Parents Visiting & Medical

We are thinking about retiring in Portugal for a period of time. We are still young and in our 50s, but my parents are in their 80s. We are from the United States and I’m wondering if there is the option of having your parents come and live with you Before six months a year. Or less than 183 days per year. Does Medicare cover them all in Portugal? Or would we buy some private insurance? Does anybody have any experience with this type of situation?