Cache total subscribers count, add tests

[MAILPOET-4416]

mailpoet/lib/Subscribers/SubscribersRepository.php

@@ -7,6 +7,7 @@ use MailPoet\Entities\SegmentEntity;
 use MailPoet\Entities\SubscriberCustomFieldEntity;
 use MailPoet\Entities\SubscriberEntity;
 use MailPoet\Entities\SubscriberSegmentEntity;
+use MailPoet\Util\License\Features\Subscribers;
 use MailPoet\WP\Functions as WPFunctions;
 use MailPoetVendor\Carbon\Carbon;
 use MailPoetVendor\Carbon\CarbonImmutable;
@@ -41,10 +42,7 @@ class SubscribersRepository extends Repository {
     return SubscriberEntity::class;
   }
 
-  /**
-   * @return int
-   */
-  public function getTotalSubscribers() {
+  public function getTotalSubscribers(): int {
     $query = $this->entityManager
       ->createQueryBuilder()
       ->select('count(n.id)')
@@ -59,6 +57,10 @@ class SubscribersRepository extends Repository {
     return (int)$query->getSingleScalarResult();
   }
 
+  public function invalidateTotalSubscribersCache(): void {
+    $this->wp->deleteTransient(Subscribers::SUBSCRIBERS_COUNT_CACHE_KEY);
+  }
+
   public function findBySegment(int $segmentId): array {
     return $this->entityManager
     ->createQueryBuilder()
@@ -116,6 +118,7 @@ class SubscribersRepository extends Repository {
       ->setParameter('ids', $ids)
       ->getQuery()->execute();
 
+    $this->invalidateTotalSubscribersCache();
     return count($ids);
   }
 
@@ -135,6 +138,7 @@ class SubscribersRepository extends Repository {
       ->setParameter('ids', $ids)
       ->getQuery()->execute();
 
+    $this->invalidateTotalSubscribersCache();
     return count($ids);
   }
 
@@ -171,6 +175,7 @@ class SubscribersRepository extends Repository {
         ->getQuery()->execute();
     });
 
+    $this->invalidateTotalSubscribersCache();
     return $count;
   }
 
@@ -282,6 +287,7 @@ class SubscribersRepository extends Repository {
       ->setParameter('ids', $ids)
       ->getQuery()->execute();
 
+    $this->invalidateTotalSubscribersCache();
     return count($ids);
   }