<?php

namespace App\Service;

use Doctrine\ORM\EntityManagerInterface;

use App\Entity\Customer;

class UniqueIdGenerator
{
    protected $em;

    public function __construct(EntityManagerInterface $em)
    {
        $this->em = $em;
    }

    public function generateCustomerUniqueId($str_length)
    {
        $em = $this->em;

        // retry until we have no duplicate generated id 
        while (true)
        {
            // generate the id
            $generated_id = $this->generateUniqueId($str_length);

            // check if generated id already exists
            $cust = $em->getRepository(Customer::class)->findOneBy(['generated_id' => $generated_id]);

            if ($cust == null)
                return $generated_id;

            sleep(1);
        }
    }

    protected function generateUniqueId($str_length)
    {
        $charset = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
        $rand_string = '';
        $desired_length = 10;

        $rand_string = substr(str_shuffle($charset), 0, $desired_length);

        $salt = time() . $rand_string;

        return substr(md5($salt), 0, $str_length);
    }
}