Rename LegacyBlockStateMapper -> BlockIdMetaUpgrader

this more accurately describes what it's used for.

src/data/bedrock/block/upgrade/BlockIdMetaUpgrader.php

@@ -0,0 +1,84 @@
+<?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\data\bedrock\block\upgrade;
+
+use pocketmine\data\bedrock\block\BlockStateData;
+use pocketmine\network\mcpe\protocol\serializer\NetworkNbtSerializer;
+use pocketmine\utils\BinaryStream;
+
+/**
+ * Handles translating legacy 1.12 block ID/meta into modern blockstates.
+ */
+final class BlockIdMetaUpgrader{
+	/**
+	 * @param BlockStateData[][] $mappingTable
+	 * @phpstan-param array<string, array<int, BlockStateData>> $mappingTable
+	 */
+	public function __construct(
+		private array $mappingTable,
+		private LegacyBlockIdToStringIdMap $legacyNumericIdMap
+	){}
+
+	public function fromStringIdMeta(string $id, int $meta) : ?BlockStateData{
+		return $this->mappingTable[$id][$meta] ?? $this->mappingTable[$id][0] ?? null;
+	}
+
+	public function fromIntIdMeta(int $id, int $meta) : ?BlockStateData{
+		$stringId = $this->legacyNumericIdMap->legacyToString($id);
+		if($stringId === null){
+			return null;
+		}
+		return $this->fromStringIdMeta($stringId, $meta);
+	}
+
+	/**
+	 * Adds a mapping of legacy block ID and meta to modern blockstate data. This may be needed for upgrading data from
+	 * stored custom blocks from older versions of PocketMine-MP.
+	 */
+	public function addMapping(string $stringId, int $intId, int $meta, BlockStateData $stateData) : void{
+		if(isset($this->mappingTable[$stringId][$meta])){
+			throw new \InvalidArgumentException("A mapping for $stringId:$meta already exists");
+		}
+		$this->mappingTable[$stringId][$meta] = $stateData;
+		$this->legacyNumericIdMap->add($stringId, $intId);
+	}
+
+	public static function loadFromString(string $data, LegacyBlockIdToStringIdMap $idMap, BlockStateUpgrader $blockStateUpgrader) : self{
+		$mappingTable = [];
+
+		$legacyStateMapReader = new BinaryStream($data);
+		$nbtReader = new NetworkNbtSerializer();
+		while(!$legacyStateMapReader->feof()){
+			$id = $legacyStateMapReader->get($legacyStateMapReader->getUnsignedVarInt());
+			$meta = $legacyStateMapReader->getLShort();
+
+			$offset = $legacyStateMapReader->getOffset();
+			$state = $nbtReader->read($legacyStateMapReader->getBuffer(), $offset)->mustGetCompoundTag();
+			$legacyStateMapReader->setOffset($offset);
+			$mappingTable[$id][$meta] = $blockStateUpgrader->upgrade(BlockStateData::fromNbt($state));
+		}
+
+		return new self($mappingTable, $idMap);
+	}
+}