How smart sharpen works?

I think that what you need is to dig into Siggraph proceedings. If you are lucky, you will find some papers describing the fundamentals of the algorithms. We here are more interested at how the magic can be put into work, not what magic needed to be applied under the hood.

No one here can uncover the proprietary algorithms and math processes used here. 

Here is some information from the online user guide about Smart Sharpen:

• Adjust image sharpness and blur - Sharpen using Smart Sharpen

And here is some additional information from Photoshop CC (2014 release) Visual Quick Start: Refocusing:

• https://www.peachpit.com/articles/article.aspx?p=2224031&seqNum=2

Although you didn't mention Unsharp Mask, Jan Kabili does an excellent job explaining it in the video on this page:

• Sharpen a photo to bring out detail