World.php

<?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\world;
 
use pocketmine\block\Air;
use pocketmine\block\Block;
use pocketmine\block\BlockTypeIds;
use pocketmine\block\RuntimeBlockStateRegistry;
use pocketmine\block\tile\Spawnable;
use pocketmine\block\tile\Tile;
use pocketmine\block\tile\TileFactory;
use pocketmine\block\UnknownBlock;
use pocketmine\block\VanillaBlocks;
use pocketmine\data\bedrock\BiomeIds;
use pocketmine\data\bedrock\block\BlockStateData;
use pocketmine\data\bedrock\block\BlockStateDeserializeException;
use pocketmine\data\SavedDataLoadingException;
use pocketmine\entity\Entity;
use pocketmine\entity\EntityFactory;
use pocketmine\entity\Location;
use pocketmine\entity\object\ExperienceOrb;
use pocketmine\entity\object\ItemEntity;
use pocketmine\event\block\BlockBreakEvent;
use pocketmine\event\block\BlockPlaceEvent;
use pocketmine\event\block\BlockUpdateEvent;
use pocketmine\event\player\PlayerInteractEvent;
use pocketmine\event\world\ChunkLoadEvent;
use pocketmine\event\world\ChunkPopulateEvent;
use pocketmine\event\world\ChunkUnloadEvent;
use pocketmine\event\world\SpawnChangeEvent;
use pocketmine\event\world\WorldDifficultyChangeEvent;
use pocketmine\event\world\WorldDisplayNameChangeEvent;
use pocketmine\event\world\WorldParticleEvent;
use pocketmine\event\world\WorldSaveEvent;
use pocketmine\event\world\WorldSoundEvent;
use pocketmine\item\Item;
use pocketmine\item\ItemUseResult;
use pocketmine\item\LegacyStringToItemParser;
use pocketmine\item\StringToItemParser;
use pocketmine\item\VanillaItems;
use pocketmine\lang\KnownTranslationFactory;
use pocketmine\math\AxisAlignedBB;
use pocketmine\math\Facing;
use pocketmine\math\Vector3;
use pocketmine\nbt\tag\IntTag;
use pocketmine\nbt\tag\StringTag;
use pocketmine\network\mcpe\convert\TypeConverter;
use pocketmine\network\mcpe\NetworkBroadcastUtils;
use pocketmine\network\mcpe\protocol\BlockActorDataPacket;
use pocketmine\network\mcpe\protocol\ClientboundPacket;
use pocketmine\network\mcpe\protocol\types\BlockPosition;
use pocketmine\network\mcpe\protocol\UpdateBlockPacket;
use pocketmine\player\Player;
use pocketmine\promise\Promise;
use pocketmine\promise\PromiseResolver;
use pocketmine\scheduler\AsyncPool;
use pocketmine\Server;
use pocketmine\ServerConfigGroup;
use pocketmine\utils\AssumptionFailedError;
use pocketmine\utils\Limits;
use pocketmine\utils\ReversePriorityQueue;
use pocketmine\world\biome\Biome;
use pocketmine\world\biome\BiomeRegistry;
use pocketmine\world\format\Chunk;
use pocketmine\world\format\io\ChunkData;
use pocketmine\world\format\io\exception\CorruptedChunkException;
use pocketmine\world\format\io\GlobalBlockStateHandlers;
use pocketmine\world\format\io\WritableWorldProvider;
use pocketmine\world\format\LightArray;
use pocketmine\world\format\SubChunk;
use pocketmine\world\generator\GeneratorManager;
use pocketmine\world\generator\GeneratorRegisterTask;
use pocketmine\world\generator\GeneratorUnregisterTask;
use pocketmine\world\generator\PopulationTask;
use pocketmine\world\light\BlockLightUpdate;
use pocketmine\world\light\LightPopulationTask;
use pocketmine\world\light\SkyLightUpdate;
use pocketmine\world\particle\BlockBreakParticle;
use pocketmine\world\particle\Particle;
use pocketmine\world\sound\BlockPlaceSound;
use pocketmine\world\sound\Sound;
use pocketmine\world\utils\SubChunkExplorer;
use pocketmine\YmlServerProperties;
use function abs;
use function array_filter;
use function array_key_exists;
use function array_keys;
use function array_map;
use function array_merge;
use function array_sum;
use function assert;
use function cos;
use function count;
use function floor;
use function get_class;
use function gettype;
use function is_a;
use function is_object;
use function lcg_value;
use function max;
use function microtime;
use function min;
use function morton2d_decode;
use function morton2d_encode;
use function morton3d_decode;
use function morton3d_encode;
use function mt_rand;
use function preg_match;
use function spl_object_id;
use function strtolower;
use function trim;
use const M_PI;
use const PHP_INT_MAX;
use const PHP_INT_MIN;
 
#include <rules/World.h>
 
class World implements ChunkManager{
 
    private static int $worldIdCounter = 1;
 
    public const Y_MAX = 320;
    public const Y_MIN = -64;
 
    public const TIME_DAY = 1000;
    public const TIME_NOON = 6000;
    public const TIME_SUNSET = 12000;
    public const TIME_NIGHT = 13000;
    public const TIME_MIDNIGHT = 18000;
    public const TIME_SUNRISE = 23000;
 
    public const TIME_FULL = 24000;
 
    public const DIFFICULTY_PEACEFUL = 0;
    public const DIFFICULTY_EASY = 1;
    public const DIFFICULTY_NORMAL = 2;
    public const DIFFICULTY_HARD = 3;
 
    public const DEFAULT_TICKED_BLOCKS_PER_SUBCHUNK_PER_TICK = 3;
 
    private array $players = [];
 
    private array $entities = [];
    private array $entityLastKnownPositions = [];
 
    private array $entitiesByChunk = [];
 
    public array $updateEntities = [];
 
    private bool $inDynamicStateRecalculation = false;
    private array $blockCache = [];
    private array $blockCollisionBoxCache = [];
 
    private int $sendTimeTicker = 0;
 
    private int $worldId;
 
    private int $providerGarbageCollectionTicker = 0;
 
    private int $minY;
    private int $maxY;
 
    private array $registeredTickingChunks = [];
 
    private array $validTickingChunks = [];
 
    private array $recheckTickingChunks = [];
 
    private array $chunkLoaders = [];
 
    private array $chunkListeners = [];
    private array $playerChunkListeners = [];
 
    private array $packetBuffersByChunk = [];
 
    private array $unloadQueue = [];
 
    private int $time;
    public bool $stopTime = false;
 
    private float $sunAnglePercentage = 0.0;
    private int $skyLightReduction = 0;
 
    private string $folderName;
    private string $displayName;
 
    private array $chunks = [];
 
    private array $changedBlocks = [];
 
    private ReversePriorityQueue $scheduledBlockUpdateQueue;
    private array $scheduledBlockUpdateQueueIndex = [];
 
    private \SplQueue $neighbourBlockUpdateQueue;
    private array $neighbourBlockUpdateQueueIndex = [];
 
    private array $activeChunkPopulationTasks = [];
    private array $chunkLock = [];
    private int $maxConcurrentChunkPopulationTasks = 2;
    private array $chunkPopulationRequestMap = [];
    private \SplQueue $chunkPopulationRequestQueue;
    private array $chunkPopulationRequestQueueIndex = [];
 
    private array $generatorRegisteredWorkers = [];
 
    private bool $autoSave = true;
 
    private int $sleepTicks = 0;
 
    private int $chunkTickRadius;
    private int $tickedBlocksPerSubchunkPerTick = self::DEFAULT_TICKED_BLOCKS_PER_SUBCHUNK_PER_TICK;
    private array $randomTickBlocks = [];
 
    public WorldTimings $timings;
 
    public float $tickRateTime = 0;
 
    private bool $doingTick = false;
 
    private string $generator;
 
    private bool $unloaded = false;
    private array $unloadCallbacks = [];
 
    private ?BlockLightUpdate $blockLightUpdate = null;
    private ?SkyLightUpdate $skyLightUpdate = null;
 
    private \Logger $logger;
 
    public static function chunkHash(int $x, int $z) : int{
        return morton2d_encode($x, $z);
    }
 
    private const MORTON3D_BIT_SIZE = 21;
    private const BLOCKHASH_Y_BITS = 9;
    private const BLOCKHASH_Y_PADDING = 64; //size (in blocks) of padding after both boundaries of the Y axis
    private const BLOCKHASH_Y_OFFSET = self::BLOCKHASH_Y_PADDING - self::Y_MIN;
    private const BLOCKHASH_Y_MASK = (1 << self::BLOCKHASH_Y_BITS) - 1;
    private const BLOCKHASH_XZ_MASK = (1 << self::MORTON3D_BIT_SIZE) - 1;
    private const BLOCKHASH_XZ_EXTRA_BITS = (self::MORTON3D_BIT_SIZE - self::BLOCKHASH_Y_BITS) >> 1;
    private const BLOCKHASH_XZ_EXTRA_MASK = (1 << self::BLOCKHASH_XZ_EXTRA_BITS) - 1;
    private const BLOCKHASH_XZ_SIGN_SHIFT = 64 - self::MORTON3D_BIT_SIZE - self::BLOCKHASH_XZ_EXTRA_BITS;
    private const BLOCKHASH_X_SHIFT = self::BLOCKHASH_Y_BITS;
    private const BLOCKHASH_Z_SHIFT = self::BLOCKHASH_X_SHIFT + self::BLOCKHASH_XZ_EXTRA_BITS;
 
    public static function blockHash(int $x, int $y, int $z) : int{
        $shiftedY = $y + self::BLOCKHASH_Y_OFFSET;
        if(($shiftedY & (~0 << self::BLOCKHASH_Y_BITS)) !== 0){
            throw new \InvalidArgumentException("Y coordinate $y is out of range!");
        }
        //morton3d gives us 21 bits on each axis, but the Y axis only requires 9
        //so we use the extra space on Y (12 bits) and add 6 extra bits from X and Z instead.
        //if we ever need more space for Y (e.g. due to expansion), take bits from X/Z to compensate.
        return morton3d_encode(
            $x & self::BLOCKHASH_XZ_MASK,
            ($shiftedY /* & self::BLOCKHASH_Y_MASK */) |
                ((($x >> self::MORTON3D_BIT_SIZE) & self::BLOCKHASH_XZ_EXTRA_MASK) << self::BLOCKHASH_X_SHIFT) |
                ((($z >> self::MORTON3D_BIT_SIZE) & self::BLOCKHASH_XZ_EXTRA_MASK) << self::BLOCKHASH_Z_SHIFT),
            $z & self::BLOCKHASH_XZ_MASK
        );
    }
 
    public static function chunkBlockHash(int $x, int $y, int $z) : int{
        return morton3d_encode($x, $y, $z);
    }
 
    public static function getBlockXYZ(int $hash, ?int &$x, ?int &$y, ?int &$z) : void{
        [$baseX, $baseY, $baseZ] = morton3d_decode($hash);
 
        $extraX = ((($baseY >> self::BLOCKHASH_X_SHIFT) & self::BLOCKHASH_XZ_EXTRA_MASK) << self::MORTON3D_BIT_SIZE);
        $extraZ = ((($baseY >> self::BLOCKHASH_Z_SHIFT) & self::BLOCKHASH_XZ_EXTRA_MASK) << self::MORTON3D_BIT_SIZE);
 
        $x = (($baseX & self::BLOCKHASH_XZ_MASK) | $extraX) << self::BLOCKHASH_XZ_SIGN_SHIFT >> self::BLOCKHASH_XZ_SIGN_SHIFT;
        $y = ($baseY & self::BLOCKHASH_Y_MASK) - self::BLOCKHASH_Y_OFFSET;
        $z = (($baseZ & self::BLOCKHASH_XZ_MASK) | $extraZ) << self::BLOCKHASH_XZ_SIGN_SHIFT >> self::BLOCKHASH_XZ_SIGN_SHIFT;
    }
 
    public static function getXZ(int $hash, ?int &$x, ?int &$z) : void{
        [$x, $z] = morton2d_decode($hash);
    }
 
    public static function getDifficultyFromString(string $str) : int{
        switch(strtolower(trim($str))){
            case "0":
            case "peaceful":
            case "p":
                return World::DIFFICULTY_PEACEFUL;
 
            case "1":
            case "easy":
            case "e":
                return World::DIFFICULTY_EASY;
 
            case "2":
            case "normal":
            case "n":
                return World::DIFFICULTY_NORMAL;
 
            case "3":
            case "hard":
            case "h":
                return World::DIFFICULTY_HARD;
        }
 
        return -1;
    }
 
    public function __construct(
        private Server $server,
        string $name, //TODO: this should be folderName (named arguments BC break)
        private WritableWorldProvider $provider,
        private AsyncPool $workerPool
    ){
        $this->folderName = $name;
        $this->worldId = self::$worldIdCounter++;
 
        $this->displayName = $this->provider->getWorldData()->getName();
        $this->logger = new \PrefixedLogger($server->getLogger(), "World: $this->displayName");
 
        $this->minY = $this->provider->getWorldMinY();
        $this->maxY = $this->provider->getWorldMaxY();
 
        $this->server->getLogger()->info($this->server->getLanguage()->translate(KnownTranslationFactory::pocketmine_level_preparing($this->displayName)));
        $generator = GeneratorManager::getInstance()->getGenerator($this->provider->getWorldData()->getGenerator()) ??
            throw new AssumptionFailedError("WorldManager should already have checked that the generator exists");
        $generator->validateGeneratorOptions($this->provider->getWorldData()->getGeneratorOptions());
        $this->generator = $generator->getGeneratorClass();
        $this->chunkPopulationRequestQueue = new \SplQueue();
        $this->addOnUnloadCallback(function() : void{
            $this->logger->debug("Cancelling unfulfilled generation requests");
 
            foreach($this->chunkPopulationRequestMap as $chunkHash => $promise){
                $promise->reject();
                unset($this->chunkPopulationRequestMap[$chunkHash]);
            }
            if(count($this->chunkPopulationRequestMap) !== 0){
                //TODO: this might actually get hit because generation rejection callbacks might try to schedule new
                //requests, and we can't prevent that right now because there's no way to detect "unloading" state
                throw new AssumptionFailedError("New generation requests scheduled during unload");
            }
        });
 
