Move dynamic segments from Premium plugin

[MAILPOET-2382]

lib/DynamicSegments/Persistence/Loading/SingleSegmentLoader.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace MailPoet\Premium\DynamicSegments\Persistence\Loading;
+
+use MailPoet\Premium\DynamicSegments\Mappers\DBMapper;
+use MailPoet\Premium\Models\DynamicSegment;
+
+class SingleSegmentLoader {
+
+  /** @var DBMapper */
+  private $mapper;
+
+  public function __construct(DBMapper $mapper) {
+    $this->mapper = $mapper;
+  }
+
+  /**
+   * @param string|int $segment_id
+   * @return DynamicSegment
+   */
+  function load($segment_id) {
+
+    $segment = DynamicSegment::findOne($segment_id);
+    if (!$segment instanceof DynamicSegment) {
+      throw new \InvalidArgumentException('Segment not found');
+    }
+
+    $filters = $segment->dynamicSegmentFilters()->findMany();
+
+    return $this->mapper->mapSegment($segment, $filters);
+  }
+
+
+
+}