Only write the fbp and fbc cookies when there is a pixel to send to

src/Context/Fbc/CookieBasedFbcContext.php

@@ -7,6 +7,7 @@
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 use Setono\MetaConversionsApi\ValueObject\Fbc;
+use Setono\MetaConversionsApiBundle\Cookie\Cookies;
 use Symfony\Component\HttpFoundation\RequestStack;
 
 final class CookieBasedFbcContext implements FbcContextInterface
@@ -27,7 +28,7 @@ public function getFbc(): ?Fbc
             return null;
         }
 
-        $cookie = $request->cookies->get('_fbc');
+        $cookie = $request->cookies->get(Cookies::FBC);
         if (!is_string($cookie) || '' === $cookie) {
             return null;
         }

src/Context/Fbp/CookieBasedFbpContext.php

@@ -7,6 +7,7 @@
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 use Setono\MetaConversionsApi\ValueObject\Fbp;
+use Setono\MetaConversionsApiBundle\Cookie\Cookies;
 use Symfony\Component\HttpFoundation\RequestStack;
 
 final class CookieBasedFbpContext implements FbpContextInterface
@@ -28,7 +29,7 @@ public function getFbp(): Fbp
             return $this->decorated->getFbp();
         }
 
-        $cookie = $request->cookies->get('_fbp');
+        $cookie = $request->cookies->get(Cookies::FBP);
         if (!is_string($cookie) || '' === $cookie) {
             return $this->decorated->getFbp();
         }

src/Cookie/Cookies.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Setono\MetaConversionsApiBundle\Cookie;
+
+/**
+ * The cookies Meta uses, shared by the contexts that read them and the subscribers that write them
+ *
+ * See https://developers.facebook.com/docs/marketing-api/conversions-api/parameters/fbp-and-fbc
+ */
+final class Cookies
+{
+    public const FBP = '_fbp';
+
+    public const FBC = '_fbc';
+
+    /**
+     * Meta keeps these for 90 days
+     */
+    public const LIFETIME = '+90 days';
+
+    private function __construct()
+    {
+    }
+}

src/EventSubscriber/StoreFbcSubscriber.php

@@ -6,6 +6,8 @@
 
 use Setono\MetaConversionsApiBundle\ConsentChecker\ConsentCheckerInterface;
 use Setono\MetaConversionsApiBundle\Context\Fbc\FbcContextInterface;
+use Setono\MetaConversionsApiBundle\Cookie\Cookies;
+use Setono\MetaConversionsApiBundle\Provider\PixelProviderInterface;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\HttpFoundation\Cookie;
 use Symfony\Component\HttpKernel\Event\ResponseEvent;
@@ -21,6 +23,7 @@ final class StoreFbcSubscriber implements EventSubscriberInterface
     public function __construct(
         private readonly FbcContextInterface $fbcContext,
         private readonly ConsentCheckerInterface $consentChecker,
+        private readonly PixelProviderInterface $pixelProvider,
     ) {
     }
 
@@ -42,6 +45,13 @@ public function store(ResponseEvent $event): void
             return;
         }
 
+        $response = $event->getResponse();
+
+        // There is no point in remembering a click we have nowhere to send events to
+        if ([] === $this->pixelProvider->getPixels()) {
+            return;
+        }
+
         if (!$this->consentChecker->isGranted()) {
             return;
         }
@@ -51,10 +61,10 @@ public function store(ResponseEvent $event): void
             return;
         }
 
-        $event->getResponse()->headers->setCookie(Cookie::create(
-            '_fbc',
+        $response->headers->setCookie(Cookie::create(
+            Cookies::FBC,
             $fbc->value(),
-            new \DateTimeImmutable('+90 days'),
+            new \DateTimeImmutable(Cookies::LIFETIME),
         )->withHttpOnly(false));  // we need this to allow the js library to also use the cookie value
     }
 }