        $this->scheduledBlockUpdateQueue = new ReversePriorityQueue();
        $this->scheduledBlockUpdateQueue->setExtractFlags(\SplPriorityQueue::EXTR_BOTH);
 
        $this->neighbourBlockUpdateQueue = new \SplQueue();
 
        $this->time = $this->provider->getWorldData()->getTime();
 
        $cfg = $this->server->getConfigGroup();
        $this->chunkTickRadius = min($this->server->getViewDistance(), max(0, $cfg->getPropertyInt(YmlServerProperties::CHUNK_TICKING_TICK_RADIUS, 4)));
        if($cfg->getPropertyInt("chunk-ticking.per-tick", 40) <= 0){
            //TODO: this needs l10n
            $this->logger->warning("\"chunk-ticking.per-tick\" setting is deprecated, but you've used it to disable chunk ticking. Set \"chunk-ticking.tick-radius\" to 0 in \"pocketmine.yml\" instead.");
            $this->chunkTickRadius = 0;
        }
        $this->tickedBlocksPerSubchunkPerTick = $cfg->getPropertyInt(YmlServerProperties::CHUNK_TICKING_BLOCKS_PER_SUBCHUNK_PER_TICK, self::DEFAULT_TICKED_BLOCKS_PER_SUBCHUNK_PER_TICK);
        $this->maxConcurrentChunkPopulationTasks = $cfg->getPropertyInt(YmlServerProperties::CHUNK_GENERATION_POPULATION_QUEUE_SIZE, 2);
 
        $this->initRandomTickBlocksFromConfig($cfg);
 
        $this->timings = new WorldTimings($this);
 
        $this->workerPool->addWorkerStartHook($workerStartHook = function(int $workerId) : void{
            if(array_key_exists($workerId, $this->generatorRegisteredWorkers)){
                $this->logger->debug("Worker $workerId with previously registered generator restarted, flagging as unregistered");
                unset($this->generatorRegisteredWorkers[$workerId]);
            }
        });
        $workerPool = $this->workerPool;
        $this->addOnUnloadCallback(static function() use ($workerPool, $workerStartHook) : void{
            $workerPool->removeWorkerStartHook($workerStartHook);
        });
    }
 
    private function initRandomTickBlocksFromConfig(ServerConfigGroup $cfg) : void{
        $dontTickBlocks = [];
        $parser = StringToItemParser::getInstance();
        foreach($cfg->getProperty(YmlServerProperties::CHUNK_TICKING_DISABLE_BLOCK_TICKING, []) as $name){
            $name = (string) $name;
            $item = $parser->parse($name);
            if($item !== null){
                $block = $item->getBlock();
            }elseif(preg_match("/^-?\d+$/", $name) === 1){
                //TODO: this is a really sketchy hack - remove this as soon as possible
                try{
                    $blockStateData = GlobalBlockStateHandlers::getUpgrader()->upgradeIntIdMeta((int) $name, 0);
                }catch(BlockStateDeserializeException){
                    continue;
                }
                $block = RuntimeBlockStateRegistry::getInstance()->fromStateId(GlobalBlockStateHandlers::getDeserializer()->deserialize($blockStateData));
            }else{
                //TODO: we probably ought to log an error here
                continue;
            }
 
            if($block->getTypeId() !== BlockTypeIds::AIR){
                $dontTickBlocks[$block->getTypeId()] = $name;
            }
        }
 
        foreach(RuntimeBlockStateRegistry::getInstance()->getAllKnownStates() as $state){
            $dontTickName = $dontTickBlocks[$state->getTypeId()] ?? null;
            if($dontTickName === null && $state->ticksRandomly()){
                $this->randomTickBlocks[$state->getStateId()] = true;
            }
        }
    }
 
    public function getTickRateTime() : float{
        return $this->tickRateTime;
    }
 
    public function registerGeneratorToWorker(int $worker) : void{
        $this->logger->debug("Registering generator on worker $worker");
        $this->workerPool->submitTaskToWorker(new GeneratorRegisterTask($this, $this->generator, $this->provider->getWorldData()->getGeneratorOptions()), $worker);
        $this->generatorRegisteredWorkers[$worker] = true;
    }
 
    public function unregisterGenerator() : void{
        foreach($this->workerPool->getRunningWorkers() as $i){
            if(isset($this->generatorRegisteredWorkers[$i])){
                $this->workerPool->submitTaskToWorker(new GeneratorUnregisterTask($this), $i);
            }
        }
        $this->generatorRegisteredWorkers = [];
    }
 
    public function getServer() : Server{
        return $this->server;
    }
 
    public function getLogger() : \Logger{
        return $this->logger;
    }
 
    final public function getProvider() : WritableWorldProvider{
        return $this->provider;
    }
 
    final public function getId() : int{
        return $this->worldId;
    }
 
    public function isLoaded() : bool{
        return !$this->unloaded;
    }
 
    public function onUnload() : void{
        if($this->unloaded){
            throw new \LogicException("Tried to close a world which is already closed");
        }
 
        foreach($this->unloadCallbacks as $callback){
            $callback();
        }
        $this->unloadCallbacks = [];
 
        foreach($this->chunks as $chunkHash => $chunk){
            self::getXZ($chunkHash, $chunkX, $chunkZ);
            $this->unloadChunk($chunkX, $chunkZ, false);
        }
        foreach($this->entitiesByChunk as $chunkHash => $entities){
            self::getXZ($chunkHash, $chunkX, $chunkZ);
 
            $leakedEntities = 0;
            foreach($entities as $entity){
                if(!$entity->isFlaggedForDespawn()){
                    $leakedEntities++;
                }
                $entity->close();
            }
            if($leakedEntities !== 0){
                $this->logger->warning("$leakedEntities leaked entities found in ungenerated chunk $chunkX $chunkZ during unload, they won't be saved!");
            }
        }
 
        $this->save();
 
        $this->unregisterGenerator();
 
        $this->provider->close();
        $this->blockCache = [];
        $this->blockCollisionBoxCache = [];
 
        $this->unloaded = true;
    }
 
    public function addOnUnloadCallback(\Closure $callback) : void{
        $this->unloadCallbacks[spl_object_id($callback)] = $callback;
    }
 
    public function removeOnUnloadCallback(\Closure $callback) : void{
        unset($this->unloadCallbacks[spl_object_id($callback)]);
    }
 
    private function filterViewersForPosition(Vector3 $pos, array $allowed) : array{
        $candidates = $this->getViewersForPosition($pos);
        $filtered = [];
        foreach($allowed as $player){
            $k = spl_object_id($player);
            if(isset($candidates[$k])){
                $filtered[$k] = $candidates[$k];
            }
        }
 
        return $filtered;
    }
 
    public function addSound(Vector3 $pos, Sound $sound, ?array $players = null) : void{
        $players ??= $this->getViewersForPosition($pos);
 
        if(WorldSoundEvent::hasHandlers()){
            $ev = new WorldSoundEvent($this, $sound, $pos, $players);
            $ev->call();
            if($ev->isCancelled()){
                return;
            }
 
            $sound = $ev->getSound();
            $players = $ev->getRecipients();
        }
 
        $pk = $sound->encode($pos);
        if(count($pk) > 0){
            if($players === $this->getViewersForPosition($pos)){
                foreach($pk as $e){
                    $this->broadcastPacketToViewers($pos, $e);
                }
            }else{
                NetworkBroadcastUtils::broadcastPackets($this->filterViewersForPosition($pos, $players), $pk);
            }
        }
    }
 
    public function addParticle(Vector3 $pos, Particle $particle, ?array $players = null) : void{
        $players ??= $this->getViewersForPosition($pos);
 
        if(WorldParticleEvent::hasHandlers()){
            $ev = new WorldParticleEvent($this, $particle, $pos, $players);
            $ev->call();
            if($ev->isCancelled()){
                return;
            }
 
            $particle = $ev->getParticle();
            $players = $ev->getRecipients();
        }
 
        $pk = $particle->encode($pos);
        if(count($pk) > 0){
            if($players === $this->getViewersForPosition($pos)){
                foreach($pk as $e){
                    $this->broadcastPacketToViewers($pos, $e);
                }
            }else{
                NetworkBroadcastUtils::broadcastPackets($this->filterViewersForPosition($pos, $players), $pk);
            }
        }
    }
 
    public function getAutoSave() : bool{
        return $this->autoSave;
    }
 
    public function setAutoSave(bool $value) : void{
        $this->autoSave = $value;
    }
 
    public function getChunkPlayers(int $chunkX, int $chunkZ) : array{
        return $this->playerChunkListeners[World::chunkHash($chunkX, $chunkZ)] ?? [];
    }
 
    public function getChunkLoaders(int $chunkX, int $chunkZ) : array{
        return $this->chunkLoaders[World::chunkHash($chunkX, $chunkZ)] ?? [];
    }
 
    public function getViewersForPosition(Vector3 $pos) : array{
        return $this->getChunkPlayers($pos->getFloorX() >> Chunk::COORD_BIT_SIZE, $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE);
    }
 
    public function broadcastPacketToViewers(Vector3 $pos, ClientboundPacket $packet) : void{
        $this->broadcastPacketToPlayersUsingChunk($pos->getFloorX() >> Chunk::COORD_BIT_SIZE, $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE, $packet);
    }
 
    private function broadcastPacketToPlayersUsingChunk(int $chunkX, int $chunkZ, ClientboundPacket $packet) : void{
        if(!isset($this->packetBuffersByChunk[$index = World::chunkHash($chunkX, $chunkZ)])){
            $this->packetBuffersByChunk[$index] = [$packet];
        }else{
            $this->packetBuffersByChunk[$index][] = $packet;
        }
    }
 
    public function registerChunkLoader(ChunkLoader $loader, int $chunkX, int $chunkZ, bool $autoLoad = true) : void{
        $loaderId = spl_object_id($loader);
 
        if(!isset($this->chunkLoaders[$chunkHash = World::chunkHash($chunkX, $chunkZ)])){
            $this->chunkLoaders[$chunkHash] = [];
        }elseif(isset($this->chunkLoaders[$chunkHash][$loaderId])){
            return;
        }
 
        $this->chunkLoaders[$chunkHash][$loaderId] = $loader;
 
        $this->cancelUnloadChunkRequest($chunkX, $chunkZ);
 
        if($autoLoad){
            $this->loadChunk($chunkX, $chunkZ);
        }
    }
 
    public function unregisterChunkLoader(ChunkLoader $loader, int $chunkX, int $chunkZ) : void{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        $loaderId = spl_object_id($loader);
        if(isset($this->chunkLoaders[$chunkHash][$loaderId])){
            if(count($this->chunkLoaders[$chunkHash]) === 1){
                unset($this->chunkLoaders[$chunkHash]);
                $this->unloadChunkRequest($chunkX, $chunkZ, true);
                if(isset($this->chunkPopulationRequestMap[$chunkHash]) && !isset($this->activeChunkPopulationTasks[$chunkHash])){
                    $this->chunkPopulationRequestMap[$chunkHash]->reject();
                    unset($this->chunkPopulationRequestMap[$chunkHash]);
                }
            }else{
                unset($this->chunkLoaders[$chunkHash][$loaderId]);
            }
        }
    }
 
    public function registerChunkListener(ChunkListener $listener, int $chunkX, int $chunkZ) : void{
        $hash = World::chunkHash($chunkX, $chunkZ);
        if(isset($this->chunkListeners[$hash])){
            $this->chunkListeners[$hash][spl_object_id($listener)] = $listener;
        }else{
            $this->chunkListeners[$hash] = [spl_object_id($listener) => $listener];
        }
        if($listener instanceof Player){
            $this->playerChunkListeners[$hash][spl_object_id($listener)] = $listener;
        }
    }
 
    public function unregisterChunkListener(ChunkListener $listener, int $chunkX, int $chunkZ) : void{
        $hash = World::chunkHash($chunkX, $chunkZ);
        if(isset($this->chunkListeners[$hash])){
            if(count($this->chunkListeners[$hash]) === 1){
                unset($this->chunkListeners[$hash]);
                unset($this->playerChunkListeners[$hash]);
            }else{
                unset($this->chunkListeners[$hash][spl_object_id($listener)]);
                unset($this->playerChunkListeners[$hash][spl_object_id($listener)]);
            }
        }
    }
 
    public function unregisterChunkListenerFromAll(ChunkListener $listener) : void{
        foreach($this->chunkListeners as $hash => $listeners){
            World::getXZ($hash, $chunkX, $chunkZ);
            $this->unregisterChunkListener($listener, $chunkX, $chunkZ);
        }
    }
 
    public function getChunkListeners(int $chunkX, int $chunkZ) : array{
        return $this->chunkListeners[World::chunkHash($chunkX, $chunkZ)] ?? [];
    }
 
    public function sendTime(Player ...$targets) : void{
        if(count($targets) === 0){
            $targets = $this->players;
        }
        foreach($targets as $player){
            $player->getNetworkSession()->syncWorldTime($this->time);
        }
    }
 
    public function isDoingTick() : bool{
        return $this->doingTick;
    }
 
    public function doTick(int $currentTick) : void{
        if($this->unloaded){
            throw new \LogicException("Attempted to tick a world which has been closed");
        }
 
        $this->timings->doTick->startTiming();
        $this->doingTick = true;
        try{
            $this->actuallyDoTick($currentTick);
        }finally{
            $this->doingTick = false;
            $this->timings->doTick->stopTiming();
        }
    }
 
    protected function actuallyDoTick(int $currentTick) : void{
        if(!$this->stopTime){
            //this simulates an overflow, as would happen in any language which doesn't do stupid things to var types
            if($this->time === PHP_INT_MAX){
                $this->time = PHP_INT_MIN;
            }else{
                $this->time++;
            }
        }
 
        $this->sunAnglePercentage = $this->computeSunAnglePercentage(); //Sun angle depends on the current time
        $this->skyLightReduction = $this->computeSkyLightReduction(); //Sky light reduction depends on the sun angle
 
        if(++$this->sendTimeTicker === 200){
            $this->sendTime();
            $this->sendTimeTicker = 0;
        }
 
        $this->unloadChunks();
        if(++$this->providerGarbageCollectionTicker >= 6000){
            $this->provider->doGarbageCollection();
            $this->providerGarbageCollectionTicker = 0;
        }
 
