Introduce a "block write-batch" concept (#2555)

Make use of writebatch to generate trees, doors and double plants safely

- Fixes #2441 
- Fixes #2548 
- Closes #2498

src/pocketmine/level/BlockWriteBatch.php

@@ -0,0 +1,133 @@
+<?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\level;
+
+use pocketmine\block\Block;
+use pocketmine\math\Vector3;
+use pocketmine\utils\Utils;
+
+class BlockWriteBatch{
+	/** @var Block[][][] */
+	private $blocks = [];
+
+	/** @var \Closure[] */
+	private $validators = [];
+
+	public function __construct(){
+		$this->addValidator(function(ChunkManager $world, int $x, int $y, int $z) : bool{
+			return $world->isInWorld($x, $y, $z);
+		});
+	}
+
+	/**
+	 * Adds a block to the batch at the given position.
+	 *
+	 * @param Vector3 $pos
+	 * @param Block   $state
+	 *
+	 * @return $this
+	 */
+	public function addBlock(Vector3 $pos, Block $state) : self{
+		return $this->addBlockAt($pos->getFloorX(), $pos->getFloorY(), $pos->getFloorZ(), $state);
+	}
+
+	/**
+	 * Adds a block to the batch at the given coordinates.
+	 *
+	 * @param int   $x
+	 * @param int   $y
+	 * @param int   $z
+	 * @param Block $state
+	 *
+	 * @return $this
+	 */
+	public function addBlockAt(int $x, int $y, int $z, Block $state) : self{
+		$this->blocks[$x][$y][$z] = $state;
+		return $this;
+	}
+
+	/**
+	 * Validates and attempts to apply the batch to the given world. If any part of the batch fails to validate, no
+	 * changes will be made to the world.
+	 *
+	 * @param ChunkManager $world
+	 *
+	 * @return bool if the application was successful
+	 */
+	public function apply(ChunkManager $world) : bool{
+		foreach($this->getBlocks() as [$x, $y, $z, $_]){
+			foreach($this->validators as $validator){
+				if(!$validator($world, $x, $y, $z)){
+					return false;
+				}
+			}
+		}
+		foreach($this->getBlocks() as [$x, $y, $z, $block]){
+			$world->setBlockAt($x, $y, $z, $block);
+		}
+		return true;
+	}
+
+	/**
+	 * @return \Generator|mixed[] [int $x, int $y, int $z, Block $block]
+	 */
+	public function getBlocks() : \Generator{
+		foreach($this->blocks as $x => $yLine){
+			foreach($yLine as $y => $zLine){
+				foreach($zLine as $z => $block){
+					yield [$x, $y, $z, $block];
+				}
+			}
+		}
+	}
+
+	/**
+	 * Add a validation predicate which will be used to validate every block.
+	 * The callable signature should be the same as the below dummy function.
+	 * @see BlockWriteBatch::dummyValidator()
+	 *
+	 * @param callable $validator
+	 */
+	public function addValidator(callable $validator) : void{
+		Utils::validateCallableSignature([$this, 'dummyValidator'], $validator);
+		$this->validators[] = $validator;
+	}
+
+	/**
+	 * Dummy function demonstrating the required closure signature for validators.
+	 * @see BlockWriteBatch::addValidator()
+	 *
+	 * @dummy
+	 *
+	 * @param ChunkManager $world
+	 * @param int          $x
+	 * @param int          $y
+	 * @param int          $z
+	 *
+	 * @return bool
+	 */
+	public function dummyValidator(ChunkManager $world, int $x, int $y, int $z) : bool{
+		return true;
+	}
+}