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src/block/utils/AnimatedContainer.php

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+<?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\block\utils;
+
+interface AnimatedContainer{
+	/**
+	 * Do actions when the container block is opened by a player.
+	 * If you have a custom viewer counter (like ender chests), you should increment it here.
+	 */
+	public function onContainerOpen() : void;
+
+	/**
+	 * Do actions when the container block is closed by a player.
+	 * As above, you should decrement your custom viewer counter here, if you have one.
+	 */
+	public function onContainerClose() : void;
+}

src/block/utils/AnimatedContainerTrait.php

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+<?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\block\utils;
+
+use pocketmine\inventory\InventoryHolder;
+use pocketmine\world\Position;
+use pocketmine\world\sound\Sound;
+use function count;
+
+trait AnimatedContainerTrait{
+
+	protected function getContainerViewerCount() : int{
+		$position = $this->getPosition();
+		$tile = $position->getWorld()->getTile($position);
+		if($tile instanceof InventoryHolder){
+			return count($tile->getInventory()->getViewers());
+		}
+		return 0;
+	}
+
+	abstract protected function getContainerOpenSound() : Sound;
+
+	abstract protected function getContainerCloseSound() : Sound;
+
+	abstract protected function doContainerAnimation(Position $position, bool $isOpen) : void;
+
+	protected function playContainerSound(Position $position, bool $isOpen) : void{
+		$position->getWorld()->addSound($position->add(0.5, 0.5, 0.5), $isOpen ? $this->getContainerOpenSound() : $this->getContainerCloseSound());
+	}
+
+	abstract protected function getPosition() : Position;
+
+	protected function doContainerEffects(bool $isOpen) : void{
+		$position = $this->getPosition();
+		$this->doContainerAnimation($position, $isOpen);
+		$this->playContainerSound($position, $isOpen);
+	}
+
+	public function onContainerOpen() : void{
+		if($this->getContainerViewerCount() === 1){
+			$this->doContainerEffects(true);
+		}
+	}
+
+	public function onContainerClose() : void{
+		if($this->getContainerViewerCount() === 1){
+			$this->doContainerEffects(false);
+		}
+	}
+}