Implemented an InventoryEventProcessor, fixes #1986 (#2176)

* Implemented InventoryEventProcessor, fixes #1986
Event processors can now be registered and unregistered at will. Entity inventory/armor change events are now handled by event processors instead of the inventories themselves, which allows enabling/disabling the calling of these events at will.
This now avoids stupid things happening when initializing inventory contents, since the callers for those events are now registered _after_ the contents are initialized.

src/pocketmine/entity/Human.php

@@ -30,6 +30,7 @@ use pocketmine\event\entity\EntityRegainHealthEvent;
 use pocketmine\event\player\PlayerExhaustEvent;
 use pocketmine\event\player\PlayerExperienceChangeEvent;
 use pocketmine\inventory\EnderChestInventory;
+use pocketmine\inventory\EntityInventoryEventProcessor;
 use pocketmine\inventory\InventoryHolder;
 use pocketmine\inventory\PlayerInventory;
 use pocketmine\item\Consumable;
@@ -570,6 +571,9 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 
 		$inventoryTag = $this->namedtag->getListTag("Inventory");
 		if($inventoryTag !== null){
+			$armorListener = $this->armorInventory->getEventProcessor();
+			$this->armorInventory->setEventProcessor(null);
+
 			/** @var CompoundTag $item */
 			foreach($inventoryTag as $i => $item){
 				$slot = $item->getByte("Slot");
@@ -581,6 +585,8 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 					$this->inventory->setItem($slot - 9, Item::nbtDeserialize($item));
 				}
 			}
+
+			$this->armorInventory->setEventProcessor($armorListener);
 		}
 
 		$enderChestInventoryTag = $this->namedtag->getListTag("EnderChestInventory");
@@ -593,6 +599,7 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 
 		$this->inventory->setHeldItemIndex($this->namedtag->getInt("SelectedInventorySlot", 0), false);
 
+		$this->inventory->setEventProcessor(new EntityInventoryEventProcessor($this));
 
 		$this->setFood((float) $this->namedtag->getInt("foodLevel", (int) $this->getFood(), true));
 		$this->setExhaustion($this->namedtag->getFloat("foodExhaustionLevel", $this->getExhaustion(), true));

src/pocketmine/entity/Living.php

@@ -31,6 +31,7 @@ use pocketmine\event\entity\EntityDeathEvent;
 use pocketmine\event\entity\EntityEffectAddEvent;
 use pocketmine\event\entity\EntityEffectRemoveEvent;
 use pocketmine\inventory\ArmorInventory;
+use pocketmine\inventory\ArmorInventoryEventProcessor;
 use pocketmine\item\Armor;
 use pocketmine\item\Consumable;
 use pocketmine\item\enchantment\Enchantment;
@@ -76,6 +77,8 @@ abstract class Living extends Entity implements Damageable{
 		parent::initEntity();
 
 		$this->armorInventory = new ArmorInventory($this);
+		//TODO: load/save armor inventory contents
+		$this->armorInventory->setEventProcessor(new ArmorInventoryEventProcessor($this));
 
 		$health = $this->getMaxHealth();
 

src/pocketmine/inventory/ArmorInventory.php

@@ -24,13 +24,11 @@ declare(strict_types=1);
 namespace pocketmine\inventory;
 
 use pocketmine\entity\Living;
-use pocketmine\event\entity\EntityArmorChangeEvent;
 use pocketmine\item\Item;
 use pocketmine\network\mcpe\protocol\InventoryContentPacket;
 use pocketmine\network\mcpe\protocol\InventorySlotPacket;
 use pocketmine\network\mcpe\protocol\MobArmorEquipmentPacket;
 use pocketmine\Player;
-use pocketmine\Server;
 
 class ArmorInventory extends BaseInventory{
 	public const SLOT_HEAD = 0;
@@ -90,15 +88,6 @@ class ArmorInventory extends BaseInventory{
 		return $this->setItem(self::SLOT_FEET, $boots);
 	}
 
