{
+	/**
+	 * @return bool Return true, if the item CAN be placed in the given slot of the given inventory.
+	 * Otherwise, return false and the transaction will be cancelled.
+	 */
 	public function validate(Inventory $inventory, Item $item, int $slot) : bool;
 }

From 69e4db604f64dfb3f4d6987b3a9008525927d385 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Sun, 24 Mar 2024 21:07:53 +0100
Subject: [PATCH 03/15] Use an object set for the validators instead of an
 array

---
 src/inventory/ArmorInventory.php         |  9 ++---
 src/inventory/SlotSafeInventory.php      | 14 ++++----
 src/inventory/SlotSafeInventoryTrait.php | 45 ++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 11 deletions(-)
 create mode 100644 src/inventory/SlotSafeInventoryTrait.php

diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index cf4988f6b0c..d461092ab3c 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -26,8 +26,11 @@
 use pocketmine\entity\Living;
 use pocketmine\inventory\transaction\validator\ArmorInventoryValidator;
 use pocketmine\item\Item;
+use pocketmine\utils\ObjectSet;
 
 class ArmorInventory extends SimpleInventory implements SlotSafeInventory{
+	use SlotSafeInventoryTrait;
+
 	public const SLOT_HEAD = 0;
 	public const SLOT_CHEST = 1;
 	public const SLOT_LEGS = 2;
@@ -75,9 +78,7 @@ public function setBoots(Item $boots) : void{
 		$this->setItem(self::SLOT_FEET, $boots);
 	}
 
-	public static function getSlotValidators() : array{
-		return [
-			new ArmorInventoryValidator()
-		];
+	protected static function initSlotValidators(ObjectSet $validators) : void{
+		$validators->add(new ArmorInventoryValidator());
 	}
 }
diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index c1d5989c920..913517aedb7 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -24,22 +24,22 @@
 namespace pocketmine\inventory;
 
 use pocketmine\inventory\transaction\validator\InventoryTransactionValidator;
+use pocketmine\utils\ObjectSet;
 
 /**
- * A "slot safe inventory" is an inventory that has a set of rules that determine whether or not an item can be placed in a
+ * A "slot safe inventory" is an inventory that has a set of rules that determine whether an item can be placed in a
  * particular slot. This ensures that the inventory's internal state is always valid and consistent.
  */
 interface SlotSafeInventory{
 	/**
-	 * Return a list of validators that will be used to determine whether or not an item can be placed in a particular slot.
+	 * Return a set of validators that will be used to determine whether an item can be placed in a particular slot.
 	 * All validators need to return true for the transaction to be allowed.
 	 * If one of the validators returns false, the transaction will be cancelled.
 	 *
-	 * There is no guarantee that the validators will be called in any particular order. All validators need to be stateless
-	 * and not depend on the order in which they are called.
+	 * There is no guarantee that the validators will be called in any particular order.
+	 * All validators need to be stateless and not depend on the order in which they are called.
 	 *
-	 * @return InventoryTransactionValidator[]
-	 * @phpstan-return InventoryTransactionValidator[]
+	 * @phpstan-return ObjectSet<InventoryTransactionValidator>
 	 */
-	public static function getSlotValidators() : array;
+	public static function getSlotValidators() : ObjectSet;
 }
diff --git a/src/inventory/SlotSafeInventoryTrait.php b/src/inventory/SlotSafeInventoryTrait.php
new file mode 100644
index 00000000000..972c0ed47b7
--- /dev/null
+++ b/src/inventory/SlotSafeInventoryTrait.php
@@ -0,0 +1,45 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory;
+
+use pocketmine\utils\ObjectSet;
+
+trait SlotSafeInventoryTrait{
+	private static ObjectSet $validators;
+
+	/**
+	 * Initialize the set of validators.
+	 * Put here all the internal validators of the inventory.
+	 */
+	abstract protected static function initSlotValidators(ObjectSet $validators) : void;
+
+	public static function getSlotValidators() : ObjectSet {
+		if(!isset(self::$validators)){
+			self::$validators = new ObjectSet();
+			self::initSlotValidators(self::$validators);
+		}
+
+		return self::$validators;
+	}
+}

From 62f3e47eedf08305858f133c78a66e7450bea076 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Mon, 25 Mar 2024 17:47:22 +0100
Subject: [PATCH 04/15] use Closure and add SlotSafeInventory into
 BaseInventory by default

