feat: Add handleYoutube function

Author: Mynacol

config.default.ini.php

@@ -132,6 +132,18 @@
 ; Defines how often an error must occur before it is reported to the user
 report_limit = 1
 
+[youtube]
+
+; Whether to use an iframe to directly embed YouTube videos in feeds.
+; If false, a clickable video thumbnail is used instead. This avoids sending a referrer to YouTube or only getting the error 153 if suppressing the referrer browser-wide.
+iframe = true
+
+; Use the youtube-nocookie.com domain instead of youtube.com for iframe embeds.
+; Only relevant if youtube.iframe is true.
+; See the following for a description:
+; https://support.google.com/youtube/answer/171780?hl=en#zippy=%2Cturn-on-privacy-enhanced-mode
+nocookie = false
+
 ; --- Cache specific configuration ---------------------------------------------
 
 [FileCache]

docs/06_Helper_functions/index.md

@@ -355,3 +355,20 @@ foreach ($urls as $url) {
     $lastmod = $url['lastmod'];
 }
 ```
+
+# handleYoutube(string $html): string
+
+Use this function to throw a YouTube link, iframe tag or video ID and get a HTML snippet that returns a normalized iframe tag or clickable image thumbnail, depending on system configuration.
+
+```php
+$result = handleYoutube('naYc5X6EL_Y');
+
+$result = handleYoutube('https://www.youtube.com/watch?v=naYc5X6EL_Y');
+
+$result = handleYoutube('https://www.youtube.com/embed/naYc5X6EL_Y');
+
+$iframe = '<iframe width="560" height="315" src="https://www.youtube.com/embed/naYc5X6EL_Y?si=abcdefgh" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>';
+$result = handleYoutube($iframe);
+```
+
+[Defined in lib/html.php](https://github.com/RSS-Bridge/rss-bridge/blob/master/lib/html.php)

lib/html.php

@@ -477,3 +477,67 @@ function markdownToHtml($string, $config = [])
     }
     return $Parsedown->text($string);
 }
+
+/**
+ * Handle a YouTube video by either returning an iframe that embeds the video
+ * or by returning a clickable image (an <img> in a <a> tag).
+ * The system config can specify which to use, and whether to use youtube-nocookie.com over youtube.com.
+ *
+ * @param string $string A string containing a YouTube video URL or directly a video ID.
+ * @return string A HTML snippet either with an iframe or a clickable thumbnail. An empty string if no YouTube video ID is found.
+ */
+function handleYoutube(string $string)
+{
+    $useIframe = Configuration::getConfig('youtube', 'iframe');
+    $useNocookie = Configuration::getConfig('youtube', 'nocookie');
+
+    // sourced from https://gist.github.com/afeld/1254889?permalink_comment_id=3580082#gistcomment-3580082
+    $regex = '#(?:https?://|//)?(?:www\.|m\.|.+\.)?(?:youtu\.be/|youtube(?:-nocookie)\.com/(?:embed/|v/|shorts/|feeds/api/videos/|watch\?v=|watch\?.+&v=))([\w-]{11})#i';
+    if (preg_match($regex, $string, $matches) === 1) {
+        $videoID = $matches[1];
+    } elseif (preg_match('#[\w-]{11}#i', $string, $matches2) === 1) {
+        $videoID = $matches2[0];
+    } else {
+        return '';
+    }
+
+    if ($useIframe) {
+        if ($useNocookie) {
+            $embedUri = 'https://www.youtube-nocookie.com/embed/' . $videoID;
+        } else {
+            $embedUri = 'https://www.youtube.com/embed/' . $videoID;
+        }
+
+        return sprintf(<<<EOD
+<iframe width="560" height="315" src="%s" title="YouTube video player" frameborder="0"
+allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
+referrerpolicy="strict-origin" allowfullscreen></iframe>'
+EOD
+         , $embedUri);
+    } else {
+        $videoUri = 'https://www.youtube.com/watch?v=' . $videoID;
+
+        $thumbnailJpegBaseUri = 'https://i.ytimg.com/vi/' . $videoID;
+        $jpegSrcset = sprintf(
+            '%1$s/mqdefault.jpg 320w, %1$s/0.jpg 480w, %1$s/hqdefault.jpg 481w, %1$s/sddefault.jpg 640w, %1$s/hq720.jpg 720w, %1$s/maxresdefault.jpg 721w',
+            $thumbnailJpegBaseUri
+        );
+
+        $thumbnailWebpBaseUri = 'https://i.ytimg.com/vi_webp/' . $videoID;
+        $webpSrcset = sprintf(
+            '%1$s/mqdefault.webp 320w, %1$s/0.webp 480w, %1$s/hqdefault.webp 481w, %1$s/sddefault.webp 640w, %1$s/hq720.webp 720w, %1$s/maxresdefault.webp 721w',
+            $thumbnailWebpBaseUri
+        );
+
+        $fallbackUri = $thumbnailJpegBaseUri . '/maxresdefault.jpg';
+
+        return sprintf(<<<EOD
+<a href="%s">
+    <picture>
+        <source srcset="%s" type="image/webp" referrerpolicy="no-referrer" />
+        <img srcset="%s" src="%s" alt="Video thumbnail" title="YouTube video thumbnail" referrerpolicy="no-referrer" />
+    </picture>
+</a>
+EOD, $videoUri, $webpSrcset, $jpegSrcset, $fallbackUri);
+    }
+}