class ContextualHooks

class ContextualHooks {
    
    /**
     * Implements hook_toolbar().
     */
    public function toolbar() {
        $items = [];
        $items['contextual'] = [
            '#cache' => [
                'contexts' => [
                    'user.permissions',
                ],
            ],
        ];
        if (!\Drupal::currentUser()->hasPermission('access contextual links')) {
            return $items;
        }
        $items['contextual'] += [
            '#type' => 'toolbar_item',
            'tab' => [
                '#type' => 'html_tag',
                '#tag' => 'button',
                '#value' => t('Edit'),
                '#attributes' => [
                    'class' => [
                        'toolbar-icon',
                        'toolbar-icon-edit',
                    ],
                    'aria-pressed' => 'false',
                    'type' => 'button',
                ],
            ],
            '#wrapper_attributes' => [
                'class' => [
                    'hidden',
                    'contextual-toolbar-tab',
                ],
            ],
            '#attached' => [
                'library' => [
                    'contextual/drupal.contextual-toolbar',
                ],
            ],
        ];
        return $items;
    }
    
    /**
     * Implements hook_page_attachments().
     *
     * Adds the drupal.contextual-links library to the page for any user who has the
     * 'access contextual links' permission.
     *
     * @see contextual_preprocess()
     */
    public function pageAttachments(array &$page) {
        if (!\Drupal::currentUser()->hasPermission('access contextual links')) {
            return;
        }
        $page['#attached']['library'][] = 'contextual/drupal.contextual-links';
    }
    
    /**
     * Implements hook_help().
     */
    public function help($route_name, RouteMatchInterface $route_match) {
        switch ($route_name) {
            case 'help.page.contextual':
                $output = '';
                $output .= '<h2>' . t('About') . '</h2>';
                $output .= '<p>' . t('The Contextual links module gives users with the <em>Use contextual links</em> permission quick access to tasks associated with certain areas of pages on your site. For example, a menu displayed as a block has links to edit the menu and configure the block. For more information, see the <a href=":contextual">online documentation for the Contextual Links module</a>.', [
                    ':contextual' => 'https://www.drupal.org/docs/8/core/modules/contextual',
                ]) . '</p>';
                $output .= '<h2>' . t('Uses') . '</h2>';
                $output .= '<dl>';
                $output .= '<dt>' . t('Displaying contextual links') . '</dt>';
                $output .= '<dd>';
                $output .= t('Contextual links for an area on a page are displayed using a contextual links button. There are two ways to make the contextual links button visible:');
                $output .= '<ol>';
                $sample_picture = [
                    '#theme' => 'image',
                    '#uri' => 'core/misc/icons/bebebe/pencil.svg',
                    '#alt' => t('contextual links button'),
                ];
                $sample_picture = \Drupal::service('renderer')->render($sample_picture);
                $output .= '<li>' . t('Hovering over the area of interest will temporarily make the contextual links button visible (which looks like a pencil in most themes, and is normally displayed in the upper right corner of the area). The icon typically looks like this: @picture', [
                    '@picture' => $sample_picture,
                ]) . '</li>';
                $output .= '<li>' . t('If you have the <a href=":toolbar">Toolbar module</a> installed, clicking the contextual links button in the toolbar (which looks like a pencil) will make all contextual links buttons on the page visible. Clicking this button again will toggle them to invisible.', [
                    ':toolbar' => \Drupal::moduleHandler()->moduleExists('toolbar') ? Url::fromRoute('help.page', [
                        'name' => 'toolbar',
                    ])->toString() : '#',
                ]) . '</li>';
                $output .= '</ol>';
                $output .= t('Once the contextual links button for the area of interest is visible, click the button to display the links.');
                $output .= '</dd>';
                $output .= '</dl>';
                return $output;
        }
    }
    
    /**
     * Implements hook_contextual_links_view_alter().
     *
     * @see \Drupal\contextual\Plugin\views\field\ContextualLinks::render()
     */
    public function contextualLinksViewAlter(&$element, $items) {
        if (isset($element['#contextual_links']['contextual'])) {
            $encoded_links = $element['#contextual_links']['contextual']['metadata']['contextual-views-field-links'];
            $element['#links'] = Json::decode(rawurldecode($encoded_links));
        }
    }

}