---
 src/inventory/ArmorInventory.php              | 22 +++++----
 src/inventory/BaseInventory.php               | 12 ++++-
 src/inventory/SlotSafeInventory.php           | 11 ++---
 src/inventory/SlotSafeInventoryTrait.php      | 45 -------------------
 .../validator/ArmorInventoryValidator.php     | 44 ------------------
 .../InventoryTransactionValidator.php         | 41 -----------------
 6 files changed, 30 insertions(+), 145 deletions(-)
 delete mode 100644 src/inventory/SlotSafeInventoryTrait.php
 delete mode 100644 src/inventory/transaction/validator/ArmorInventoryValidator.php
 delete mode 100644 src/inventory/transaction/validator/InventoryTransactionValidator.php

diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index d461092ab3c..cba341287be 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -23,14 +23,14 @@
 
 namespace pocketmine\inventory;
 
+use pocketmine\block\BlockTypeIds;
+use pocketmine\block\MobHead;
 use pocketmine\entity\Living;
-use pocketmine\inventory\transaction\validator\ArmorInventoryValidator;
+use pocketmine\item\Armor;
 use pocketmine\item\Item;
-use pocketmine\utils\ObjectSet;
-
-class ArmorInventory extends SimpleInventory implements SlotSafeInventory{
-	use SlotSafeInventoryTrait;
+use pocketmine\item\ItemBlock;
 
+class ArmorInventory extends SimpleInventory{
 	public const SLOT_HEAD = 0;
 	public const SLOT_CHEST = 1;
 	public const SLOT_LEGS = 2;
@@ -40,6 +40,14 @@ public function __construct(
 		protected Living $holder
 	){
 		parent::__construct(4);
+
+		$this->validators->add(function (Inventory $inventory, Item $item, int $slot) : bool {
+			return ($item instanceof Armor && $item->getArmorSlot() === $slot) ||
+				($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
+						$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||
+						$item->getBlock() instanceof MobHead
+					));
+		});
 	}
 
 	public function getHolder() : Living{
@@ -77,8 +85,4 @@ public function setLeggings(Item $leggings) : void{
 	public function setBoots(Item $boots) : void{
 		$this->setItem(self::SLOT_FEET, $boots);
 	}
-
-	protected static function initSlotValidators(ObjectSet $validators) : void{
-		$validators->add(new ArmorInventoryValidator());
-	}
 }
diff --git a/src/inventory/BaseInventory.php b/src/inventory/BaseInventory.php
index 254e44b1ea0..93b74ded2de 100644
--- a/src/inventory/BaseInventory.php
+++ b/src/inventory/BaseInventory.php
@@ -37,7 +37,7 @@
 /**
  * This class provides everything needed to implement an inventory, minus the underlying storage system.
  */
-abstract class BaseInventory implements Inventory{
+abstract class BaseInventory implements Inventory, SlotSafeInventory{
 	protected int $maxStackSize = Inventory::MAX_STACK;
 	/** @var Player[] */
 	protected array $viewers = [];
@@ -46,9 +46,15 @@ abstract class BaseInventory implements Inventory{
 	 * @phpstan-var ObjectSet<InventoryListener>
 	 */
 	protected ObjectSet $listeners;
+	/**
+	 * @var Closure[]|ObjectSet
+	 * @phpstan-var ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool>
+	 */
+	protected ObjectSet $validators;
 
 	public function __construct(){
 		$this->listeners = new ObjectSet();
+		$this->validators = new ObjectSet();
 	}
 
 	public function getMaxStackSize() : int{
@@ -398,4 +404,8 @@ public function slotExists(int $slot) : bool{
 	public function getListeners() : ObjectSet{
 		return $this->listeners;
 	}
+
+	public function getSlotValidators() : ObjectSet{
+		return $this->validators;
+	}
 }
diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index 913517aedb7..ace9883eddc 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -23,7 +23,7 @@
 
 namespace pocketmine\inventory;
 
-use pocketmine\inventory\transaction\validator\InventoryTransactionValidator;
+use pocketmine\item\Item;
 use pocketmine\utils\ObjectSet;
 
