URL Shortener service w/o DB

<?php

namespace App\Helpers;

use Hashids\Hashids;
use Illuminate\Support\Facades\Route;

class UrlShortener
{
    private $hashids;
    private $bannedWords;

    public function __construct()
    {
        $this->hashids = new Hashids(config('app.url_shortener_salt'), 6);
        $this->bannedWords = $this->getBannedWords();
    }

    public function encode($url)
    {
        do {
            $prefix = substr(md5($url), 0, 2); // Generate a 2-character prefix from MD5
            $suffix = substr(sha1($url), -2); // Generate a 2-character suffix from SHA1
            $id = crc32($url);
            $hash = $this->hashids->encode($id);
            $shortUrl = $prefix . $hash . $suffix; // Combine prefix, hash, and suffix
        } while ($this->isBannedWord($shortUrl));

        return $shortUrl;
    }

    private function getBannedWords()
    {
        $bannedWords = [];
        $routes = Route::getRoutes();

        foreach ($routes as $route) {
            $uri = $route->uri();
            if (!in_array($uri, $bannedWords)) {
                $bannedWords[] = $uri;
            }
        }

        return $bannedWords;
    }

    private function isBannedWord($shortUrl)
    {
        return in_array($shortUrl, $this->bannedWords);
    }
    public function decode($hash)
    {
        $prefix = substr($hash, 0, 2);
        $suffix = substr($hash, -2);
        $hash = substr($hash, 2, -2);
        $decoded = $this->hashids->decode($hash);
        if (!empty($decoded)) {
            $urlId = $decoded[0];
            // Verify the prefix and suffix by calculating them again
            if ($prefix === substr(md5($urlId), 0, 2) && $suffix === substr(sha1($urlId), -2)) {
                return $urlId;
            }
        }
        return null;
    }
}