MDL-62401 Media: Embed Youtube Videos with nocookie extension

Refactor YouTube media player to use templates.
Use mustache templates for rendering YouTube embed
iframe code.

media/player/youtube/classes/plugin.php

@@ -62,6 +62,8 @@ public function list_supported_urls(array $urls, array $options = array()) {
     }
 
     protected function embed_external(moodle_url $url, $name, $width, $height, $options) {
+        global $OUTPUT;
+        $nocookie = get_config('media_youtube', 'nocookie');
 
         $info = trim($name ?? '');
         if (empty($info) or strpos($info, 'http') === 0) {
@@ -71,40 +73,60 @@ protected function embed_external(moodle_url $url, $name, $width, $height, $opti
 
         self::pick_video_size($width, $height);
 
-        if ($this->isplaylist) {
+        // Template context.
+        $context = [
+                'width' => $width,
+                'height' => $height,
+                'title' => $info
+        ];
 
+        if ($this->isplaylist) {
             $site = $this->matches[1];
             $playlist = $this->matches[3];
 
-            return <<<OET
-<span class="mediaplugin mediaplugin_youtube">
-<iframe width="$width" height="$height" src="https://$site/embed/videoseries?list=$playlist" frameborder="0"
-  allowfullscreen="1" style="max-width: 100%;"></iframe>
-</span>
-OET;
-        } else {
+            $params = ['list' => $playlist];
+
+            // Handle no cookie option.
+            if (!$nocookie) {
+                $embedurl = new moodle_url("https://$site/embed/videoseries", $params);
+            } else {
+                $embedurl = new moodle_url('https://www.youtube-nocookie.com/embed/videoseries', $params );
+            }
+            $context['embedurl'] = $embedurl->out(false);
+
+            // Return the rendered template.
+            return $OUTPUT->render_from_template('media_youtube/embed', $context);
 
+        } else {
             $videoid = end($this->matches);
-            $params = '';
+            $params = [];
             $start = self::get_start_time($url);
             if ($start > 0) {
-                $params .= "start=$start&amp;";
+                $params['start'] = $start;
             }
 
             $listid = $url->param('list');
             // Check for non-empty but valid playlist ID.
             if (!empty($listid) && !preg_match('/[^a-zA-Z0-9\-_]/', $listid)) {
                 // This video is part of a playlist, and we want to embed it as such.
-                $params .= "list=$listid&amp;";
+                $params['list'] = $listid;
             }
 
-            return <<<OET
-<span class="mediaplugin mediaplugin_youtube">
-<iframe title="$info" width="$width" height="$height"
-  src="https://www.youtube.com/embed/$videoid?{$params}rel=0&amp;wmode=transparent" frameborder="0"
-  allowfullscreen="1" style="max-width: 100%;"></iframe>
-</span>
-OET;
+            // Add parameters to object to be passed to the mustache template.
+            $params['rel'] = 0;
+            $params['wmode'] = 'transparent';
+
+            // Handle no cookie option.
+            if (!$nocookie) {
+                $embedurl = new moodle_url('https://www.youtube.com/embed/' . $videoid, $params );
+            } else {
+                $embedurl = new moodle_url('https://www.youtube-nocookie.com/embed/' . $videoid, $params );
+            }
+
+            $context['embedurl'] = $embedurl->out(false);
+
+            // Return the rendered template.
+            return $OUTPUT->render_from_template('media_youtube/embed', $context);
         }
 
     }

media/player/youtube/templates/embed.mustache

@@ -0,0 +1,41 @@
+{{!
+    This file is part of Moodle - http://moodle.org/
+
+    Moodle is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Moodle is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+}}
+{{!
+    @template media/embed
+
+    This template will render the YouTube embeded player.
+
+    Variables required for this template:
+    * info: The title of the video.
+    * width: The width of the video.
+    * height: The height of the video.
+    * embedurl: The URL to the video.
+
+    Example context (json):
+    {
+        "info": "YouTube video",
+        "width": 640,
+        "height": 360,
+        "embedurl": "https://www.youtube.com/embed/9bZkp7q19f0?rel=0&amp;wmode=transparent"
+    }
+
+}}
+
+<span class="mediaplugin mediaplugin_youtube">
+<iframe title="{{info}}" width="{{width}}" height="{{height}}" style="border:0;"
+        src="{{{embedurl}}}" allow="fullscreen"></iframe>
+</span>