# StateMiddleware Utility Audit

**Date**: 2025-01-27  
**Action**: 4.6.1.4  
**Status**: ✅ Complete

## Summary

The `stateMiddleware` utility (`apps/web/src/utils/stateMiddleware.ts`) is **completely unused** in production code. It was previously used by the Library Store but was removed when domain data was migrated to React Query (Action 4.1.2.7).

## Usage Analysis

### Imports
- ❌ **No imports found** in production code
- ✅ **Only used in test file**: `apps/web/src/utils/stateMiddleware.test.ts`
- ✅ Only mentioned in comments/docs indicating it was removed

### Functions Exported
1. `stateMiddleware<T>()` - Zustand middleware for logging, analytics, error handling
2. `createWithMiddleware<T>()` - Helper to create a store with state middleware

**Both functions are unused in production code.**

## Historical Context

- Previously used by Library Store for logging, analytics, and error handling on domain data
- Removed in Action 4.1.2.7 when Library Store domain data was migrated to React Query
- React Query handles data fetching and caching, making this middleware unnecessary for domain data
- UI state stores (Library Store now only has filters) don't need this level of middleware complexity

## Current State

The Library Store now only contains UI state (filters):
```typescript
export const useLibraryStore = create<LibraryStore>()(
  devtools(
    persist(
      (set) => ({
        filters: {},
        setFilters: (filters) => set({ filters }),
      }),
      // ...
    ),
  ),
);
```

No middleware needed for simple UI state.

## Recommendation

✅ **Safe to remove** - The utility is completely unused in production code and can be deleted along with:
- `apps/web/src/utils/stateMiddleware.ts` (431 lines)
- `apps/web/src/utils/stateMiddleware.test.ts` (test file, 251 lines)

## Next Steps

- **Action 4.6.1.4**: Simplify stateMiddleware if still needed ✅ (confirmed unused, can be removed)
