flyer-crawler.projectium.com/plans/adr-0005-phase-3-summary.md

ADR-0005 Phase 3 Implementation Summary

Date: 2026-01-08 Status: ✅ Complete

Overview

Successfully completed Phase 3 of ADR-0005 enforcement by creating all mutation hooks for data modifications using TanStack Query mutations.

Files Created

Mutation Hooks

All mutation hooks follow a consistent pattern:

• Automatic cache invalidation via queryClient.invalidateQueries()
• Success/error notifications via notification service
• Proper TypeScript types for parameters
• Comprehensive JSDoc documentation with examples

Watched Items Mutations

1. src/hooks/mutations/useAddWatchedItemMutation.ts

   • Adds an item to the user's watched items list
   • Parameters: { itemName: string, category?: string }
   • Invalidates: ['watched-items'] query

2. src/hooks/mutations/useRemoveWatchedItemMutation.ts

   • Removes an item from the user's watched items list
   • Parameters: { masterItemId: number }
   • Invalidates: ['watched-items'] query

Shopping List Mutations

3. src/hooks/mutations/useCreateShoppingListMutation.ts

   • Creates a new shopping list
   • Parameters: { name: string }
   • Invalidates: ['shopping-lists'] query

4. src/hooks/mutations/useDeleteShoppingListMutation.ts

   • Deletes an entire shopping list
   • Parameters: { listId: number }
   • Invalidates: ['shopping-lists'] query

5. src/hooks/mutations/useAddShoppingListItemMutation.ts

   • Adds an item to a shopping list
   • Parameters: { listId: number, item: { masterItemId?: number, customItemName?: string } }
   • Supports both master items and custom items
   • Invalidates: ['shopping-lists'] query

6. src/hooks/mutations/useUpdateShoppingListItemMutation.ts

   • Updates a shopping list item (quantity, notes, purchased status)
   • Parameters: { itemId: number, updates: Partial<ShoppingListItem> }
   • Updatable fields: custom_item_name, quantity, is_purchased, notes
   • Invalidates: ['shopping-lists'] query

7. src/hooks/mutations/useRemoveShoppingListItemMutation.ts

   • Removes an item from a shopping list
   • Parameters: { itemId: number }
   • Invalidates: ['shopping-lists'] query

Barrel Export

8. src/hooks/mutations/index.ts
   • Centralized export for all mutation hooks
   • Easy imports: import { useAddWatchedItemMutation } from '../hooks/mutations'

Mutation Hook Pattern

All mutation hooks follow this consistent structure:

export const useSomeMutation = () => {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: async (params) => {
      const response = await apiClient.someMethod(params);

      if (!response.ok) {
        const error = await response.json().catch(() => ({
          message: `Request failed with status ${response.status}`,
        }));
        throw new Error(error.message || 'Failed to perform action');
      }

      return response.json();
    },
    onSuccess: () => {
      // Invalidate affected queries
      queryClient.invalidateQueries({ queryKey: ['some-query'] });
      notifySuccess('Action completed successfully');
    },
    onError: (error: Error) => {
      notifyError(error.message || 'Failed to perform action');
    },
  });
};

Usage Examples

Adding a Watched Item

import { useAddWatchedItemMutation } from '../hooks/mutations';

function WatchedItemsManager() {
  const addWatchedItem = useAddWatchedItemMutation();

  const handleAdd = () => {
    addWatchedItem.mutate(
      { itemName: 'Milk', category: 'Dairy' },
      {
        onSuccess: () => console.log('Added to watched list!'),
        onError: (error) => console.error('Failed:', error),
      }
    );
  };

  return (
    <button
      onClick={handleAdd}
      disabled={addWatchedItem.isPending}
    >
      {addWatchedItem.isPending ? 'Adding...' : 'Add to Watched List'}
    </button>
  );
}

Managing Shopping Lists

import {
  useCreateShoppingListMutation,
  useAddShoppingListItemMutation,
  useUpdateShoppingListItemMutation
} from '../hooks/mutations';

function ShoppingListManager() {
  const createList = useCreateShoppingListMutation();
  const addItem = useAddShoppingListItemMutation();
  const updateItem = useUpdateShoppingListItemMutation();

  const handleCreateList = () => {
    createList.mutate({ name: 'Weekly Groceries' });
  };

  const handleAddItem = (listId: number, masterItemId: number) => {
    addItem.mutate({
      listId,
      item: { masterItemId }
    });
  };

  const handleMarkPurchased = (itemId: number) => {
    updateItem.mutate({
      itemId,
      updates: { is_purchased: true }
    });
  };

  return (
    <div>
      <button onClick={handleCreateList}>Create List</button>
      {/* ... other UI */}
    </div>
  );
}

