Use 'enchanting' terminology

'enchant' just didn't feel right, being a verb.
All these things pertain to the act of enchanting.

This is now also consistent with CraftingTransaction etc. The ship already sailed on EnchantInventory, which will have to be renamed at a later datte. However, that was already inconsistent with 'enchanting table', so that's the odd one out here.

src/item/enchantment/EnchantingHelper.php

@@ -0,0 +1,233 @@
+<?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\item\enchantment;
+
+use pocketmine\block\BlockTypeIds;
+use pocketmine\item\enchantment\AvailableEnchantmentRegistry as EnchantmentRegistry;
+use pocketmine\item\Item;
+use pocketmine\item\ItemTypeIds;
+use pocketmine\item\VanillaItems as Items;
+use pocketmine\utils\Limits;
+use pocketmine\utils\Random;
+use pocketmine\world\Position;
+use function abs;
+use function array_filter;
+use function chr;
+use function count;
+use function floor;
+use function max;
+use function min;
+use function mt_rand;
+use function ord;
+use function round;
+
+/**
+ * Helper methods used for enchanting using the enchanting table.
+ */
+final class EnchantingHelper{
+	private const MAX_BOOKSHELF_COUNT = 15;
+
+	private function __construct(){
+		//NOOP
+	}
+
+	/**
+	 * Generates a new random seed for enchant option randomization.
+	 */
+	public static function generateSeed() : int{
+		return mt_rand(Limits::INT32_MIN, Limits::INT32_MAX);
+	}
+
+	/**
+	 * @param EnchantmentInstance[] $enchantments
+	 */
+	public static function enchantItem(Item $item, array $enchantments) : Item{
+		$resultItem = $item->getTypeId() === ItemTypeIds::BOOK ? Items::ENCHANTED_BOOK() : clone $item;
+
+		foreach($enchantments as $enchantment){
+			$resultItem->addEnchantment($enchantment);
+		}
+
+		return $resultItem;
+	}
+
+	/**
+	 * @return EnchantingOption[]
+	 */
+	public static function generateOptions(Position $tablePos, Item $input, int $seed) : array{
+		if($input->isNull() || $input->hasEnchantments()){
+			return [];
+		}
+
+		$random = new Random($seed);
+
+		$bookshelfCount = self::countBookshelves($tablePos);
+		$baseRequiredLevel = $random->nextRange(1, 8) + ($bookshelfCount >> 1) + $random->nextRange(0, $bookshelfCount);
+		$topRequiredLevel = (int) floor(max($baseRequiredLevel / 3, 1));
+		$middleRequiredLevel = (int) floor($baseRequiredLevel * 2 / 3 + 1);
+		$bottomRequiredLevel = max($baseRequiredLevel, $bookshelfCount * 2);
+
+		return [
+			self::createOption($random, $input, $topRequiredLevel),
+			self::createOption($random, $input, $middleRequiredLevel),
+			self::createOption($random, $input, $bottomRequiredLevel),
+		];
+	}
+
+	private static function countBookshelves(Position $tablePos) : int{
+		$bookshelfCount = 0;
+		$world = $tablePos->getWorld();
+
+		for($x = -2; $x <= 2; $x++){
+			for($z = -2; $z <= 2; $z++){
+				// We only check blocks at a distance of 2 blocks from the enchanting table
+				if(abs($x) !== 2 && abs($z) !== 2){
+					continue;
+				}
+
+				// Ensure the space between the bookshelf stack at this X/Z and the enchanting table is empty
+				for($y = 0; $y <= 1; $y++){
+					// Calculate the coordinates of the space between the bookshelf and the enchanting table
+					$spaceX = max(min($x, 1), -1);
+					$spaceZ = max(min($z, 1), -1);
+					$spaceBlock = $world->getBlock($tablePos->add($spaceX, $y, $spaceZ));
+					if($spaceBlock->getTypeId() !== BlockTypeIds::AIR){
+						continue 2;
+					}
+				}
+
+				// Finally, check the number of bookshelves at the current position
