How to map a single click into a double-click?

I have a multi-button mouse. I can change the order of the buttons, for example so the left swaps with the right, using:

xinput set-button-map "Mouse Name" 3 2 1 4 

When I press the 4th button once, I want it to be interpreted as a double click on the left button.

What's the modern way to achieve that?