Promise.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\promise;
 
use function count;
use function spl_object_id;
 
final class Promise{
    public function __construct(private PromiseSharedData $shared){}
 
    public function onCompletion(\Closure $onSuccess, \Closure $onFailure) : void{
        $state = $this->shared->state;
        if($state === true){
            $onSuccess($this->shared->result);
        }elseif($state === false){
            $onFailure();
        }else{
            $this->shared->onSuccess[spl_object_id($onSuccess)] = $onSuccess;
            $this->shared->onFailure[spl_object_id($onFailure)] = $onFailure;
        }
    }
 
    public function isResolved() : bool{
        //TODO: perhaps this should return true when rejected? currently there's no way to tell if a promise was
        //rejected or just hasn't been resolved yet
        return $this->shared->state === true;
    }
 
    public static function all(array $promises) : Promise{
        if(count($promises) === 0){
            throw new \InvalidArgumentException("At least one promise must be provided");
        }
        $resolver = new PromiseResolver();
        $values = [];
        $toResolve = count($promises);
        $continue = true;
 
        foreach($promises as $key => $promise){
            $promise->onCompletion(
                function(mixed $value) use ($resolver, $key, $toResolve, &$values) : void{
                    $values[$key] = $value;
 
                    if(count($values) === $toResolve){
                        $resolver->resolve($values);
                    }
                },
                function() use ($resolver, &$continue) : void{
                    if($continue){
                        $continue = false;
                        $resolver->reject();
                    }
                }
            );
 
            if(!$continue){
                break;
            }
        }
 
        return $resolver->getPromise();
    }
}