src/EventSubscriber/StoreFbpSubscriber.php

@@ -7,6 +7,8 @@
 use Setono\MetaConversionsApi\ValueObject\Fbp;
 use Setono\MetaConversionsApiBundle\ConsentChecker\ConsentCheckerInterface;
 use Setono\MetaConversionsApiBundle\Context\Fbp\FbpContextInterface;
+use Setono\MetaConversionsApiBundle\Cookie\Cookies;
+use Setono\MetaConversionsApiBundle\Provider\PixelProviderInterface;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\HttpFoundation\Cookie;
 use Symfony\Component\HttpFoundation\Request;
@@ -20,11 +22,10 @@
  */
 final class StoreFbpSubscriber implements EventSubscriberInterface
 {
-    private const COOKIE_NAME = '_fbp';
-
     public function __construct(
         private readonly FbpContextInterface $fbpContext,
         private readonly ConsentCheckerInterface $consentChecker,
+        private readonly PixelProviderInterface $pixelProvider,
     ) {
     }
 
@@ -41,33 +42,36 @@ public function store(ResponseEvent $event): void
             return;
         }
 
+        $response = $event->getResponse();
+
+        // There is no point in identifying a browser we have nowhere to send events to
+        if ([] === $this->pixelProvider->getPixels()) {
+            return;
+        }
+
         if (!$this->consentChecker->isGranted()) {
             return;
         }
 
         $fbp = $this->fbpContext->getFbp();
 
-        if (!$this->setCookie($event->getRequest(), $fbp)) {
+        if (!$this->shouldSetCookie($event->getRequest(), $fbp)) {
             return;
         }
 
-        $cookie = Cookie::create(
-            self::COOKIE_NAME,
+        $response->headers->setCookie(Cookie::create(
+            Cookies::FBP,
             $fbp->value(),
-            new \DateTimeImmutable('+90 days'),
-        )
-            ->withHttpOnly(false) // we need this to allow the js library to also use the cookie value
-        ;
-
-        $event->getResponse()->headers->setCookie($cookie);
+            new \DateTimeImmutable(Cookies::LIFETIME),
+        )->withHttpOnly(false)); // we need this to allow the js library to also use the cookie value
     }
 
     /**
      * Returns true if the cookie should be created/updated
      */
-    private function setCookie(Request $request, Fbp $fbp): bool
+    private function shouldSetCookie(Request $request, Fbp $fbp): bool
     {
-        if (!$request->cookies->has(self::COOKIE_NAME)) {
+        if (!$request->cookies->has(Cookies::FBP)) {
             return true;
         }
 

src/Resources/config/services/event_subscriber.xml

@@ -63,13 +63,15 @@
         <service id="Setono\MetaConversionsApiBundle\EventSubscriber\StoreFbcSubscriber">
             <argument type="service" id="Setono\MetaConversionsApiBundle\Context\Fbc\FbcContextInterface"/>
             <argument type="service" id="Setono\MetaConversionsApiBundle\ConsentChecker\ConsentCheckerInterface"/>
+            <argument type="service" id="Setono\MetaConversionsApiBundle\Provider\PixelProviderInterface"/>
 
             <tag name="kernel.event_subscriber"/>
         </service>
 
         <service id="Setono\MetaConversionsApiBundle\EventSubscriber\StoreFbpSubscriber">
             <argument type="service" id="Setono\MetaConversionsApiBundle\Context\Fbp\FbpContextInterface"/>
             <argument type="service" id="Setono\MetaConversionsApiBundle\ConsentChecker\ConsentCheckerInterface"/>
+            <argument type="service" id="Setono\MetaConversionsApiBundle\Provider\PixelProviderInterface"/>
 
