### Separate the code in short and simple functions

Your current functions are way too long: for example, `main()` has 1282 lines. That's much more than acceptable.

While the exact maximal number of lines is a subjective thing, there are some good rules of thumb. For example, this [question][1] mentions 100 to 200 lines as the upper bound. Ideally, every function should do just one thing and do it well - this called SRP, [single responsibility principle][2].

In many programs `main()` is somewhat an exception of this, as it usually does both initialization (by calling an `init()` or similar function) and the main loop. Still, the main loop should consist mainly of calls to other functions and/or state machine logic. I believe the other answers give more details on structuring it.

  [1]: https://softwareengineering.stackexchange.com/q/133404/139851
  [2]: https://en.wikipedia.org/wiki/Single_responsibility_principle