Pushing Data to Clients Using the Mercure Protocol

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// src/Controller/DiscoverController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Mercure\Discovery;

class DiscoverController extends AbstractController
{
    public function __invoke(Request $request, Discovery $discovery): JsonResponse
    {
        // Link: <http://localhost:3000/.well-known/mercure>; rel="mercure"
        $discovery->addLink($request);

        return $this->json([
            '@id' => '/books/1',
            'availability' => 'https://schema.org/InStock',
        ]);
    }
}

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// src/Controller/Publish.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Mercure\Update;

class PublishController extends AbstractController
{
    public function publish(HubInterface $hub): Response
    {
        $update = new Update(
            'http://example.com/books/1',
            json_encode(['status' => 'OutOfStock']),
            true // private
        );

        // Publisher's JWT must contain this topic, a URI template it matches or * in mercure.publish or you'll get a 401
        // Subscriber's JWT must contain this topic, a URI template it matches or * in mercure.subscribe to receive the update
        $hub->publish($update);

        return new Response('private update published!');
    }
}

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// src/Controller/DiscoverController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Mercure\Authorization;
use Symfony\Component\Mercure\Discovery;

class DiscoverController extends AbstractController
{
    public function publish(Request $request, Discovery $discovery, Authorization $authorization): Response
    {
        $discovery->addLink($request);

        $response = new JsonResponse([
            '@id' => '/demo/books/1',
            'availability' => 'https://schema.org/InStock'
        ]);

        $response->headers->setCookie(
            $authorization->createCookie($request,  ["http://example.com/books/1"])
        );

        return $response;
    }
}

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// src/Mercure/MyTokenProvider.php
namespace App\Mercure;

use Symfony\Component\Mercure\Jwt\TokenProviderInterface;

final class MyTokenProvider implements TokenProviderInterface
{
    public function getJwt(): string
    {
        return 'the-JWT';
    }
}

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// src/Entity/Book.php
namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use Doctrine\ORM\Mapping as ORM;

/**
* @ApiResource(mercure=true)
* @ORM\Entity
*/
class Book
{
    /**
     * @ORM\Id
     * @ORM\Column
     */
    public $name;

    /**
     * @ORM\Column
     */
    public $status;
}

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// tests/FunctionalTest.php
namespace App\Tests\Unit\Controller;

use App\Controller\MessageController;
use Symfony\Component\Mercure\HubInterface;
use Symfony\Component\Mercure\JWT\StaticTokenProvider;
use Symfony\Component\Mercure\MockHub;
use Symfony\Component\Mercure\Update;

class MessageControllerTest extends TestCase
{
    public function testPublishing()
    {
        $hub = new MockHub('https://internal/.well-known/mercure', new StaticTokenProvider('foo'), function(Update $update): string {
            // $this->assertTrue($update->isPrivate());

            return 'id';
        });

        $controller = new MessageController($hub);

        // ...
    }
}

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// tests/Functional/Fixtures/HubStub.php
namespace App\Tests\Functional\Fixtures;

use Symfony\Component\Mercure\HubInterface;
use Symfony\Component\Mercure\Update;

class HubStub implements HubInterface
{
    public function publish(Update $update): string
    {
        return 'id';
    }

    // implement rest of HubInterface methods here
}

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// src/Controller/PublishController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Mercure\Update;
use Symfony\Component\Messenger\MessageBusInterface;

class PublishController extends AbstractController
{
    public function publish(MessageBusInterface $bus): Response
    {
        $update = new Update(
            'http://example.com/books/1',
            json_encode(['status' => 'OutOfStock'])
        );

        // Sync, or async (Doctrine, RabbitMQ, Kafka...)
        $bus->dispatch($update);

        return new Response('published!');
    }
}