Purpose / Description

Creating a deck A::B, if B subdeck is empty and parent A is empty, clicking on the parent it should show 'this deck is empty', instead of the finished deck message.

Fixes

• Fixes "This deck is empty" should appear even when the deck has empty subdeck #17965

Approach

The earlier code just checked for the following conditions:

• If the deck clicked has subdecks (at the topmost list level only) - getNodeByDid(did).children.isEmpty()
• If only the deck clicked has 0 cards - decks.isEmpty(did)

This would fail at cases where the deck has subdecks, which are also empty.

Now the check is done to not just check subdecks, but the count of cards of these subdecks too.

• using the forEach recursive function of DeckNode to traverse the entire tree of subdecks to check if all of them are empty for triggering the empty deck snackbar

How Has This Been Tested?

ran all tests from ./gradlew jacocoTestReport on emulator (android 15 VanillaIceCream)
PC config:
processor: i5 12500H
RAM: 16GB
SDK: 21
results: ran with 0 failures
Also I tested with creation of "A::B::C", "A::B" decks, and adding the cards to the subdecks.

clicking on A	shows finished deck on A click

clicking on B	shows finished deck on B

After fix

clicking on A	clicking on B

Update commit - 2e33db4

Now uses a new function isDeckAndSubdeckEmpty, and DeckNode implements Iterable, and hence the entire tree empty check is done using deckNode.all{}, which efficiently returns true or false.
Also refactored the previous query function that returned enums.

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