Improve default dkim selector #34

Author: bwalkerl

classes/form/create_dkim.php

@@ -24,6 +24,7 @@
  */
 
 namespace tool_emailutils\form;
+use tool_emailutils\dns_util;
 
 defined('MOODLE_INTERNAL') || die;
 
@@ -53,7 +54,7 @@ public function definition() {
 
         $group[] =& $mform->createElement('text', 'selector', array("size" => 20));
 
-        $selector = \userdate(time(), get_string('selectordefault', 'tool_emailutils'));
+        $selector = $this->get_default_selector();
         $mform->setDefault("selector", $selector);
         $mform->setType('selector', PARAM_HOST);
 
@@ -74,4 +75,38 @@ public function validation($data, $files) {
         $errors = parent::validation($data, $files);
         return $errors;
     }
+
+    /**
+     * Gets a selector value to use as a default
+     *
+     * @return string default selector
+     */
+    private function get_default_selector() {
+        GLOBAL $CFG;
+        // Add date to default.
+        $selector = \userdate(time(), get_string('selectordefault', 'tool_emailutils'));
+
+        // Add subdomain to default.
+        $dns = new dns_util();
+        $url = new \moodle_url($CFG->wwwroot);
+        $domain = $url->get_host();
+        $subdomains = $dns->get_subdomains($domain);
+
+        // Clean the subdomains to remove foreign language chars.
+        // Email filter is enough because domains don't contain the other allowed chars.
+        $cleanedsubdomains = trim(filter_var($subdomains, FILTER_SANITIZE_EMAIL), '.');
+
+        if (!empty($cleanedsubdomains)) {
+            $formatteddomain = str_replace('.', '-', $cleanedsubdomains);
+        } else {
+            $partdomain = explode('.', $domain)[0];
+            $formatteddomain = filter_var($partdomain, FILTER_SANITIZE_EMAIL);
+        }
+
+        if ($formatteddomain && $formatteddomain != 'www') {
+            $selector .= '-' . $formatteddomain;
+        }
+        return $selector;
+    }
+
 }