Benefits Achieved

Performance

• ✅ Automatic cache updates - Queries automatically refetch after mutations
• ✅ Request deduplication - Multiple mutation calls are properly queued
• ✅ Optimistic updates ready - Infrastructure in place for Phase 4

Code Quality

• ✅ Standardized pattern - All mutations follow the same structure
• ✅ Comprehensive documentation - JSDoc with examples for every hook
• ✅ Type safety - Full TypeScript types for all parameters
• ✅ Error handling - Consistent error handling and user notifications

Developer Experience

• ✅ React Query Devtools - Inspect mutation states in real-time
• ✅ Easy imports - Barrel export for clean imports
• ✅ Consistent API - Same pattern across all mutations
• ✅ Built-in loading states - isPending, isError, isSuccess states

User Experience

• ✅ Automatic notifications - Success/error toasts on all mutations
• ✅ Fresh data - Queries automatically update after mutations
• ✅ Loading states - UI can show loading indicators during mutations
• ✅ Error feedback - Clear error messages on failures

Current State

Completed

• ✅ All 7 mutation hooks created
• ✅ Barrel export created for easy imports
• ✅ Comprehensive documentation with examples
• ✅ Consistent error handling and notifications
• ✅ Automatic cache invalidation on all mutations

Not Yet Migrated

The following custom hooks still use the old useApi pattern with manual state management:

1. src/hooks/useWatchedItems.tsx (74 lines)

   • Uses useApi for add/remove operations
   • Manually updates state via setWatchedItems
   • Should be refactored to use mutation hooks

2. src/hooks/useShoppingLists.tsx (222 lines)

   • Uses useApi for all CRUD operations
   • Manually updates state via setShoppingLists
   • Complex manual state synchronization logic
   • Should be refactored to use mutation hooks

These hooks are actively used throughout the application and will need careful refactoring in Phase 4.

Remaining Work

Phase 4: Hook Refactoring & Cleanup

Step 1: Refactor useWatchedItems

• Replace useApi calls with mutation hooks
• Remove manual state management logic
• Simplify to just wrap mutation hooks with custom logic
• Update all tests

Step 2: Refactor useShoppingLists

• Replace useApi calls with mutation hooks
• Remove manual state management logic
• Remove complex state synchronization
• Keep activeListId state (still needed)
• Update all tests

Step 3: Remove Deprecated Code

• Remove setWatchedItems from UserDataContext
• Remove setShoppingLists from UserDataContext
• Remove useApi hook (if no longer used)
• Remove useApiOnMount hook (already deprecated)

Step 4: Add Optimistic Updates (Optional)

• Implement optimistic updates for better UX
• Use onMutate to update cache before server response
• Implement rollback on error

Step 5: Documentation & Testing

• Update all component documentation
• Update developer onboarding guide
• Add integration tests for mutation flows
• Create migration guide for other developers

Testing Recommendations

Before considering Phase 4:

1. Manual Testing

   • Add/remove watched items
   • Create/delete shopping lists
   • Add/remove/update shopping list items
   • Verify cache updates correctly
   • Check success/error notifications

2. React Query Devtools

   • Open devtools in development
   • Watch mutations execute
   • Verify cache invalidation
   • Check mutation states (pending, success, error)

3. Network Tab

   • Verify API calls are correct
   • Check request/response payloads
   • Ensure no duplicate requests

4. Error Scenarios

   • Test with network offline
   • Test with invalid data
   • Verify error notifications appear
   • Check cache remains consistent

Migration Path for Components

Components currently using useWatchedItems or useShoppingLists can continue using them as-is. When we refactor those hooks in Phase 4, the component interface will remain the same.

For new components, you can use mutation hooks directly:

// Old way (still works)
import { useWatchedItems } from '../hooks/useWatchedItems';

function MyComponent() {
  const { addWatchedItem, removeWatchedItem } = useWatchedItems();
  // ...
}

// New way (recommended for new code)
import { useAddWatchedItemMutation, useRemoveWatchedItemMutation } from '../hooks/mutations';

function MyComponent() {
  const addWatchedItem = useAddWatchedItemMutation();
  const removeWatchedItem = useRemoveWatchedItemMutation();
  // ...
}

Documentation Updates

• Created Phase 3 Summary
• Update ADR-0005 (mark Phase 3 complete)
• Update component documentation (Phase 4)
• Update developer onboarding guide (Phase 4)

Conclusion

Phase 3 successfully created all mutation hooks following TanStack Query best practices. The application now has a complete set of standardized mutation operations with automatic cache invalidation and user notifications.

Next Steps: Proceed to Phase 4 to refactor existing custom hooks (useWatchedItems and useShoppingLists) to use the new mutation hooks, then remove deprecated state setters and cleanup old code.