        $this->timings->scheduledBlockUpdates->startTiming();
        //Delayed updates
        while($this->scheduledBlockUpdateQueue->count() > 0 && $this->scheduledBlockUpdateQueue->current()["priority"] <= $currentTick){
            $vec = $this->scheduledBlockUpdateQueue->extract()["data"];
            unset($this->scheduledBlockUpdateQueueIndex[World::blockHash($vec->x, $vec->y, $vec->z)]);
            if(!$this->isInLoadedTerrain($vec)){
                continue;
            }
            $block = $this->getBlock($vec);
            $block->onScheduledUpdate();
        }
        $this->timings->scheduledBlockUpdates->stopTiming();
 
        $this->timings->neighbourBlockUpdates->startTiming();
        //Normal updates
        while($this->neighbourBlockUpdateQueue->count() > 0){
            $index = $this->neighbourBlockUpdateQueue->dequeue();
            unset($this->neighbourBlockUpdateQueueIndex[$index]);
            World::getBlockXYZ($index, $x, $y, $z);
            if(!$this->isChunkLoaded($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE)){
                continue;
            }
 
            $block = $this->getBlockAt($x, $y, $z);
 
            if(BlockUpdateEvent::hasHandlers()){
                $ev = new BlockUpdateEvent($block);
                $ev->call();
                if($ev->isCancelled()){
                    continue;
                }
            }
            foreach($this->getNearbyEntities(AxisAlignedBB::one()->offset($x, $y, $z)) as $entity){
                $entity->onNearbyBlockChange();
            }
            $block->onNearbyBlockChange();
        }
 
        $this->timings->neighbourBlockUpdates->stopTiming();
 
        $this->timings->entityTick->startTiming();
        //Update entities that need update
        foreach($this->updateEntities as $id => $entity){
            if($entity->isClosed() || $entity->isFlaggedForDespawn() || !$entity->onUpdate($currentTick)){
                unset($this->updateEntities[$id]);
            }
            if($entity->isFlaggedForDespawn()){
                $entity->close();
            }
        }
        $this->timings->entityTick->stopTiming();
 
        $this->timings->randomChunkUpdates->startTiming();
        $this->tickChunks();
        $this->timings->randomChunkUpdates->stopTiming();
 
        $this->executeQueuedLightUpdates();
 
        if(count($this->changedBlocks) > 0){
            if(count($this->players) > 0){
                foreach($this->changedBlocks as $index => $blocks){
                    if(count($blocks) === 0){ //blocks can be set normally and then later re-set with direct send
                        continue;
                    }
                    World::getXZ($index, $chunkX, $chunkZ);
                    if(!$this->isChunkLoaded($chunkX, $chunkZ)){
                        //a previous chunk may have caused this one to be unloaded by a ChunkListener
                        continue;
                    }
                    if(count($blocks) > 512){
                        $chunk = $this->getChunk($chunkX, $chunkZ) ?? throw new AssumptionFailedError("We already checked that the chunk is loaded");
                        foreach($this->getChunkPlayers($chunkX, $chunkZ) as $p){
                            $p->onChunkChanged($chunkX, $chunkZ, $chunk);
                        }
                    }else{
                        foreach($this->createBlockUpdatePackets($blocks) as $packet){
                            $this->broadcastPacketToPlayersUsingChunk($chunkX, $chunkZ, $packet);
                        }
                    }
                }
            }
 
            $this->changedBlocks = [];
 
        }
 
        if($this->sleepTicks > 0 && --$this->sleepTicks <= 0){
            $this->checkSleep();
        }
 
        foreach($this->packetBuffersByChunk as $index => $entries){
            World::getXZ($index, $chunkX, $chunkZ);
            $chunkPlayers = $this->getChunkPlayers($chunkX, $chunkZ);
            if(count($chunkPlayers) > 0){
                NetworkBroadcastUtils::broadcastPackets($chunkPlayers, $entries);
            }
        }
 
        $this->packetBuffersByChunk = [];
    }
 
    public function checkSleep() : void{
        if(count($this->players) === 0){
            return;
        }
 
        $resetTime = true;
        foreach($this->getPlayers() as $p){
            if(!$p->isSleeping()){
                $resetTime = false;
                break;
            }
        }
 
        if($resetTime){
            $time = $this->getTimeOfDay();
 
            if($time >= World::TIME_NIGHT && $time < World::TIME_SUNRISE){
                $this->setTime($this->getTime() + World::TIME_FULL - $time);
 
                foreach($this->getPlayers() as $p){
                    $p->stopSleep();
                }
            }
        }
    }
 
    public function setSleepTicks(int $ticks) : void{
        $this->sleepTicks = $ticks;
    }
 
    public function createBlockUpdatePackets(array $blocks) : array{
        $packets = [];
 
        $blockTranslator = TypeConverter::getInstance()->getBlockTranslator();
 
        foreach($blocks as $b){
            if(!($b instanceof Vector3)){
                throw new \TypeError("Expected Vector3 in blocks array, got " . (is_object($b) ? get_class($b) : gettype($b)));
            }
 
            $fullBlock = $this->getBlockAt($b->x, $b->y, $b->z);
            $blockPosition = BlockPosition::fromVector3($b);
 
            $tile = $this->getTileAt($b->x, $b->y, $b->z);
            if($tile instanceof Spawnable){
                $expectedClass = $fullBlock->getIdInfo()->getTileClass();
                if($expectedClass !== null && $tile instanceof $expectedClass && count($fakeStateProperties = $tile->getRenderUpdateBugWorkaroundStateProperties($fullBlock)) > 0){
                    $originalStateData = $blockTranslator->internalIdToNetworkStateData($fullBlock->getStateId());
                    $fakeStateData = new BlockStateData(
                        $originalStateData->getName(),
                        array_merge($originalStateData->getStates(), $fakeStateProperties),
                        $originalStateData->getVersion()
                    );
                    $packets[] = UpdateBlockPacket::create(
                        $blockPosition,
                        $blockTranslator->getBlockStateDictionary()->lookupStateIdFromData($fakeStateData) ?? throw new AssumptionFailedError("Unmapped fake blockstate data: " . $fakeStateData->toNbt()),
                        UpdateBlockPacket::FLAG_NETWORK,
                        UpdateBlockPacket::DATA_LAYER_NORMAL
                    );
                }
            }
            $packets[] = UpdateBlockPacket::create(
                $blockPosition,
                $blockTranslator->internalIdToNetworkId($fullBlock->getStateId()),
                UpdateBlockPacket::FLAG_NETWORK,
                UpdateBlockPacket::DATA_LAYER_NORMAL
            );
 
            if($tile instanceof Spawnable){
                $packets[] = BlockActorDataPacket::create($blockPosition, $tile->getSerializedSpawnCompound());
            }
        }
 
        return $packets;
    }
 
    public function clearCache(bool $force = false) : void{
        if($force){
            $this->blockCache = [];
            $this->blockCollisionBoxCache = [];
        }else{
            $count = 0;
            foreach($this->blockCache as $list){
                $count += count($list);
                if($count > 2048){
                    $this->blockCache = [];
                    break;
                }
            }
 
            $count = 0;
            foreach($this->blockCollisionBoxCache as $list){
                $count += count($list);
                if($count > 2048){
                    //TODO: Is this really the best logic?
                    $this->blockCollisionBoxCache = [];
                    break;
                }
            }
        }
    }
 
    public function getRandomTickedBlocks() : array{
        return $this->randomTickBlocks;
    }
 
    public function addRandomTickedBlock(Block $block) : void{
        if($block instanceof UnknownBlock){
            throw new \InvalidArgumentException("Cannot do random-tick on unknown block");
        }
        $this->randomTickBlocks[$block->getStateId()] = true;
    }
 
    public function removeRandomTickedBlock(Block $block) : void{
        unset($this->randomTickBlocks[$block->getStateId()]);
    }
 
    public function getChunkTickRadius() : int{
        return $this->chunkTickRadius;
    }
 
    public function setChunkTickRadius(int $radius) : void{
        $this->chunkTickRadius = $radius;
    }
 
    public function getTickingChunks() : array{
        return array_keys($this->validTickingChunks);
    }
 
    public function registerTickingChunk(ChunkTicker $ticker, int $chunkX, int $chunkZ) : void{
        $chunkPosHash = World::chunkHash($chunkX, $chunkZ);
        $this->registeredTickingChunks[$chunkPosHash][spl_object_id($ticker)] = $ticker;
        $this->recheckTickingChunks[$chunkPosHash] = $chunkPosHash;
    }
 
    public function unregisterTickingChunk(ChunkTicker $ticker, int $chunkX, int $chunkZ) : void{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        $tickerId = spl_object_id($ticker);
        if(isset($this->registeredTickingChunks[$chunkHash][$tickerId])){
            if(count($this->registeredTickingChunks[$chunkHash]) === 1){
                unset(
                    $this->registeredTickingChunks[$chunkHash],
                    $this->recheckTickingChunks[$chunkHash],
                    $this->validTickingChunks[$chunkHash]
                );
            }else{
                unset($this->registeredTickingChunks[$chunkHash][$tickerId]);
            }
        }
    }
 
    private function tickChunks() : void{
        if($this->chunkTickRadius <= 0 || count($this->registeredTickingChunks) === 0){
            return;
        }
 
        if(count($this->recheckTickingChunks) > 0){
            $this->timings->randomChunkUpdatesChunkSelection->startTiming();
 
            $chunkTickableCache = [];
 
            foreach($this->recheckTickingChunks as $hash => $_){
                World::getXZ($hash, $chunkX, $chunkZ);
                if($this->isChunkTickable($chunkX, $chunkZ, $chunkTickableCache)){
                    $this->validTickingChunks[$hash] = $hash;
                }
            }
            $this->recheckTickingChunks = [];
 
            $this->timings->randomChunkUpdatesChunkSelection->stopTiming();
        }
 
        foreach($this->validTickingChunks as $index => $_){
            World::getXZ($index, $chunkX, $chunkZ);
 
            $this->tickChunk($chunkX, $chunkZ);
        }
    }
 
    private function isChunkTickable(int $chunkX, int $chunkZ, array &$cache) : bool{
        for($cx = -1; $cx <= 1; ++$cx){
            for($cz = -1; $cz <= 1; ++$cz){
                $chunkHash = World::chunkHash($chunkX + $cx, $chunkZ + $cz);
                if(isset($cache[$chunkHash])){
                    if(!$cache[$chunkHash]){
                        return false;
                    }
                    continue;
                }
                if($this->isChunkLocked($chunkX + $cx, $chunkZ + $cz)){
                    $cache[$chunkHash] = false;
                    return false;
                }
                $adjacentChunk = $this->getChunk($chunkX + $cx, $chunkZ + $cz);
                if($adjacentChunk === null || !$adjacentChunk->isPopulated()){
                    $cache[$chunkHash] = false;
                    return false;
                }
                $lightPopulatedState = $adjacentChunk->isLightPopulated();
                if($lightPopulatedState !== true){
                    if($lightPopulatedState === false){
                        $this->orderLightPopulation($chunkX + $cx, $chunkZ + $cz);
                    }
                    $cache[$chunkHash] = false;
                    return false;
                }
 
                $cache[$chunkHash] = true;
            }
        }
 
        return true;
    }
 
    private function markTickingChunkForRecheck(int $chunkX, int $chunkZ) : void{
        for($cx = -1; $cx <= 1; ++$cx){
            for($cz = -1; $cz <= 1; ++$cz){
                $chunkHash = World::chunkHash($chunkX + $cx, $chunkZ + $cz);
                unset($this->validTickingChunks[$chunkHash]);
                if(isset($this->registeredTickingChunks[$chunkHash])){
                    $this->recheckTickingChunks[$chunkHash] = $chunkHash;
                }else{
                    unset($this->recheckTickingChunks[$chunkHash]);
                }
            }
        }
    }
 
    private function orderLightPopulation(int $chunkX, int $chunkZ) : void{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        $lightPopulatedState = $this->chunks[$chunkHash]->isLightPopulated();
        if($lightPopulatedState === false){
            $this->chunks[$chunkHash]->setLightPopulated(null);
            $this->markTickingChunkForRecheck($chunkX, $chunkZ);
 
            $this->workerPool->submitTask(new LightPopulationTask(
                $this->chunks[$chunkHash],
                function(array $blockLight, array $skyLight, array $heightMap) use ($chunkX, $chunkZ) : void{
                    if($this->unloaded || ($chunk = $this->getChunk($chunkX, $chunkZ)) === null || $chunk->isLightPopulated() === true){
                        return;
                    }
                    //TODO: calculated light information might not be valid if the terrain changed during light calculation
 
                    $chunk->setHeightMapArray($heightMap);
                    foreach($blockLight as $y => $lightArray){
                        $chunk->getSubChunk($y)->setBlockLightArray($lightArray);
                    }
                    foreach($skyLight as $y => $lightArray){
                        $chunk->getSubChunk($y)->setBlockSkyLightArray($lightArray);
                    }
                    $chunk->setLightPopulated(true);
                    $this->markTickingChunkForRecheck($chunkX, $chunkZ);
                }
            ));
        }
    }
 
    private function tickChunk(int $chunkX, int $chunkZ) : void{
        $chunk = $this->getChunk($chunkX, $chunkZ);
        if($chunk === null){
            //the chunk may have been unloaded during a previous chunk's update (e.g. during BlockGrowEvent)
            return;
        }
        foreach($this->getChunkEntities($chunkX, $chunkZ) as $entity){
            $entity->onRandomUpdate();
        }
 
        $blockFactory = RuntimeBlockStateRegistry::getInstance();
        foreach($chunk->getSubChunks() as $Y => $subChunk){
            if(!$subChunk->isEmptyFast()){
                $k = 0;
                for($i = 0; $i < $this->tickedBlocksPerSubchunkPerTick; ++$i){
                    if(($i % 5) === 0){
                        //60 bits will be used by 5 blocks (12 bits each)
                        $k = mt_rand(0, (1 << 60) - 1);
                    }
                    $x = $k & SubChunk::COORD_MASK;
                    $y = ($k >> SubChunk::COORD_BIT_SIZE) & SubChunk::COORD_MASK;
                    $z = ($k >> (SubChunk::COORD_BIT_SIZE * 2)) & SubChunk::COORD_MASK;
                    $k >>= (SubChunk::COORD_BIT_SIZE * 3);
 
