Introduce Item Lock API mainly for Client-Side inventory action prevention

src/inventory/transaction/InventoryTransaction.php

@@ -25,12 +25,16 @@
 
 use pocketmine\event\inventory\InventoryTransactionEvent;
 use pocketmine\inventory\Inventory;
+use pocketmine\inventory\PlayerCursorInventory;
+use pocketmine\inventory\PlayerInventory;
 use pocketmine\inventory\transaction\action\InventoryAction;
 use pocketmine\inventory\transaction\action\SlotChangeAction;
 use pocketmine\item\Item;
+use pocketmine\item\ItemLockMode;
 use pocketmine\player\Player;
 use pocketmine\utils\Utils;
 use function array_keys;
+use function array_push;
 use function array_values;
 use function assert;
 use function count;
@@ -135,30 +139,14 @@ private function shuffleActions() : void{
 	/**
 	 * @param Item[] $needItems
 	 * @param Item[] $haveItems
+	 * @phpstan-param list<Item> $needItems
+	 * @phpstan-param list<Item> $haveItems
 	 * @phpstan-param-out list<Item> $needItems
 	 * @phpstan-param-out list<Item> $haveItems
 	 *
 	 * @throws TransactionValidationException
 	 */
-	protected function matchItems(array &$needItems, array &$haveItems) : void{
-		$needItems = [];
-		$haveItems = [];
-		foreach($this->actions as $key => $action){
-			if(!$action->getTargetItem()->isNull()){
-				$needItems[] = $action->getTargetItem();
-			}
-
-			try{
-				$action->validate($this->source);
-			}catch(TransactionValidationException $e){
-				throw new TransactionValidationException(get_class($action) . "#" . spl_object_id($action) . ": " . $e->getMessage(), 0, $e);
-			}
-
-			if(!$action->getSourceItem()->isNull()){
-				$haveItems[] = $action->getSourceItem();
-			}
-		}
-
+	public function computeDiff(array &$needItems, array &$haveItems) : void{
 		foreach($needItems as $i => $needItem){
 			foreach($haveItems as $j => $haveItem){
 				if($needItem->canStackWith($haveItem)){
@@ -179,6 +167,62 @@ protected function matchItems(array &$needItems, array &$haveItems) : void{
 		$haveItems = array_values($haveItems);
 	}
 
+	/**
+	 * @param Item[] $needItems
+	 * @param Item[] $haveItems
+	 * @phpstan-param-out list<Item> $needItems
+	 * @phpstan-param-out list<Item> $haveItems
+	 *
+	 * @throws TransactionValidationException
+	 */
+	protected function matchItems(array &$needItems, array &$haveItems) : void{
+		$needItems = [];
+		$haveItems = [];
+
+		$boundLockedNeedItems = [];
+		$boundLockedHaveItems = [];
+		foreach($this->actions as $key => $action){
+			$checkBoundLockedItem = $action instanceof SlotChangeAction &&
+				(($inventory = $action->getInventory()) instanceof PlayerInventory || $inventory instanceof PlayerCursorInventory);
+			$targetItem = $action->getTargetItem();
+			if(!$targetItem->isNull()){
+				if($checkBoundLockedItem && $targetItem->getLockMode() === ItemLockMode::INVENTORY){
+					$boundLockedNeedItems[] = $targetItem;
+				}else{
+					$needItems[] = $targetItem;
+				}
+			}
+
+			try{
+				$action->validate($this->source);
+			}catch(TransactionValidationException $e){
+				throw new TransactionValidationException(get_class($action) . "#" . spl_object_id($action) . ": " . $e->getMessage(), 0, $e);
+			}
+
+			$sourceItem = $action->getSourceItem();
+			if(!$sourceItem->isNull()){
+				if($checkBoundLockedItem && $sourceItem->getLockMode() === ItemLockMode::INVENTORY){
+					$boundLockedHaveItems[] = $sourceItem;
+				}else{
+					$haveItems[] = $sourceItem;
+				}
+			}
+		}
+
+		$this->computeDiff($needItems, $haveItems);
+
+		if(count($boundLockedNeedItems) > 0 || count($boundLockedHaveItems) > 0){
+			//first, try to balance bound locked items with items already bound to the player's inventory
+			$this->computeDiff($boundLockedNeedItems, $boundLockedHaveItems);
+			//then, check if there are unbound locked items the player moved into its inventory
+			//this allows moving locked items from e.g. a chest -> player's inventory, but not the other way round
+			$this->computeDiff($boundLockedNeedItems, $haveItems);
+
+			array_push($needItems, ...$boundLockedNeedItems);
+			array_push($haveItems, ...$boundLockedHaveItems);
+		}
+	}
+
 	/**
 	 * Iterates over SlotChangeActions in this transaction and compacts any which refer to the same slot in the same
 	 * inventory so they can be correctly handled.

