Implement request handler for maintenance mode

src/Foundation/InstalledApp.php

@@ -18,9 +18,7 @@ use Flarum\Foundation\Console\CacheClearCommand;
 use Flarum\Foundation\Console\InfoCommand;
 use Flarum\Http\Middleware\DispatchRoute;
 use Flarum\Settings\SettingsRepositoryInterface;
-use Zend\Diactoros\Response\HtmlResponse;
 use Zend\Stratigility\MiddlewarePipe;
-use function Zend\Stratigility\middleware;
 use function Zend\Stratigility\path;
 
 class InstalledApp implements AppInterface
@@ -47,7 +45,7 @@ class InstalledApp implements AppInterface
     public function getRequestHandler()
     {
         if ($this->inMaintenanceMode()) {
-            return $this->getMaintenanceHandler();
+            return new MaintenanceModeHandler();
         } elseif ($this->needsUpdate()) {
             return $this->getUpdaterHandler();
         }
@@ -66,24 +64,6 @@ class InstalledApp implements AppInterface
         return $this->config['offline'] ?? false;
     }
 
-    /**
-     * @return \Psr\Http\Server\RequestHandlerInterface
-     */
-    private function getMaintenanceHandler()
-    {
-        $pipe = new MiddlewarePipe;
-
-        $pipe->pipe(middleware(function () {
-            // FIXME: Fix path to 503.html
-            // TODO: FOR API render JSON-API error document for HTTP 503
-            return new HtmlResponse(
-                file_get_contents(__DIR__.'/../../503.html'), 503
-            );
-        }));
-
-        return $pipe;
-    }
-
     private function needsUpdate(): bool
     {
         $settings = $this->laravel->make(SettingsRepositoryInterface::class);

src/Foundation/MaintenanceModeHandler.php

@@ -0,0 +1,58 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Foundation;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Tobscure\JsonApi\Document;
+use Zend\Diactoros\Response\HtmlResponse;
+use Zend\Diactoros\Response\JsonResponse;
+
+class MaintenanceModeHandler implements RequestHandlerInterface
+{
+    const MESSAGE = 'Currently down for maintenance. Please come back later.';
+
+    /**
+     * Handle the request and return a response.
+     */
+    public function handle(ServerRequestInterface $request): ResponseInterface
+    {
+        // Special handling for API requests: they get a proper API response
+        if ($this->isApiRequest($request)) {
+            return $this->apiResponse();
+        }
+
+        // By default, return a simple text message.
+        return new HtmlResponse(self::MESSAGE, 503);
+    }
+
+    private function isApiRequest(ServerRequestInterface $request): bool
+    {
+        return str_contains(
+            $request->getHeaderLine('Accept'),
+            'application/vnd.api+json'
+        );
+    }
+
+    private function apiResponse(): ResponseInterface
+    {
+        return new JsonResponse(
+            (new Document)->setErrors([
+                'status' => '503',
+                'title' => self::MESSAGE
+            ]),
+            503,
+            ['Content-Type' => 'application/vnd.api+json']
+        );
+    }
+}