private function buildVersionsList($service)
    {
        $dir = "{$this->modelsDir}/{$service}/";

        if (!is_dir($dir)) {
            return;
        }

        // Get versions, remove . and .., and sort in descending order.
        $results = array_diff(scandir($dir, SCANDIR_SORT_DESCENDING), ['..', '.']);

        if (!$results) {
            $this->manifest[$service] = ['versions' => []];
        } else {
            $this->manifest[$service] = [
                'versions' => [
                    'latest' => $results[0]
                ]
            ];
            $this->manifest[$service]['versions'] += array_combine($results, $results);
        }
    }