We need a lot more information about the wiring you want to monitor.
In particular, what voltage is used? What current will flow? And what is the button connected to?
I don't know if this project is mains voltage, or whether you are familiar with working with mains.
But please be aware that mistakes with mains can kill you or others, can burn property, and can destroy a Pi faster than you can say "Pi".
You must abide by your local wiring codes of practice. If you are not an electrician, you should consult one.
Location: 345th cell on the right of the 210th row of L2 cache