Replace response body on cache hit

Replacing the response body on cache hits to reduce data transmission

Author: JimTools

src/Cache.php

@@ -11,9 +11,11 @@
 
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Message\StreamFactoryInterface;
 use Psr\Http\Server\MiddlewareInterface;
 use Psr\Http\Server\RequestHandlerInterface;
 
+use Slim\Psr7\Factory\StreamFactory;
 use function in_array;
 use function is_array;
 use function is_numeric;
@@ -45,18 +47,28 @@ class Cache implements MiddlewareInterface
      */
     protected $mustRevalidate;
 
+    /**
+     * @var StreamFactoryInterface
+     */
+    protected $streamFactory;
+
     /**
      * Create new HTTP cache
      *
      * @param string $type           The cache type: "public" or "private"
      * @param int    $maxAge         The maximum age of client-side cache
      * @param bool   $mustRevalidate must-revalidate
      */
-    public function __construct(string $type = 'private', int $maxAge = 86400, bool $mustRevalidate = false)
-    {
+    public function __construct(
+        StreamFactoryInterface $streamFactory,
+        string $type = 'private',
+        int $maxAge = 86400,
+        bool $mustRevalidate = false
+    ) {
         $this->type = $type;
         $this->maxAge = $maxAge;
         $this->mustRevalidate = $mustRevalidate;
+        $this->streamFactory = $streamFactory;
     }
 
     /**
@@ -101,7 +113,8 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
             if ($ifNoneMatch) {
                 $etagList = preg_split('@\s*,\s*@', $ifNoneMatch);
                 if (is_array($etagList) && (in_array($etag, $etagList) || in_array('*', $etagList))) {
-                    return $response->withStatus(304);
+                    return $response->withStatus(304)
+                        ->withBody($this->streamFactory->createStream(''));
                 }
             }
         }
@@ -118,7 +131,8 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
             $ifModifiedSince = $request->getHeaderLine('If-Modified-Since');
 
             if ($ifModifiedSince && $lastModified <= strtotime($ifModifiedSince)) {
-                return $response->withStatus(304);
+                return $response->withStatus(304)
+                    ->withBody($this->streamFactory->createStream(''));
             }
         }