class ThemeTestHooks

class ThemeTestHooks {
  
  /**
   * Implements hook_theme().
   */
  public function theme($existing, $type, $theme, $path) : array {
    $items['theme_test'] = [
      'file' => 'theme_test.inc',
      'variables' => [
        'foo' => '',
      ],
    ];
    $items['theme_test_template_test'] = [
      'template' => 'theme_test.template_test',
    ];
    $items['theme_test_template_test_2'] = [
      'template' => 'theme_test.template_test',
    ];
    $items['theme_test_suggestion_provided'] = [
      'variables' => [],
    ];
    $items['theme_test_specific_suggestions'] = [
      'variables' => [],
    ];
    $items['theme_test_suggestions'] = [
      'variables' => [],
    ];
    $items['theme_test_general_suggestions'] = [
      'variables' => [
        'module_hook' => 'theme_test_theme',
        'theme_hook' => 'none',
      ],
    ];
    $items['theme_test_foo'] = [
      'variables' => [
        'foo' => NULL,
      ],
    ];
    $items['theme_test_render_element'] = [
      'render element' => 'elements',
    ];
    $items['theme_test_render_element_children'] = [
      'render element' => 'element',
    ];
    $items['theme_test_preprocess_suggestions'] = [
      'variables' => [
        'foo' => '',
        'bar' => '',
      ],
    ];
    $items['theme_test_preprocess_callback'] = [
      'variables' => [
        'foo' => '',
      ],
    ];
    $items['theme_test_registered_by_module'] = [
      'render element' => 'content',
      'base hook' => 'container',
    ];
    $items['theme_test_theme_class'] = [
      'variables' => [
        'message' => '',
      ],
    ];
    $items['theme_test_deprecations_preprocess'] = [
      'variables' => [
        'foo' => '',
        'bar' => '',
        'gaz' => '',
        'set_var' => '',
        'for_var' => '',
        'contents' => [],
      ],
    ];
    $items['theme_test_deprecations_child'] = [
      'variables' => [
        'foo' => '',
        'bar' => '',
        'gaz' => '',
      ],
    ];
    $items['theme_test_deprecations_hook_theme'] = [
      'variables' => [
        'foo' => '',
        'bar' => '',
        'deprecations' => [
          'foo' => "'foo' is deprecated in drupal:X.0.0 and is removed from drupal:Y.0.0. Use 'new_foo' instead. See https://www.example.com.",
          'bar' => "'bar' is deprecated in drupal:X.0.0 and is removed from drupal:Y.0.0. Use 'new_bar' instead. See https://www.example.com.",
        ],
      ],
    ];
    return $items;
  }
  
  /**
   * Implements hook_theme_registry_alter().
   */
  public function themeRegistryAlter(&$registry) : void {
    $registry['theme_test_preprocess_callback']['preprocess functions'][] = [
      '\\Drupal\\theme_test\\ThemeTestPreprocess',
      'preprocess',
    ];
  }
  
  /**
   * Implements hook_page_bottom().
   */
  public function pageBottom(array &$page_bottom) : void {
    $page_bottom['theme_test_page_bottom'] = [
      '#markup' => 'theme test page bottom markup',
    ];
  }
  
  /**
   * Implements hook_theme_suggestions_alter().
   */
  public function themeSuggestionsAlter(array &$suggestions, array $variables, $hook) : void {
    \Drupal::messenger()->addStatus('theme_test_theme_suggestions_alter() executed for ' . $hook . '.');
  }
  
  /**
   * Implements hook_theme_suggestions_HOOK_alter().
   */
  public function themeSuggestionsThemeTestSuggestionsAlter(array &$suggestions, array $variables) : void {
    \Drupal::messenger()->addStatus('theme_test_theme_suggestions_theme_test_suggestions_alter() executed.');
  }
  
  /**
   * Implements hook_system_info_alter().
   *
   * @see \Drupal\system\Tests\Theme\ThemeInfoTest::testChanges()
   */
  public function systemInfoAlter(array &$info, Extension $file, $type) : void {
    if ($type == 'theme' && $file->getName() == 'test_theme' && \Drupal::state()->get('theme_test.modify_info_files')) {
      // Add a library to see if the system picks it up.
      $info += [
        'libraries' => [],
      ];
      $info['libraries'][] = 'core/once';
    }
  }
  
  /**
   * Implements hook_library_info_alter().
   */
  public function libraryInfoAlter(array &$libraries, string $extension) : void {
    // Allow test code to simulate library changes in a particular extension by
    // setting a state key in the form `theme_test_library_info_alter
    // $extension`, whose values is an array containing everything that should
    // be recursively merged into the given extension's library definitions.
    $info = \Drupal::state()->get('theme_test_library_info_alter' . " {$extension}");
    if (is_array($info)) {
      $libraries = NestedArray::mergeDeep($libraries, $info);
    }
  }

}