What is the correct word for a "pathological rescuer"?

The kind of people who aways fall for and want to help other people who need help. Like drunks/druggies, homeless, jobless, people and thought they could actually help them. What is the correct word to call the person who will go out of their way and destroy their own life trying to help someone else get their life together? Even destroy their credit to help another person who will never appreciate it.