1 files changed, 88 insertions, 0 deletions
diff --git a/lib/classes/htmlpurifier/HTMLPurifier_Injector_OembedToIframe.php b/lib/classes/htmlpurifier/HTMLPurifier_Injector_OembedToIframe.php
new file mode 100644
index 0000000..501fbad
--- /dev/null
+++ b/lib/classes/htmlpurifier/HTMLPurifier_Injector_OembedToIframe.php
@@ -0,0 +1,88 @@
+<?php
+
+/**
+ * Converts oembed tags to embedded content like the ckeditor does in its `previewInData` feature.
+ * But we only store the oembed into the database and perform the transformation here (with purify)
+ *
+ * Basically replaced <oembed url="..."></oembed> with a styled iframe.
+ * Currently only Youtube embed are supported
+ * TODO CKEditor also supports several other embed, which could also be implemented
+ */
+class HTMLPurifier_Injector_OembedToIframe extends HTMLPurifier_Injector
+{
+    public $name = 'OEmbed';
+    public $needed = ['div', 'iframe'];
+
+    /** @var array[] mapping the corresponding embed url to all their valid urls */
+    const VALID_URLS = [
+        'https://www.youtube.com/embed/' => [
+            // See https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-media-embed/src/mediaembedediting.ts#L95
+            '/^(?:m\.)?youtube\.com\/watch\?v=([\w-]+)(?:&t=(\d+))?/',
+            '/^(?:m\.)?youtube\.com\/shorts\/([\w-]+)(?:\?t=(\d+))?/',
+            '/^(?:m\.)?youtube\.com\/v\/([\w-]+)(?:\?t=(\d+))?/',
+            '/^youtube\.com\/embed\/([\w-]+)(?:\?start=(\d+))?/',
+            '/^youtu\.be\/([\w-]+)(?:\?t=(\d+))?/'
+        ]
+    ];
+
+    public function handleElement(&$token)
+    {
+        if ($token->name !== 'oembed') {
+            return;
+        }
+
+        $url = $token->attr['url'] ?? '';
+        $embedUrl = self::toEmbedUrl($url);
+        if (!$embedUrl) {
+            $token = false;
+            return;
+        }
+
+        // See https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-media-embed/src/mediaembedediting.ts#L108
+        // The css is in content.scss and matches the css of ckeditor5
+        $token = [
+            new HTMLPurifier_Token_Start('div', [
+                'data-oembed-url' => $embedUrl
+            ]),
+            new HTMLPurifier_Token_Start('div', [
+                'class' => 'ckeditor-embed-container'
+            ]),
+            new HTMLPurifier_Token_Empty('iframe', [
+                'src' => $embedUrl,
+                'class' => 'ckeditor-embed',
+            ]),
+            new HTMLPurifier_Token_End('div'),
+            new HTMLPurifier_Token_End('div'),
+        ];
+    }
+
+    /**
+     * Transforms a valid url into a embed url
+     * @param string $url
+     * @return string|null
+     */
+    private static function toEmbedUrl(string $url): ?string
+    {
+        if (empty($url)) {
+            return null;
+        }
+        $cleanUrl = preg_replace('/^https?:\/\/(?:www\.)?/', '', $url);
+        foreach (self::VALID_URLS as $embedUrl => $patterns) {
+            foreach ($patterns as $pattern) {
+                if (preg_match($pattern, $cleanUrl, $matches)) {
+                    $videoId = $matches[1];
+                    $timestamp = !empty($matches[2]) ? $matches[2] : null;
+
+                    $full_url = $embedUrl . $videoId;
+                    if ($timestamp) {
+                        $full_url .= '?start=' . $timestamp;
+                    }
+
+                    return $full_url;
+                }
+            }
+        }
+
+        return null;
+    }
+}