Adds method to subscribe to single or multiple lists

lib/API/MP/v1/API.php

@@ -2,6 +2,9 @@
 namespace MailPoet\API\MP\v1;
 
 use MailPoet\Models\CustomField;
+use MailPoet\Models\Segment;
+use MailPoet\Models\Subscriber;
+use MailPoet\Models\SubscriberSegment;
 
 if(!defined('ABSPATH')) exit;
 
@@ -32,4 +35,39 @@ class API {
 
     return $data;
   }
+
+  function subscribeToList($subscriber_id, $segment_id) {
+    return $this->subscribeToLists($subscriber_id, array($segment_id));
+  }
+
+  function subscribeToLists($subscriber_id, array $segments_ids) {
+    $subscriber = Subscriber::findOne((int)$subscriber_id);
+    // throw exception when subscriber does not exist
+    if(!$subscriber) {
+      throw new \Exception(__('This subscriber does not exist.', 'mailpoet'));
+    }
+
+    // throw exception when none of the segments exist
+    $found_segments = Segment::whereIn('id', $segments_ids)->findMany();
+    if(!$found_segments) {
+      throw new \Exception(__('These lists do not exists.', 'mailpoet'));
+    }
+
+    // throw exception when trying to subscribe to a WP Users segment
+    $found_segments_ids = array();
+    foreach($found_segments as $found_segment) {
+      if($found_segment->type === Segment::TYPE_WP_USERS) {
+        throw new \Exception(__(sprintf("Can't subscribe to a WordPress Users list with ID %d.", $found_segment->id), 'mailpoet'));
+      }
+      $found_segments_ids[] = $found_segment->id;
+    }
+
+    // throw an exception when one or more segments do not exist
+    if(count($found_segments_ids) !== count($segments_ids)) {
+      $missing_ids = array_values(array_diff($segments_ids, $found_segments_ids));
+      throw new \Exception(__(sprintf('Lists with ID %s do not exist.', implode(', ', $missing_ids)), 'mailpoet'));
+    }
+
+    return SubscriberSegment::subscribeToSegments($subscriber, $found_segments_ids);
+  }
 }