             <tag name="kernel.event_subscriber"/>
         </service>

tests/Unit/EventSubscriber/StoreFbcSubscriberTest.php

@@ -0,0 +1,151 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Setono\MetaConversionsApiBundle\Tests\Unit\EventSubscriber;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Setono\MetaConversionsApi\Pixel\Pixel;
+use Setono\MetaConversionsApi\ValueObject\Fbc;
+use Setono\MetaConversionsApiBundle\ConsentChecker\ConsentCheckerInterface;
+use Setono\MetaConversionsApiBundle\Context\Fbc\FbcContextInterface;
+use Setono\MetaConversionsApiBundle\Cookie\Cookies;
+use Setono\MetaConversionsApiBundle\EventSubscriber\StoreFbcSubscriber;
+use Setono\MetaConversionsApiBundle\Provider\PixelProviderInterface;
+use Symfony\Component\HttpFoundation\Cookie;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Event\ResponseEvent;
+use Symfony\Component\HttpKernel\HttpKernelInterface;
+
+#[CoversClass(StoreFbcSubscriber::class)]
+final class StoreFbcSubscriberTest extends TestCase
+{
+    #[Test]
+    public function it_stores_the_click_id(): void
+    {
+        $event = self::event(new Request(['fbclid' => 'IwAR0rmfgHgx']), new Response());
+
+        self::subscriber()->store($event);
+
+        $cookie = self::cookie($event);
+        self::assertNotNull($cookie);
+        self::assertStringEndsWith('.IwAR0rmfgHgx', (string) $cookie->getValue());
+        // The browser pixel has to be able to read it
+        self::assertFalse($cookie->isHttpOnly());
+    }
+
+    #[Test]
+    public function it_does_nothing_without_a_click_id_on_the_request(): void
+    {
+        $event = self::event(new Request(), new Response());
+
+        self::subscriber()->store($event);
+
+        self::assertNull(self::cookie($event));
+    }
+
+    #[Test]
+    public function it_does_nothing_without_consent(): void
+    {
+        $event = self::event(new Request(['fbclid' => 'IwAR0rmfgHgx']), new Response());
+
+        self::subscriber(consentGranted: false)->store($event);
+
+        self::assertNull(self::cookie($event));
+    }
+
+    #[Test]
+    public function it_does_nothing_without_pixels(): void
+    {
+        // A Set-Cookie header makes the response uncacheable, and there is nowhere to send events to anyway
+        $event = self::event(new Request(['fbclid' => 'IwAR0rmfgHgx']), new Response());
+
+        self::subscriber(pixels: [])->store($event);
+
+        self::assertNull(self::cookie($event));
+    }
+
+    #[Test]
+    public function it_does_nothing_when_the_context_has_no_fbc(): void
+    {
+        $event = self::event(new Request(['fbclid' => 'IwAR0rmfgHgx']), new Response());
+
+        self::subscriber(fbc: null)->store($event);
+
+        self::assertNull(self::cookie($event));
+    }
+
+    #[Test]
+    public function it_ignores_sub_requests(): void
+    {
+        $event = self::event(new Request(['fbclid' => 'IwAR0rmfgHgx']), new Response(), HttpKernelInterface::SUB_REQUEST);
+
+        self::subscriber()->store($event);
+
+        self::assertNull(self::cookie($event));
+    }
+
+    private static function cookie(ResponseEvent $event): ?Cookie
+    {
+        foreach ($event->getResponse()->headers->getCookies() as $cookie) {
+            if (Cookies::FBC === $cookie->getName()) {
+                return $cookie;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * @param list<Pixel>|null $pixels
+     */
+    private static function subscriber(
+        ?Fbc $fbc = new Fbc('IwAR0rmfgHgx'),
+        bool $consentGranted = true,
+        ?array $pixels = null,
+    ): StoreFbcSubscriber {
+        return new StoreFbcSubscriber(
+            new class($fbc) implements FbcContextInterface {
+                public function __construct(private readonly ?Fbc $fbc)
+                {
+                }
+
+                public function getFbc(): ?Fbc
+                {
+                    return $this->fbc;
+                }
+            },
+            new class($consentGranted) implements ConsentCheckerInterface {
+                public function __construct(private readonly bool $granted)
+                {
+                }
+
+                public function isGranted(): bool
+                {
+                    return $this->granted;
+                }
+            },
+            new class($pixels ?? [new Pixel('1234', 's3cr3t')]) implements PixelProviderInterface {
+                /**
+                 * @param list<Pixel> $pixels
+                 */
+                public function __construct(private readonly array $pixels)
+                {
+                }
+
+                public function getPixels(): array
+                {
+                    return $this->pixels;
+                }
+            },
+        );
+    }
+
+    private static function event(Request $request, Response $response, int $requestType = HttpKernelInterface::MAIN_REQUEST): ResponseEvent
+    {
+        return new ResponseEvent(self::createStub(HttpKernelInterface::class), $request, $requestType, $response);
+    }
+}