<?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\runtime;

use function ceil;
use function count;
use function log;
use function spl_object_id;
use function usort;

/**
 * A big hack to allow lazily associating enum cases with packed bit values for RuntimeDataDescriber :)
 *
 * @internal
 * @phpstan-template T of \UnitEnum
 */
final class RuntimeEnumMetadata{
	public readonly int $bits;

	/**
	 * @var object[]
	 * @phpstan-var list<T>
	 */
	private readonly array $intToEnum;
	/**
	 * @var int[]
	 * @phpstan-var array<int, int>
	 */
	private readonly array $enumToInt;

	/**
	 * @param \UnitEnum[] $members
	 * @phpstan-param list<T> $members
	 */
	public function __construct(
		array $members
	){
		usort($members, fn(\UnitEnum $a, \UnitEnum $b) => $a->name <=> $b->name); //sort by name to ensure consistent ordering (and thus consistent bit assignments)

		$this->bits = (int) ceil(log(count($members), 2));
		$this->intToEnum = $members; //usort strips keys so this is already a list

		$reversed = [];
		foreach($this->intToEnum as $int => $enum){
			$reversed[spl_object_id($enum)] = $int;
		}

		$this->enumToInt = $reversed;
	}

	/**
	 * @phpstan-return T|null
	 */
	public function intToEnum(int $value) : ?object{
		return $this->intToEnum[$value] ?? null;
	}

	/**
	 * @phpstan-param T $enum
	 */
	public function enumToInt(object $enum) : int{
		return $this->enumToInt[spl_object_id($enum)];
	}

	/**
	 * @var self[]
	 * @phpstan-var array<class-string, object>
	 */
	private static array $cache = [];

	/**
	 * @phpstan-template TEnum of \UnitEnum
	 * @phpstan-param TEnum $case
	 *
	 * @phpstan-return self<TEnum>
	 */
	public static function from(\UnitEnum $case) : self{
		$class = $case::class;
		/** @phpstan-var self<TEnum>|null $metadata */
		$metadata = self::$cache[$class] ?? null;
		if($metadata === null){
			/**
			 * PHPStan can't infer this correctly :( https://github.com/phpstan/phpstan/issues/7162
			 * @phpstan-var list<TEnum> $cases
			 */
			$cases = $case::cases();
			self::$cache[$class] = $metadata = new self($cases);
		}

		return $metadata;
	}
}