                    $state = $subChunk->getBlockStateId($x, $y, $z);
 
                    if(isset($this->randomTickBlocks[$state])){
                        $block = $blockFactory->fromStateId($state);
                        $block->position($this, $chunkX * Chunk::EDGE_LENGTH + $x, ($Y << SubChunk::COORD_BIT_SIZE) + $y, $chunkZ * Chunk::EDGE_LENGTH + $z);
                        $block->onRandomTick();
                    }
                }
            }
        }
    }
 
    public function __debugInfo() : array{
        return [];
    }
 
    public function save(bool $force = false) : bool{
 
        if(!$this->getAutoSave() && !$force){
            return false;
        }
 
        (new WorldSaveEvent($this))->call();
 
        $timings = $this->timings->syncDataSave;
        $timings->startTiming();
 
        $this->provider->getWorldData()->setTime($this->time);
        $this->saveChunks();
        $this->provider->getWorldData()->save();
 
        $timings->stopTiming();
 
        return true;
    }
 
    public function saveChunks() : void{
        $this->timings->syncChunkSave->startTiming();
        try{
            foreach($this->chunks as $chunkHash => $chunk){
                self::getXZ($chunkHash, $chunkX, $chunkZ);
                $this->provider->saveChunk($chunkX, $chunkZ, new ChunkData(
                    $chunk->getSubChunks(),
                    $chunk->isPopulated(),
                    array_map(fn(Entity $e) => $e->saveNBT(), array_filter($this->getChunkEntities($chunkX, $chunkZ), fn(Entity $e) => $e->canSaveWithChunk())),
                    array_map(fn(Tile $t) => $t->saveNBT(), $chunk->getTiles()),
                ), $chunk->getTerrainDirtyFlags());
                $chunk->clearTerrainDirtyFlags();
            }
        }finally{
            $this->timings->syncChunkSave->stopTiming();
        }
    }
 
    public function scheduleDelayedBlockUpdate(Vector3 $pos, int $delay) : void{
        if(
            !$this->isInWorld($pos->x, $pos->y, $pos->z) ||
            (isset($this->scheduledBlockUpdateQueueIndex[$index = World::blockHash($pos->x, $pos->y, $pos->z)]) && $this->scheduledBlockUpdateQueueIndex[$index] <= $delay)
        ){
            return;
        }
        $this->scheduledBlockUpdateQueueIndex[$index] = $delay;
        $this->scheduledBlockUpdateQueue->insert(new Vector3((int) $pos->x, (int) $pos->y, (int) $pos->z), $delay + $this->server->getTick());
    }
 
    private function tryAddToNeighbourUpdateQueue(int $x, int $y, int $z) : void{
        if($this->isInWorld($x, $y, $z)){
            $hash = World::blockHash($x, $y, $z);
            if(!isset($this->neighbourBlockUpdateQueueIndex[$hash])){
                $this->neighbourBlockUpdateQueue->enqueue($hash);
                $this->neighbourBlockUpdateQueueIndex[$hash] = true;
            }
        }
    }
 
    private function internalNotifyNeighbourBlockUpdate(int $x, int $y, int $z) : void{
        $this->tryAddToNeighbourUpdateQueue($x, $y, $z);
        foreach(Facing::OFFSET as [$dx, $dy, $dz]){
            $this->tryAddToNeighbourUpdateQueue($x + $dx, $y + $dy, $z + $dz);
        }
    }
 
    public function notifyNeighbourBlockUpdate(Vector3 $pos) : void{
        $this->internalNotifyNeighbourBlockUpdate($pos->getFloorX(), $pos->getFloorY(), $pos->getFloorZ());
    }
 
    public function getCollisionBlocks(AxisAlignedBB $bb, bool $targetFirst = false) : array{
        $minX = (int) floor($bb->minX - 1);
        $minY = (int) floor($bb->minY - 1);
        $minZ = (int) floor($bb->minZ - 1);
        $maxX = (int) floor($bb->maxX + 1);
        $maxY = (int) floor($bb->maxY + 1);
        $maxZ = (int) floor($bb->maxZ + 1);
 
        $collides = [];
 
        if($targetFirst){
            for($z = $minZ; $z <= $maxZ; ++$z){
                for($x = $minX; $x <= $maxX; ++$x){
                    for($y = $minY; $y <= $maxY; ++$y){
                        $block = $this->getBlockAt($x, $y, $z);
                        if($block->collidesWithBB($bb)){
                            return [$block];
                        }
                    }
                }
            }
        }else{
            for($z = $minZ; $z <= $maxZ; ++$z){
                for($x = $minX; $x <= $maxX; ++$x){
                    for($y = $minY; $y <= $maxY; ++$y){
                        $block = $this->getBlockAt($x, $y, $z);
                        if($block->collidesWithBB($bb)){
                            $collides[] = $block;
                        }
                    }
                }
            }
        }
 
        return $collides;
    }
 
    private function getBlockCollisionBoxesForCell(int $x, int $y, int $z) : array{
        $block = $this->getBlockAt($x, $y, $z);
        $boxes = $block->getCollisionBoxes();
 
        $cellBB = AxisAlignedBB::one()->offset($x, $y, $z);
        foreach(Facing::OFFSET as [$dx, $dy, $dz]){
            $extraBoxes = $this->getBlockAt($x + $dx, $y + $dy, $z + $dz)->getCollisionBoxes();
            foreach($extraBoxes as $extraBox){
                if($extraBox->intersectsWith($cellBB)){
                    $boxes[] = $extraBox;
                }
            }
        }
 
        return $boxes;
    }
 
    public function getBlockCollisionBoxes(AxisAlignedBB $bb) : array{
        $minX = (int) floor($bb->minX);
        $minY = (int) floor($bb->minY);
        $minZ = (int) floor($bb->minZ);
        $maxX = (int) floor($bb->maxX);
        $maxY = (int) floor($bb->maxY);
        $maxZ = (int) floor($bb->maxZ);
 
        $collides = [];
 
        for($z = $minZ; $z <= $maxZ; ++$z){
            for($x = $minX; $x <= $maxX; ++$x){
                $chunkPosHash = World::chunkHash($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE);
                for($y = $minY; $y <= $maxY; ++$y){
                    $relativeBlockHash = World::chunkBlockHash($x, $y, $z);
 
                    $boxes = $this->blockCollisionBoxCache[$chunkPosHash][$relativeBlockHash] ??= $this->getBlockCollisionBoxesForCell($x, $y, $z);
 
                    foreach($boxes as $blockBB){
                        if($blockBB->intersectsWith($bb)){
                            $collides[] = $blockBB;
                        }
                    }
                }
            }
        }
 
        return $collides;
    }
 
    public function getCollisionBoxes(Entity $entity, AxisAlignedBB $bb, bool $entities = true) : array{
        $collides = $this->getBlockCollisionBoxes($bb);
 
        if($entities){
            foreach($this->getCollidingEntities($bb->expandedCopy(0.25, 0.25, 0.25), $entity) as $ent){
                $collides[] = clone $ent->boundingBox;
            }
        }
 
        return $collides;
    }
 
    public function computeSunAnglePercentage() : float{
        $timeProgress = ($this->time % self::TIME_FULL) / self::TIME_FULL;
 
        //0.0 needs to be high noon, not dusk
        $sunProgress = $timeProgress + ($timeProgress < 0.25 ? 0.75 : -0.25);
 
        //Offset the sun progress to be above the horizon longer at dusk and dawn
        //this is roughly an inverted sine curve, which pushes the sun progress back at dusk and forwards at dawn
        $diff = (((1 - ((cos($sunProgress * M_PI) + 1) / 2)) - $sunProgress) / 3);
 
        return $sunProgress + $diff;
    }
 
    public function getSunAnglePercentage() : float{
        return $this->sunAnglePercentage;
    }
 
    public function getSunAngleRadians() : float{
        return $this->sunAnglePercentage * 2 * M_PI;
    }
 
    public function getSunAngleDegrees() : float{
        return $this->sunAnglePercentage * 360.0;
    }
 
    public function computeSkyLightReduction() : int{
        $percentage = max(0, min(1, -(cos($this->getSunAngleRadians()) * 2 - 0.5)));
 
        //TODO: check rain and thunder level
 
        return (int) ($percentage * 11);
    }
 
    public function getSkyLightReduction() : int{
        return $this->skyLightReduction;
    }
 
    public function getFullLight(Vector3 $pos) : int{
        $floorX = $pos->getFloorX();
        $floorY = $pos->getFloorY();
        $floorZ = $pos->getFloorZ();
        return $this->getFullLightAt($floorX, $floorY, $floorZ);
    }
 
    public function getFullLightAt(int $x, int $y, int $z) : int{
        $skyLight = $this->getRealBlockSkyLightAt($x, $y, $z);
        if($skyLight < 15){
            return max($skyLight, $this->getBlockLightAt($x, $y, $z));
        }else{
            return $skyLight;
        }
    }
 
    public function getHighestAdjacentFullLightAt(int $x, int $y, int $z) : int{
        return $this->getHighestAdjacentLight($x, $y, $z, $this->getFullLightAt(...));
    }
 
    public function getPotentialLight(Vector3 $pos) : int{
        $floorX = $pos->getFloorX();
        $floorY = $pos->getFloorY();
        $floorZ = $pos->getFloorZ();
        return $this->getPotentialLightAt($floorX, $floorY, $floorZ);
    }
 
    public function getPotentialLightAt(int $x, int $y, int $z) : int{
        return max($this->getPotentialBlockSkyLightAt($x, $y, $z), $this->getBlockLightAt($x, $y, $z));
    }
 
    public function getHighestAdjacentPotentialLightAt(int $x, int $y, int $z) : int{
        return $this->getHighestAdjacentLight($x, $y, $z, $this->getPotentialLightAt(...));
    }
 
    public function getPotentialBlockSkyLightAt(int $x, int $y, int $z) : int{
        if(!$this->isInWorld($x, $y, $z)){
            return $y >= self::Y_MAX ? 15 : 0;
        }
        if(($chunk = $this->getChunk($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE)) !== null && $chunk->isLightPopulated() === true){
            return $chunk->getSubChunk($y >> Chunk::COORD_BIT_SIZE)->getBlockSkyLightArray()->get($x & SubChunk::COORD_MASK, $y & SubChunk::COORD_MASK, $z & SubChunk::COORD_MASK);
        }
        return 0; //TODO: this should probably throw instead (light not calculated yet)
    }
 
    public function getRealBlockSkyLightAt(int $x, int $y, int $z) : int{
        $light = $this->getPotentialBlockSkyLightAt($x, $y, $z) - $this->skyLightReduction;
        return $light < 0 ? 0 : $light;
    }
 
    public function getBlockLightAt(int $x, int $y, int $z) : int{
        if(!$this->isInWorld($x, $y, $z)){
            return 0;
        }
        if(($chunk = $this->getChunk($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE)) !== null && $chunk->isLightPopulated() === true){
            return $chunk->getSubChunk($y >> Chunk::COORD_BIT_SIZE)->getBlockLightArray()->get($x & SubChunk::COORD_MASK, $y & SubChunk::COORD_MASK, $z & SubChunk::COORD_MASK);
        }
        return 0; //TODO: this should probably throw instead (light not calculated yet)
    }
 
    public function updateAllLight(int $x, int $y, int $z) : void{
        if(($chunk = $this->getChunk($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE)) === null || $chunk->isLightPopulated() !== true){
            return;
        }
 
        $blockFactory = RuntimeBlockStateRegistry::getInstance();
        $this->timings->doBlockSkyLightUpdates->startTiming();
        if($this->skyLightUpdate === null){
            $this->skyLightUpdate = new SkyLightUpdate(new SubChunkExplorer($this), $blockFactory->lightFilter, $blockFactory->blocksDirectSkyLight);
        }
        $this->skyLightUpdate->recalculateNode($x, $y, $z);
        $this->timings->doBlockSkyLightUpdates->stopTiming();
 
        $this->timings->doBlockLightUpdates->startTiming();
        if($this->blockLightUpdate === null){
            $this->blockLightUpdate = new BlockLightUpdate(new SubChunkExplorer($this), $blockFactory->lightFilter, $blockFactory->light);
        }
        $this->blockLightUpdate->recalculateNode($x, $y, $z);
        $this->timings->doBlockLightUpdates->stopTiming();
    }
 
    private function getHighestAdjacentLight(int $x, int $y, int $z, \Closure $lightGetter) : int{
        $max = 0;
        foreach(Facing::OFFSET as [$offsetX, $offsetY, $offsetZ]){
            $x1 = $x + $offsetX;
            $y1 = $y + $offsetY;
            $z1 = $z + $offsetZ;
            if(
                !$this->isInWorld($x1, $y1, $z1) ||
                ($chunk = $this->getChunk($x1 >> Chunk::COORD_BIT_SIZE, $z1 >> Chunk::COORD_BIT_SIZE)) === null ||
                $chunk->isLightPopulated() !== true
            ){
                continue;
            }
            $max = max($max, $lightGetter($x1, $y1, $z1));
        }
        return $max;
    }
 
    public function getHighestAdjacentPotentialBlockSkyLight(int $x, int $y, int $z) : int{
        return $this->getHighestAdjacentLight($x, $y, $z, $this->getPotentialBlockSkyLightAt(...));
    }
 
    public function getHighestAdjacentRealBlockSkyLight(int $x, int $y, int $z) : int{
        return $this->getHighestAdjacentPotentialBlockSkyLight($x, $y, $z) - $this->skyLightReduction;
    }
 
    public function getHighestAdjacentBlockLight(int $x, int $y, int $z) : int{
        return $this->getHighestAdjacentLight($x, $y, $z, $this->getBlockLightAt(...));
    }
 
    private function executeQueuedLightUpdates() : void{
        if($this->blockLightUpdate !== null){
            $this->timings->doBlockLightUpdates->startTiming();
            $this->blockLightUpdate->execute();
            $this->blockLightUpdate = null;
            $this->timings->doBlockLightUpdates->stopTiming();
        }
 
        if($this->skyLightUpdate !== null){
            $this->timings->doBlockSkyLightUpdates->startTiming();
            $this->skyLightUpdate->execute();
            $this->skyLightUpdate = null;
            $this->timings->doBlockSkyLightUpdates->stopTiming();
        }
    }
 
    public function isInWorld(int $x, int $y, int $z) : bool{
        return (
            $x <= Limits::INT32_MAX && $x >= Limits::INT32_MIN &&
            $y < $this->maxY && $y >= $this->minY &&
            $z <= Limits::INT32_MAX && $z >= Limits::INT32_MIN
        );
    }
 
    public function getBlock(Vector3 $pos, bool $cached = true, bool $addToCache = true) : Block{
        return $this->getBlockAt((int) floor($pos->x), (int) floor($pos->y), (int) floor($pos->z), $cached, $addToCache);
    }
 
    public function getBlockAt(int $x, int $y, int $z, bool $cached = true, bool $addToCache = true) : Block{
        $relativeBlockHash = null;
        $chunkHash = World::chunkHash($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE);
 
        if($this->isInWorld($x, $y, $z)){
            $relativeBlockHash = World::chunkBlockHash($x, $y, $z);
 
            if($cached && isset($this->blockCache[$chunkHash][$relativeBlockHash])){
                return $this->blockCache[$chunkHash][$relativeBlockHash];
            }
 
