From a052bfd5909a70825dbc654dfd16204ea661cb1c Mon Sep 17 00:00:00 2001
From: Michal Kleiner <michal.kleiner@cub3.com>
Date: Thu, 22 Jun 2023 01:13:08 +1000
Subject: [PATCH] Add extension to correctly support element preview

---
 _config/extensions.yml                 |  9 +++++++
 src/Extensions/BaseElementSubsites.php | 33 ++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 src/Extensions/BaseElementSubsites.php

diff --git a/_config/extensions.yml b/_config/extensions.yml
index 32731f5..976385f 100644
--- a/_config/extensions.yml
+++ b/_config/extensions.yml
@@ -64,3 +64,12 @@ SilverStripe\Subsites\Admin\SubsiteAdmin:
 SilverStripe\SiteConfig\SiteConfigLeftAndMain:
   extensions:
     - SilverStripe\Subsites\Extensions\SubsiteMenuExtension
+
+---
+Name: subsite-preview-elemental
+Only:
+  classexists: DNADesign\Elemental\Models\BaseElement
+---
+DNADesign\Elemental\Models\BaseElement:
+  extensions:
+    - SilverStripe\Subsites\Extensions\BaseElementSubsites
diff --git a/src/Extensions/BaseElementSubsites.php b/src/Extensions/BaseElementSubsites.php
new file mode 100644
index 0000000..02235b6
--- /dev/null
+++ b/src/Extensions/BaseElementSubsites.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace SilverStripe\Subsites\Extensions;
+
+use SilverStripe\Control\HTTP;
+use SilverStripe\ORM\DataExtension;
+
+/**
+ * Extension for the BaseElement object to add subsites support for CMS previews
+ */
+class BaseElementSubsites extends DataExtension
+{
+    /**
+     * Set SubsiteID to avoid errors when a page doesn't exist on the CMS domain.
+     *
+     * @param string &$link
+     * @param string|null $action
+     * @return string
+     */
+    public function updatePreviewLink(&$link)
+    {
+        // Get subsite ID from the element or from its page. Defaults to 0 automatically.
+        $subsiteID = $this->owner->SubsiteID;
+        if (is_null($subsiteID)) {
+            $page = $this->owner->getPage();
+            if ($page) {
+                $subsiteID = $page->SubsiteID;
+            }
+        }
+
+        $link = HTTP::setGetVar('SubsiteID', intval($subsiteID), $link);
+    }
+}