email_verification.module

<?php

/**
 * @file
 * Contains email_verification.module.
 */

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

/**
 * Implements hook_help().
 */
function email_verification_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    // Main module help for the email_verification module.
    case 'help.page.email_verification':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('Verify User Emails before registration') . '</p>';
      return $output;

    default:
  }
}

/**
 * Implements hook_form_alter().
 */
function email_verification_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  // If email verify flag absent in url then redirect it to user verification
  // form.
  if ($form_id == 'user_register_form') {
    // Only work for Anonymous users.
    if (!\Drupal::currentUser()->isAnonymous()) {
      return;
    }
    $form['#cache'] = ['max-age' => 0];
    $verify = \Drupal::request()->query->get('verify');
    if (empty($verify)) {
      $targetUrl = Url::fromRoute('email_verification.user_verification_form')->toString();
      $response = new RedirectResponse($targetUrl, 301);
      $response->send();

      return;
    }
    // Once md5 has present with actual email in url then compare it
    // to make sure its same email address.
    $email = \Drupal::request()->query->get('email');
    $config = \Drupal::configFactory()->getEditable('email_verification.settings');
    $salt = $config->get('user_email_verification_salt') ?? 'email';
    $key = md5($salt . $email);
    // If not same then redirect back to user verification screen.
    if ($key == $verify) {
      $form['account']['mail']['#default_value'] = $email;
      // Set field to read only.
      $form['account']['mail']['#attributes']['readonly'] = 'readonly';
    }
    else {
      $targetUrl = Url::fromRoute('email_verification.user_verification_form')->toString();
      $response = new RedirectResponse($targetUrl, 301);
      $response->send();
      exit;
    }
  }
}

/**
 * Implements hook_mail().
 */
function email_verification_mail($key, &$message, $params) {
  $options = [
    'langcode' => $message['langcode'],
  ];
  switch ($key) {
    case 'email_verification':
      $message['from'] = \Drupal::config('system.site')->get('mail');
      $message['subject'] = t('@title', ['@title' => $params['title']], $options);
      $message['body'][] = Html::escape($params['message']);
      break;
  }
}