LinkCollectionNormalizer.php

<?php

namespace Drupal\jsonapi\Normalizer;

use Drupal\Component\Utility\Crypt;
use Drupal\jsonapi\JsonApiResource\LinkCollection;
use Drupal\jsonapi\JsonApiResource\Link;
use Drupal\jsonapi\Normalizer\Value\CacheableNormalization;

/**
 * Normalizes a LinkCollection object.
 *
 * The JSON:API specification has the concept of a "links collection". A links
 * collection is a JSON object where each member of the object is a
 * "link object". Unfortunately, this means that it is not possible to have more
 * than one link for a given key.
 *
 * When normalizing more than one link in a LinkCollection with the same key, a
 * unique and random string is appended to the link's key after a double dash
 * (--) to differentiate the links.
 *
 * This may change with a later version of the JSON:API specification.
 *
 * @internal JSON:API maintains no PHP API since its API is the HTTP API. This
 *   class may change at any time and this will break any dependencies on it.
 *
 * @see https://www.drupal.org/project/drupal/issues/3032787
 * @see jsonapi.api.php
 */
class LinkCollectionNormalizer extends NormalizerBase {
    
    /**
     * The normalizer $context key name for the key of an individual link.
     *
     * @var string
     */
    const LINK_KEY = 'jsonapi_links_object_link_key';
    
    /**
     * The normalizer $context key name for the context object of the link.
     *
     * @var string
     */
    const LINK_CONTEXT = 'jsonapi_links_object_context';
    
    /**
     * {@inheritdoc}
     */
    protected $supportedInterfaceOrClass = LinkCollection::class;
    
    /**
     * A random string to use when hashing links.
     *
     * This string is unique per instance of a link collection, but always the
     * same within it. This means that link key hashes will be non-deterministic
     * for outside observers, but two links within the same collection will always
     * have the same hash value.
     *
     * This is not used for cryptographic purposes.
     *
     * @var string
     */
    protected $hashSalt;
    
    /**
     * {@inheritdoc}
     */
    public function normalize($object, $format = NULL, array $context = []) {
        assert($object instanceof LinkCollection);
        $normalized = [];
        
        /* @var \Drupal\jsonapi\JsonApiResource\Link $link */
        foreach ($object as $key => $links) {
            $is_multiple = count($links) > 1;
            foreach ($links as $link) {
                $link_key = $is_multiple ? sprintf('%s--%s', $key, $this->hashByHref($link)) : $key;
                $attributes = $link->getTargetAttributes();
                $normalization = array_merge([
                    'href' => $link->getHref(),
                ], !empty($attributes) ? [
                    'meta' => $attributes,
                ] : []);
                $normalized[$link_key] = new CacheableNormalization($link, $normalization);
            }
        }
        return CacheableNormalization::aggregate($normalized);
    }
    
    /**
     * Hashes a link by its href.
     *
     * @param \Drupal\jsonapi\JsonApiResource\Link $link
     *   A link to be hashed.
     *
     * @return string
     *   A 7 character alphanumeric hash.
     */
    protected function hashByHref(Link $link) {
        if (!$this->hashSalt) {
            $this->hashSalt = Crypt::randomBytesBase64();
        }
        return substr(str_replace([
            '-',
            '_',
        ], '', Crypt::hashBase64($this->hashSalt . $link->getHref())), 0, 7);
    }

}