silverstripe-cms/code/GraphQL/LinkablePlugin.php

<?php


namespace SilverStripe\CMS\GraphQL;

use GraphQL\Type\Definition\ResolveInfo;
use SilverStripe\CMS\Model\SiteTree;
use SilverStripe\Core\Config\Configurable;
use SilverStripe\Core\Injector\Injectable;
use SilverStripe\GraphQL\Schema\DataObject\Plugin\QueryFilter\QueryFilter;
use SilverStripe\GraphQL\Schema\Exception\SchemaBuilderException;
use SilverStripe\GraphQL\Schema\Field\ModelQuery;
use SilverStripe\GraphQL\Schema\Interfaces\ModelQueryPlugin;
use SilverStripe\GraphQL\Schema\Schema;
use SilverStripe\ORM\DataList;

if (!interface_exists(ModelQueryPlugin::class)) {
    return;
}

class LinkablePlugin implements ModelQueryPlugin
{
    use Configurable;
    use Injectable;

    const IDENTIFIER = 'getByLink';

    /**
     * @var string
     * @config
     */
    private static $field_name = 'link';

    /**
     * @return string
     */
    public function getIdentifier(): string
    {
        return self::IDENTIFIER;
    }

    /**
     * @param ModelQuery $query
     * @param Schema $schema
     * @param array $config
     * @throws SchemaBuilderException
     */
    public function apply(ModelQuery $query, Schema $schema, array $config = []): void
    {
        $class = $query->getModel()->getSourceClass();
        // Only site trees have the get_by_link capability
        if ($class !== SiteTree::class && !is_subclass_of($class, SiteTree::class)) {
            return;
        }
        Schema::invariant(
            !$query->isList(),
            'Plugin %s cannot be applied to queries that return lists. Query "%s" is a list',
            static::getIdentifier(),
            $query->getName()
        );
        $fieldName = $this->config()->get('field_name');
        
        $query->addArg($fieldName, 'String');
        $query->addResolverAfterware([static::class, 'applyLinkFilter']);
    }

    /**
     * @param $obj
     * @param array $args
     * @param array $context
     * @param ResolveInfo $info
     * @param callable $done
     * @return SiteTree|DataList|null
     */
    public static function applyLinkFilter(
        $obj,
        array $args,
        array $context,
        ResolveInfo $info,
        callable $done
    ) {
        $fieldName = static::config()->get('field_name');
        $filterLink = $args['filter'][$fieldName] ?? null;
        $argLink = $args[$fieldName] ?? null;
        $filterLink = $filterLink ?: $argLink;

        if ($filterLink) {
            $done();
            return SiteTree::get_by_link($filterLink);
        }

        return $obj;
    }
}