Slowvote - add ability to destroy a poll

Summary: Fixes T5773.

Test Plan: Made a poll and voted on it. Deleted it via ./bin/remove destory V1. No errors and the poll is gone.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5773

Differential Revision: https://secure.phabricator.com/D10167

src/applications/slowvote/storage/PhabricatorSlowvotePoll.php

@@ -6,7 +6,8 @@ final class PhabricatorSlowvotePoll extends PhabricatorSlowvoteDAO
     PhabricatorSubscribableInterface,
     PhabricatorFlaggableInterface,
     PhabricatorTokenReceiverInterface,
-    PhabricatorProjectInterface {
+    PhabricatorProjectInterface,
+    PhabricatorDestructibleInterface {
 
   const RESPONSES_VISIBLE = 0;
   const RESPONSES_VOTERS  = 1;
@@ -139,4 +140,26 @@ final class PhabricatorSlowvotePoll extends PhabricatorSlowvoteDAO
     return array($this->getAuthorPHID());
   }
 
+/* -(  PhabricatorDestructableInterface  )----------------------------------- */
+
+  public function destroyObjectPermanently(
+    PhabricatorDestructionEngine $engine) {
+
+    $this->openTransaction();
+      $choices = id(new PhabricatorSlowvoteChoice())->loadAllWhere(
+        'pollID = %d',
+        $this->getID());
+      foreach ($choices as $choice) {
+        $choice->delete();
+      }
+      $options = id(new PhabricatorSlowvoteOption())->loadAllWhere(
+        'pollID = %d',
+        $this->getID());
+      foreach ($options as $option) {
+        $option->delete();
+      }
+      $this->delete();
+    $this->saveTransaction();
+  }
+
 }