            $chunk = $this->chunks[$chunkHash] ?? null;
            if($chunk !== null){
                $block = RuntimeBlockStateRegistry::getInstance()->fromStateId($chunk->getBlockStateId($x & Chunk::COORD_MASK, $y, $z & Chunk::COORD_MASK));
            }else{
                $addToCache = false;
                $block = VanillaBlocks::AIR();
            }
        }else{
            $block = VanillaBlocks::AIR();
        }
 
        $block->position($this, $x, $y, $z);
 
        if($this->inDynamicStateRecalculation){
            //this call was generated by a parent getBlock() call calculating dynamic stateinfo
            //don't calculate dynamic state and don't add to block cache (since it won't have dynamic state calculated).
            //this ensures that it's impossible for dynamic state properties to recursively depend on each other.
            $addToCache = false;
        }else{
            $this->inDynamicStateRecalculation = true;
            $replacement = $block->readStateFromWorld();
            if($replacement !== $block){
                $replacement->position($this, $x, $y, $z);
                $block = $replacement;
            }
            $this->inDynamicStateRecalculation = false;
        }
 
        if($addToCache && $relativeBlockHash !== null){
            $this->blockCache[$chunkHash][$relativeBlockHash] = $block;
        }
 
        return $block;
    }
 
    public function setBlock(Vector3 $pos, Block $block, bool $update = true) : void{
        $this->setBlockAt((int) floor($pos->x), (int) floor($pos->y), (int) floor($pos->z), $block, $update);
    }
 
    public function setBlockAt(int $x, int $y, int $z, Block $block, bool $update = true) : void{
        if(!$this->isInWorld($x, $y, $z)){
            throw new \InvalidArgumentException("Pos x=$x,y=$y,z=$z is outside of the world bounds");
        }
        $chunkX = $x >> Chunk::COORD_BIT_SIZE;
        $chunkZ = $z >> Chunk::COORD_BIT_SIZE;
        if($this->loadChunk($chunkX, $chunkZ) === null){ //current expected behaviour is to try to load the terrain synchronously
            throw new WorldException("Cannot set a block in un-generated terrain");
        }
 
        $this->timings->setBlock->startTiming();
 
        $this->unlockChunk($chunkX, $chunkZ, null);
 
        $block = clone $block;
 
        $block->position($this, $x, $y, $z);
        $block->writeStateToWorld();
        $pos = new Vector3($x, $y, $z);
 
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        $relativeBlockHash = World::chunkBlockHash($x, $y, $z);
 
        unset($this->blockCache[$chunkHash][$relativeBlockHash]);
        unset($this->blockCollisionBoxCache[$chunkHash][$relativeBlockHash]);
        //blocks like fences have collision boxes that reach into neighbouring blocks, so we need to invalidate the
        //caches for those blocks as well
        foreach(Facing::OFFSET as [$offsetX, $offsetY, $offsetZ]){
            $sideChunkPosHash = World::chunkHash(($x + $offsetX) >> Chunk::COORD_BIT_SIZE, ($z + $offsetZ) >> Chunk::COORD_BIT_SIZE);
            $sideChunkBlockHash = World::chunkBlockHash($x + $offsetX, $y + $offsetY, $z + $offsetZ);
            unset($this->blockCollisionBoxCache[$sideChunkPosHash][$sideChunkBlockHash]);
        }
 
        if(!isset($this->changedBlocks[$chunkHash])){
            $this->changedBlocks[$chunkHash] = [];
        }
        $this->changedBlocks[$chunkHash][$relativeBlockHash] = $pos;
 
        foreach($this->getChunkListeners($chunkX, $chunkZ) as $listener){
            $listener->onBlockChanged($pos);
        }
 
        if($update){
            $this->updateAllLight($x, $y, $z);
            $this->internalNotifyNeighbourBlockUpdate($x, $y, $z);
        }
 
        $this->timings->setBlock->stopTiming();
    }
 
    public function dropItem(Vector3 $source, Item $item, ?Vector3 $motion = null, int $delay = 10) : ?ItemEntity{
        if($item->isNull()){
            return null;
        }
 
        $itemEntity = new ItemEntity(Location::fromObject($source, $this, lcg_value() * 360, 0), $item);
 
        $itemEntity->setPickupDelay($delay);
        $itemEntity->setMotion($motion ?? new Vector3(lcg_value() * 0.2 - 0.1, 0.2, lcg_value() * 0.2 - 0.1));
        $itemEntity->spawnToAll();
 
        return $itemEntity;
    }
 
    public function dropExperience(Vector3 $pos, int $amount) : array{
        $orbs = [];
 
        foreach(ExperienceOrb::splitIntoOrbSizes($amount) as $split){
            $orb = new ExperienceOrb(Location::fromObject($pos, $this, lcg_value() * 360, 0), $split);
 
            $orb->setMotion(new Vector3((lcg_value() * 0.2 - 0.1) * 2, lcg_value() * 0.4, (lcg_value() * 0.2 - 0.1) * 2));
            $orb->spawnToAll();
 
            $orbs[] = $orb;
        }
 
        return $orbs;
    }
 
    public function useBreakOn(Vector3 $vector, Item &$item = null, ?Player $player = null, bool $createParticles = false, array &$returnedItems = []) : bool{
        $vector = $vector->floor();
 
        $chunkX = $vector->getFloorX() >> Chunk::COORD_BIT_SIZE;
        $chunkZ = $vector->getFloorZ() >> Chunk::COORD_BIT_SIZE;
        if(!$this->isChunkLoaded($chunkX, $chunkZ) || $this->isChunkLocked($chunkX, $chunkZ)){
            return false;
        }
 
        $target = $this->getBlock($vector);
        $affectedBlocks = $target->getAffectedBlocks();
 
        if($item === null){
            $item = VanillaItems::AIR();
        }
 
        $drops = [];
        if($player === null || $player->hasFiniteResources()){
            $drops = array_merge(...array_map(fn(Block $block) => $block->getDrops($item), $affectedBlocks));
        }
 
        $xpDrop = 0;
        if($player !== null && $player->hasFiniteResources()){
            $xpDrop = array_sum(array_map(fn(Block $block) => $block->getXpDropForTool($item), $affectedBlocks));
        }
 
        if($player !== null){
            $ev = new BlockBreakEvent($player, $target, $item, $player->isCreative(), $drops, $xpDrop);
 
            if($target instanceof Air || ($player->isSurvival() && !$target->getBreakInfo()->isBreakable()) || $player->isSpectator()){
                $ev->cancel();
            }
 
            if($player->isAdventure(true) && !$ev->isCancelled()){
                $canBreak = false;
                $itemParser = LegacyStringToItemParser::getInstance();
                foreach($item->getCanDestroy() as $v){
                    $entry = $itemParser->parse($v);
                    if($entry->getBlock()->hasSameTypeId($target)){
                        $canBreak = true;
                        break;
                    }
                }
 
                if(!$canBreak){
                    $ev->cancel();
                }
            }
 
            $ev->call();
            if($ev->isCancelled()){
                return false;
            }
 
            $drops = $ev->getDrops();
            $xpDrop = $ev->getXpDropAmount();
 
        }elseif(!$target->getBreakInfo()->isBreakable()){
            return false;
        }
 
        foreach($affectedBlocks as $t){
            $this->destroyBlockInternal($t, $item, $player, $createParticles, $returnedItems);
        }
 
        $item->onDestroyBlock($target, $returnedItems);
 
        if(count($drops) > 0){
            $dropPos = $vector->add(0.5, 0.5, 0.5);
            foreach($drops as $drop){
                if(!$drop->isNull()){
                    $this->dropItem($dropPos, $drop);
                }
            }
        }
 
        if($xpDrop > 0){
            $this->dropExperience($vector->add(0.5, 0.5, 0.5), $xpDrop);
        }
 
        return true;
    }
 
    private function destroyBlockInternal(Block $target, Item $item, ?Player $player, bool $createParticles, array &$returnedItems) : void{
        if($createParticles){
            $this->addParticle($target->getPosition()->add(0.5, 0.5, 0.5), new BlockBreakParticle($target));
        }
 
        $target->onBreak($item, $player, $returnedItems);
 
        $tile = $this->getTile($target->getPosition());
        if($tile !== null){
            $tile->onBlockDestroyed();
        }
    }
 
    public function useItemOn(Vector3 $vector, Item &$item, int $face, ?Vector3 $clickVector = null, ?Player $player = null, bool $playSound = false, array &$returnedItems = []) : bool{
        $blockClicked = $this->getBlock($vector);
        $blockReplace = $blockClicked->getSide($face);
 
        if($clickVector === null){
            $clickVector = new Vector3(0.0, 0.0, 0.0);
        }else{
            $clickVector = new Vector3(
                min(1.0, max(0.0, $clickVector->x)),
                min(1.0, max(0.0, $clickVector->y)),
                min(1.0, max(0.0, $clickVector->z))
            );
        }
 
        if(!$this->isInWorld($blockReplace->getPosition()->x, $blockReplace->getPosition()->y, $blockReplace->getPosition()->z)){
            //TODO: build height limit messages for custom world heights and mcregion cap
            return false;
        }
        $chunkX = $blockReplace->getPosition()->getFloorX() >> Chunk::COORD_BIT_SIZE;
        $chunkZ = $blockReplace->getPosition()->getFloorZ() >> Chunk::COORD_BIT_SIZE;
        if(!$this->isChunkLoaded($chunkX, $chunkZ) || $this->isChunkLocked($chunkX, $chunkZ)){
            return false;
        }
 
        if($blockClicked->getTypeId() === BlockTypeIds::AIR){
            return false;
        }
 
        if($player !== null){
            $ev = new PlayerInteractEvent($player, $item, $blockClicked, $clickVector, $face, PlayerInteractEvent::RIGHT_CLICK_BLOCK);
            if($player->isSpectator()){
                $ev->cancel(); //set it to cancelled so plugins can bypass this
            }
 
            $ev->call();
            if(!$ev->isCancelled()){
                if((!$player->isSneaking() || $item->isNull()) && $blockClicked->onInteract($item, $face, $clickVector, $player, $returnedItems)){
                    return true;
                }
 
                $result = $item->onInteractBlock($player, $blockReplace, $blockClicked, $face, $clickVector, $returnedItems);
                if($result !== ItemUseResult::NONE){
                    return $result === ItemUseResult::SUCCESS;
                }
            }else{
                return false;
            }
        }elseif($blockClicked->onInteract($item, $face, $clickVector, $player, $returnedItems)){
            return true;
        }
 
        if($item->isNull() || !$item->canBePlaced()){
            return false;
        }
        $hand = $item->getBlock($face);
        $hand->position($this, $blockReplace->getPosition()->x, $blockReplace->getPosition()->y, $blockReplace->getPosition()->z);
 
        if($hand->canBePlacedAt($blockClicked, $clickVector, $face, true)){
            $blockReplace = $blockClicked;
            //TODO: while this mimics the vanilla behaviour with replaceable blocks, we should really pass some other
            //value like NULL and let place() deal with it. This will look like a bug to anyone who doesn't know about
            //the vanilla behaviour.
            $face = Facing::UP;
            $hand->position($this, $blockReplace->getPosition()->x, $blockReplace->getPosition()->y, $blockReplace->getPosition()->z);
        }elseif(!$hand->canBePlacedAt($blockReplace, $clickVector, $face, false)){
            return false;
        }
 
        $tx = new BlockTransaction($this);
        if(!$hand->place($tx, $item, $blockReplace, $blockClicked, $face, $clickVector, $player)){
            return false;
        }
 
        foreach($tx->getBlocks() as [$x, $y, $z, $block]){
            $block->position($this, $x, $y, $z);
            foreach($block->getCollisionBoxes() as $collisionBox){
                if(count($this->getCollidingEntities($collisionBox)) > 0){
                    return false;  //Entity in block
                }
            }
        }
 
        if($player !== null){
            $ev = new BlockPlaceEvent($player, $tx, $blockClicked, $item);
            if($player->isSpectator()){
                $ev->cancel();
            }
 
            if($player->isAdventure(true) && !$ev->isCancelled()){
                $canPlace = false;
                $itemParser = LegacyStringToItemParser::getInstance();
                foreach($item->getCanPlaceOn() as $v){
                    $entry = $itemParser->parse($v);
                    if($entry->getBlock()->hasSameTypeId($blockClicked)){
                        $canPlace = true;
                        break;
                    }
                }
 
                if(!$canPlace){
                    $ev->cancel();
                }
            }
 
            $ev->call();
            if($ev->isCancelled()){
                return false;
            }
        }
 
        if(!$tx->apply()){
            return false;
        }
        foreach($tx->getBlocks() as [$x, $y, $z, $_]){
            $tile = $this->getTileAt($x, $y, $z);
            if($tile !== null){
                //TODO: seal this up inside block placement
                $tile->copyDataFromItem($item);
            }
 
            $this->getBlockAt($x, $y, $z)->onPostPlace();
        }
 
        if($playSound){
            $this->addSound($hand->getPosition(), new BlockPlaceSound($hand));
        }
 
