Added TransactionBuilderInventory for server-side inventory transaction generation

src/inventory/transaction/TransactionBuilderInventory.php

@@ -0,0 +1,106 @@
+<?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;
+
+use pocketmine\inventory\BaseInventory;
+use pocketmine\inventory\Inventory;
+use pocketmine\inventory\transaction\action\SlotChangeAction;
+use pocketmine\item\Item;
+use pocketmine\item\ItemFactory;
+
+/**
+ * This class facilitates generating SlotChangeActions to build an inventory transaction.
+ * It wraps around the inventory you want to modify under transaction, and generates a diff of changes.
+ * This allows you to use the normal Inventory API methods like addItem() and so on to build a transaction, without
+ * modifying the original inventory.
+ */
+final class TransactionBuilderInventory extends BaseInventory{
+
+	/**
+	 * @var \SplFixedArray|(Item|null)[]
+	 * @phpstan-var \SplFixedArray<Item|null>
+	 */
+	private \SplFixedArray $changedSlots;
+
+	public function __construct(
+		private Inventory $actualInventory
+	){
+		parent::__construct();
+		$this->changedSlots = new \SplFixedArray($this->actualInventory->getSize());
+	}
+
+	protected function internalSetContents(array $items) : void{
+		for($i = 0, $size = $this->getSize(); $i < $size; ++$i){
+			if(!isset($items[$i])){
+				$this->clear($i);
+			}else{
+				$this->setItem($i, $items[$i]);
+			}
+		}
+	}
+
+	protected function internalSetItem(int $index, Item $item) : void{
+		if(!$item->equalsExact($this->actualInventory->getItem($index))){
+			$this->changedSlots[$index] = $item->isNull() ? ItemFactory::air() : clone $item;
+		}
+	}
+
+	public function getSize() : int{
+		return $this->actualInventory->getSize();
+	}
+
+	public function getItem(int $index) : Item{
+		return $this->changedSlots[$index] !== null ? clone $this->changedSlots[$index] : $this->actualInventory->getItem($index);
+	}
+
+	public function getContents(bool $includeEmpty = false) : array{
+		$contents = $this->actualInventory->getContents($includeEmpty);
+		foreach($this->changedSlots as $index => $item){
+			if($item !== null){
+				if($includeEmpty || !$item->isNull()){
+					$contents[$index] = clone $item;
+				}else{
+					unset($contents[$index]);
+				}
+			}
+		}
+		return $contents;
+	}
+
+	/**
+	 * @return SlotChangeAction[]
+	 */
+	public function generateActions() : array{
+		$result = [];
+		foreach($this->changedSlots as $index => $newItem){
+			if($newItem !== null){
+				$oldItem = $this->actualInventory->getItem($index);
+				if(!$newItem->equalsExact($oldItem)){
+					$result[] = new SlotChangeAction($this->actualInventory, $index, $oldItem, $newItem);
+				}
+			}
+		}
+		return $result;
+	}
+}