bookinventory/app/Http/Controllers/LookupController.php

<?php

namespace App\Http\Controllers;

use Cache;
use App\Services\BookInformation\GoogleBooks;
use Symfony\Component\HttpKernel\Exception\HttpException;

class LookupController {
    public function lookup($isbn) {
        if (!preg_match('/^(\d+)$/', $isbn)) {
            throw new HttpException(400);
        }

        return Cache::remember('isbn_' . $isbn, 86400, function() use ($isbn) {
            $google_books = new GoogleBooks();

            return $google_books->lookup($isbn);
        });
    }
}