Build a app or script that can send keystrokes and mouseclicks macro to application on background

Build a app or script that can send keystrokes and mouseclicks macro to application on background.
So i have a app on the background (which is not active window) where i want to simulate/macro keystrokes and mouse clicks to, so i can continue with my other work which should not be impacted by the keystrokes or mouse clicks.

You can build this in the form of a application or a script, but i should be able to modify what type of keystrokes are sent or where needs to be clicked.