class Parallel
{
    private array $threads = [];

    private array $process = [];

    public function add(PromiseInterface $promise): self
    {
        $this->threads[] = $promise;
        return $this;
    }

    public function run(): void
    {

        foreach ($this->threads as $thread) {
            $descriptors = [
                0 => ['pipe', 'r'], // stdin
                1 => ['pipe', 'w'], // stdout
                2 => ['pipe', 'w'], // stderr
            ];

            $process = proc_open('php', $descriptors, $pipes);

            if (is_resource($process)) {
                fwrite($pipes[0], $this->generatePhpCode($thread));
                fclose($pipes[0]);
                fclose($pipes[2]);
                $this->process [] = [
                    'pipe' => $pipes[1],
                    'process' => $process,
                    'thread' => $thread
                ];
            }
        }
    }

    /***
     * @return void
     */
    public function wait(): void
    {
        while (!empty($this->process)) {
            foreach ($this->process as $key => $value) {

                [
                    'pipe' => $pipe,
                    'process' => $process,
                    'thread' => $thread
                ] = $value;

                if (is_resource($process)) {
                    $status = proc_get_status($process);
                    if ($status['running']) {
                        continue;
                    }
                    /**
                     * @var PromiseInterface $thread
                     */
                    $thread->then(stream_get_contents($pipe));
                    echo PHP_EOL;
                    proc_close($process);
                    unset($this->process[$key]);
                }

            }
        }
    }

    /***
     * @param PromiseInterface $promise
     * @return string
     */
    private function generatePhpCode(PromiseInterface $promise): string
    {
        $serialize=serialize($promise);
        return "<?php require_once 'vendor/autoload.php';\$closure = unserialize('$serialize');echo \$closure(); ?>";
    }
}