public function make($host)
    {
        $host = $this->resolver->resolve($host, '/');
        $hash = md5($host);

        if (isset($this->instances[$hash])) {
            return $this->instances[$hash];
        }

        $dir = sprintf(
            '%s/%s',
            rtrim($this->cacheDir, '/'),
            $hash
        );
        $instance = new Capabilities(
            $host,
            $this->http,
            new FileCache(sprintf(
                '%s/capabilities.php',
                $dir
            )),
            $this->loader->make($host),
            $this->resolver
        );
        $this->instances[$hash] = $instance;

        return $instance;
    }