captcha_questions.module

<?php

/**
 * @file
 * Module file for the Captcha questions module.
 *
 * The module hooks into forms and adds a configurable question field and a
 * custom validate function returning an error if the answer is wrong.
 */

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Component\Utility\Html;
use Drupal\Component\Utility\Unicode;
use Symfony\Component\HttpFoundation;

/**
 * Implements hook_help().
 */
function captcha_questions_help($route_name, RouteMatchInterface $route_match) {
  if ($route_name == 'help.page.captcha_questions') {
    return t('Captcha questions allows the site administrator to add a question to selected forms');
  }
}

/**
 * Implements hook_form_alter().
 */
function captcha_questions_form_alter(&$form, FormStateInterface $form_state, $form_id) {

  // Only show captcha questions if user is anonymous.
  if (\Drupal::currentUser()->isAnonymous()) {
    // Fetching variables for form ids, question and description.
    $captcha_questions_form_ids = \Drupal::config('captcha_questions.settings')->get('captcha_questions_form_ids');
    $question = \Drupal::config('captcha_questions.settings')->get('captcha_questions_question');
    $description = \Drupal::config('captcha_questions.settings')->get('captcha_questions_description');

    foreach ($captcha_questions_form_ids as $key => $value) {
      if ($value === $form_id) {
        // If we're on a multi page form, find current page.
        $form_page_count = isset($form['details']['page_num']['#value']) ? $form['details']['page_num']['#value'] : 1;
        // Set field to hidden unless on the first page.
        $form['captcha_questions_answer_given'] = array(
          '#type' => $form_page_count == 1 ? 'textfield' : 'hidden',
          '#description' => t("@description", array('@description' => $description)),
          '#title' => Html::escape($question),
          '#size' => 60,
          '#required' => TRUE,
        );
        $form['#validate'][] = 'captcha_questions_form_validate';
      }
    }

    return $form;
  }
}

/**
 * Implements hook_form_validate().
 */
function captcha_questions_form_validate(&$form, FormStateInterface $form_state) {
  $user = \Drupal::currentUser();
  $ip = \Drupal::request()->getClientIp();
  $form_id = $form_state->getValue('form_id');
  $question_asked = \Drupal::config('captcha_questions.settings')->get('captcha_questions_question');
  $answers = \Drupal::config('captcha_questions.settings')->get('captcha_questions_answers');
  $answer_given = $form_state->getValue('captcha_questions_answer_given');

  // Comparison is done in lowercase, ensure answers are lowercase.
  $answers = array_map('strtolower', $answers);
  $answer_given = Unicode::strtolower($answer_given);

  // Check answer.
  if (in_array($answer_given, $answers) == FALSE) {
    // Log to watchdog if enabled.
    if (\Drupal::config('captcha_questions.settings')->get('captcha_questions_watchdog')) {
      $message = t('Blocked submission of form with form_id !form_id. Answer given was %answer_given', array('!form_id' => $form_id, '%answer_given' => $form_state->getValue('captcha_questions_answer_given')));
      \Drupal::logger('captcha_questions')->error($message);
    }
    // Log to dblog if enabled and module exists and enabled.
    $dblog_enabled = \Drupal::config('captcha_questions.settings')->get('captcha_questions_dblog');
    $dblog_module_exists = \Drupal::moduleHandler()->moduleExists('captcha_questions_dblog') ? TRUE : FALSE;
    if ($dblog_enabled && $dblog_module_exists) {
      db_insert('captcha_questions_dblog')
        ->fields(array(
          'timestamp' => REQUEST_TIME,
          'ip' => $ip,
          'form_id' => $form_id,
          'question_asked' => Html::escape($question_asked),
          'answer_given' => Html::escape($answer_given),
          'answer_correct' => implode(",", $answers),
        ))
        ->execute();
    }
    // Display error.
    $form_state->setErrorByName('captcha_questions_answer_given', t('Invalid answer'));
  }
}