 /**
@@ -33,13 +33,14 @@
 interface SlotSafeInventory{
 	/**
 	 * Return a set of validators that will be used to determine whether an item can be placed in a particular slot.
-	 * All validators need to return true for the transaction to be allowed.
-	 * If one of the validators returns false, the transaction will be cancelled.
+	 * One validator need to return true for the transaction to be allowed.
+	 * If all the validators returns false, the transaction will be cancelled.
 	 *
 	 * There is no guarantee that the validators will be called in any particular order.
 	 * All validators need to be stateless and not depend on the order in which they are called.
 	 *
-	 * @phpstan-return ObjectSet<InventoryTransactionValidator>
+	 * @return \Closure[]|ObjectSet
+	 * @phpstan-return ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool>
 	 */
-	public static function getSlotValidators() : ObjectSet;
+	public function getSlotValidators() : ObjectSet;
 }
diff --git a/src/inventory/SlotSafeInventoryTrait.php b/src/inventory/SlotSafeInventoryTrait.php
deleted file mode 100644
index 972c0ed47b7..00000000000
--- a/src/inventory/SlotSafeInventoryTrait.php
+++ /dev/null
@@ -1,45 +0,0 @@
-<?php
-
-/*
- *
- *  ____            _        _   __  __ _                  __  __ ____
- * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
- * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
- * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
- * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * @author PocketMine Team
- * @link http://www.pocketmine.net/
- *
- *
- */
-
-declare(strict_types=1);
-
-namespace pocketmine\inventory;
-
-use pocketmine\utils\ObjectSet;
-
-trait SlotSafeInventoryTrait{
-	private static ObjectSet $validators;
-
-	/**
-	 * Initialize the set of validators.
-	 * Put here all the internal validators of the inventory.
-	 */
-	abstract protected static function initSlotValidators(ObjectSet $validators) : void;
-
-	public static function getSlotValidators() : ObjectSet {
-		if(!isset(self::$validators)){
-			self::$validators = new ObjectSet();
-			self::initSlotValidators(self::$validators);
-		}
-
-		return self::$validators;
-	}
-}
diff --git a/src/inventory/transaction/validator/ArmorInventoryValidator.php b/src/inventory/transaction/validator/ArmorInventoryValidator.php
deleted file mode 100644
index 41fccac423f..00000000000
--- a/src/inventory/transaction/validator/ArmorInventoryValidator.php
+++ /dev/null
@@ -1,44 +0,0 @@
-<?php
-
-/*
- *
- *  ____            _        _   __  __ _                  __  __ ____
- * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
- * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
- * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
- * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * @author PocketMine Team
- * @link http://www.pocketmine.net/
- *
- *
- */
-
-declare(strict_types=1);
-
-namespace pocketmine\inventory\transaction\validator;
-
-use pocketmine\block\BlockTypeIds;
-use pocketmine\block\MobHead;
-use pocketmine\inventory\ArmorInventory;
-use pocketmine\inventory\Inventory;
-use pocketmine\item\Armor;
-use pocketmine\item\Item;
-use pocketmine\item\ItemBlock;
-
-class ArmorInventoryValidator implements InventoryTransactionValidator{
-	public function validate(Inventory $inventory, Item $item, int $slot) : bool{
-		return $inventory instanceof ArmorInventory && (
-				($item instanceof Armor && $item->getArmorSlot() === $slot) ||
-				($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
-						$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||
-						$item->getBlock() instanceof MobHead
-					))
-			);
-	}
-}
diff --git a/src/inventory/transaction/validator/InventoryTransactionValidator.php b/src/inventory/transaction/validator/InventoryTransactionValidator.php
deleted file mode 100644
index afc6e976c99..00000000000
--- a/src/inventory/transaction/validator/InventoryTransactionValidator.php
+++ /dev/null
@@ -1,41 +0,0 @@
-<?php
-
-/*
- *
- *  ____            _        _   __  __ _                  __  __ ____
- * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
- * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
- * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
- * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * @author PocketMine Team
- * @link http://www.pocketmine.net/
- *
- *
- */
-
-declare(strict_types=1);
-
-namespace pocketmine\inventory\transaction\validator;
-
-use pocketmine\inventory\Inventory;
-use pocketmine\inventory\SlotSafeInventory;
-use pocketmine\item\Item;
-
-/**
- * This interface is used to validate the transactions of a "safe" inventory. {@see SlotSafeInventory}
- *
- * In this way, each inventory can determine whether or not an item has the right to be placed in a particular slot.
- */
-interface InventoryTransactionValidator{
-	/**
-	 * @return bool Return true, if the item CAN be placed in the given slot of the given inventory.
-	 * Otherwise, return false and the transaction will be cancelled.
-	 */
-	public function validate(Inventory $inventory, Item $item, int $slot) : bool;
-}

From ca29bb599e3118f00b07ffc6ce2a06ddd9d89ea2 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Mon, 25 Mar 2024 18:11:35 +0100
Subject: [PATCH 05/15] All validators need to approve the transaction

