Issue #3086495 by wundo: Add CaptchaService

src/Service/CaptchaService.php

+<?php
+
+namespace Drupal\captcha\Service;
+
+/**
+ * Helper service for CAPTCHA module.
+ */
+class CaptchaService {
+
+  /**
+   * Return an array with the available CAPTCHA types.
+   *
+   * For use as options array for a select form elements.
+   *
+   * @param bool $add_special_options
+   *   If true: also add the 'default' option.
+   *
+   * @return array
+   *   An associative array mapping "$module/$type" to
+   *   "$type (from module $module)" with $module the module name
+   *   implementing the CAPTCHA and $type the name of the CAPTCHA type.
+   */
+  public function getAvailableChallengeTypes($add_special_options = TRUE) {
+    $challenges = [];
+
+    if ($add_special_options) {
+      $challenges['default'] = t('Default challenge type');
+    }
+
+    // We do our own version of Drupal's module_invoke_all() here because
+    // we want to build an array with custom keys and values.
+    foreach (\Drupal::moduleHandler()->getImplementations('captcha') as $module) {
+      $result = call_user_func_array($module . '_captcha', ['list']);
+      if (is_array($result)) {
+        foreach ($result as $type) {
+          $challenges["$module/$type"] = t('@type (from module @module)', [
+            '@type' => $type,
+            '@module' => $module,
+          ]);
+        }
+      }
+    }
+
+    return $challenges;
+  }
+}