Created middleware to cache generated QR codes

module/Common/src/Factory/CacheFactory.php

@@ -3,6 +3,7 @@ namespace Shlinkio\Shlink\Common\Factory;
 
 use Doctrine\Common\Cache\ApcuCache;
 use Doctrine\Common\Cache\ArrayCache;
+use Doctrine\Common\Cache\FilesystemCache;
 use Interop\Container\ContainerInterface;
 use Interop\Container\Exception\ContainerException;
 use Zend\ServiceManager\Exception\ServiceNotCreatedException;

module/Core/config/dependencies.config.php

@@ -1,6 +1,7 @@
 <?php
 use Acelaya\ZsmAnnotatedServices\Factory\V3\AnnotatedFactory;
 use Shlinkio\Shlink\Core\Action;
+use Shlinkio\Shlink\Core\Middleware;
 use Shlinkio\Shlink\Core\Options\AppOptions;
 use Shlinkio\Shlink\Core\Service;
 
@@ -19,6 +20,7 @@ return [
             // Middleware
             Action\RedirectAction::class => AnnotatedFactory::class,
             Action\QrCodeAction::class => AnnotatedFactory::class,
+            Middleware\QrCodeCacheMiddleware::class => AnnotatedFactory::class,
         ],
     ],
 

module/Core/config/routes.config.php

@@ -1,5 +1,6 @@
 <?php
 use Shlinkio\Shlink\Core\Action;
+use Shlinkio\Shlink\Core\Middleware;
 
 return [
 
@@ -13,7 +14,10 @@ return [
         [
             'name' => 'short-url-qr-code',
             'path' => '/qr/{shortCode}[/{size:[0-9]+}]',
-            'middleware' => Action\QrCodeAction::class,
+            'middleware' => [
+                Middleware\QrCodeCacheMiddleware::class,
+                Action\QrCodeAction::class,
+            ],
             'allowed_methods' => ['GET'],
         ],
     ],

module/Core/src/Middleware/QrCodeCacheMiddleware.php

@@ -0,0 +1,73 @@
+<?php
+namespace Shlinkio\Shlink\Core\Middleware;
+
+use Acelaya\ZsmAnnotatedServices\Annotation\Inject;
+use Doctrine\Common\Cache\Cache;
+use Psr\Http\Message\ResponseInterface as Response;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Zend\Stratigility\MiddlewareInterface;
+
+class QrCodeCacheMiddleware implements MiddlewareInterface
+{
+    /**
+     * @var Cache
+     */
+    private $cache;
+
+    /**
+     * QrCodeCacheMiddleware constructor.
+     * @param Cache $cache
+     *
+     * @Inject({Cache::class})
+     */
+    public function __construct(Cache $cache)
+    {
+        $this->cache = $cache;
+    }
+
+    /**
+     * Process an incoming request and/or response.
+     *
+     * Accepts a server-side request and a response instance, and does
+     * something with them.
+     *
+     * If the response is not complete and/or further processing would not
+     * interfere with the work done in the middleware, or if the middleware
+     * wants to delegate to another process, it can use the `$out` callable
+     * if present.
+     *
+     * If the middleware does not return a value, execution of the current
+     * request is considered complete, and the response instance provided will
+     * be considered the response to return.
+     *
+     * Alternately, the middleware may return a response instance.
+     *
+     * Often, middleware will `return $out();`, with the assumption that a
+     * later middleware will return a response.
+     *
+     * @param Request $request
+     * @param Response $response
+     * @param null|callable $out
+     * @return null|Response
+     */
+    public function __invoke(Request $request, Response $response, callable $out = null)
+    {
+        $cacheKey = $request->getUri()->getPath();
+
+        // If this QR code is already cached, just return it
+        if ($this->cache->contains($cacheKey)) {
+            $qrData = $this->cache->fetch($cacheKey);
+            $response->getBody()->write($qrData['body']);
+            return $response->withHeader('Content-Type', $qrData['content-type']);
+        }
+
+        // If not, call the next middleware and cache it
+        /** @var Response $resp */
+        $resp = $out($request, $response);
+        $this->cache->save($cacheKey, [
+            'body' => $resp->getBody()->__toString(),
+            'content-type' => $resp->getHeaderLine('Content-Type'),
+        ]);
+        return $resp;
+    }
+}