Translate incoming requests to over another Proxy (http/s, socks4/5)

[ErcinDedeoglu]

Hello folks,
First of all, fantastic job you accomplished here. Thank you!

My quest is I need a make a rotating proxy server.
I saw this ticket already:
#69

I have a shared proxy pool that contains HTTP/HTTPS/Socks4 and Socks5 proxies.
Most of them are not working well!

So I would like to intercept the incoming request, place one of the WORKING proxies, and continue requesting.
But to understand if the proxy is working (because maybe target knows that it's a proxy and already blocked), I must try it. So if the request fails, I'll try another endpoint. So which place should I look for?

If it's unclear, I can create a UML diagram if needed.

Best,