src/inventory/transaction/action/DropItemAction.php

@@ -45,6 +45,9 @@ public function validate(Player $source) : void{
 		if($this->targetItem->getCount() > $this->targetItem->getMaxStackSize()){
 			throw new TransactionValidationException("Target item exceeds item type max stack size");
 		}
+		if($this->targetItem->getLockMode() !== null){
+			throw new TransactionValidationException("Target item is locked in inventory or slot");
+		}
 	}
 
 	public function onPreExecute(Player $source) : bool{

src/inventory/transaction/action/SlotChangeAction.php

@@ -27,6 +27,7 @@
 use pocketmine\inventory\SlotValidatedInventory;
 use pocketmine\inventory\transaction\TransactionValidationException;
 use pocketmine\item\Item;
+use pocketmine\item\ItemLockMode;
 use pocketmine\player\Player;
 
 /**
@@ -74,6 +75,12 @@ 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->targetItem->getLockMode() === ItemLockMode::SLOT){
+			throw new TransactionValidationException("Target item is locked in slot");
+		}
+		if($this->sourceItem->getLockMode() === ItemLockMode::SLOT){
+			throw new TransactionValidationException("Source item is locked in slot");
+		}
 		if($this->inventory instanceof SlotValidatedInventory && !$this->targetItem->isNull()){
 			foreach($this->inventory->getSlotValidators() as $validator){
 				$ret = $validator->validate($this->inventory, $this->targetItem, $this->inventorySlot);

src/item/Item.php

@@ -66,12 +66,16 @@ class Item implements \JsonSerializable{
 
 	public const TAG_DISPLAY = "display";
 	public const TAG_BLOCK_ENTITY_TAG = "BlockEntityTag";
+	public const TAG_ITEM_LOCK = "minecraft:item_lock";
 
 	public const TAG_DISPLAY_NAME = "Name";
 	public const TAG_DISPLAY_LORE = "Lore";
 
 	public const TAG_KEEP_ON_DEATH = "minecraft:keep_on_death";
 
+	public const VALUE_ITEM_LOCK_IN_SLOT = 1;
+	public const VALUE_ITEM_LOCK_IN_INVENTORY = 2;
+
 	private const TAG_CAN_PLACE_ON = "CanPlaceOn"; //TAG_List<TAG_String>
 	private const TAG_CAN_DESTROY = "CanDestroy"; //TAG_List<TAG_String>
 
@@ -100,6 +104,8 @@ class Item implements \JsonSerializable{
 
 	protected bool $keepOnDeath = false;
 
+	protected ?ItemLockMode $lockMode = null;
+
 	/**
 	 * Constructs a new Item type. This constructor should ONLY be used when constructing a new item TYPE to register
 	 * into the index.
@@ -227,6 +233,15 @@ public function setCanDestroy(array $canDestroy) : void{
 		}
 	}
 
+	public function getLockMode() : ?ItemLockMode{
+		return $this->lockMode;
+	}
+
+	public function setLockMode(?ItemLockMode $lockMode) : self{
+		$this->lockMode = $lockMode;
+		return $this;
+	}
+
 	/**
 	 * Returns whether players will retain this item on death. If a non-player dies it will be excluded from the drops.
 	 */
@@ -338,6 +353,12 @@ protected function deserializeCompoundTag(CompoundTag $tag) : void{
 		}
 
 		$this->keepOnDeath = $tag->getByte(self::TAG_KEEP_ON_DEATH, 0) !== 0;
+
+		$this->lockMode = match($tag->getByte(self::TAG_ITEM_LOCK, 0)){
+			self::VALUE_ITEM_LOCK_IN_SLOT => ItemLockMode::SLOT,
+			self::VALUE_ITEM_LOCK_IN_INVENTORY => ItemLockMode::INVENTORY,
+			default => null
+		};
 	}
 
 	protected function serializeCompoundTag(CompoundTag $tag) : void{
@@ -406,6 +427,14 @@ protected function serializeCompoundTag(CompoundTag $tag) : void{
 		}else{
 			$tag->removeTag(self::TAG_KEEP_ON_DEATH);
 		}
+		if($this->lockMode !== null){
+			$tag->setByte(self::TAG_ITEM_LOCK, match($this->lockMode){
+				ItemLockMode::SLOT => self::VALUE_ITEM_LOCK_IN_SLOT,
+				ItemLockMode::INVENTORY => self::VALUE_ITEM_LOCK_IN_INVENTORY,
+			});
+		}else{
+			$tag->removeTag("minecraft:item_lock");
+		}
 	}
 
 	public function getCount() : int{

src/item/ItemLockMode.php

@@ -0,0 +1,29 @@
+<?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\item;
+
+enum ItemLockMode{
+	case SLOT;
+	case INVENTORY;
+}