Created new action to track visits, which returns an empty pixel

composer.json

@@ -22,10 +22,9 @@
         "doctrine/dbal": "^2.5",
         "doctrine/migrations": "^1.4",
         "doctrine/orm": "^2.5",
-        "endroid/qrcode": "^1.7",
+        "endroid/qr-code": "^1.7",
         "firebase/php-jwt": "^4.0",
         "guzzlehttp/guzzle": "^6.2",
-        "http-interop/http-middleware": "^0.4.1",
         "mikehaertl/phpwkhtmltopdf": "^2.2",
         "monolog/monolog": "^1.21",
         "roave/security-advisories": "dev-master",

module/Common/src/Response/PixelResponse.php

@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Common\Response;
+
+use Psr\Http\Message\StreamInterface;
+use Zend\Diactoros\Response;
+use Zend\Diactoros\Stream;
+
+class PixelResponse extends Response
+{
+    private const BASE_64_IMAGE = 'R0lGODlhAQABAJAAAP8AAAAAACH5BAUQAAAALAAAAAABAAEAAAICBAEAOw==';
+    private const CONTENT_TYPE = 'image/gif';
+
+    public function __construct(int $status = 200, array $headers = [])
+    {
+        $headers['content-type'] = self::CONTENT_TYPE;
+        parent::__construct($this->createBody(), $status, $headers);
+    }
+
+    /**
+     * Create the message body.
+     *
+     * @return StreamInterface
+     */
+    private function createBody(): StreamInterface
+    {
+        $body = new Stream('php://temp', 'wb+');
+        $body->write(\base64_decode(self::BASE_64_IMAGE));
+        $body->rewind();
+        return $body;
+    }
+}

module/Core/config/dependencies.config.php

@@ -28,6 +28,7 @@ return [
 
             // Middleware
             Action\RedirectAction::class => ConfigAbstractFactory::class,
+            Action\PixelAction::class => ConfigAbstractFactory::class,
             Action\QrCodeAction::class => ConfigAbstractFactory::class,
             Action\PreviewAction::class => ConfigAbstractFactory::class,
             Middleware\QrCodeCacheMiddleware::class => ConfigAbstractFactory::class,
@@ -60,6 +61,11 @@ return [
             Service\VisitsTracker::class,
             Options\AppOptions::class,
         ],
+        Action\PixelAction::class => [
+            Service\UrlShortener::class,
+            Service\VisitsTracker::class,
+            Options\AppOptions::class,
+        ],
         Action\QrCodeAction::class => [RouterInterface::class, Service\UrlShortener::class, 'Logger_Shlink'],
         Action\PreviewAction::class => [PreviewGenerator::class, Service\UrlShortener::class],
         Middleware\QrCodeCacheMiddleware::class => [Cache::class],

module/Core/config/routes.config.php

@@ -13,6 +13,12 @@ return [
             'middleware' => Action\RedirectAction::class,
             'allowed_methods' => ['GET'],
         ],
+        [
+            'name' => 'pixel-tracking',
+            'path' => '/{shortCode}/track',
+            'middleware' => Action\PixelAction::class,
+            'allowed_methods' => ['GET'],
+        ],
         [
             'name' => 'short-url-qr-code',
             'path' => '/{shortCode}/qr-code[/{size:[0-9]+}]',

module/Core/src/Action/AbstractTrackingAction.php

@@ -0,0 +1,74 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Core\Action;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Shlinkio\Shlink\Core\Action\Util\ErrorResponseBuilderTrait;
+use Shlinkio\Shlink\Core\Exception\EntityDoesNotExistException;
+use Shlinkio\Shlink\Core\Exception\InvalidShortCodeException;
+use Shlinkio\Shlink\Core\Options\AppOptions;
+use Shlinkio\Shlink\Core\Service\UrlShortenerInterface;
+use Shlinkio\Shlink\Core\Service\VisitsTrackerInterface;
+
+abstract class AbstractTrackingAction implements MiddlewareInterface
+{
+    use ErrorResponseBuilderTrait;
+
+    /**
+     * @var UrlShortenerInterface
+     */
+    private $urlShortener;
+    /**
+     * @var VisitsTrackerInterface
+     */
+    private $visitTracker;
+    /**
+     * @var AppOptions
+     */
+    private $appOptions;
+
+    public function __construct(
+        UrlShortenerInterface $urlShortener,
+        VisitsTrackerInterface $visitTracker,
+        AppOptions $appOptions
+    ) {
+        $this->urlShortener = $urlShortener;
+        $this->visitTracker = $visitTracker;
+        $this->appOptions = $appOptions;
+    }
+
+    /**
+     * Process an incoming server request and return a response, optionally delegating
+     * to the next middleware component to create the response.
+     *
+     * @param ServerRequestInterface $request
+     * @param RequestHandlerInterface $handler
+     *
+     * @return ResponseInterface
+     */
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        $shortCode = $request->getAttribute('shortCode', '');
+        $query = $request->getQueryParams();
+        $disableTrackParam = $this->appOptions->getDisableTrackParam();
+
+        try {
+            $longUrl = $this->urlShortener->shortCodeToUrl($shortCode);
+
+            // Track visit to this short code
+            if ($disableTrackParam === null || ! \array_key_exists($disableTrackParam, $query)) {
+                $this->visitTracker->track($shortCode, $request);
+            }
+
+            return $this->createResp($longUrl);
+        } catch (InvalidShortCodeException | EntityDoesNotExistException $e) {
+            return $this->buildErrorResponse($request, $handler);
+        }
+    }
+
+    abstract protected function createResp(string $longUrl): ResponseInterface;
+}

