silverstripe-cms/code/Forms/AnchorSelectorField.php

<?php

namespace SilverStripe\CMS\Forms;

use SilverStripe\CMS\Model\SiteTree;
use SilverStripe\Control\HTTPRequest;
use SilverStripe\Forms\TextField;

/**
 * Assists with selecting anchors on a given page
 */
class AnchorSelectorField extends TextField
{
    protected $schemaComponent = 'AnchorSelectorField';

    private static $allowed_actions = [
        'anchors',
    ];

    private static $url_handlers = [
        'anchors/$PageID' => 'anchors',
    ];

    public function getSchemaDataDefaults()
    {
        $schema = parent::getSchemaDataDefaults();
        $schema['data']['endpoint'] = $this->Link('anchors/:id');
        return $schema;
    }

    /**
     * Find all anchors available on the given page.
     *
     * @param HTTPRequest $request
     * @return array
     */
    public function anchors(HTTPRequest $request)
    {
        $id = (int)$this->getRequest()->param('PageID');
        $anchors = $this->getAnchorsInPage($id);

        return json_encode($anchors);
    }

    /**
     * Get anchors in the given page ID.
     *
     * @param int $id
     * @return array
     */
    protected function getAnchorsInPage($id)
    {
        $page = SiteTree::get()->byID($id);

        if (!$page || !$page->canView()) {
            return [];
        }

        return $page->getAnchorsOnPage();
    }
}