AcceptHeaderMatcher.php

<?php

namespace Drupal\accept_header_routing_test\Routing;

use Drupal\Core\Routing\FilterInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\Exception\NotAcceptableHttpException;
use Symfony\Component\Routing\RouteCollection;

/**
 * Filters routes based on the media type specified in the HTTP Accept headers.
 */
class AcceptHeaderMatcher implements FilterInterface {
    
    /**
     * {@inheritdoc}
     */
    public function filter(RouteCollection $collection, Request $request) {
        // Generates a list of Symfony formats matching the acceptable MIME types.
        // @todo replace by proper content negotiation library.
        $acceptable_mime_types = $request->getAcceptableContentTypes();
        $acceptable_formats = array_filter(array_map([
            $request,
            'getFormat',
        ], $acceptable_mime_types));
        $primary_format = $request->getRequestFormat();
        foreach ($collection as $name => $route) {
            // _format could be a |-delimited list of supported formats.
            $supported_formats = array_filter(explode('|', $route->getRequirement('_format') ?? ''));
            if (empty($supported_formats)) {
                // No format restriction on the route, so it always matches. Move it to
                // the end of the collection by re-adding it.
                $collection->add($name, $route);
            }
            elseif (in_array($primary_format, $supported_formats)) {
                // Perfect match, which will get a higher priority by leaving the route
                // on top of the list.
            }
            elseif (in_array('*/*', $acceptable_mime_types) || array_intersect($acceptable_formats, $supported_formats)) {
                // Move it to the end of the list.
                $collection->add($name, $route);
            }
            else {
                // Remove the route if it does not match at all.
                $collection->remove($name);
            }
        }
        if (count($collection)) {
            return $collection;
        }
        // We do not throw a
        // \Symfony\Component\Routing\Exception\ResourceNotFoundException here
        // because we don't want to return a 404 status code, but rather a 406.
        throw new NotAcceptableHttpException('No route found for the specified formats ' . implode(' ', $acceptable_mime_types));
    }

}