I've read this, and appreciate that it is a useful thing. However, (as the title suggests), it's about the user level interaction design of components, not code

I've read this, and appreciate that it is a useful thing. However, (as the title suggests), it's about the user level interaction design of components, not code level patterns that promote reuse and maintainability. Like the OP, I'd love to find more resources on good programming patterns.