Close #88 - Remove the "Already authenticated" error on login forms

app/Http/Kernel.php

@@ -70,6 +70,7 @@ class Kernel extends HttpKernel
     protected $routeMiddleware = [
         'auth' => \App\Http\Middleware\Authenticate::class,
         'guest' => \App\Http\Middleware\RejectIfAuthenticated::class,
+        'SkipIfAuthenticated' => \App\Http\Middleware\SkipIfAuthenticated::class,
         'throttle' => \Illuminate\Routing\Middleware\ThrottleRequests::class,
         'rejectIfDemoMode' => \App\Http\Middleware\RejectIfDemoMode::class,
         'rejectIfReverseProxy' => \App\Http\Middleware\RejectIfReverseProxy::class,

app/Http/Middleware/SkipIfAuthenticated.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Auth;
+
+class SkipIfAuthenticated
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @param  \Closure  $next
+     * @param  string|null  ...$guards
+     * @return mixed
+     */
+    public function handle(Request $request, Closure $next, ...$guards)
+    {
+        $guards = empty($guards) ? [null] : $guards;
+
+        foreach ($guards as $guard) {
+            if (Auth::guard($guard)->check()) {
+                $user = Auth::guard($guard)->user()->name;
+
+                return response()->json([
+                    'message' => 'authenticated',
+                    'name' => $user
+                ], 200);
+            }
+        }
+
+        return $next($request);
+    }
+}

routes/web.php

@@ -30,7 +30,7 @@
  * Routes that only work for unauthenticated user (return an error otherwise)
  * that can be requested max 10 times per minute by the same IP
  */
-Route::group(['middleware' => ['guest', 'throttle:10,1']], function () {
+Route::group(['middleware' => ['SkipIfAuthenticated', 'throttle:10,1']], function () {
     Route::post('user/login', 'Auth\LoginController@login')->name('user.login');
     Route::post('webauthn/login', [WebAuthnLoginController::class, 'login'])->name('webauthn.login');
 });