home_redirect_lang.module

<?php

/**
 * @file
 * Provides functionality for handling postal addresses.
 */

use Drupal\Core\Block\BlockPluginInterface;
use Drupal\home_redirect_lang\HomeRedirectLangInterface;

/**
 * Implements hook_preprocess_HOOK().
 *
 * Add both cache context based on cookie and referer for homepage.
 */
function home_redirect_lang_preprocess_page(&$variables): void {
  if (!$variables['is_front']) {
    return;
  }

  $variables['#cache']['contexts'][] = 'cookies:' . HomeRedirectLangInterface::COOKIE_PREFERRED_LANGCODE;
  $variables['#cache']['contexts'][] = 'headers:REFERER';

  $browser_config = \Drupal::configFactory()->get('home_redirect_lang.browser_fallback');

  // When the Fallback on browser language is enabled for the first visit.
  if ($browser_config->get('enable_browser_fallback')) {
    $variables['#cache']['contexts'][] = 'headers:' . HomeRedirectLangInterface::BROWSER_HTTP_HEADER_PREFERRED_LANGCODE;
  }
}

/**
 * Implements hook_block_view_alter().
 *
 * Inject JavaScript switcher handler of the Homepage Redirect Language module
 * when the drupal language is rendered in any page.
 */
function home_redirect_lang_block_view_alter(array &$build, BlockPluginInterface $block): void {
  if ($block->getPluginId() !== 'language_block:language_interface') {
    return;
  }

  $build['#attached']['library'][] = 'home_redirect_lang/language_switcher';
}