Correct middleware routine.

app/Http/Controllers/Import/UploadController.php

@@ -27,6 +27,7 @@ namespace App\Http\Controllers\Import;
 
 use App\Exceptions\ImporterErrorException;
 use App\Http\Controllers\Controller;
+use App\Http\Middleware\UploadControllerMiddleware;
 use App\Http\Middleware\UploadedFiles;
 use App\Services\CSV\Configuration\ConfigFileProcessor;
 use App\Services\Session\Constants;
@@ -52,7 +53,7 @@ class UploadController extends Controller
     {
         parent::__construct();
         app('view')->share('pageTitle', 'Upload files');
-        $this->middleware(UploadedFiles::class);
+        $this->middleware(UploadControllerMiddleware::class);
     }
 
     /**

app/Http/Controllers/IndexController.php

@@ -46,8 +46,9 @@ class IndexController extends Controller
 
     /**
      * @param Request $request
+     * @return mixed
      */
-    public function postIndex(Request $request)
+    public function postIndex(Request $request): mixed
     {
         // set cookie with flow:
         $flow = $request->get('flow');

app/Http/Middleware/IsReadyForStep.php

@@ -0,0 +1,123 @@
+<?php
+/*
+ * IsReadyForStep.php
+ * Copyright (c) 2021 james@firefly-iii.org
+ *
+ * This file is part of the Firefly III Data Importer
+ * (https://github.com/firefly-iii/data-importer).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace App\Http\Middleware;
+
+use App\Exceptions\ImporterErrorException;
+use App\Services\Session\Constants;
+use Illuminate\Http\RedirectResponse;
+use Illuminate\Http\Request;
+use Log;
+
+/**
+ * Trait IsReadyForStep
+ */
+trait IsReadyForStep
+{
+    /**
+     * @param Request $request
+     * @param string  $step
+     * @return bool
+     * @throws ImporterErrorException
+     */
+    protected function isReadyForStep(Request $request, string $step): bool
+    {
+        $flow = $request->cookie('flow');
+        if (null === $flow) {
+            Log::debug('isReadyForStep returns true because $flow is null');
+            return true;
+        }
+        if ('csv' === $flow) {
+            return $this->isReadyForCSVStep($request, $step);
+        }
+        if ('nordigen' === $flow) {
+            die('TODO');
+        }
+        if ('spectre' === $flow) {
+            die('TODO');
+        }
+    }
+
+    /**
+     * @param Request $request
+     * @param string  $step
+     * @return bool
+     * @throws ImporterErrorException
+     */
+    private function isReadyForCSVStep(Request $request, string $step): bool
+    {
+        Log::debug(sprintf('isReadyForCSVStep("%s")', $step));
+        switch ($step) {
+            default:
+                throw new ImporterErrorException(sprintf('isReadyForCSVStep: Cannot handle CSV step "%s"', $step));
+            case 'upload-files':
+                if (session()->has(Constants::HAS_UPLOAD) && true === session()->get(Constants::HAS_UPLOAD)) {
+                    return false;
+                }
+                return true;
+        }
+    }
+
+    /**
+     * @param Request $request
+     * @param string  $step
+     * @return RedirectResponse|null
+     * @throws ImporterErrorException
+     */
+    protected function redirectToCorrectStep(Request $request, string $step): ?RedirectResponse
+    {
+        $flow = $request->cookie('flow');
+        if (null === $flow) {
+            Log::debug('redirectToCorrectStep returns true because $flow is null');
+            return null;
+        }
+        if ('csv' === $flow) {
+            return $this->redirectToCorrectCSVStep($step);
+        }
+        if ('nordigen' === $flow) {
+            die('TODO');
+        }
+        if ('spectre' === $flow) {
+            die('TODO');
+        }
+        die('TODO');
+    }
+
+    /**
+     * @param         $step
+     * @return RedirectResponse
+     * @throws ImporterErrorException
+     */
+    private function redirectToCorrectCSVStep($step): RedirectResponse
+    {
+        Log::debug(sprintf('redirectToCorrectCSVStep("%s")', $step));
+        switch ($step) {
+            default:
+                throw new ImporterErrorException(sprintf('redirectToCorrectCSVStep: Cannot handle CSV step "%s"', $step));
+            case 'upload-files':
+                $route = route('004-configure.index');
+                Log::debug(sprintf('Return redirect to "%s"', $route));
+                return redirect($route);
+        }
+    }
+
+}

app/Http/Middleware/UploadControllerMiddleware.php

@@ -0,0 +1,64 @@
+<?php
+/*
+ * UploadControllerMiddleware.php
+ * Copyright (c) 2021 james@firefly-iii.org
+ *
+ * This file is part of the Firefly III Data Importer
+ * (https://github.com/firefly-iii/data-importer).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace App\Http\Middleware;
+
+use App\Exceptions\ImporterErrorException;
+use App\Services\Session\Constants;
+use Illuminate\Http\Request;
+use Closure;
+
+/**
+ * Class UploadControllerMiddleware
+ */
+class UploadControllerMiddleware
+{
+    use IsReadyForStep;
+
+    /**
+     * Check if the user has already uploaded files in this session. If so, continue to configuration.
+     *
+     * @param Request $request
+     * @param Closure $next
+     *
+     * @return mixed
+     *
+     */
+    public function handle(Request $request, Closure $next)
+    {
+        $step = 'upload-files';
+        $result = $this->isReadyForStep($request, $step);
+        if(true === $result) {
+            return $next($request);
+        }
+
+            $redirect = $this->redirectToCorrectStep($request, $step);
+            if(null !== $redirect) {
+                return $redirect;
+            }
+        throw new ImporterErrorException('Cannot handle upload controller');
+
+
+
+    }
+
+}