class LinkHooks

class LinkHooks {
    
    /**
     * Implements hook_help().
     */
    public function help($route_name, RouteMatchInterface $route_match) {
        switch ($route_name) {
            case 'help.page.link':
                $output = '';
                $output .= '<h2>' . t('About') . '</h2>';
                $output .= '<p>' . t('The Link module allows you to create fields that contain internal or external URLs and optional link text. See the <a href=":field">Field module help</a> and the <a href=":field_ui">Field UI help</a> pages for general information on fields and how to create and manage them. For more information, see the <a href=":link_documentation">online documentation for the Link module</a>.', [
                    ':field' => Url::fromRoute('help.page', [
                        'name' => 'field',
                    ])->toString(),
                    ':field_ui' => \Drupal::moduleHandler()->moduleExists('field_ui') ? Url::fromRoute('help.page', [
                        'name' => 'field_ui',
                    ])->toString() : '#',
                    ':link_documentation' => 'https://www.drupal.org/documentation/modules/link',
                ]) . '</p>';
                $output .= '<h2>' . t('Uses') . '</h2>';
                $output .= '<dl>';
                $output .= '<dt>' . t('Managing and displaying link fields') . '</dt>';
                $output .= '<dd>' . t('The <em>settings</em> and the <em>display</em> of the link field can be configured separately. See the <a href=":field_ui">Field UI help</a> for more information on how to manage fields and their display.', [
                    ':field_ui' => \Drupal::moduleHandler()->moduleExists('field_ui') ? Url::fromRoute('help.page', [
                        'name' => 'field_ui',
                    ])->toString() : '#',
                ]) . '</dd>';
                $output .= '<dt>' . t('Setting the allowed link type') . '</dt>';
                $output .= '<dd>' . t('In the field settings you can define the allowed link type to be <em>internal links only</em>, <em>external links only</em>, or <em>both internal and external links</em>. <em>Internal links only</em> and <em>both internal and external links</em> options enable an autocomplete widget for internal links, so a user does not have to copy or remember a URL.') . '</dd>';
                $output .= '<dt>' . t('Adding link text') . '</dt>';
                $output .= '<dd>' . t('In the field settings you can define additional link text to be <em>optional</em> or <em>required</em> in any link field.') . '</dd>';
                $output .= '<dt>' . t('Displaying link text') . '</dt>';
                $output .= '<dd>' . t('If link text has been submitted for a URL, then by default this link text is displayed as a link to the URL. If you want to display both the link text <em>and</em> the URL, choose the appropriate link format from the drop-down menu in the <em>Manage display</em> page. If you only want to display the URL even if link text has been submitted, choose <em>Link</em> as the format, and then change its <em>Format settings</em> to display <em>URL only</em>.') . '</dd>';
                $output .= '<dt>' . t('Adding attributes to links') . '</dt>';
                $output .= '<dd>' . t('You can add attributes to links, by changing the <em>Format settings</em> in the <em>Manage display</em> page. Adding <em>rel="nofollow"</em> notifies search engines that links should not be followed.') . '</dd>';
                $output .= '<dt>' . t('Validating URLs') . '</dt>';
                $output .= '<dd>' . t('All links are validated after a link field is filled in. They can include anchors or query strings.') . '</dd>';
                $output .= '</dl>';
                return $output;
        }
    }
    
    /**
     * Implements hook_theme().
     */
    public function theme() : array {
        return [
            'link_formatter_link_separate' => [
                'variables' => [
                    'title' => NULL,
                    'url_title' => NULL,
                    'url' => NULL,
                ],
            ],
        ];
    }
    
    /**
     * Implements hook_field_type_category_info_alter().
     */
    public function fieldTypeCategoryInfoAlter(&$definitions) {
        // The `link` field type belongs in the `general` category, so the libraries
        // need to be attached using an alter hook.
        $definitions[FieldTypeCategoryManagerInterface::FALLBACK_CATEGORY]['libraries'][] = 'link/drupal.link-icon';
    }

}