Laravel Upload Controller

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Requests;
use File;
use Image;

class UploadController extends Controller {

    public function upload(Request $request)
    {
        $file = $request->file('file');
        $rules = ['file' => 'image|max:2000'];
        $allowed = ['jpg','jpeg','png'];

        $tempPath = '/uploads/temp/';
        $originalPath = 'uploads/';

        $validator = \Validator::make([$file], $rules);
        if($validator->fails()) {
            return response()->json("error", 500);
        }

        $extension = strtolower($file->getClientOriginalExtension());

        if($file) {
            if(!in_array($extension, $allowed)) {
                return response()->json("Gelieve een afbeelding te selecteren", 400);
            }
            $filename = sha1(str_random()) . ".$extension";
            var_dump($filename);
            $destination = public_path() . $tempPath;

            if($upload = $file->move($destination, $filename)) {
                $image = Image::make($destination . $filename);
                $width = $image->width();
                $height = $image->height();

                if($width >= $height) {
                    $image->resize(750, null, function($constraint) {
                        $constraint->aspectRatio();
                    })->save($originalPath.$filename);
                } else {
                    $image->resize(null, 750, function($constraint) {
                        $constraint->aspectRatio();
                    })->save($originalPath.$filename);
                }
            }

        } else {
            return response()->json("error", 400);
        }
    }
}