Added logic to resolve crawlable short codes

module/Core/config/dependencies.config.php

@@ -59,7 +59,7 @@ return [
 
             Importer\ImportedLinksProcessor::class => ConfigAbstractFactory::class,
 
-            Crawling\CrawlingHelper::class => InvokableFactory::class,
+            Crawling\CrawlingHelper::class => ConfigAbstractFactory::class,
         ],
 
         'aliases' => [
@@ -150,6 +150,8 @@ return [
             Service\ShortUrl\ShortCodeHelper::class,
             Util\DoctrineBatchHelper::class,
         ],
+
+        Crawling\CrawlingHelper::class => ['em'],
     ],
 
 ];

module/Core/src/Crawling/CrawlingHelper.php

@@ -4,10 +4,23 @@ declare(strict_types=1);
 
 namespace Shlinkio\Shlink\Core\Crawling;
 
+use Doctrine\ORM\EntityManagerInterface;
+use Shlinkio\Shlink\Core\Entity\ShortUrl;
+use Shlinkio\Shlink\Core\Repository\ShortUrlRepositoryInterface;
+
 class CrawlingHelper implements CrawlingHelperInterface
 {
+    private EntityManagerInterface $em;
+
+    public function __construct(EntityManagerInterface $em)
+    {
+        $this->em = $em;
+    }
+
     public function listCrawlableShortCodes(): iterable
     {
-        return [];
+        /** @var ShortUrlRepositoryInterface $repo */
+        $repo = $this->em->getRepository(ShortUrl::class);
+        yield from $repo->findCrawlableShortCodes();
     }
 }

module/Core/src/Repository/ShortUrlRepository.php

@@ -288,4 +288,28 @@ class ShortUrlRepository extends EntitySpecificationRepository implements ShortU
             $qb->andWhere($qb->expr()->isNull('s.domain'));
         }
     }
+
+    public function findCrawlableShortCodes(): iterable
+    {
+        $blockSize = 1000;
+        $qb = $this->getEntityManager()->createQueryBuilder();
+        $qb->select('DISTINCT s.shortCode')
+           ->from(ShortUrl::class, 's')
+           ->where($qb->expr()->eq('s.crawlable', ':crawlable'))
+           ->setParameter('crawlable', true)
+           ->setMaxResults($blockSize);
+
+        $page = 0;
+        do {
+            $qbClone = (clone $qb)->setFirstResult($blockSize * $page);
+            $iterator = $qbClone->getQuery()->toIterable();
+            $resultsFound = false;
+            $page++;
+
+            foreach ($iterator as ['shortCode' => $shortCode]) {
+                $resultsFound = true;
+                yield $shortCode;
+            }
+        } while ($resultsFound);
+    }
 }

module/Core/src/Repository/ShortUrlRepositoryInterface.php

@@ -41,4 +41,6 @@ interface ShortUrlRepositoryInterface extends ObjectRepository, EntitySpecificat
     public function findOneMatching(ShortUrlMeta $meta): ?ShortUrl;
 
     public function findOneByImportedUrl(ImportedShlinkUrl $url): ?ShortUrl;
+
+    public function findCrawlableShortCodes(): iterable;
 }

module/Core/src/Repository/VisitRepository.php

@@ -66,11 +66,11 @@ class VisitRepository extends EntitySpecificationRepository implements VisitRepo
 
         do {
             $qb = (clone $originalQueryBuilder)->andWhere($qb->expr()->gt('v.id', $lastId));
-            $iterator = $qb->getQuery()->iterate();
+            $iterator = $qb->getQuery()->toIterable();
             $resultsFound = false;
 
             /** @var Visit $visit */
-            foreach ($iterator as $key => [$visit]) {
+            foreach ($iterator as $key => $visit) {
                 $resultsFound = true;
                 yield $key => $visit;
             }

module/Core/test/Crawling/CrawlingHelperTest.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ShlinkioTest\Shlink\Core\Crawling;
+
+use Doctrine\ORM\EntityManagerInterface;
+use PHPUnit\Framework\TestCase;
+use Prophecy\PhpUnit\ProphecyTrait;
+use Prophecy\Prophecy\ObjectProphecy;
+use Shlinkio\Shlink\Core\Crawling\CrawlingHelper;
+use Shlinkio\Shlink\Core\Entity\ShortUrl;
+use Shlinkio\Shlink\Core\Repository\ShortUrlRepositoryInterface;
+
+class CrawlingHelperTest extends TestCase
+{
+    use ProphecyTrait;
+
+    private CrawlingHelper $helper;
+    private ObjectProphecy $em;
+
+    protected function setUp(): void
+    {
+        $this->em = $this->prophesize(EntityManagerInterface::class);
+        $this->helper = new CrawlingHelper($this->em->reveal());
+    }
+
+    /** @test */
+    public function listCrawlableShortCodesDelegatesIntoRepository(): void
+    {
+        $repo = $this->prophesize(ShortUrlRepositoryInterface::class);
+        $findCrawlableShortCodes = $repo->findCrawlableShortCodes()->willReturn([]);
+        $getRepo = $this->em->getRepository(ShortUrl::class)->willReturn($repo->reveal());
+
+        $result = $this->helper->listCrawlableShortCodes();
+        foreach ($result as $shortCode) {
+            // Result is a generator and therefore, it needs to be iterated
+        }
+
+        $findCrawlableShortCodes->shouldHaveBeenCalledOnce();
+        $getRepo->shouldHaveBeenCalledOnce();
+    }
+}