---
 src/inventory/transaction/action/SlotChangeAction.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index 8467e7b2577..3d55eba48f4 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -77,9 +77,9 @@ public function validate(Player $source) : void{
 			throw new TransactionValidationException("Target item exceeds inventory max stack size");
 		}
 		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->equals(VanillaItems::AIR())){
-			$result = false;
-			foreach($this->inventory::getSlotValidators() as $validator){
-				if(($result = $validator->validate($this->inventory, $this->targetItem, $this->inventorySlot))){
+			$result = true;
+			foreach($this->inventory->getSlotValidators() as $validator){
+				if(($result = $validator($this->inventory, $this->targetItem, $this->inventorySlot))){
 					break;
 				}
 			}

From 4637a0092a19ee2315457f831cb993a7fabf0753 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Mon, 25 Mar 2024 18:13:03 +0100
Subject: [PATCH 06/15] use static closure

---
 src/inventory/ArmorInventory.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index cba341287be..073e299808c 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -41,7 +41,7 @@ public function __construct(
 	){
 		parent::__construct(4);
 
-		$this->validators->add(function (Inventory $inventory, Item $item, int $slot) : bool {
+		$this->validators->add(static function (Inventory $inventory, Item $item, int $slot) : bool {
 			return ($item instanceof Armor && $item->getArmorSlot() === $slot) ||
 				($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
 						$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||

From f3c85769a2278bb0c681d5df5fd7712225190329 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Mon, 25 Mar 2024 18:19:28 +0100
Subject: [PATCH 07/15] fix PHPstan

---
 src/inventory/ArmorInventory.php    | 2 +-
 src/inventory/BaseInventory.php     | 6 ++----
 src/inventory/SlotSafeInventory.php | 2 +-
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index 073e299808c..e1d3f598833 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -41,7 +41,7 @@ public function __construct(
 	){
 		parent::__construct(4);
 
-		$this->validators->add(static function (Inventory $inventory, Item $item, int $slot) : bool {
+		$this->validators->add(static function (Inventory $inventory, Item $item, int $slot) : bool{
 			return ($item instanceof Armor && $item->getArmorSlot() === $slot) ||
 				($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
 						$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||
diff --git a/src/inventory/BaseInventory.php b/src/inventory/BaseInventory.php
index 93b74ded2de..58201af7bb3 100644
--- a/src/inventory/BaseInventory.php
+++ b/src/inventory/BaseInventory.php
@@ -23,6 +23,7 @@
 
 namespace pocketmine\inventory;
 
+use Closure;
 use pocketmine\item\Item;
 use pocketmine\item\VanillaItems;
 use pocketmine\player\Player;
@@ -46,10 +47,7 @@ abstract class BaseInventory implements Inventory, SlotSafeInventory{
 	 * @phpstan-var ObjectSet<InventoryListener>
 	 */
 	protected ObjectSet $listeners;
-	/**
-	 * @var Closure[]|ObjectSet
-	 * @phpstan-var ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool>
-	 */
+	/** @phpstan-var ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool> */
 	protected ObjectSet $validators;
 
 	public function __construct(){
diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index ace9883eddc..009f8aa52ec 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -23,6 +23,7 @@
 
 namespace pocketmine\inventory;
 
+use Closure;
 use pocketmine\item\Item;
 use pocketmine\utils\ObjectSet;
 
@@ -39,7 +40,6 @@ interface SlotSafeInventory{
 	 * There is no guarantee that the validators will be called in any particular order.
 	 * All validators need to be stateless and not depend on the order in which they are called.
 	 *
-	 * @return \Closure[]|ObjectSet
 	 * @phpstan-return ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool>
 	 */
 	public function getSlotValidators() : ObjectSet;

From b1b51b45ca7c3ee5b7180c66e3bffc18033c7181 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Fri, 29 Mar 2024 21:25:49 +0100
Subject: [PATCH 08/15] Many changes