-	protected function doSetItemEvents(int $index, Item $newItem) : ?Item{
-		Server::getInstance()->getPluginManager()->callEvent($ev = new EntityArmorChangeEvent($this->getHolder(), $this->getItem($index), $newItem, $index));
-		if($ev->isCancelled()){
-			return null;
-		}
-
-		return $ev->getNewItem();
-	}
-
 	public function sendSlot(int $index, $target) : void{
 		if($target instanceof Player){
 			$target = [$target];

src/pocketmine/inventory/ArmorInventoryEventProcessor.php

@@ -0,0 +1,47 @@
+<?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\entity\Entity;
+use pocketmine\event\entity\EntityArmorChangeEvent;
+use pocketmine\item\Item;
+use pocketmine\Server;
+
+class ArmorInventoryEventProcessor implements InventoryEventProcessor{
+	/** @var Entity */
+	private $entity;
+
+	public function __construct(Entity $entity){
+		$this->entity = $entity;
+	}
+
+	public function onSlotChange(Inventory $inventory, int $slot, Item $oldItem, Item $newItem) : ?Item{
+		Server::getInstance()->getPluginManager()->callEvent($ev = new EntityArmorChangeEvent($this->entity, $oldItem, $newItem, $slot));
+		if($ev->isCancelled()){
+			return null;
+		}
+
+		return $ev->getNewItem();
+	}
+}

src/pocketmine/inventory/BaseInventory.php

@@ -45,6 +45,8 @@ abstract class BaseInventory implements Inventory{
 	protected $slots = [];
 	/** @var Player[] */
 	protected $viewers = [];
+	/** @var InventoryEventProcessor */
+	protected $eventProcessor;
 
 	/**
 	 * @param Item[] $items
@@ -153,10 +155,6 @@ abstract class BaseInventory implements Inventory{
 		$this->clearAll();
 	}
 
-	protected function doSetItemEvents(int $index, Item $newItem) : ?Item{
-		return $newItem;
-	}
-
 	public function setItem(int $index, Item $item, bool $send = true) : bool{
 		if($item->isNull()){
 			$item = ItemFactory::get(Item::AIR, 0, 0);
@@ -164,14 +162,18 @@ abstract class BaseInventory implements Inventory{
 			$item = clone $item;
 		}
 
-		$newItem = $this->doSetItemEvents($index, $item);
-		if($newItem === null){
-			return false;
+		$oldItem = $this->getItem($index);
+		if($this->eventProcessor !== null){
+			$newItem = $this->eventProcessor->onSlotChange($this, $index, $oldItem, $item);
+			if($newItem === null){
+				return false;
+			}
+		}else{
+			$newItem = $item;
 		}
 
-		$old = $this->getItem($index);
 		$this->slots[$index] = $newItem->isNull() ? null : $newItem;
-		$this->onSlotChange($index, $old, $send);
+		$this->onSlotChange($index, $oldItem, $send);
 
 		return true;
 	}
@@ -471,4 +473,12 @@ abstract class BaseInventory implements Inventory{
 	public function slotExists(int $slot) : bool{
 		return $slot >= 0 and $slot < $this->slots->getSize();
 	}
+
+	public function getEventProcessor() : ?InventoryEventProcessor{
+		return $this->eventProcessor;
+	}
+
+	public function setEventProcessor(?InventoryEventProcessor $eventProcessor) : void{
+		$this->eventProcessor = $eventProcessor;
+	}
 }

src/pocketmine/inventory/EntityInventoryEventProcessor.php

@@ -28,28 +28,20 @@ use pocketmine\event\entity\EntityInventoryChangeEvent;
 use pocketmine\item\Item;
 use pocketmine\Server;
 
-abstract class EntityInventory extends BaseInventory{
+class EntityInventoryEventProcessor implements InventoryEventProcessor{
 	/** @var Entity */
-	protected $holder;
+	private $entity;
 
-	public function __construct(Entity $holder, array $items = [], int $size = null, string $title = null){
-		$this->holder = $holder;
-		parent::__construct($items, $size, $title);
+	public function __construct(Entity $entity){
+		$this->entity = $entity;
 	}
 