module/Core/src/Action/PixelAction.php

@@ -0,0 +1,15 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Core\Action;
+
+use Psr\Http\Message\ResponseInterface;
+use Shlinkio\Shlink\Common\Response\PixelResponse;
+
+class PixelAction extends AbstractTrackingAction
+{
+    protected function createResp(string $longUrl): ResponseInterface
+    {
+        return new PixelResponse();
+    }
+}

module/Core/src/Action/RedirectAction.php

@@ -4,74 +4,14 @@ declare(strict_types=1);
 namespace Shlinkio\Shlink\Core\Action;
 
 use Psr\Http\Message\ResponseInterface as Response;
-use Psr\Http\Message\ServerRequestInterface as Request;
-use Psr\Http\Server\MiddlewareInterface;
-use Psr\Http\Server\RequestHandlerInterface;
-use Shlinkio\Shlink\Core\Action\Util\ErrorResponseBuilderTrait;
-use Shlinkio\Shlink\Core\Exception\EntityDoesNotExistException;
-use Shlinkio\Shlink\Core\Exception\InvalidShortCodeException;
-use Shlinkio\Shlink\Core\Options\AppOptions;
-use Shlinkio\Shlink\Core\Service\UrlShortenerInterface;
-use Shlinkio\Shlink\Core\Service\VisitsTrackerInterface;
 use Zend\Diactoros\Response\RedirectResponse;
 
-class RedirectAction implements MiddlewareInterface
+class RedirectAction extends AbstractTrackingAction
 {
-    use ErrorResponseBuilderTrait;
-
-    /**
-     * @var UrlShortenerInterface
-     */
-    private $urlShortener;
-    /**
-     * @var VisitsTrackerInterface
-     */
-    private $visitTracker;
-    /**
-     * @var AppOptions
-     */
-    private $appOptions;
-
-    public function __construct(
-        UrlShortenerInterface $urlShortener,
-        VisitsTrackerInterface $visitTracker,
-        AppOptions $appOptions
-    ) {
-        $this->urlShortener = $urlShortener;
-        $this->visitTracker = $visitTracker;
-        $this->appOptions = $appOptions;
-    }
-
-    /**
-     * Process an incoming server request and return a response, optionally delegating
-     * to the next middleware component to create the response.
-     *
-     * @param Request $request
-     * @param RequestHandlerInterface $handler
-     *
-     * @return Response
-     */
-    public function process(Request $request, RequestHandlerInterface $handler): Response
+    protected function createResp(string $longUrl): Response
     {
-        $shortCode = $request->getAttribute('shortCode', '');
-        $query = $request->getQueryParams();
-        $disableTrackParam = $this->appOptions->getDisableTrackParam();
-
-        try {
-            $longUrl = $this->urlShortener->shortCodeToUrl($shortCode);
-
-            // Track visit to this short code
-            if ($disableTrackParam === null || ! \array_key_exists($disableTrackParam, $query)) {
-                $this->visitTracker->track($shortCode, $request);
-            }
-
-            // Return a redirect response to the long URL.
-            // Use a temporary redirect to make sure browsers always hit the server for analytics purposes
-            return new RedirectResponse($longUrl);
-        } catch (InvalidShortCodeException $e) {
-            return $this->buildErrorResponse($request, $handler);
-        } catch (EntityDoesNotExistException $e) {
-            return $this->buildErrorResponse($request, $handler);
-        }
+        // Return a redirect response to the long URL.
+        // Use a temporary redirect to make sure browsers always hit the server for analytics purposes
+        return new RedirectResponse($longUrl);
     }
 }