Implement middleware for presenting pretty error pages

framework/core/src/Forum/Middleware/HandleErrors.php

@@ -0,0 +1,44 @@
+<?php namespace Flarum\Forum\Middleware;
+
+use Psr\Http\Message\ResponseInterface as Response;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Zend\Diactoros\Response\StringResponse;
+use Zend\Stratigility\ErrorMiddlewareInterface;
+
+class HandleErrors implements ErrorMiddlewareInterface
+{
+    protected $templateDir;
+
+    public function __construct($templateDir)
+    {
+        $this->templateDir = $templateDir;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function __invoke($error, Request $request, Response $response, callable $out = null)
+    {
+        $status = 500;
+
+        // If it seems to be a valid HTTP status code, we pass on the
+        // exception's status.
+        $errorCode = $error->getCode();
+        if (is_int($errorCode) && $errorCode >= 400 && $errorCode < 600) {
+            $status = $errorCode;
+        }
+
+        $errorPage = $this->getErrorPage($status);
+
+        return StringResponse::html($errorPage, $status);
+    }
+
+    protected function getErrorPage($status)
+    {
+        if (!file_exists($errorPage = $this->templateDir."/$status.html")) {
+            $errorPage = $this->templateDir.'/500.html';
+        }
+
+        return file_get_contents($errorPage);
+    }
+}