-	protected function doSetItemEvents(int $index, Item $newItem) : ?Item{
-		Server::getInstance()->getPluginManager()->callEvent($ev = new EntityInventoryChangeEvent($this->getHolder(), $this->getItem($index), $newItem, $index));
+	public function onSlotChange(Inventory $inventory, int $slot, Item $oldItem, Item $newItem) : ?Item{
+		Server::getInstance()->getPluginManager()->callEvent($ev = new EntityInventoryChangeEvent($this->entity, $oldItem, $newItem, $slot));
 		if($ev->isCancelled()){
 			return null;
 		}
 
 		return $ev->getNewItem();
 	}
-
-	/**
-	 * @return Entity
-	 */
-	public function getHolder(){
-		return $this->holder;
-	}
 }

src/pocketmine/inventory/FurnaceInventory.php

@@ -102,10 +102,4 @@ class FurnaceInventory extends ContainerInventory{
 	public function setSmelting(Item $item) : bool{
 		return $this->setItem(0, $item);
 	}
-
-	public function onSlotChange(int $index, Item $before, bool $send) : void{
-		parent::onSlotChange($index, $before, $send);
-
-		$this->getHolder()->scheduleUpdate();
-	}
 }

src/pocketmine/inventory/Inventory.php

@@ -247,4 +247,14 @@ interface Inventory{
 	 * @return bool
 	 */
 	public function slotExists(int $slot) : bool;
+
+	/**
+	 * @return null|InventoryEventProcessor
+	 */
+	public function getEventProcessor() : ?InventoryEventProcessor;
+
+	/**
+	 * @param null|InventoryEventProcessor $eventProcessor
+	 */
+	public function setEventProcessor(?InventoryEventProcessor $eventProcessor) : void;
 }

src/pocketmine/inventory/InventoryEventProcessor.php

@@ -0,0 +1,48 @@
+<?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\item\Item;
+
+/**
+ * This interface can be used to listen for events on a specific Inventory.
+ *
+ * If you want to listen to changes on an inventory, create a class implementing this interface and implement its
+ * methods, then register it onto the inventory or inventories that you want to receive events for.
+ */
+interface InventoryEventProcessor{
+
+	/**
+	 * Called prior to a slot in the given inventory changing. This is called by inventories that this listener is
+	 * attached to.
+	 *
+	 * @param Inventory $inventory
+	 * @param int       $slot
+	 * @param Item      $oldItem
+	 * @param Item      $newItem
+	 *
+	 * @return Item|null that should be used in place of $newItem, or null if the slot change should not proceed.
+	 */
+	public function onSlotChange(Inventory $inventory, int $slot, Item $oldItem, Item $newItem) : ?Item;
+}

src/pocketmine/inventory/PlayerInventory.php

@@ -31,7 +31,7 @@ use pocketmine\network\mcpe\protocol\MobEquipmentPacket;
 use pocketmine\network\mcpe\protocol\types\ContainerIds;
 use pocketmine\Player;
 
-class PlayerInventory extends EntityInventory{
+class PlayerInventory extends BaseInventory{
 
 	/** @var Human */
 	protected $holder;
@@ -43,7 +43,8 @@ class PlayerInventory extends EntityInventory{
 	 * @param Human $player
 	 */
 	public function __construct(Human $player){
-		parent::__construct($player);
+		$this->holder = $player;
+		parent::__construct();
 	}
 
 	public function getName() : string{
@@ -210,5 +211,4 @@ class PlayerInventory extends EntityInventory{
 	public function getHolder(){
 		return $this->holder;
 	}
-
 }

src/pocketmine/tile/Furnace.php

@@ -29,6 +29,8 @@ use pocketmine\event\inventory\FurnaceBurnEvent;
 use pocketmine\event\inventory\FurnaceSmeltEvent;
 use pocketmine\inventory\FurnaceInventory;
 use pocketmine\inventory\FurnaceRecipe;
+use pocketmine\inventory\Inventory;
+use pocketmine\inventory\InventoryEventProcessor;
 use pocketmine\inventory\InventoryHolder;
 use pocketmine\item\Item;
 use pocketmine\item\ItemFactory;
@@ -79,6 +81,20 @@ class Furnace extends Spawnable implements InventoryHolder, Container, Nameable{
 
 		$this->inventory = new FurnaceInventory($this);
 		$this->loadItems($nbt);
+	
+		$this->inventory->setEventProcessor(new class($this) implements InventoryEventProcessor{
+			/** @var Furnace */
+			private $furnace;
+
+			public function __construct(Furnace $furnace){
+				$this->furnace = $furnace;
+			}
+
+			public function onSlotChange(Inventory $inventory, int $slot, Item $oldItem, Item $newItem) : ?Item{
+				$this->furnace->scheduleUpdate();
+				return $newItem;
+			}
+		});
 	}
 
 	protected function writeSaveData(CompoundTag $nbt) : void{