<?php
/**
 * @file src/Util/JsonLD.php
 */
namespace Friendica\Util;

use Friendica\Core\Cache;
use digitalbazaar\jsonld as DBJsonLD;

/**
 * @brief This class contain methods to work with JsonLD data
 */
class JsonLD
{
	public static function documentLoader($url)
	{
		$recursion = 0;

		$x = debug_backtrace();
		if ($x) {
			foreach ($x as $n) {
				if ($n['function'] === __FUNCTION__)  {
					$recursion ++;
				}
			}
		}

		if ($recursion > 5) {
			logger('jsonld bomb detected at: ' . $url);
			exit();
		}

		$result = Cache::get('documentLoader:' . $url);
		if (!is_null($result)) {
			return $result;
		}

		$data = jsonld_default_document_loader($url);
		Cache::set('documentLoader:' . $url, $data, CACHE_DAY);
		return $data;
	}

	public static function normalize($json)
	{
		jsonld_set_document_loader('Friendica\Util\JsonLD::documentLoader');

		$jsonobj = json_decode(json_encode($json));

		return jsonld_normalize($jsonobj, array('algorithm' => 'URDNA2015', 'format' => 'application/nquads'));
	}

	public static function compact($json)
	{
		jsonld_set_document_loader('Friendica\Util\JsonLD::documentLoader');

		$context = (object)['as' => 'https://www.w3.org/ns/activitystreams',
			'w3sec' => 'https://w3id.org/security',
			'ostatus' => (object)['@id' => 'http://ostatus.org#', '@type' => '@id'],
			'vcard' => (object)['@id' => 'http://www.w3.org/2006/vcard/ns#', '@type' => '@id'],
			'uuid' => (object)['@id' => 'http://schema.org/identifier', '@type' => '@id']];

		$jsonobj = json_decode(json_encode($json));

		$compacted = jsonld_compact($jsonobj, $context);

		return json_decode(json_encode($compacted), true);
	}
}