Extracts file-based navigation logic from HomePage into pure function
with comprehensive test coverage.
New behavior:
- Opening 1 file from empty → switch to viewer (activeFileIndex: 0)
- Opening 2+ files from empty → switch to fileEditor
- pdfTextEditor tool → no auto-navigation (handles own empty state)
- Non-startup transitions (N→M files) → no navigation
Benefits:
- Pure function → easy to test and reason about
- Clear separation of concerns
- Preserves all existing behavior including pdfTextEditor special case
- Adds new multi-file startup behavior
Changes:
- HomePage.tsx: use getStartupNavigationAction() utility
- homePageNavigation.ts: pure navigation logic
- homePageNavigation.test.ts: comprehensive unit tests
Note: prevFileCountRef initialization kept as useRef(activeFiles.length)
to correctly handle files restored from IndexedDB on app startup.
# Description of Changes
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Please provide a summary of the changes, including:
- What was changed
- Why the change was made
- Any challenges encountered
Closes #(issue_number)
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## Checklist
### General
- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings
### Documentation
- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)
### Translations (if applicable)
- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)
### UI Changes (if applicable)
- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)
### Testing (if applicable)
- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.
Reece BrowneandGitHub
Anthony StirlingandGitHub