pixelfed/app/Http/Controllers/AuthorizeInteractionController.php

<?php

namespace App\Http\Controllers;

use App\Util\ActivityPub\Helpers;
use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;

class AuthorizeInteractionController extends Controller
{
    public function get(Request $request): RedirectResponse
    {
        $request->validate([
            'uri' => 'required|url',
        ]);

        abort_unless((bool) config_cache('federation.activitypub.enabled'), 404);

        $uri = Helpers::validateUrl($request->input('uri'));
        abort_unless($uri, 404);

        if (! $request->user()) {
            // Store the current Pixelfed URL so Laravel's redirect()->intended()
            // returns here after login. The `next` query param was never
            // consumed by the login flow, so the remote-follow interaction was
            // lost after authenticating.
            $request->session()->put('url.intended', $request->fullUrl());

            return redirect('/login');
        }

        $status = Helpers::statusFetch($uri);
        if ($status && isset($status['id'])) {
            return redirect('/i/web/post/'.$status['id']);
        }

        $profile = Helpers::profileFetch($uri);
        if ($profile && isset($profile['id'])) {
            return redirect('/i/web/profile/'.$profile['id']);
        }

        return redirect('/i/web');
    }
}