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/block/Door.php

@@ -25,6 +25,7 @@ namespace pocketmine\block;
 
 use pocketmine\block\utils\BlockDataValidator;
 use pocketmine\item\Item;
+use pocketmine\level\BlockWriteBatch;
 use pocketmine\level\sound\DoorSound;
 use pocketmine\math\AxisAlignedBB;
 use pocketmine\math\Bearing;
@@ -124,9 +125,10 @@ abstract class Door extends Transparent{
 			$topHalf = clone $this;
 			$topHalf->top = true;
 
-			parent::place($item, $blockReplace, $blockClicked, $face, $clickVector, $player);
-			$this->level->setBlock($blockUp, $topHalf); //Top
-			return true;
+			$write = new BlockWriteBatch();
+			$write->addBlock($blockReplace, $this)->addBlock($blockUp, $topHalf);
+
+			return $write->apply($this->level);
 		}
 
 		return false;

src/pocketmine/block/DoublePlant.php

@@ -24,6 +24,7 @@ declare(strict_types=1);
 namespace pocketmine\block;
 
 use pocketmine\item\Item;
+use pocketmine\level\BlockWriteBatch;
 use pocketmine\math\Facing;
 use pocketmine\math\Vector3;
 use pocketmine\Player;
@@ -49,12 +50,12 @@ class DoublePlant extends Flowable{
 	public function place(Item $item, Block $blockReplace, Block $blockClicked, int $face, Vector3 $clickVector, Player $player = null) : bool{
 		$id = $blockReplace->getSide(Facing::DOWN)->getId();
 		if(($id === Block::GRASS or $id === Block::DIRT) and $blockReplace->getSide(Facing::UP)->canBeReplaced()){
-			$this->getLevel()->setBlock($blockReplace, $this, false);
 			$top = clone $this;
 			$top->top = true;
-			$this->getLevel()->setBlock($blockReplace->getSide(Facing::UP), $top, false);
 
-			return true;
+			$write = new BlockWriteBatch();
+			$write->addBlock($blockReplace, $this)->addBlock($blockReplace->getSide(Facing::UP), $top);
+			return $write->apply($this->level);
 		}
 
 		return false;

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;
+	}
+}

src/pocketmine/level/generator/object/SpruceTree.php

@@ -26,6 +26,7 @@ namespace pocketmine\level\generator\object;
 use pocketmine\block\Block;
 use pocketmine\block\BlockFactory;
 use pocketmine\block\Wood;
+use pocketmine\level\BlockWriteBatch;
 use pocketmine\level\ChunkManager;
 use pocketmine\utils\Random;
 
@@ -35,14 +36,18 @@ class SpruceTree extends Tree{
 		parent::__construct(BlockFactory::get(Block::LOG, Wood::SPRUCE), BlockFactory::get(Block::LEAVES, Wood::SPRUCE), 10);
 	}
 
+	protected function generateChunkHeight(Random $random) : int{
+		return $this->treeHeight - $random->nextBoundedInt(3);
+	}
+
 	public function placeObject(ChunkManager $level, int $x, int $y, int $z, Random $random) : void{
 		$this->treeHeight = $random->nextBoundedInt(4) + 6;
+		parent::placeObject($level, $x, $y, $z, $random);
+	}
 
+	protected function placeCanopy(ChunkManager $level, int $x, int $y, int $z, Random $random, BlockWriteBatch $write) : void{
 		$topSize = $this->treeHeight - (1 + $random->nextBoundedInt(2));
 		$lRadius = 2 + $random->nextBoundedInt(2);
-
-		$this->placeTrunk($level, $x, $y, $z, $random, $this->treeHeight - $random->nextBoundedInt(3));
-
 		$radius = $random->nextBoundedInt(2);
 		$maxR = 1;
 		$minR = 0;
@@ -59,7 +64,7 @@ class SpruceTree extends Tree{
 					}
 
 					if(!$level->getBlockAt($xx, $yyy, $zz)->isSolid()){
-						$level->setBlockAt($xx, $yyy, $zz, $this->leafBlock);
+						$write->addBlockAt($xx, $yyy, $zz, $this->leafBlock);
 					}
 				}
 			}

src/pocketmine/level/generator/object/Tree.php

@@ -29,6 +29,7 @@ use pocketmine\block\Leaves;
 use pocketmine\block\Sapling;
 use pocketmine\block\utils\WoodType;
 use pocketmine\block\Wood;
+use pocketmine\level\BlockWriteBatch;
 use pocketmine\level\ChunkManager;
 use pocketmine\utils\Random;
 
@@ -100,8 +101,29 @@ abstract class Tree{
 	}
 
 	public function placeObject(ChunkManager $level, int $x, int $y, int $z, Random $random) : void{
-		$this->placeTrunk($level, $x, $y, $z, $random, $this->treeHeight - 1);
+		$write = new BlockWriteBatch();
+		$this->placeTrunk($level, $x, $y, $z, $random, $this->generateChunkHeight($random), $write);
+		$this->placeCanopy($level, $x, $y, $z, $random, $write);
 
+		$write->apply($level); //TODO: handle return value on failure
+	}
+
+	protected function generateChunkHeight(Random $random) : int{
+		return $this->treeHeight - 1;
+	}
+
+	protected function placeTrunk(ChunkManager $level, int $x, int $y, int $z, Random $random, int $trunkHeight, BlockWriteBatch $write) : void{
+		// The base dirt block
+		$write->addBlockAt($x, $y - 1, $z, BlockFactory::get(Block::DIRT));
+
+		for($yy = 0; $yy < $trunkHeight; ++$yy){
+			if($this->canOverride($level->getBlockAt($x, $y + $yy, $z))){
+				$write->addBlockAt($x, $y + $yy, $z, $this->trunkBlock);
+			}
+		}
+	}
+
+	protected function placeCanopy(ChunkManager $level, int $x, int $y, int $z, Random $random, BlockWriteBatch $write) : void{
 		for($yy = $y - 3 + $this->treeHeight; $yy <= $y + $this->treeHeight; ++$yy){
 			$yOff = $yy - ($y + $this->treeHeight);
 			$mid = (int) (1 - $yOff / 2);
@@ -113,24 +135,13 @@ abstract class Tree{
 						continue;
 					}
 					if(!$level->getBlockAt($xx, $yy, $zz)->isSolid()){
-						$level->setBlockAt($xx, $yy, $zz, $this->leafBlock);
+						$write->addBlockAt($xx, $yy, $zz, $this->leafBlock);
 					}
 				}
 			}
 		}
 	}
 
-	protected function placeTrunk(ChunkManager $level, int $x, int $y, int $z, Random $random, int $trunkHeight) : void{
-		// The base dirt block
-		$level->setBlockAt($x, $y - 1, $z, BlockFactory::get(Block::DIRT));
-
-		for($yy = 0; $yy < $trunkHeight; ++$yy){
-			if($this->canOverride($level->getBlockAt($x, $y + $yy, $z))){
-				$level->setBlockAt($x, $y + $yy, $z, $this->trunkBlock);
-			}
-		}
-	}
-
 	protected function canOverride(Block $block) : bool{
 		return $block->canBeReplaced() or $block instanceof Sapling or $block instanceof Leaves;
 	}