Refactor migration logic for preview URLs and add fix for orphaned previews,

It considts of 2 parts, first the fix for migration 107, in which the problem was that the update only happened when the new preview has a value, which ends up with not updating those previews that have no search/player.
The second part, is a fix via a new migration step, by which it reads the previews again and try to locate the orphaned previews with json decoded string and then update them either with null or an URL value.

Author: ferishili

migrations/107_migrate_previews.php

@@ -16,27 +16,26 @@ public function up()
 
 
         while ($data = $result->fetch()) {
-            $new_preview = null;
+            $new_preview_url = null;
             $previews = json_decode($data['preview'], true);
 
             if (!empty($previews)) {
                 if (!empty($previews['player'])) {
-                    $new_preview = $previews['player'];
+                    $new_preview_url = $previews['player'];
                 } else if (!empty($previews['search'])) {
-                    $new_preview = $previews['search'];
+                    $new_preview_url = $previews['search'];
                 }
             }
 
-            if (!empty($new_preview)) {
-                $stmt->execute([
-                    ':preview' => $new_preview,
-                    ':id' => $data['id']
-                ]);
-            }
+            // Since we are migrating previews to preview URL, we update the preview regardless of the value of the new preview url, whether it is empty or not!
+            $stmt->execute([
+                ':preview' => $new_preview_url,
+                ':id' => $data['id']
+            ]);
         }
     }
 
     public function down()
     {
     }
-}
+}

migrations/110_fix_orphaned_previews.php

@@ -0,0 +1,42 @@
+<?php
+
+class FixOrphanedPreviews extends Migration
+{
+    public function description()
+    {
+        return 'Fix for previews that could not get migrated in 107.';
+    }
+
+    public function up()
+    {
+        $db = DBManager::get();
+
+        $stmt = $db->prepare('UPDATE oc_video SET preview = :preview WHERE id = :id');
+        $result = $db->query('SELECT id, preview FROM oc_video WHERE preview IS NOT NULL');
+
+
+        while ($data = $result->fetch()) {
+            $new_preview_url = null;
+            $previews = json_decode($data['preview'], true);
+
+            // We want to handle the case where the preview is still a json object.
+            if (!empty($previews)) {
+                // Last chance to present the preview URL.
+                if (!empty($previews['player'])) {
+                    $new_preview_url = $previews['player'];
+                } else if (!empty($previews['search'])) {
+                    $new_preview_url = $previews['search'];
+                }
+
+                $stmt->execute([
+                    ':preview' => $new_preview_url,
+                    ':id' => $data['id']
+                ]);
+            }
+        }
+    }
+
+    public function down()
+    {
+    }
+}