        $item->pop();
 
        return true;
    }
 
    public function getEntity(int $entityId) : ?Entity{
        return $this->entities[$entityId] ?? null;
    }
 
    public function getEntities() : array{
        return $this->entities;
    }
 
    public function getCollidingEntities(AxisAlignedBB $bb, ?Entity $entity = null) : array{
        $nearby = [];
 
        foreach($this->getNearbyEntities($bb, $entity) as $ent){
            if($ent->canBeCollidedWith() && ($entity === null || $entity->canCollideWith($ent))){
                $nearby[] = $ent;
            }
        }
 
        return $nearby;
    }
 
    public function getNearbyEntities(AxisAlignedBB $bb, ?Entity $entity = null) : array{
        $nearby = [];
 
        $minX = ((int) floor($bb->minX - 2)) >> Chunk::COORD_BIT_SIZE;
        $maxX = ((int) floor($bb->maxX + 2)) >> Chunk::COORD_BIT_SIZE;
        $minZ = ((int) floor($bb->minZ - 2)) >> Chunk::COORD_BIT_SIZE;
        $maxZ = ((int) floor($bb->maxZ + 2)) >> Chunk::COORD_BIT_SIZE;
 
        for($x = $minX; $x <= $maxX; ++$x){
            for($z = $minZ; $z <= $maxZ; ++$z){
                foreach($this->getChunkEntities($x, $z) as $ent){
                    if($ent !== $entity && $ent->boundingBox->intersectsWith($bb)){
                        $nearby[] = $ent;
                    }
                }
            }
        }
 
        return $nearby;
    }
 
    public function getNearestEntity(Vector3 $pos, float $maxDistance, string $entityType = Entity::class, bool $includeDead = false) : ?Entity{
        assert(is_a($entityType, Entity::class, true));
 
        $minX = ((int) floor($pos->x - $maxDistance)) >> Chunk::COORD_BIT_SIZE;
        $maxX = ((int) floor($pos->x + $maxDistance)) >> Chunk::COORD_BIT_SIZE;
        $minZ = ((int) floor($pos->z - $maxDistance)) >> Chunk::COORD_BIT_SIZE;
        $maxZ = ((int) floor($pos->z + $maxDistance)) >> Chunk::COORD_BIT_SIZE;
 
        $currentTargetDistSq = $maxDistance ** 2;
 
        $currentTarget = null;
 
        for($x = $minX; $x <= $maxX; ++$x){
            for($z = $minZ; $z <= $maxZ; ++$z){
                foreach($this->getChunkEntities($x, $z) as $entity){
                    if(!($entity instanceof $entityType) || $entity->isFlaggedForDespawn() || (!$includeDead && !$entity->isAlive())){
                        continue;
                    }
                    $distSq = $entity->getPosition()->distanceSquared($pos);
                    if($distSq < $currentTargetDistSq){
                        $currentTargetDistSq = $distSq;
                        $currentTarget = $entity;
                    }
                }
            }
        }
 
        return $currentTarget;
    }
 
    public function getPlayers() : array{
        return $this->players;
    }
 
    public function getTile(Vector3 $pos) : ?Tile{
        return $this->getTileAt((int) floor($pos->x), (int) floor($pos->y), (int) floor($pos->z));
    }
 
    public function getTileAt(int $x, int $y, int $z) : ?Tile{
        return ($chunk = $this->loadChunk($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE)) !== null ? $chunk->getTile($x & Chunk::COORD_MASK, $y, $z & Chunk::COORD_MASK) : null;
    }
 
    public function getBiomeId(int $x, int $y, int $z) : int{
        if(($chunk = $this->loadChunk($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE)) !== null){
            return $chunk->getBiomeId($x & Chunk::COORD_MASK, $y & Chunk::COORD_MASK, $z & Chunk::COORD_MASK);
        }
        return BiomeIds::OCEAN; //TODO: this should probably throw instead (terrain not generated yet)
    }
 
    public function getBiome(int $x, int $y, int $z) : Biome{
        return BiomeRegistry::getInstance()->getBiome($this->getBiomeId($x, $y, $z));
    }
 
    public function setBiomeId(int $x, int $y, int $z, int $biomeId) : void{
        $chunkX = $x >> Chunk::COORD_BIT_SIZE;
        $chunkZ = $z >> Chunk::COORD_BIT_SIZE;
        $this->unlockChunk($chunkX, $chunkZ, null);
        if(($chunk = $this->loadChunk($chunkX, $chunkZ)) !== null){
            $chunk->setBiomeId($x & Chunk::COORD_MASK, $y & Chunk::COORD_MASK, $z & Chunk::COORD_MASK, $biomeId);
        }else{
            //if we allowed this, the modifications would be lost when the chunk is created
            throw new WorldException("Cannot set biome in a non-generated chunk");
        }
    }
 
    public function getLoadedChunks() : array{
        return $this->chunks;
    }
 
    public function getChunk(int $chunkX, int $chunkZ) : ?Chunk{
        return $this->chunks[World::chunkHash($chunkX, $chunkZ)] ?? null;
    }
 
    public function getChunkEntities(int $chunkX, int $chunkZ) : array{
        return $this->entitiesByChunk[World::chunkHash($chunkX, $chunkZ)] ?? [];
    }
 
    public function getOrLoadChunkAtPosition(Vector3 $pos) : ?Chunk{
        return $this->loadChunk($pos->getFloorX() >> Chunk::COORD_BIT_SIZE, $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE);
    }
 
    public function getAdjacentChunks(int $x, int $z) : array{
        $result = [];
        for($xx = -1; $xx <= 1; ++$xx){
            for($zz = -1; $zz <= 1; ++$zz){
                if($xx === 0 && $zz === 0){
                    continue; //center chunk
                }
                $result[World::chunkHash($xx, $zz)] = $this->loadChunk($x + $xx, $z + $zz);
            }
        }
 
        return $result;
    }
 
    public function lockChunk(int $chunkX, int $chunkZ, ChunkLockId $lockId) : void{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        if(isset($this->chunkLock[$chunkHash])){
            throw new \InvalidArgumentException("Chunk $chunkX $chunkZ is already locked");
        }
        $this->chunkLock[$chunkHash] = $lockId;
        $this->markTickingChunkForRecheck($chunkX, $chunkZ);
    }
 
    public function unlockChunk(int $chunkX, int $chunkZ, ?ChunkLockId $lockId) : bool{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        if(isset($this->chunkLock[$chunkHash]) && ($lockId === null || $this->chunkLock[$chunkHash] === $lockId)){
            unset($this->chunkLock[$chunkHash]);
            $this->markTickingChunkForRecheck($chunkX, $chunkZ);
            return true;
        }
        return false;
    }
 
    public function isChunkLocked(int $chunkX, int $chunkZ) : bool{
        return isset($this->chunkLock[World::chunkHash($chunkX, $chunkZ)]);
    }
 
    public function setChunk(int $chunkX, int $chunkZ, Chunk $chunk) : void{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        $oldChunk = $this->loadChunk($chunkX, $chunkZ);
        if($oldChunk !== null && $oldChunk !== $chunk){
            $deletedTiles = 0;
            $transferredTiles = 0;
            foreach($oldChunk->getTiles() as $oldTile){
                $tilePosition = $oldTile->getPosition();
                $localX = $tilePosition->getFloorX() & Chunk::COORD_MASK;
                $localY = $tilePosition->getFloorY();
                $localZ = $tilePosition->getFloorZ() & Chunk::COORD_MASK;
 
                $newBlock = RuntimeBlockStateRegistry::getInstance()->fromStateId($chunk->getBlockStateId($localX, $localY, $localZ));
                $expectedTileClass = $newBlock->getIdInfo()->getTileClass();
                if(
                    $expectedTileClass === null || //new block doesn't expect a tile
                    !($oldTile instanceof $expectedTileClass) || //new block expects a different tile
                    (($newTile = $chunk->getTile($localX, $localY, $localZ)) !== null && $newTile !== $oldTile) //new chunk already has a different tile
                ){
                    $oldTile->close();
                    $deletedTiles++;
                }else{
                    $transferredTiles++;
                    $chunk->addTile($oldTile);
                    $oldChunk->removeTile($oldTile);
                }
            }
            if($deletedTiles > 0 || $transferredTiles > 0){
                $this->logger->debug("Replacement of chunk $chunkX $chunkZ caused deletion of $deletedTiles obsolete/conflicted tiles, and transfer of $transferredTiles");
            }
        }
 
        $this->chunks[$chunkHash] = $chunk;
 
        unset($this->blockCache[$chunkHash]);
        unset($this->blockCollisionBoxCache[$chunkHash]);
        unset($this->changedBlocks[$chunkHash]);
        $chunk->setTerrainDirty();
        $this->markTickingChunkForRecheck($chunkX, $chunkZ); //this replacement chunk may not meet the conditions for ticking
 
        if(!$this->isChunkInUse($chunkX, $chunkZ)){
            $this->unloadChunkRequest($chunkX, $chunkZ);
        }
 
        if($oldChunk === null){
            if(ChunkLoadEvent::hasHandlers()){
                (new ChunkLoadEvent($this, $chunkX, $chunkZ, $chunk, true))->call();
            }
 
            foreach($this->getChunkListeners($chunkX, $chunkZ) as $listener){
                $listener->onChunkLoaded($chunkX, $chunkZ, $chunk);
            }
        }else{
            foreach($this->getChunkListeners($chunkX, $chunkZ) as $listener){
                $listener->onChunkChanged($chunkX, $chunkZ, $chunk);
            }
        }
 
        for($cX = -1; $cX <= 1; ++$cX){
            for($cZ = -1; $cZ <= 1; ++$cZ){
                foreach($this->getChunkEntities($chunkX + $cX, $chunkZ + $cZ) as $entity){
                    $entity->onNearbyBlockChange();
                }
            }
        }
    }
 
    public function getHighestBlockAt(int $x, int $z) : ?int{
        if(($chunk = $this->loadChunk($x >> Chunk::COORD_BIT_SIZE, $z >> Chunk::COORD_BIT_SIZE)) !== null){
            return $chunk->getHighestBlockAt($x & Chunk::COORD_MASK, $z & Chunk::COORD_MASK);
        }
        throw new WorldException("Cannot get highest block in an ungenerated chunk");
    }
 
    public function isInLoadedTerrain(Vector3 $pos) : bool{
        return $this->isChunkLoaded($pos->getFloorX() >> Chunk::COORD_BIT_SIZE, $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE);
    }
 
    public function isChunkLoaded(int $x, int $z) : bool{
        return isset($this->chunks[World::chunkHash($x, $z)]);
    }
 
    public function isChunkGenerated(int $x, int $z) : bool{
        return $this->loadChunk($x, $z) !== null;
    }
 
    public function isChunkPopulated(int $x, int $z) : bool{
        $chunk = $this->loadChunk($x, $z);
        return $chunk !== null && $chunk->isPopulated();
    }
 
    public function getSpawnLocation() : Position{
        return Position::fromObject($this->provider->getWorldData()->getSpawn(), $this);
    }
 
    public function setSpawnLocation(Vector3 $pos) : void{
        $previousSpawn = $this->getSpawnLocation();
        $this->provider->getWorldData()->setSpawn($pos);
        (new SpawnChangeEvent($this, $previousSpawn))->call();
 
        $location = Position::fromObject($pos, $this);
        foreach($this->players as $player){
            $player->getNetworkSession()->syncWorldSpawnPoint($location);
        }
    }
 
    public function addEntity(Entity $entity) : void{
        if($entity->isClosed()){
            throw new \InvalidArgumentException("Attempted to add a garbage closed Entity to world");
        }
        if($entity->getWorld() !== $this){
            throw new \InvalidArgumentException("Invalid Entity world");
        }
        if(array_key_exists($entity->getId(), $this->entities)){
            if($this->entities[$entity->getId()] === $entity){
                throw new \InvalidArgumentException("Entity " . $entity->getId() . " has already been added to this world");
            }else{
                throw new AssumptionFailedError("Found two different entities sharing entity ID " . $entity->getId());
            }
        }
        $pos = $entity->getPosition()->asVector3();
        $this->entitiesByChunk[World::chunkHash($pos->getFloorX() >> Chunk::COORD_BIT_SIZE, $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE)][$entity->getId()] = $entity;
        $this->entityLastKnownPositions[$entity->getId()] = $pos;
 
        if($entity instanceof Player){
            $this->players[$entity->getId()] = $entity;
        }
        $this->entities[$entity->getId()] = $entity;
    }
 
    public function removeEntity(Entity $entity) : void{
        if($entity->getWorld() !== $this){
            throw new \InvalidArgumentException("Invalid Entity world");
        }
        if(!array_key_exists($entity->getId(), $this->entities)){
            throw new \InvalidArgumentException("Entity is not tracked by this world (possibly already removed?)");
        }
        $pos = $this->entityLastKnownPositions[$entity->getId()];
        $chunkHash = World::chunkHash($pos->getFloorX() >> Chunk::COORD_BIT_SIZE, $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE);
        if(isset($this->entitiesByChunk[$chunkHash][$entity->getId()])){
            if(count($this->entitiesByChunk[$chunkHash]) === 1){
                unset($this->entitiesByChunk[$chunkHash]);
            }else{
                unset($this->entitiesByChunk[$chunkHash][$entity->getId()]);
            }
        }
        unset($this->entityLastKnownPositions[$entity->getId()]);
 
        if($entity instanceof Player){
            unset($this->players[$entity->getId()]);
            $this->checkSleep();
        }
 
        unset($this->entities[$entity->getId()]);
        unset($this->updateEntities[$entity->getId()]);
    }
 
    public function onEntityMoved(Entity $entity) : void{
        if(!array_key_exists($entity->getId(), $this->entityLastKnownPositions)){
            //this can happen if the entity was teleported before addEntity() was called
            return;
        }
        $oldPosition = $this->entityLastKnownPositions[$entity->getId()];
        $newPosition = $entity->getPosition();
 
