public static function source($file, $line)
    {
        if ($line <= 0 || is_file($file) === false) {
            return null;
        } elseif ($line > 5) {
            $init = $line - 5;
            $end  = $line + 5;
            $breakpoint = 6;
        } else {
            $init = 0;
            $end  = 5;
            $breakpoint = $line;
        }

        return array(
            'breakpoint' => $breakpoint,
            'preview' => preg_split('#\r\n|\n#',
                trim( File::portion($file, $init, $end, true), "\r\n")
            )
        );
    }