---
 src/block/BlockTypeTags.php                           | 1 +
 src/inventory/ArmorInventory.php                      | 3 +--
 src/inventory/SlotSafeInventory.php                   | 9 ++++-----
 src/inventory/transaction/action/SlotChangeAction.php | 3 +--
 4 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/src/block/BlockTypeTags.php b/src/block/BlockTypeTags.php
index 19a4825d965..0aabab609a4 100644
--- a/src/block/BlockTypeTags.php
+++ b/src/block/BlockTypeTags.php
@@ -31,4 +31,5 @@ final class BlockTypeTags{
 	public const SAND = self::PREFIX . "sand";
 	public const POTTABLE_PLANTS = self::PREFIX . "pottable";
 	public const FIRE = self::PREFIX . "fire";
+	public const MOB_HEAD = self::PREFIX . "mob_head";
 }
diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index e1d3f598833..f9e935b0191 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -24,7 +24,6 @@
 namespace pocketmine\inventory;
 
 use pocketmine\block\BlockTypeIds;
-use pocketmine\block\MobHead;
 use pocketmine\entity\Living;
 use pocketmine\item\Armor;
 use pocketmine\item\Item;
@@ -45,7 +44,7 @@ public function __construct(
 			return ($item instanceof Armor && $item->getArmorSlot() === $slot) ||
 				($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
 						$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||
-						$item->getBlock() instanceof MobHead
+						$item->getBlock()->getTypeId() === BlockTypeIds::MOB_HEAD
 					));
 		});
 	}
diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index 009f8aa52ec..62f3998c72d 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -28,17 +28,16 @@
 use pocketmine\utils\ObjectSet;
 
 /**
- * A "slot safe inventory" is an inventory that has a set of rules that determine whether an item can be placed in a
- * particular slot. This ensures that the inventory's internal state is always valid and consistent.
+ * A "slot safe inventory" has validators which may restrict items
+ * from being placed in particular slots of the inventory.
  */
 interface SlotSafeInventory{
 	/**
 	 * Return a set of validators that will be used to determine whether an item can be placed in a particular slot.
-	 * One validator need to return true for the transaction to be allowed.
-	 * If all the validators returns false, the transaction will be cancelled.
+	 * All validator need to return true for the transaction to be allowed.
+	 * If one of the validators returns false, the transaction will be cancelled.
 	 *
 	 * There is no guarantee that the validators will be called in any particular order.
-	 * All validators need to be stateless and not depend on the order in which they are called.
 	 *
 	 * @phpstan-return ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool>
 	 */
diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index 3d55eba48f4..3da1cf58d24 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -28,7 +28,6 @@
 use pocketmine\inventory\transaction\InventoryTransaction;
 use pocketmine\inventory\transaction\TransactionValidationException;
 use pocketmine\item\Item;
-use pocketmine\item\VanillaItems;
 use pocketmine\player\Player;
 
 /**
@@ -76,7 +75,7 @@ public function validate(Player $source) : void{
 		if($this->targetItem->getCount() > $this->inventory->getMaxStackSize()){
 			throw new TransactionValidationException("Target item exceeds inventory max stack size");
 		}
-		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->equals(VanillaItems::AIR())){
+		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->isNull()){
 			$result = true;
 			foreach($this->inventory->getSlotValidators() as $validator){
 				if(($result = $validator($this->inventory, $this->targetItem, $this->inventorySlot))){

From 80d2edb65c330723213e7a4638840f9f225590a5 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Fri, 29 Mar 2024 21:30:32 +0100
Subject: [PATCH 09/15] use @phpstan-type

---
 src/inventory/BaseInventory.php     | 5 +++--
 src/inventory/SlotSafeInventory.php | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/inventory/BaseInventory.php b/src/inventory/BaseInventory.php
index 58201af7bb3..5b3299bb1d7 100644
--- a/src/inventory/BaseInventory.php
+++ b/src/inventory/BaseInventory.php
@@ -23,7 +23,6 @@
 
 namespace pocketmine\inventory;
 
-use Closure;
 use pocketmine\item\Item;
 use pocketmine\item\VanillaItems;
 use pocketmine\player\Player;
@@ -37,6 +36,8 @@
 
 /**
  * This class provides everything needed to implement an inventory, minus the underlying storage system.
+ *
+ * @phpstan-import-type SlotValidators from SlotSafeInventory
  */
 abstract class BaseInventory implements Inventory, SlotSafeInventory{
 	protected int $maxStackSize = Inventory::MAX_STACK;
@@ -47,7 +48,7 @@ abstract class BaseInventory implements Inventory, SlotSafeInventory{
 	 * @phpstan-var ObjectSet<InventoryListener>
 	 */
 	protected ObjectSet $listeners;
-	/** @phpstan-var ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool> */
+	/** @phpstan-var SlotValidators */
 	protected ObjectSet $validators;
 
 	public function __construct(){
diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index 62f3998c72d..20732f6941c 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -23,13 +23,14 @@
 
 namespace pocketmine\inventory;
 
