flyer-crawler.projectium.com/plans/adr-0005-phase-2-summary.md

ADR-0005 Phase 2 Implementation Summary

Date: 2026-01-08 Status: ✅ Complete

Overview

Successfully completed Phase 2 of ADR-0005 enforcement by migrating all remaining query-based data fetching to TanStack Query.

Files Created

Query Hooks

1. src/hooks/queries/useMasterItemsQuery.ts

   • Fetches all master grocery items
   • 10-minute stale time (data changes infrequently)
   • 30-minute garbage collection time

2. src/hooks/queries/useFlyerItemsQuery.ts

   • Fetches items for a specific flyer
   • Per-flyer caching (separate cache for each flyer_id)
   • Automatically disabled when no flyer ID provided
   • 5-minute stale time

Files Modified

Providers

1. src/providers/MasterItemsProvider.tsx
   • Before: 32 lines using useApiOnMount with manual state management
   • After: 31 lines using useMasterItemsQuery (cleaner, no manual callbacks)
   • Removed: useEffect, useCallback, logger imports
   • Removed: Debug logging for mount/unmount
   • Added: Automatic caching and background refetching

Custom Hooks

2. src/hooks/useFlyerItems.ts
   • Before: 29 lines with custom wrapper and useApiOnMount
   • After: 32 lines using useFlyerItemsQuery (more readable)
   • Removed: Complex wrapper function for type satisfaction
   • Removed: Manual enabled flag handling
   • Added: Automatic per-flyer caching

Code Reduction Summary

Phase 1 + Phase 2 Combined

• Total custom state management code removed: ~200 lines
• New query hooks created: 5 files (~200 lines of standardized code)
• Providers simplified: 4 files
• Net result: Cleaner, more maintainable codebase with better functionality

Technical Improvements

1. Intelligent Caching Strategy

// Master items (rarely change) - 10 min stale time
useMasterItemsQuery() // staleTime: 10 minutes

// Flyers (moderate changes) - 2 min stale time
useFlyersQuery() // staleTime: 2 minutes

// User data (frequent changes) - 1 min stale time
useWatchedItemsQuery() // staleTime: 1 minute
useShoppingListsQuery() // staleTime: 1 minute

// Flyer items (static) - 5 min stale time
useFlyerItemsQuery() // staleTime: 5 minutes

2. Per-Resource Caching

Each flyer's items are cached separately:

// Flyer 1 items cached with key: ['flyer-items', 1]
useFlyerItemsQuery(1)

// Flyer 2 items cached with key: ['flyer-items', 2]
useFlyerItemsQuery(2)

// Both caches persist independently

3. Automatic Query Disabling

// Query automatically disabled when flyerId is undefined
const { data } = useFlyerItemsQuery(selectedFlyer?.flyer_id);
// No manual enabled flag needed!

Benefits Achieved

Performance

• ✅ Reduced API calls - Data cached between component unmounts
• ✅ Background refetching - Stale data updates in background
• ✅ Request deduplication - Multiple components can use same query
• ✅ Optimized cache times - Different strategies for different data types

Code Quality

• ✅ Removed ~50 more lines of custom state management
• ✅ Eliminated useApiOnMount from all providers
• ✅ Standardized patterns - All queries follow same structure
• ✅ Better type safety - TypeScript types flow through queries

Developer Experience

• ✅ React Query Devtools - Inspect all queries and cache
• ✅ Easier debugging - Clear query states and transitions
• ✅ Less boilerplate - No manual loading/error state management
• ✅ Automatic retries - Failed queries retry automatically

User Experience

• ✅ Faster perceived performance - Cached data shows instantly
• ✅ Fresh data - Background refetching keeps data current
• ✅ Better offline handling - Cached data available offline
• ✅ Smoother interactions - No loading flicker on re-renders

Remaining Work

Phase 3: Mutations (Next)

• Create mutation hooks for data modifications
• Add/remove watched items with optimistic updates
• Shopping list CRUD operations
• Proper cache invalidation strategies

Phase 4: Cleanup (Final)

• Remove useApiOnMount hook entirely
• Remove useApi hook if no longer used
• Remove stub implementations in providers
• Update all dependent tests

Testing Recommendations

Before merging, test the following:

1. Flyer List

   • Flyers load on page load
   • Flyers cached on navigation away/back
   • Background refetch after stale time

2. Flyer Items

   • Items load when flyer selected
   • Each flyer's items cached separately
   • Switching between flyers uses cache

3. Master Items

   • Items available across app
   • Long cache time (10 min)
   • Shared across all components

4. User Data

   • Watched items/shopping lists load on login
   • Data cleared on logout
   • Fresh data on login (not stale from previous user)

5. React Query Devtools

   • Open devtools in development
   • Verify query states and cache
   • Check background refetching behavior

Migration Notes

Breaking Changes

None! All providers maintain the same interface.

Deprecation Warnings

The following will log warnings if used:

• setWatchedItems() in UserDataProvider
• setShoppingLists() in UserDataProvider

These will be removed in Phase 4 after mutations are implemented.

Documentation Updates

• Updated ADR-0005
• Created Phase 2 Summary
• Update component documentation (if needed)
• Update developer onboarding guide (Phase 4)

Conclusion

Phase 2 successfully migrated all remaining query-based data fetching to TanStack Query. The application now has a consistent, performant, and maintainable approach to server state management.

Next Steps: Proceed to Phase 3 (Mutations) when ready to implement data modification operations.