Updated logic to generate random short codes, increasing entropy

module/Core/src/Entity/ShortUrl.php

@@ -7,6 +7,7 @@ namespace Shlinkio\Shlink\Core\Entity;
 use Cake\Chronos\Chronos;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
+use PUGX\Shortid\Factory as ShortIdFactory;
 use Shlinkio\Shlink\Common\Entity\AbstractEntity;
 use Shlinkio\Shlink\Core\Domain\Resolver\DomainResolverInterface;
 use Shlinkio\Shlink\Core\Domain\Resolver\SimpleDomainResolver;
@@ -20,6 +21,8 @@ use function Functional\invoke;
 
 class ShortUrl extends AbstractEntity
 {
+    private const BASE62 = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
+
     /** @var string */
     private $longUrl;
     /** @var string */
@@ -53,10 +56,15 @@ class ShortUrl extends AbstractEntity
         $this->validSince = $meta->getValidSince();
         $this->validUntil = $meta->getValidUntil();
         $this->maxVisits = $meta->getMaxVisits();
-        $this->shortCode = $meta->getCustomSlug() ?? ''; // TODO logic to calculate short code should be passed somehow
+        $this->shortCode = $meta->getCustomSlug() ?? $this->generateShortCode();
         $this->domain = ($domainResolver ?? new SimpleDomainResolver())->resolveDomain($meta->getDomain());
     }
 
+    private function generateShortCode(): string
+    {
+        return (new ShortIdFactory())->generate(6, self::BASE62)->serialize();
+    }
+
     public function getLongUrl(): string
     {
         return $this->longUrl;
@@ -67,13 +75,6 @@ class ShortUrl extends AbstractEntity
         return $this->shortCode;
     }
 
-    // TODO Short code is currently calculated based on the ID, so a setter is needed
-    public function setShortCode(string $shortCode): self
-    {
-        $this->shortCode = $shortCode;
-        return $this;
-    }
-
     public function getDateCreated(): Chronos
     {
         return $this->dateCreated;

module/Core/src/Options/UrlShortenerOptions.php

@@ -8,26 +8,12 @@ use Zend\Stdlib\AbstractOptions;
 
 class UrlShortenerOptions extends AbstractOptions
 {
-    public const DEFAULT_CHARS = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
-
     // phpcs:disable
     protected $__strictMode__ = false;
     // phpcs:enable
 
-    private $shortcodeChars = self::DEFAULT_CHARS;
     private $validateUrl = true;
 
-    public function getChars(): string
-    {
-        return $this->shortcodeChars;
-    }
-
-    protected function setShortcodeChars(string $shortcodeChars): self
-    {
-        $this->shortcodeChars = empty($shortcodeChars) ? self::DEFAULT_CHARS : $shortcodeChars;
-        return $this;
-    }
-
     public function isUrlValidationEnabled(): bool
     {
         return $this->validateUrl;

module/Core/src/Service/UrlShortener.php

@@ -24,17 +24,11 @@ use Shlinkio\Shlink\Core\Util\TagManagerTrait;
 use Throwable;
 
 use function array_reduce;
-use function floor;
-use function fmod;
-use function preg_match;
-use function strlen;
 
 class UrlShortener implements UrlShortenerInterface
 {
     use TagManagerTrait;
 
-    private const ID_INCREMENT = 200000;
-
     /** @var ClientInterface */
     private $httpClient;
     /** @var EntityManagerInterface */
@@ -77,16 +71,8 @@ class UrlShortener implements UrlShortenerInterface
 
             // First, create the short URL with an empty short code
             $shortUrl = new ShortUrl($url, $meta, new PersistenceDomainResolver($this->em));
-            $this->em->persist($shortUrl);
-            $this->em->flush();
-
-            // Generate the short code and persist it if no custom slug was provided
-            if (! $meta->hasCustomSlug()) {
-                // TODO Somehow provide the logic to calculate the shortCode to avoid the need of a setter
-                $shortCode = $this->convertAutoincrementIdToShortCode((float) $shortUrl->getId());
-                $shortUrl->setShortCode($shortCode);
-            }
             $shortUrl->setTags($this->tagNamesToEntities($this->em, $tags));
+            $this->em->persist($shortUrl);
             $this->em->flush();
 
             $this->em->commit();
@@ -155,36 +141,12 @@ class UrlShortener implements UrlShortenerInterface
         }
     }
 
-    private function convertAutoincrementIdToShortCode(float $id): string
-    {
-        $id += self::ID_INCREMENT; // Increment the Id so that the generated shortcode is not too short
-        $chars = $this->options->getChars();
-
-        $length = strlen($chars);
-        $code = '';
-
-        while ($id > 0) {
-            // Determine the value of the next higher character in the short code and prepend it
-            $code = $chars[(int) fmod($id, $length)] . $code;
-            $id = floor($id / $length);
-        }
-
-        return $chars[(int) $id] . $code;
-    }
-
     /**
      * @throws InvalidShortCodeException
      * @throws EntityDoesNotExistException
      */
     public function shortCodeToUrl(string $shortCode, ?string $domain = null): ShortUrl
     {
-        $chars = $this->options->getChars();
-
-        // Validate short code format
-        if (! preg_match('|[' . $chars . ']+|', $shortCode)) {
-            throw InvalidShortCodeException::fromCharset($shortCode, $chars);
-        }
-
         /** @var ShortUrlRepository $shortUrlRepo */
         $shortUrlRepo = $this->em->getRepository(ShortUrl::class);
         $shortUrl = $shortUrlRepo->findOneByShortCode($shortCode, $domain);