refactor+perf(study-screen): custom scheduler

[BrayanDSO]

Approach

In the commits

How Has This Been Tested?

Emulator 31:

1. Go to deck options > Advanced > Custom scheduler
2. Add console.log("some message"); there
3. Open the new study screen
4. See the log in logcat

Checklist

Please, go through these checks before submitting the PR.

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[david-allison]

Soft approve

[david-allison]

Likely off-topic & could be moved to another issue.

I'm concerned there's no cancellation support.

What happens when a card is flipped, but this hasn't run yet? What if there's an error, or the code is slow?

[BrayanDSO]

Functionally, the only difference in comparison with the previous approach is how it waits for the signal, i.e. while...delay(50) vs CompletableDeferred.await().

Should it have some kind of timeout instead of waiting indefinitely? Perhaps.

Is the custom scheduler logic convoluted? Yes. And that is a consequence of how Anki desktop is architectured. I'm mostly following how the desktop version make the reviewer work, even in a barely used setting like this one.

ReviewerFragmentTest tests if the custom scheduler is working, so that is covered.

Making the logic safer to future refactors need some integration tests, and I'm still far from them.

So, create another issue if you want. Or simply wait until this turns into a problem (or not).

[david-allison]

Wasn't expecting the infinite loops to be handled here, only flagging that they're an issue.

A TODO is probably the best call, it wouldn't meet 'priority: low' yet, but leaving that one up to you