-use Closure;
 use pocketmine\item\Item;
 use pocketmine\utils\ObjectSet;
 
 /**
  * A "slot safe inventory" has validators which may restrict items
  * from being placed in particular slots of the inventory.
+ *
+ * @phpstan-type SlotValidators ObjectSet<\Closure(Inventory $inventory, Item $item, int $slot): bool>
  */
 interface SlotSafeInventory{
 	/**
@@ -39,7 +40,7 @@ interface SlotSafeInventory{
 	 *
 	 * There is no guarantee that the validators will be called in any particular order.
 	 *
-	 * @phpstan-return ObjectSet<Closure(Inventory $inventory, Item $item, int $slot): bool>
+	 * @phpstan-return SlotValidators
 	 */
 	public function getSlotValidators() : ObjectSet;
 }

From 6b061b63edbe8b9786ea9678c50ad3ca6f9d5638 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Fri, 29 Mar 2024 21:38:46 +0100
Subject: [PATCH 10/15] all validators must validate the transaction to be
 allowed

---
 src/inventory/transaction/action/SlotChangeAction.php | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index 3da1cf58d24..d1573a4a02b 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -76,15 +76,11 @@ public function validate(Player $source) : void{
 			throw new TransactionValidationException("Target item exceeds inventory max stack size");
 		}
 		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->isNull()){
-			$result = true;
 			foreach($this->inventory->getSlotValidators() as $validator){
-				if(($result = $validator($this->inventory, $this->targetItem, $this->inventorySlot))){
-					break;
+				if(!$validator($this->inventory, $this->targetItem, $this->inventorySlot)){
+					throw new TransactionValidationException("Target item is not accepted by the inventory");
 				}
 			}
-			if(!$result){
-				throw new TransactionValidationException("Target item is not accepted by the inventory");
-			}
 		}
 	}
 

From a87398dcc171246b2f85e54d3ef1d145473dbe26 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Fri, 29 Mar 2024 21:40:18 +0100
Subject: [PATCH 11/15] oops

---
 src/block/BlockTypeTags.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/block/BlockTypeTags.php b/src/block/BlockTypeTags.php
index 0aabab609a4..19a4825d965 100644
--- a/src/block/BlockTypeTags.php
+++ b/src/block/BlockTypeTags.php
@@ -31,5 +31,4 @@ final class BlockTypeTags{
 	public const SAND = self::PREFIX . "sand";
 	public const POTTABLE_PLANTS = self::PREFIX . "pottable";
 	public const FIRE = self::PREFIX . "fire";
-	public const MOB_HEAD = self::PREFIX . "mob_head";
 }

From ba1b6ea05bda6ae6baeee5d8330b5d0baf8679f8 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Mon, 1 Apr 2024 17:30:58 +0200
Subject: [PATCH 12/15] Apply suggestions from code review

Co-authored-by: Dylan T. <dktapps@pmmp.io>
---
 src/inventory/SlotSafeInventory.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index 20732f6941c..fbc04e0b038 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -34,8 +34,8 @@
  */
 interface SlotSafeInventory{
 	/**
-	 * Return a set of validators that will be used to determine whether an item can be placed in a particular slot.
-	 * All validator need to return true for the transaction to be allowed.
+	 * Returns a set of validators that will be used to determine whether an item can be placed in a particular slot.
+	 * All validators need to return true for the transaction to be allowed.
 	 * If one of the validators returns false, the transaction will be cancelled.
 	 *
 	 * There is no guarantee that the validators will be called in any particular order.

From 2c1ca33c9ebe0979f9e18858ee3e82e78a7e79fc Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Mon, 1 Apr 2024 17:39:38 +0200
Subject: [PATCH 13/15] catch TransactionValidationException

---
 src/inventory/transaction/action/SlotChangeAction.php | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index d1573a4a02b..4e238b40e7e 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -77,8 +77,12 @@ public function validate(Player $source) : void{
 		}
 		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->isNull()){
 			foreach($this->inventory->getSlotValidators() as $validator){
-				if(!$validator($this->inventory, $this->targetItem, $this->inventorySlot)){
-					throw new TransactionValidationException("Target item is not accepted by the inventory");
+				try{
+					if(!$validator($this->inventory, $this->targetItem, $this->inventorySlot)){
+						throw new TransactionValidationException("Target item is not accepted by the inventory");
+					}
+				}catch(TransactionValidationException $e){
+					throw new TransactionValidationException("Target item is not accepted by the inventory: " . $e->getMessage());
 				}
 			}
 		}