        $oldChunkX = $oldPosition->getFloorX() >> Chunk::COORD_BIT_SIZE;
        $oldChunkZ = $oldPosition->getFloorZ() >> Chunk::COORD_BIT_SIZE;
        $newChunkX = $newPosition->getFloorX() >> Chunk::COORD_BIT_SIZE;
        $newChunkZ = $newPosition->getFloorZ() >> Chunk::COORD_BIT_SIZE;
 
        if($oldChunkX !== $newChunkX || $oldChunkZ !== $newChunkZ){
            $oldChunkHash = World::chunkHash($oldChunkX, $oldChunkZ);
            if(isset($this->entitiesByChunk[$oldChunkHash][$entity->getId()])){
                if(count($this->entitiesByChunk[$oldChunkHash]) === 1){
                    unset($this->entitiesByChunk[$oldChunkHash]);
                }else{
                    unset($this->entitiesByChunk[$oldChunkHash][$entity->getId()]);
                }
            }
 
            $newViewers = $this->getViewersForPosition($newPosition);
            foreach($entity->getViewers() as $player){
                if(!isset($newViewers[spl_object_id($player)])){
                    $entity->despawnFrom($player);
                }else{
                    unset($newViewers[spl_object_id($player)]);
                }
            }
            foreach($newViewers as $player){
                $entity->spawnTo($player);
            }
 
            $newChunkHash = World::chunkHash($newChunkX, $newChunkZ);
            $this->entitiesByChunk[$newChunkHash][$entity->getId()] = $entity;
        }
        $this->entityLastKnownPositions[$entity->getId()] = $newPosition->asVector3();
    }
 
    public function addTile(Tile $tile) : void{
        if($tile->isClosed()){
            throw new \InvalidArgumentException("Attempted to add a garbage closed Tile to world");
        }
        $pos = $tile->getPosition();
        if(!$pos->isValid() || $pos->getWorld() !== $this){
            throw new \InvalidArgumentException("Invalid Tile world");
        }
        if(!$this->isInWorld($pos->getFloorX(), $pos->getFloorY(), $pos->getFloorZ())){
            throw new \InvalidArgumentException("Tile position is outside the world bounds");
        }
 
        $chunkX = $pos->getFloorX() >> Chunk::COORD_BIT_SIZE;
        $chunkZ = $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE;
 
        if(isset($this->chunks[$hash = World::chunkHash($chunkX, $chunkZ)])){
            $this->chunks[$hash]->addTile($tile);
        }else{
            throw new \InvalidArgumentException("Attempted to create tile " . get_class($tile) . " in unloaded chunk $chunkX $chunkZ");
        }
 
        //delegate tile ticking to the corresponding block
        $this->scheduleDelayedBlockUpdate($pos->asVector3(), 1);
    }
 
    public function removeTile(Tile $tile) : void{
        $pos = $tile->getPosition();
        if(!$pos->isValid() || $pos->getWorld() !== $this){
            throw new \InvalidArgumentException("Invalid Tile world");
        }
 
        $chunkX = $pos->getFloorX() >> Chunk::COORD_BIT_SIZE;
        $chunkZ = $pos->getFloorZ() >> Chunk::COORD_BIT_SIZE;
 
        if(isset($this->chunks[$hash = World::chunkHash($chunkX, $chunkZ)])){
            $this->chunks[$hash]->removeTile($tile);
        }
        foreach($this->getChunkListeners($chunkX, $chunkZ) as $listener){
            $listener->onBlockChanged($pos->asVector3());
        }
    }
 
    public function isChunkInUse(int $x, int $z) : bool{
        return isset($this->chunkLoaders[$index = World::chunkHash($x, $z)]) && count($this->chunkLoaders[$index]) > 0;
    }
 
    public function loadChunk(int $x, int $z) : ?Chunk{
        if(isset($this->chunks[$chunkHash = World::chunkHash($x, $z)])){
            return $this->chunks[$chunkHash];
        }
 
        $this->timings->syncChunkLoad->startTiming();
 
        $this->cancelUnloadChunkRequest($x, $z);
 
        $this->timings->syncChunkLoadData->startTiming();
 
        $loadedChunkData = null;
 
        try{
            $loadedChunkData = $this->provider->loadChunk($x, $z);
        }catch(CorruptedChunkException $e){
            $this->logger->critical("Failed to load chunk x=$x z=$z: " . $e->getMessage());
        }
 
        $this->timings->syncChunkLoadData->stopTiming();
 
        if($loadedChunkData === null){
            $this->timings->syncChunkLoad->stopTiming();
            return null;
        }
 
        $chunkData = $loadedChunkData->getData();
        $chunk = new Chunk($chunkData->getSubChunks(), $chunkData->isPopulated());
        if(!$loadedChunkData->isUpgraded()){
            $chunk->clearTerrainDirtyFlags();
        }else{
            $this->logger->debug("Chunk $x $z has been upgraded, will be saved at the next autosave opportunity");
        }
        $this->chunks[$chunkHash] = $chunk;
        unset($this->blockCache[$chunkHash]);
        unset($this->blockCollisionBoxCache[$chunkHash]);
 
        $this->initChunk($x, $z, $chunkData);
 
        if(ChunkLoadEvent::hasHandlers()){
            (new ChunkLoadEvent($this, $x, $z, $this->chunks[$chunkHash], false))->call();
        }
 
        if(!$this->isChunkInUse($x, $z)){
            $this->logger->debug("Newly loaded chunk $x $z has no loaders registered, will be unloaded at next available opportunity");
            $this->unloadChunkRequest($x, $z);
        }
        foreach($this->getChunkListeners($x, $z) as $listener){
            $listener->onChunkLoaded($x, $z, $this->chunks[$chunkHash]);
        }
        $this->markTickingChunkForRecheck($x, $z); //tickers may have been registered before the chunk was loaded
 
        $this->timings->syncChunkLoad->stopTiming();
 
        return $this->chunks[$chunkHash];
    }
 
    private function initChunk(int $chunkX, int $chunkZ, ChunkData $chunkData) : void{
        $logger = new \PrefixedLogger($this->logger, "Loading chunk $chunkX $chunkZ");
 
        if(count($chunkData->getEntityNBT()) !== 0){
            $this->timings->syncChunkLoadEntities->startTiming();
            $entityFactory = EntityFactory::getInstance();
            foreach($chunkData->getEntityNBT() as $k => $nbt){
                try{
                    $entity = $entityFactory->createFromData($this, $nbt);
                }catch(SavedDataLoadingException $e){
                    $logger->error("Bad entity data at list position $k: " . $e->getMessage());
                    $logger->logException($e);
                    continue;
                }
                if($entity === null){
                    $saveIdTag = $nbt->getTag("identifier") ?? $nbt->getTag("id");
                    $saveId = "<unknown>";
                    if($saveIdTag instanceof StringTag){
                        $saveId = $saveIdTag->getValue();
                    }elseif($saveIdTag instanceof IntTag){ //legacy MCPE format
                        $saveId = "legacy(" . $saveIdTag->getValue() . ")";
                    }
                    $logger->warning("Deleted unknown entity type $saveId");
                }
                //TODO: we can't prevent entities getting added to unloaded chunks if they were saved in the wrong place
                //here, because entities currently add themselves to the world
            }
 
            $this->timings->syncChunkLoadEntities->stopTiming();
        }
 
        if(count($chunkData->getTileNBT()) !== 0){
            $this->timings->syncChunkLoadTileEntities->startTiming();
            $tileFactory = TileFactory::getInstance();
            foreach($chunkData->getTileNBT() as $k => $nbt){
                try{
                    $tile = $tileFactory->createFromData($this, $nbt);
                }catch(SavedDataLoadingException $e){
                    $logger->error("Bad tile entity data at list position $k: " . $e->getMessage());
                    $logger->logException($e);
                    continue;
                }
                if($tile === null){
                    $logger->warning("Deleted unknown tile entity type " . $nbt->getString("id", "<unknown>"));
                    continue;
                }
 
                $tilePosition = $tile->getPosition();
                if(!$this->isChunkLoaded($tilePosition->getFloorX() >> Chunk::COORD_BIT_SIZE, $tilePosition->getFloorZ() >> Chunk::COORD_BIT_SIZE)){
                    $logger->error("Found tile saved on wrong chunk - unable to fix due to correct chunk not loaded");
                }elseif(!$this->isInWorld($tilePosition->getFloorX(), $tilePosition->getFloorY(), $tilePosition->getFloorZ())){
                    $logger->error("Cannot add tile with position outside the world bounds: x=$tilePosition->x,y=$tilePosition->y,z=$tilePosition->z");
                }elseif($this->getTile($tilePosition) !== null){
                    $logger->error("Cannot add tile at x=$tilePosition->x,y=$tilePosition->y,z=$tilePosition->z: Another tile is already at that position");
                }else{
                    $this->addTile($tile);
                }
            }
 
            $this->timings->syncChunkLoadTileEntities->stopTiming();
        }
    }
 
    private function queueUnloadChunk(int $x, int $z) : void{
        $this->unloadQueue[World::chunkHash($x, $z)] = microtime(true);
    }
 
    public function unloadChunkRequest(int $x, int $z, bool $safe = true) : bool{
        if(($safe && $this->isChunkInUse($x, $z)) || $this->isSpawnChunk($x, $z)){
            return false;
        }
 
        $this->queueUnloadChunk($x, $z);
 
        return true;
    }
 
    public function cancelUnloadChunkRequest(int $x, int $z) : void{
        unset($this->unloadQueue[World::chunkHash($x, $z)]);
    }
 
    public function unloadChunk(int $x, int $z, bool $safe = true, bool $trySave = true) : bool{
        if($safe && $this->isChunkInUse($x, $z)){
            return false;
        }
 
        if(!$this->isChunkLoaded($x, $z)){
            return true;
        }
 
        $this->timings->doChunkUnload->startTiming();
 
        $chunkHash = World::chunkHash($x, $z);
 
        $chunk = $this->chunks[$chunkHash] ?? null;
 
        if($chunk !== null){
            if(ChunkUnloadEvent::hasHandlers()){
                $ev = new ChunkUnloadEvent($this, $x, $z, $chunk);
                $ev->call();
                if($ev->isCancelled()){
                    $this->timings->doChunkUnload->stopTiming();
 
                    return false;
                }
            }
 
            if($trySave && $this->getAutoSave()){
                $this->timings->syncChunkSave->startTiming();
                try{
                    $this->provider->saveChunk($x, $z, new ChunkData(
                        $chunk->getSubChunks(),
                        $chunk->isPopulated(),
                        array_map(fn(Entity $e) => $e->saveNBT(), array_filter($this->getChunkEntities($x, $z), fn(Entity $e) => $e->canSaveWithChunk())),
                        array_map(fn(Tile $t) => $t->saveNBT(), $chunk->getTiles()),
                    ), $chunk->getTerrainDirtyFlags());
                }finally{
                    $this->timings->syncChunkSave->stopTiming();
                }
            }
 
            foreach($this->getChunkListeners($x, $z) as $listener){
                $listener->onChunkUnloaded($x, $z, $chunk);
            }
 
            foreach($this->getChunkEntities($x, $z) as $entity){
                if($entity instanceof Player){
                    continue;
                }
                $entity->close();
            }
 
            $chunk->onUnload();
        }
 
        unset($this->chunks[$chunkHash]);
        unset($this->blockCache[$chunkHash]);
        unset($this->blockCollisionBoxCache[$chunkHash]);
        unset($this->changedBlocks[$chunkHash]);
        unset($this->registeredTickingChunks[$chunkHash]);
        $this->markTickingChunkForRecheck($x, $z);
 
        if(array_key_exists($chunkHash, $this->chunkPopulationRequestMap)){
            $this->logger->debug("Rejecting population promise for chunk $x $z");
            $this->chunkPopulationRequestMap[$chunkHash]->reject();
            unset($this->chunkPopulationRequestMap[$chunkHash]);
            if(isset($this->activeChunkPopulationTasks[$chunkHash])){
                $this->logger->debug("Marking population task for chunk $x $z as orphaned");
                $this->activeChunkPopulationTasks[$chunkHash] = false;
            }
        }
 
        $this->timings->doChunkUnload->stopTiming();
 
        return true;
    }
 
    public function isSpawnChunk(int $X, int $Z) : bool{
        $spawn = $this->getSpawnLocation();
        $spawnX = $spawn->x >> Chunk::COORD_BIT_SIZE;
        $spawnZ = $spawn->z >> Chunk::COORD_BIT_SIZE;
 
        return abs($X - $spawnX) <= 1 && abs($Z - $spawnZ) <= 1;
    }
 
    public function requestSafeSpawn(?Vector3 $spawn = null) : Promise{
        $resolver = new PromiseResolver();
        $spawn ??= $this->getSpawnLocation();
        /*
         * TODO: this relies on the assumption that getSafeSpawn() will only alter the Y coordinate of the provided
         * position, which is currently OK, but might be a problem in the future.
         */
        $this->requestChunkPopulation($spawn->getFloorX() >> Chunk::COORD_BIT_SIZE, $spawn->getFloorZ() >> Chunk::COORD_BIT_SIZE, null)->onCompletion(
            function() use ($spawn, $resolver) : void{
                $spawn = $this->getSafeSpawn($spawn);
                $resolver->resolve($spawn);
            },
            function() use ($resolver) : void{
                $resolver->reject();
            }
        );
 
        return $resolver->getPromise();
    }
 
    public function getSafeSpawn(?Vector3 $spawn = null) : Position{
        if(!($spawn instanceof Vector3) || $spawn->y <= $this->minY){
            $spawn = $this->getSpawnLocation();
        }
 
        $max = $this->maxY;
        $v = $spawn->floor();
        $chunk = $this->getOrLoadChunkAtPosition($v);
        if($chunk === null){
            throw new WorldException("Cannot find a safe spawn point in non-generated terrain");
        }
        $x = (int) $v->x;
        $z = (int) $v->z;
        $y = (int) min($max - 2, $v->y);
        $wasAir = $this->getBlockAt($x, $y - 1, $z)->getTypeId() === BlockTypeIds::AIR; //TODO: bad hack, clean up
        for(; $y > $this->minY; --$y){
            if($this->getBlockAt($x, $y, $z)->isFullCube()){
                if($wasAir){
                    $y++;
                }
                break;
            }else{
                $wasAir = true;
            }
        }
 
        for(; $y >= $this->minY && $y < $max; ++$y){
            if(!$this->getBlockAt($x, $y + 1, $z)->isFullCube()){
                if(!$this->getBlockAt($x, $y, $z)->isFullCube()){
                    return new Position($spawn->x, $y === (int) $spawn->y ? $spawn->y : $y, $spawn->z, $this);
                }
            }else{
                ++$y;
            }
        }
 
        return new Position($spawn->x, $y, $spawn->z, $this);
    }
 
    public function getTime() : int{
        return $this->time;
    }
 
    public function getTimeOfDay() : int{
        return $this->time % self::TIME_FULL;
    }
 
    public function getDisplayName() : string{
        return $this->displayName;
    }
 
    public function setDisplayName(string $name) : void{
        (new WorldDisplayNameChangeEvent($this, $this->displayName, $name))->call();
 
