Auto-Ranging circuit using op-amp

[Anitech]

I am trying to understand the attached schematic and trying to scale it to my specifications. Can anyone help me understand the circuit here?
The application is to measure current in the uA and Ampere range as well. Which I need to change the shunt resistor automatically when the current consumption of DUT changes beyond the range. 
I am open to other suggestions for other implementations to solve the purpose.

[gamalot]

https://www.eevblog.com/forum/beginners/how-does-this-op-amp-autoswitcher-from-nordic-ppk2-works/msg4096165/

[Anitech]

Thanks a lot for referring to the relevant thread. But the solution is still missing there.

[1audio]

This is a link to an autoranger to go in front of a soundcard. https://www.diyaudio.com/community/threads/autoranger-for-soundcards.299635/post-4815633 Its loosely based on the input circuit of the Boonton 1120 audio analyzer. The thread is long but you should be able to get some good ideas in the first few messages.