Phase 2: Implement React hooks, context, and routing for Angular to React migration

[devin-ai-integration]

Phase 2: Implement React hooks, context, and routing for Angular to React migration

Summary

This PR implements Phase 2 of the Angular to React migration by creating parallel React infrastructure without modifying the existing Angular application. The React code is isolated in src/react/ and uses a separate Vite build system.

Key Changes:

• useHackerNewsAPI hook (src/react/hooks/useHackerNewsAPI.ts): Migrated from Angular's RxJS-based HackerNewsAPIService to native fetch with async/await. Includes fetchFeed, fetchItemContent (with concurrent poll fetching via Promise.all), and fetchUser methods.
• SettingsContext + useSettings hook (src/react/contexts/SettingsContext.tsx): Migrated from Angular's SettingsService with localStorage persistence for theme, font size, and list spacing. Includes system dark mode detection via matchMedia listener with proper cleanup.
• React Router setup (src/react/App.tsx): Configured all 7 routes matching Angular (news, newest, show, ask, jobs, item, user) with lazy loading for item and user pages using React.lazy() and Suspense.
• Placeholder page components: Created FeedPage, ItemDetailsPage, and UserPage with basic routing verification (actual implementation is Phase 3).
• Vite build system: Configured for React development on port 3000 (separate from Angular).

Dependencies Added:

• React 19.2.0, React-DOM 19.2.0, React-Router-DOM 7.9.4
• Vite 7.1.12, @vitejs/plugin-react 5.1.0

The React build (npm run react:build) completes successfully with no TypeScript errors. The dev server (npm run react:dev) starts and serves the app at http://localhost:3000.

Review & Testing Checklist for Human

⚠️ Important: This PR has NOT been comprehensively tested. The implementation compiles and basic routing works, but critical functionality remains unverified.

High Priority - Must Test:

• Test API hook with real API calls: The useHackerNewsAPI hook has not been tested with actual API requests. Create a test component that calls fetchFeed, fetchItemContent, and fetchUser to verify the API integration works correctly and error handling is robust.
• Test Settings Context functionality: Verify localStorage persistence, theme switching (default/night/AMOLED black), font size changes, list spacing changes, and system dark mode detection by:
  • Changing settings in a test UI
  • Refreshing the page to verify persistence
  • Changing OS dark mode preference to test matchMedia listener
• Verify all 7 routes: Only /news/1 and /item/12345 were tested. Manually navigate to all routes (/newest/:page, /show/:page, /ask/:page, /jobs/:page, /user/:id) to ensure routing works correctly.
• Resolve package manager conflict: The project uses Yarn (yarn.lock exists) but this PR used npm, creating a package-lock.json. Decide on one package manager and remove the other lockfile to avoid dependency resolution issues.

Medium Priority - Should Verify:

• Check lazy loading: Open browser DevTools Network tab and verify that ItemDetailsPage and UserPage are loaded as separate chunks only when navigating to those routes.
• Verify no console errors: Check browser console for any runtime errors, warnings, or React warnings.
• Test concurrent poll fetching: The fetchItemContent method uses Promise.all to fetch poll options concurrently. Test with a poll item (if available in the API) to verify it works correctly.

Notes

• No Angular code was modified - all changes are additive in src/react/ directory
• Both apps can run simultaneously - Angular on default port, React on port 3000
• Phase 3 TODO: Implement actual page components with data fetching and UI rendering
• CI may need updates: The CI pipeline might not know about the React build yet. Consider adding npm run react:build to CI checks.

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Link to Devin run: https://app.devin.ai/sessions/0b996b4ba2d046b29651d5302f56efeb
Requested by: @eashansinha

Screenshots:

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