+				for($y = 0; $y <= 1; $y++){
+					$block = $world->getBlock($tablePos->add($x, $y, $z));
+					if($block->getTypeId() === BlockTypeIds::BOOKSHELF){
+						$bookshelfCount++;
+						if($bookshelfCount === self::MAX_BOOKSHELF_COUNT){
+							return $bookshelfCount;
+						}
+					}
+				}
+			}
+		}
+
+		return $bookshelfCount;
+	}
+
+	private static function createOption(Random $random, Item $inputItem, int $requiredXpLevel) : EnchantingOption{
+		$enchantingPower = $requiredXpLevel;
+
+		$enchantability = $inputItem->getEnchantability();
+		$enchantingPower = $enchantingPower + $random->nextRange(0, $enchantability >> 2) + $random->nextRange(0, $enchantability >> 2) + 1;
+		// Random bonus for enchanting power between 0.85 and 1.15
+		$bonus = 1 + ($random->nextFloat() + $random->nextFloat() - 1) * 0.15;
+		$enchantingPower = (int) round($enchantingPower * $bonus);
+
+		$resultEnchantments = [];
+		$availableEnchantments = self::getAvailableEnchantments($enchantingPower, $inputItem);
+
+		$lastEnchantment = self::getRandomWeightedEnchantment($random, $availableEnchantments);
+		if($lastEnchantment !== null){
+			$resultEnchantments[] = $lastEnchantment;
+
+			// With probability (power + 1) / 50, continue adding enchantments
+			while($random->nextFloat() <= ($enchantingPower + 1) / 50){
+				// Remove from the list of available enchantments anything that conflicts
+				// with previously-chosen enchantments
+				$availableEnchantments = array_filter(
+					$availableEnchantments,
+					function(EnchantmentInstance $e) use ($lastEnchantment){
+						return $e->getType() !== $lastEnchantment->getType() &&
+							$e->getType()->isCompatibleWith($lastEnchantment->getType());
+					}
+				);
+
+				$lastEnchantment = self::getRandomWeightedEnchantment($random, $availableEnchantments);
+				if($lastEnchantment === null){
+					break;
+				}
+
+				$resultEnchantments[] = $lastEnchantment;
+				$enchantingPower >>= 1;
+			}
+		}
+
+		return new EnchantingOption($requiredXpLevel, self::getRandomOptionName($random), $resultEnchantments);
+	}
+
+	/**
+	 * @return EnchantmentInstance[]
+	 */
+	private static function getAvailableEnchantments(int $enchantingPower, Item $item) : array{
+		$list = [];
+
+		foreach(EnchantmentRegistry::getInstance()->getPrimaryEnchantmentsForItem($item) as $enchantment){
+			for($lvl = $enchantment->getMaxLevel(); $lvl > 0; $lvl--){
+				if($enchantingPower >= $enchantment->getMinEnchantingPower($lvl) &&
+					$enchantingPower <= $enchantment->getMaxEnchantingPower($lvl)
+				){
+					$list[] = new EnchantmentInstance($enchantment, $lvl);
+					break;
+				}
+			}
+		}
+
+		return $list;
+	}
+
+	/**
+	 * @param EnchantmentInstance[] $enchantments
+	 */
+	private static function getRandomWeightedEnchantment(Random $random, array $enchantments) : ?EnchantmentInstance{
+		if(count($enchantments) === 0){
+			return null;
+		}
+
+		$totalWeight = 0;
+		foreach($enchantments as $enchantment){
+			$totalWeight += $enchantment->getType()->getRarity();
+		}
+
+		$result = null;
+		$randomWeight = $random->nextRange(1, $totalWeight);
+
+		foreach($enchantments as $enchantment){
+			$randomWeight -= $enchantment->getType()->getRarity();
+
+			if($randomWeight <= 0){
+				$result = $enchantment;
+				break;
+			}
+		}
+
+		return $result;
+	}
+
+	private static function getRandomOptionName(Random $random) : string{
+		$name = "";
+		for($i = $random->nextRange(5, 15); $i > 0; $i--){
+			$name .= chr($random->nextRange(ord("a"), ord("z")));
+		}
+
+		return $name;
+	}
+}