Add core extension for Google Groups (#2838)

* Add core extension for Google Groups

#Fix https://github.com/FreshRSS/FreshRSS/issues/2835
Add ability to discover RSS feeds for Google Groups
Based on https://github.com/FreshRSS/FreshRSS/pull/2837

* Allow HTTP in addition of HTTPS

3 files changed, 21 insertions, 0 deletions

diff --git a/lib/core-extensions/Google-Groups/README.md b/lib/core-extensions/Google-Groups/README.md
new file mode 100644
index 000000000..21b901ded
--- /dev/null
+++ b/lib/core-extensions/Google-Groups/README.md
@@ -0,0 +1,3 @@
+# Google Groups
+
+Needed for discovering RSS feeds from [Google Groups](https://groups.google.com).
diff --git a/lib/core-extensions/Google-Groups/extension.php b/lib/core-extensions/Google-Groups/extension.php
new file mode 100644
index 000000000..656bf9b8f
--- /dev/null
+++ b/lib/core-extensions/Google-Groups/extension.php
@@ -0,0 +1,10 @@
+<?php
+class GoogleGroupsExtension extends Minz_Extension {
+	public function init() {
+		$this->registerHook('check_url_before_add', array('GoogleGroupsExtension', 'findFeed'));
+	}
+
+	public static function findFeed($url) {
+		return preg_replace('%^(https?://groups.google.com/forum)/#!forum/(.+)$%i', '$1/feed/$2/msgs/rss.xml', $url);
+	}
+}
diff --git a/lib/core-extensions/Google-Groups/metadata.json b/lib/core-extensions/Google-Groups/metadata.json
new file mode 100644
index 000000000..afaa18392
--- /dev/null
+++ b/lib/core-extensions/Google-Groups/metadata.json
@@ -0,0 +1,8 @@
+{
+	"name": "Google-Groups",
+	"author": "Alkarex",
+	"description": "To discover RSS feeds for Google Groups",
+	"version": 1.0,
+	"entrypoint": "GoogleGroups",
+	"type": "system"
+}