From 2d8449e9aaad1859673394f9aab0128c4860e1b1 Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Wed, 3 Apr 2024 21:45:24 +0200
Subject: [PATCH 14/15] Use of an interface instead of a wild Closure

---
 src/inventory/ArmorInventory.php              | 26 ++++++++---
 src/inventory/SlotSafeInventory.php           |  8 ++--
 .../transaction/action/SlotChangeAction.php   |  9 ++--
 .../validator/CallbackSlotValidator.php       | 44 +++++++++++++++++++
 .../action/validator/SlotValidator.php        | 38 ++++++++++++++++
 5 files changed, 108 insertions(+), 17 deletions(-)
 create mode 100644 src/inventory/transaction/action/validator/CallbackSlotValidator.php
 create mode 100644 src/inventory/transaction/action/validator/SlotValidator.php

diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index f9e935b0191..4bd6668b27e 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -25,6 +25,8 @@
 
 use pocketmine\block\BlockTypeIds;
 use pocketmine\entity\Living;
+use pocketmine\inventory\transaction\action\validator\CallbackSlotValidator;
+use pocketmine\inventory\transaction\TransactionValidationException;
 use pocketmine\item\Armor;
 use pocketmine\item\Item;
 use pocketmine\item\ItemBlock;
@@ -40,13 +42,7 @@ public function __construct(
 	){
 		parent::__construct(4);
 
-		$this->validators->add(static function (Inventory $inventory, Item $item, int $slot) : bool{
-			return ($item instanceof Armor && $item->getArmorSlot() === $slot) ||
-				($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
-						$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||
-						$item->getBlock()->getTypeId() === BlockTypeIds::MOB_HEAD
-					));
-		});
+		$this->validators->add(new CallbackSlotValidator($this->validate(...)));
 	}
 
 	public function getHolder() : Living{
@@ -84,4 +80,20 @@ public function setLeggings(Item $leggings) : void{
 	public function setBoots(Item $boots) : void{
 		$this->setItem(self::SLOT_FEET, $boots);
 	}
+
+	private function validate(Inventory $inventory, Item $item, int $slot) : null|TransactionValidationException{
+		if($item instanceof Armor && $item->getArmorSlot() === $slot){
+			if($item->getArmorSlot() !== $slot){
+				return new TransactionValidationException("Armor item in wrong slot");
+			}
+		}else{
+			if(!($slot === ArmorInventory::SLOT_HEAD && $item instanceof ItemBlock && (
+					$item->getBlock()->getTypeId() === BlockTypeIds::CARVED_PUMPKIN ||
+					$item->getBlock()->getTypeId() === BlockTypeIds::MOB_HEAD
+				))){
+				return new TransactionValidationException("Item not accepted in an armor slot");
+			}
+		}
+		return null;
+	}
 }
diff --git a/src/inventory/SlotSafeInventory.php b/src/inventory/SlotSafeInventory.php
index fbc04e0b038..b3c4b5a88d8 100644
--- a/src/inventory/SlotSafeInventory.php
+++ b/src/inventory/SlotSafeInventory.php
@@ -23,20 +23,20 @@
 
 namespace pocketmine\inventory;
 
-use pocketmine\item\Item;
+use pocketmine\inventory\transaction\action\validator\SlotValidator;
 use pocketmine\utils\ObjectSet;
 
