Performance: Optimized data loading of course

[Sh-AhsanArif]

• Optimized data loading on app dashboard screen (cached data first)
• Optimized data loading on course outline screen (cached data first)
• Minor code refactoring

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[e0d]

@Sh-AhsanArif as you are covered by the Arbisoft entity CLA, I've added you to the triage team. This will allow tests to run automatically on your PRs. Please accept the invite.

[PavloNetrebchuk]

@Sh-AhsanArif
Hi, great job. If you are moving the logic to Flow, it would be great to make methods that do not return Flow private. What do you think?

[Sh-AhsanArif]

Hi @PavloNetrebchuk

Thank you for your feedback! That’s a great suggestion, and I completely agree that moving all relevant methods to return Flow would improve consistency. However, making these changes in this PR would increase its scope and require additional effort and testing.
If the experience with Flow in this implementation turns out to be positive, we should consider replacing all previous methods accordingly. I’d be more than happy to take that up in a separate PR to ensure a smooth transition.

Let me know what you think!

[PavloNetrebchuk]

@Sh-AhsanArif
Okay, please resolve the conflicts and I'll approve

[PavloNetrebchuk]

Hi, @Sh-AhsanArif

I’ve reviewed the app again and have a few questions:
1. When opening a course in a fresh install of the app, we encounter a NoCachedDataException. Could you please take a look and fix this?
2. The Result layer seems unnecessary and inconsistent with the rest of the app. Since we typically use catch, it would be great if we could stick to this approach for consistency.
3. I have some doubts regarding the following code in CourseContainerViewModel and similar code in CourseOutlineViewModel:

courseFlow.take(1).combine(enrollmentFlow.take(1)) { course, enrollment ->
    course to enrollment
}	

Could you clarify why we are using take(1) here? Would it be possible to achieve the same result with:

courseFlow.combine(enrollmentFlow) { course, enrollment ->
    ...
}

[omerhabib26]

Hey @Sh-AhsanArif, thank you so much for this improvement! I had a chance to take a quick look, and I noticed a couple of small UI issues in your repo, as shown in the video:

• There’s a glitch on the home screen when the user lands for the first time. IMO, it should show a loader instead.
• The API seems to be crashing on the Course dashboard with the error org.openedx.core.exception.NoCachedDataException.

OpenEdxPR.webm