Introduce CancellableClosureTask

before anyone picks a fight about the naming, take it up with shoghi... let's be consistently wrong at least

src/pocketmine/scheduler/CancellableClosureTask.php

@@ -0,0 +1,73 @@
+<?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\scheduler;
+
+use pocketmine\utils\Utils;
+
+/**
+ * This class permits scheduling a self-cancelling closure to run. This is useful for repeating tasks.
+ * The given closure must return a bool which indicates whether it should continue executing.
+ *
+ * Example usage:
+ *
+ * ```
+ * TaskScheduler->scheduleTask(new CancellableClosureTask(function(int $currentTick) : bool{
+ *     echo "HI on $currentTick\n";
+ *     $continue = false;
+ *     return $continue; //stop repeating
+ * });
+ * ```
+ *
+ * @see ClosureTask
+ */
+class CancellableClosureTask extends Task{
+	public const CONTINUE = true;
+	public const CANCEL = false;
+
+	/** @var \Closure */
+	private $closure;
+
+	/**
+	 * CancellableClosureTask constructor.
+	 *
+	 * The closure should follow the signature callback(int $currentTick) : bool. The return value will be used to
+	 * decide whether to continue repeating.
+	 *
+	 * @param \Closure $closure
+	 */
+	public function __construct(\Closure $closure){
+		Utils::validateCallableSignature(function(int $currentTick) : bool{ return false; }, $closure);
+		$this->closure = $closure;
+	}
+
+	public function getName() : string{
+		return Utils::getNiceClosureName($this->closure);
+	}
+
+	public function onRun(int $currentTick) : void{
+		if(!($this->closure)($currentTick)){
+			$this->getHandler()->cancel();
+		}
+	}
+}