        $this->displayName = $name;
        $this->provider->getWorldData()->setName($name);
    }
 
    public function getFolderName() : string{
        return $this->folderName;
    }
 
    public function setTime(int $time) : void{
        $this->time = $time;
        $this->sendTime();
    }
 
    public function stopTime() : void{
        $this->stopTime = true;
        $this->sendTime();
    }
 
    public function startTime() : void{
        $this->stopTime = false;
        $this->sendTime();
    }
 
    public function getSeed() : int{
        return $this->provider->getWorldData()->getSeed();
    }
 
    public function getMinY() : int{
        return $this->minY;
    }
 
    public function getMaxY() : int{
        return $this->maxY;
    }
 
    public function getDifficulty() : int{
        return $this->provider->getWorldData()->getDifficulty();
    }
 
    public function setDifficulty(int $difficulty) : void{
        if($difficulty < 0 || $difficulty > 3){
            throw new \InvalidArgumentException("Invalid difficulty level $difficulty");
        }
        (new WorldDifficultyChangeEvent($this, $this->getDifficulty(), $difficulty))->call();
        $this->provider->getWorldData()->setDifficulty($difficulty);
 
        foreach($this->players as $player){
            $player->getNetworkSession()->syncWorldDifficulty($this->getDifficulty());
        }
    }
 
    private function addChunkHashToPopulationRequestQueue(int $chunkHash) : void{
        if(!isset($this->chunkPopulationRequestQueueIndex[$chunkHash])){
            $this->chunkPopulationRequestQueue->enqueue($chunkHash);
            $this->chunkPopulationRequestQueueIndex[$chunkHash] = true;
        }
    }
 
    private function enqueuePopulationRequest(int $chunkX, int $chunkZ, ?ChunkLoader $associatedChunkLoader) : Promise{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        $this->addChunkHashToPopulationRequestQueue($chunkHash);
        $resolver = $this->chunkPopulationRequestMap[$chunkHash] = new PromiseResolver();
        if($associatedChunkLoader === null){
            $temporaryLoader = new class implements ChunkLoader{};
            $this->registerChunkLoader($temporaryLoader, $chunkX, $chunkZ);
            $resolver->getPromise()->onCompletion(
                fn() => $this->unregisterChunkLoader($temporaryLoader, $chunkX, $chunkZ),
                static function() : void{}
            );
        }
        return $resolver->getPromise();
    }
 
    private function drainPopulationRequestQueue() : void{
        $failed = [];
        while(count($this->activeChunkPopulationTasks) < $this->maxConcurrentChunkPopulationTasks && !$this->chunkPopulationRequestQueue->isEmpty()){
            $nextChunkHash = $this->chunkPopulationRequestQueue->dequeue();
            unset($this->chunkPopulationRequestQueueIndex[$nextChunkHash]);
            World::getXZ($nextChunkHash, $nextChunkX, $nextChunkZ);
            if(isset($this->chunkPopulationRequestMap[$nextChunkHash])){
                assert(!($this->activeChunkPopulationTasks[$nextChunkHash] ?? false), "Population for chunk $nextChunkX $nextChunkZ already running");
                if(
                    !$this->orderChunkPopulation($nextChunkX, $nextChunkZ, null)->isResolved() &&
                    !isset($this->activeChunkPopulationTasks[$nextChunkHash])
                ){
                    $failed[] = $nextChunkHash;
                }
            }
        }
 
        //these requests failed even though they weren't rate limited; we can't directly re-add them to the back of the
        //queue because it would result in an infinite loop
        foreach($failed as $hash){
            $this->addChunkHashToPopulationRequestQueue($hash);
        }
    }
 
    private function checkChunkPopulationPreconditions(int $chunkX, int $chunkZ) : array{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
        $resolver = $this->chunkPopulationRequestMap[$chunkHash] ?? null;
        if($resolver !== null && isset($this->activeChunkPopulationTasks[$chunkHash])){
            //generation is already running
            return [$resolver, false];
        }
 
        $temporaryChunkLoader = new class implements ChunkLoader{};
        $this->registerChunkLoader($temporaryChunkLoader, $chunkX, $chunkZ);
        $chunk = $this->loadChunk($chunkX, $chunkZ);
        $this->unregisterChunkLoader($temporaryChunkLoader, $chunkX, $chunkZ);
        if($chunk !== null && $chunk->isPopulated()){
            //chunk is already populated; return a pre-resolved promise that will directly fire callbacks assigned
            $resolver ??= new PromiseResolver();
            unset($this->chunkPopulationRequestMap[$chunkHash]);
            $resolver->resolve($chunk);
            return [$resolver, false];
        }
        return [$resolver, true];
    }
 
    public function requestChunkPopulation(int $chunkX, int $chunkZ, ?ChunkLoader $associatedChunkLoader) : Promise{
        [$resolver, $proceedWithPopulation] = $this->checkChunkPopulationPreconditions($chunkX, $chunkZ);
        if(!$proceedWithPopulation){
            return $resolver?->getPromise() ?? $this->enqueuePopulationRequest($chunkX, $chunkZ, $associatedChunkLoader);
        }
 
        if(count($this->activeChunkPopulationTasks) >= $this->maxConcurrentChunkPopulationTasks){
            //too many chunks are already generating; delay resolution of the request until later
            return $resolver?->getPromise() ?? $this->enqueuePopulationRequest($chunkX, $chunkZ, $associatedChunkLoader);
        }
        return $this->internalOrderChunkPopulation($chunkX, $chunkZ, $associatedChunkLoader, $resolver);
    }
 
    public function orderChunkPopulation(int $chunkX, int $chunkZ, ?ChunkLoader $associatedChunkLoader) : Promise{
        [$resolver, $proceedWithPopulation] = $this->checkChunkPopulationPreconditions($chunkX, $chunkZ);
        if(!$proceedWithPopulation){
            return $resolver?->getPromise() ?? $this->enqueuePopulationRequest($chunkX, $chunkZ, $associatedChunkLoader);
        }
 
        return $this->internalOrderChunkPopulation($chunkX, $chunkZ, $associatedChunkLoader, $resolver);
    }
 
    private function internalOrderChunkPopulation(int $chunkX, int $chunkZ, ?ChunkLoader $associatedChunkLoader, ?PromiseResolver $resolver) : Promise{
        $chunkHash = World::chunkHash($chunkX, $chunkZ);
 
        $timings = $this->timings->chunkPopulationOrder;
        $timings->startTiming();
 
        try{
            for($xx = -1; $xx <= 1; ++$xx){
                for($zz = -1; $zz <= 1; ++$zz){
                    if($this->isChunkLocked($chunkX + $xx, $chunkZ + $zz)){
                        //chunk is already in use by another generation request; queue the request for later
                        return $resolver?->getPromise() ?? $this->enqueuePopulationRequest($chunkX, $chunkZ, $associatedChunkLoader);
                    }
                }
            }
 
            $this->activeChunkPopulationTasks[$chunkHash] = true;
            if($resolver === null){
                $resolver = new PromiseResolver();
                $this->chunkPopulationRequestMap[$chunkHash] = $resolver;
            }
 
            $chunkPopulationLockId = new ChunkLockId();
 
            $temporaryChunkLoader = new class implements ChunkLoader{
            };
            for($xx = -1; $xx <= 1; ++$xx){
                for($zz = -1; $zz <= 1; ++$zz){
                    $this->lockChunk($chunkX + $xx, $chunkZ + $zz, $chunkPopulationLockId);
                    $this->registerChunkLoader($temporaryChunkLoader, $chunkX + $xx, $chunkZ + $zz);
                }
            }
 
            $centerChunk = $this->loadChunk($chunkX, $chunkZ);
            $adjacentChunks = $this->getAdjacentChunks($chunkX, $chunkZ);
            $task = new PopulationTask(
                $this->worldId,
                $chunkX,
                $chunkZ,
                $centerChunk,
                $adjacentChunks,
                function(Chunk $centerChunk, array $adjacentChunks) use ($chunkPopulationLockId, $chunkX, $chunkZ, $temporaryChunkLoader) : void{
                    if(!$this->isLoaded()){
                        return;
                    }
 
                    $this->generateChunkCallback($chunkPopulationLockId, $chunkX, $chunkZ, $centerChunk, $adjacentChunks, $temporaryChunkLoader);
                }
            );
            $workerId = $this->workerPool->selectWorker();
            if(!isset($this->workerPool->getRunningWorkers()[$workerId]) && isset($this->generatorRegisteredWorkers[$workerId])){
                $this->logger->debug("Selected worker $workerId previously had generator registered, but is now offline");
                unset($this->generatorRegisteredWorkers[$workerId]);
            }
            if(!isset($this->generatorRegisteredWorkers[$workerId])){
                $this->registerGeneratorToWorker($workerId);
            }
            $this->workerPool->submitTaskToWorker($task, $workerId);
 
            return $resolver->getPromise();
        }finally{
            $timings->stopTiming();
        }
    }
 
    private function generateChunkCallback(ChunkLockId $chunkLockId, int $x, int $z, Chunk $chunk, array $adjacentChunks, ChunkLoader $temporaryChunkLoader) : void{
        $timings = $this->timings->chunkPopulationCompletion;
        $timings->startTiming();
 
        $dirtyChunks = 0;
        for($xx = -1; $xx <= 1; ++$xx){
            for($zz = -1; $zz <= 1; ++$zz){
                $this->unregisterChunkLoader($temporaryChunkLoader, $x + $xx, $z + $zz);
                if(!$this->unlockChunk($x + $xx, $z + $zz, $chunkLockId)){
                    $dirtyChunks++;
                }
            }
        }
 
        $index = World::chunkHash($x, $z);
        if(!isset($this->activeChunkPopulationTasks[$index])){
            throw new AssumptionFailedError("This should always be set, regardless of whether the task was orphaned or not");
        }
        if(!$this->activeChunkPopulationTasks[$index]){
            $this->logger->debug("Discarding orphaned population result for chunk x=$x,z=$z");
            unset($this->activeChunkPopulationTasks[$index]);
        }else{
            if($dirtyChunks === 0){
                $oldChunk = $this->loadChunk($x, $z);
                $this->setChunk($x, $z, $chunk);
 
                foreach($adjacentChunks as $relativeChunkHash => $adjacentChunk){
                    World::getXZ($relativeChunkHash, $relativeX, $relativeZ);
                    if($relativeX < -1 || $relativeX > 1 || $relativeZ < -1 || $relativeZ > 1){
                        throw new AssumptionFailedError("Adjacent chunks should be in range -1 ... +1 coordinates");
                    }
                    $this->setChunk($x + $relativeX, $z + $relativeZ, $adjacentChunk);
                }
 
                if(($oldChunk === null || !$oldChunk->isPopulated()) && $chunk->isPopulated()){
                    if(ChunkPopulateEvent::hasHandlers()){
                        (new ChunkPopulateEvent($this, $x, $z, $chunk))->call();
                    }
 
                    foreach($this->getChunkListeners($x, $z) as $listener){
                        $listener->onChunkPopulated($x, $z, $chunk);
                    }
                }
            }else{
                $this->logger->debug("Discarding population result for chunk x=$x,z=$z - terrain was modified on the main thread before async population completed");
            }
 
            //This needs to be in this specific spot because user code might call back to orderChunkPopulation().
            //If it does, and finds the promise, and doesn't find an active task associated with it, it will schedule
            //another PopulationTask. We don't want that because we're here processing the results.
            //We can't remove the promise from the array before setting the chunks in the world because that would lead
            //to the same problem. Therefore, it's necessary that this code be split into two if/else, with this in the
            //middle.
            unset($this->activeChunkPopulationTasks[$index]);
 
            if($dirtyChunks === 0){
                $promise = $this->chunkPopulationRequestMap[$index] ?? null;
                if($promise !== null){
                    unset($this->chunkPopulationRequestMap[$index]);
                    $promise->resolve($chunk);
                }else{
                    //Handlers of ChunkPopulateEvent, ChunkLoadEvent, or just ChunkListeners can cause this
                    $this->logger->debug("Unable to resolve population promise for chunk x=$x,z=$z - populated chunk was forcibly unloaded while setting modified chunks");
                }
            }else{
                //request failed, stick it back on the queue
                //we didn't resolve the promise or touch it in any way, so any fake chunk loaders are still valid and
                //don't need to be added a second time.
                $this->addChunkHashToPopulationRequestQueue($index);
            }
 
            $this->drainPopulationRequestQueue();
        }
        $timings->stopTiming();
    }
 
    public function doChunkGarbageCollection() : void{
        $this->timings->doChunkGC->startTiming();
 
        foreach($this->chunks as $index => $chunk){
            if(!isset($this->unloadQueue[$index])){
                World::getXZ($index, $X, $Z);
                if(!$this->isSpawnChunk($X, $Z)){
                    $this->unloadChunkRequest($X, $Z, true);
                }
            }
            $chunk->collectGarbage();
        }
 
        $this->provider->doGarbageCollection();
 
        $this->timings->doChunkGC->stopTiming();
    }
 
    public function unloadChunks(bool $force = false) : void{
        if(count($this->unloadQueue) > 0){
            $maxUnload = 96;
            $now = microtime(true);
            foreach($this->unloadQueue as $index => $time){
                World::getXZ($index, $X, $Z);
 
                if(!$force){
                    if($maxUnload <= 0){
                        break;
                    }elseif($time > ($now - 30)){
                        continue;
                    }
                }
 
                //If the chunk can't be unloaded, it stays on the queue
                if($this->unloadChunk($X, $Z, true)){
                    unset($this->unloadQueue[$index]);
                    --$maxUnload;
                }
            }
        }
    }
}