 /**
  * A "slot safe inventory" has validators which may restrict items
  * from being placed in particular slots of the inventory.
  *
- * @phpstan-type SlotValidators ObjectSet<\Closure(Inventory $inventory, Item $item, int $slot): bool>
+ * @phpstan-type SlotValidators ObjectSet<SlotValidator>
  */
 interface SlotSafeInventory{
 	/**
 	 * Returns a set of validators that will be used to determine whether an item can be placed in a particular slot.
-	 * All validators need to return true for the transaction to be allowed.
-	 * If one of the validators returns false, the transaction will be cancelled.
+	 * All validators need to return null for the transaction to be allowed.
+	 * If one of the validators returns an exception, the transaction will be cancelled.
 	 *
 	 * There is no guarantee that the validators will be called in any particular order.
 	 *
diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index 4e238b40e7e..3a482e5d8b4 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -77,12 +77,9 @@ public function validate(Player $source) : void{
 		}
 		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->isNull()){
 			foreach($this->inventory->getSlotValidators() as $validator){
-				try{
-					if(!$validator($this->inventory, $this->targetItem, $this->inventorySlot)){
-						throw new TransactionValidationException("Target item is not accepted by the inventory");
-					}
-				}catch(TransactionValidationException $e){
-					throw new TransactionValidationException("Target item is not accepted by the inventory: " . $e->getMessage());
+				$ret = $validator->validate($this->inventory, $this->targetItem, $this->inventorySlot);
+				if($ret instanceof TransactionValidationException){
+					throw new TransactionValidationException("Target item is not accepted by the inventory slot: " . $ret->getMessage(), 0, $ret);
 				}
 			}
 		}
diff --git a/src/inventory/transaction/action/validator/CallbackSlotValidator.php b/src/inventory/transaction/action/validator/CallbackSlotValidator.php
new file mode 100644
index 00000000000..1670dc6232a
--- /dev/null
+++ b/src/inventory/transaction/action/validator/CallbackSlotValidator.php
@@ -0,0 +1,44 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory\transaction\action\validator;
+
+use pocketmine\inventory\Inventory;
+use pocketmine\inventory\transaction\TransactionValidationException;
+use pocketmine\item\Item;
+use pocketmine\utils\Utils;
+
+class CallbackSlotValidator implements SlotValidator{
+	/**
+	 * @phpstan-param \Closure(Inventory, Item, int) : ?TransactionValidationException $validate
+	 */
+	public function __construct(
+		private \Closure $validate
+	){
+		Utils::validateCallableSignature(function(Inventory $inventory, Item $item, int $slot) : ?TransactionValidationException{ return null; }, $validate);
+	}
+
+	public function validate(Inventory $inventory, Item $item, int $slot) : ?TransactionValidationException{
+		return ($this->validate)($inventory, $item, $slot);
+	}
+}
diff --git a/src/inventory/transaction/action/validator/SlotValidator.php b/src/inventory/transaction/action/validator/SlotValidator.php
new file mode 100644
index 00000000000..af2e779c25a
--- /dev/null
+++ b/src/inventory/transaction/action/validator/SlotValidator.php
@@ -0,0 +1,38 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory\transaction\action\validator;
+
+use pocketmine\inventory\Inventory;
+use pocketmine\inventory\transaction\TransactionValidationException;
+use pocketmine\item\Item;
+
+/**
+ * Validate a slot placement in an inventory.
+ */
+interface SlotValidator{
+	/**
+	 * Returns null if the slot placement is valid, or a TransactionValidationException if it is not.
+	 */
+	public function validate(Inventory $inventory, Item $item, int $slot) : ?TransactionValidationException;
+}

From 1d924c3657dc84cc3e468602d9c8a69e6429d2eb Mon Sep 17 00:00:00 2001
From: ShockedPlot7560 <no-reply@tchallon.fr>
Date: Thu, 4 Apr 2024 14:39:35 +0200
Subject: [PATCH 15/15] Apply suggestions from code review

Co-authored-by: ipad54 <63200545+ipad54@users.noreply.github.com>
---
 src/inventory/ArmorInventory.php                      | 2 +-
 src/inventory/transaction/action/SlotChangeAction.php | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/inventory/ArmorInventory.php b/src/inventory/ArmorInventory.php
index 4bd6668b27e..4d7ddd3e90c 100644
--- a/src/inventory/ArmorInventory.php
+++ b/src/inventory/ArmorInventory.php
@@ -81,7 +81,7 @@ public function setBoots(Item $boots) : void{
 		$this->setItem(self::SLOT_FEET, $boots);
 	}
 
-	private function validate(Inventory $inventory, Item $item, int $slot) : null|TransactionValidationException{
+	private function validate(Inventory $inventory, Item $item, int $slot) : ?TransactionValidationException{
 		if($item instanceof Armor && $item->getArmorSlot() === $slot){
 			if($item->getArmorSlot() !== $slot){
 				return new TransactionValidationException("Armor item in wrong slot");
diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index 3a482e5d8b4..9cfc544d847 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -78,7 +78,7 @@ public function validate(Player $source) : void{
 		if($this->inventory instanceof SlotSafeInventory && !$this->targetItem->isNull()){
 			foreach($this->inventory->getSlotValidators() as $validator){
 				$ret = $validator->validate($this->inventory, $this->targetItem, $this->inventorySlot);
-				if($ret instanceof TransactionValidationException){
+				if($ret !== null){
 					throw new TransactionValidationException("Target item is not accepted by the inventory slot: " . $ret->getMessage(), 0, $ret);
 				}
 			}