Add hook for certificate element classes discovery

Author: skodak

classes/element.php

@@ -69,18 +69,19 @@ public static function instance(int $id = 0, ?\stdClass $obj = null): element {
      * Helper method to create an instance from persistent
      *
      * @param \tool_certificate\persistent\element $persistent
-     * @return element
+     * @return element|null
      */
     protected static function instance_from_persistent(\tool_certificate\persistent\element $persistent): ?element {
-        // Get the class name.
-        $classname = '\\certificateelement_' . $persistent->get('element') . '\\element';
+        $elementclasses = element_helper::get_element_classes();
 
-        // Ensure the necessary class exists.
-        if (!class_exists($classname) || !is_subclass_of($classname, self::class)) {
+        $shortname = $persistent->get('element');
+        if (!isset($elementclasses[$shortname])) {
             return null;
         }
 
-        /** @var self $el */
+        /** @var class-string<element> $classname */
+        $classname = $elementclasses[$shortname];
+
         $el = new $classname($persistent);
         $el->persistent = $persistent;
         return $el;

classes/element_helper.php

@@ -446,29 +446,58 @@ public static function get_element_sequence($pageid) {
         return $sequence;
     }
 
+    /**
+     * Returns all enabled element classes.
+     *
+     * @return array<string, class-string<\tool_certificate\element>>
+     */
+    public static function get_element_classes(): array {
+        $plugins = self::get_enabled_plugins();
+
+        if (!class_exists(\core\hook\manager::class)) {
+            // Legacy code for 4.2.x and older.
+            $options = [];
+            foreach ($plugins as $plugin) {
+                /** @var element $classname */
+                $classname = '\\certificateelement_' . $plugin. '\\element';
+                // Ensure the necessary class exists.
+                if (class_exists($classname) && is_subclass_of($classname, element::class)) {
+                    $options[$plugin] = $classname;
+                }
+            }
+            return $options;
+        }
+
+        $hook = new hook\element_classes();
+
+        // Loop through the enabled plugins.
+        foreach ($plugins as $plugin) {
+            $classname = 'certificateelement_' . $plugin. '\\element';
+            $hook->add_class($plugin, $classname);
+        }
+
+        // Ask other plugins if they define more elements.
+        \core\hook\manager::get_instance()->dispatch($hook);
+
+        return $hook->get_classes();
+    }
+
     /**
      * Return the list of possible elements to add.
      *
      * @return array the list of element types that can be used.
      */
-    public static function get_available_element_types() {
-        global $CFG;
-
+    public static function get_available_element_types(): array {
         // Array to store the element types.
         $options = [];
 
-        $plugins = self::get_enabled_plugins();
+        $classes = self::get_element_classes();
 
         // Loop through the enabled plugins.
-        foreach ($plugins as $plugin) {
-            /** @var element $classname */
-            $classname = '\\certificateelement_' . $plugin. '\\element';
-            // Ensure the necessary class exists.
-            if (class_exists($classname) && is_subclass_of($classname, element::class)) {
-                // Additionally, check if the user is allowed to add the element at all.
-                if ($classname::can_add()) {
-                    $options[$plugin] = $classname::get_element_type_name();
-                }
+        foreach ($classes as $shortname => $classname) {
+            // Additionally, check if the user is allowed to add the element at all.
+            if ($classname::can_add()) {
+                $options[$shortname] = $classname::get_element_type_name();
             }
         }
 

classes/hook/element_classes.php

@@ -0,0 +1,76 @@
+<?php
+// This file is part of the tool_certificate plugin for 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/>.
+
+namespace tool_certificate\hook;
+
+/**
+ * Certification element classes discovery hook.
+ *
+ * @package     tool_certificate
+ * @copyright   2024 Petr Skoda
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+final class element_classes implements \core\hook\described_hook {
+    /**
+     * @var array<string, class-string<\tool_certificate\element>>
+     */
+    protected $classes = [];
+
+    /**
+     * Add known enabled element class.
+     *
+     * @param string $shortname name of certificateelement sub-plugin or other unique name
+     * @param class-string<\tool_certificate\element> $classname
+     */
+    public function add_class(string $shortname, string $classname): void {
+        if (!class_exists($classname) || !is_subclass_of($classname, \tool_certificate\element::class)) {
+            debugging('Invalid certificate element class: ' . $classname, DEBUG_DEVELOPER);
+            return;
+        }
+        if (isset($this->classes[$shortname])) {
+            debugging('Duplicate certificate element short name detected: ' . $shortname, DEBUG_DEVELOPER);
+            // Override previous in case admins forgot to uninstall element add-on.
+        }
+        $this->classes[$shortname] = $classname;
+    }
+
+    /**
+     * Returns known enabled element classes indexed with their short names.
+     *
+     * @return array<string, class-string<\tool_certificate\element>>
+     */
+    public function get_classes(): array {
+        return $this->classes;
+    }
+
+    /**
+     * Hook description.
+     *
+     * @return string
+     */
+    public static function get_hook_description(): string {
+        return 'Certificate element class discovery';
+    }
+
+    /**
+     * Hook tags.
+     *
+     * @return array
+     */
+    public static function get_hook_tags(): array {
+        return [];
+    }
+}

classes/output/element.php

@@ -89,11 +89,10 @@ protected static function define_other_properties(): array {
      */
     protected function get_other_values(\renderer_base $output): array {
         $element = $this->get_element();
-        $pluginname = 'certificateelement_' . $this->persistent->get('element');
         return [
             'displayname' => $element->get_display_name(),
             'editablename' => $element->get_inplace_editable()->export_for_template($output),
-            'elementtype' => get_string('pluginname', $pluginname),
+            'elementtype' => $element::get_element_type_name(),
             'movetitle' => get_string('changeelementsequence', 'tool_certificate'),
             'icon' => $output->render($this->get_element()->get_element_type_image(true)),
             'html' => $this->get_element()->render_html(),