voxblog/apps/api/REFACTORING_SUMMARY.md

# AI Generate Refactoring Summary

## Overview
Refactored `src/ai-generate.ts` (453 lines) into a clean, maintainable architecture with proper separation of concerns.

## New Structure

```
apps/api/src/
├── routes/
│   └── ai.routes.ts                    # 85 lines - Clean route handlers
├── services/
│   ├── ai/
│   │   ├── AIService.ts                # 48 lines - Main orchestrator
│   │   ├── contentGenerator.ts         # 145 lines - Content generation
│   │   ├── metadataGenerator.ts        # 63 lines - Metadata generation
│   │   └── altTextGenerator.ts         # 88 lines - Alt text generation
│   └── openai/
│       └── client.ts                   # 36 lines - Singleton client
├── utils/
│   ├── imageUtils.ts                   # 65 lines - Image utilities
│   ├── contextBuilder.ts               # 59 lines - Context building
│   ├── responseParser.ts               # 63 lines - Response parsing
│   └── errorHandler.ts                 # 60 lines - Error handling
├── types/
│   └── ai.types.ts                     # 87 lines - Type definitions
└── config/
    └── prompts.ts                      # 104 lines - Prompt templates
```

## Benefits Achieved

### ✅ Maintainability
- **Before**: 453 lines in one file
- **After**: 12 focused files, largest is 145 lines
- Each module has a single, clear responsibility
- Easy to locate and fix bugs

### ✅ Testability
- Service methods can be unit tested independently
- Utilities can be tested in isolation
- OpenAI client can be easily mocked
- Clear interfaces for all components

### ✅ Reusability
- Utils can be used across different endpoints
- Service can be used outside routes (CLI, jobs, etc.)
- Prompts centralized and easy to modify
- Image handling logic shared

### ✅ Type Safety
- Full TypeScript coverage with explicit interfaces
- Request/response types defined
- Compile-time error detection
- Better IDE autocomplete and refactoring support

### ✅ Error Handling
- Centralized error handling with consistent format
- Detailed logging with request IDs
- Debug mode for development
- Structured error responses

## Key Improvements

### 1. **Separation of Concerns**
- **Routes**: Only handle HTTP request/response
- **Services**: Business logic and AI orchestration
- **Utils**: Reusable helper functions
- **Config**: Static configuration and prompts
- **Types**: Type definitions and interfaces

### 2. **OpenAI Client Singleton**
- Single instance with optimized configuration
- 10-minute timeout for long requests
- 2 retry attempts for transient failures
- Shared across all AI operations

### 3. **Specialized Generators**
- `ContentGenerator`: Handles gpt-5-2025-08-07 with Chat Completions API
- `MetadataGenerator`: Handles gpt-5-2025-08-07 for metadata
- `AltTextGenerator`: Handles gpt-5-2025-08-07 for accessibility

### 4. **Utility Functions**
- `imageUtils`: Presigned URLs, format validation, placeholder extraction
- `contextBuilder`: Build context from transcriptions and images
- `responseParser`: Parse AI responses, strip HTML, handle JSON
- `errorHandler`: Consistent error logging and responses

### 5. **Request Tracking**
- Every request gets a unique UUID
- Logs include request ID for correlation
- Elapsed time tracking
- Detailed error context

## Migration Status

### ✅ Completed
- [x] Type definitions
- [x] Configuration extraction
- [x] Utility functions
- [x] OpenAI client singleton
- [x] Service layer implementation
- [x] Route handlers refactored
- [x] TypeScript compilation verified

### 🔄 Active
- New routes active at `/api/ai/*`
- Old `ai-generate.ts` kept as backup (commented out)

### 📋 Next Steps
1. **Test all endpoints**:
   - POST `/api/ai/generate`
   - POST `/api/ai/generate-metadata`
   - POST `/api/ai/generate-alt-text`

2. **Verify functionality**:
   - Content generation with reference images
   - Metadata generation from HTML
   - Alt text with and without captions
   - Error handling and logging

3. **Remove old code** (after validation):
   - Delete `src/ai-generate.ts`
   - Remove commented import in `index.ts`

## Testing Commands

```bash
# Start API server
cd apps/api
pnpm run dev

# Test content generation
curl -X POST http://localhost:3301/api/ai/generate \
  -H "Content-Type: application/json" \
  -d '{"prompt": "Write about TypeScript best practices"}'

# Test metadata generation
curl -X POST http://localhost:3301/api/ai/generate-metadata \
  -H "Content-Type: application/json" \
  -d '{"contentHtml": "<h1>Test Article</h1><p>Content here</p>"}'

# Test alt text generation
curl -X POST http://localhost:3301/api/ai/generate-alt-text \
  -H "Content-Type: application/json" \
  -d '{"placeholderDescription": "dashboard_screenshot"}'
```

## Rollback Plan

If issues arise, rollback is simple:

1. Edit `src/index.ts`:
   ```typescript
   // Comment out new routes
   // app.use('/api/ai', aiRoutesNew);
   
   // Uncomment old routes
   app.use('/api/ai', aiGenerateRouter);
   ```

2. Restart server

3. Old functionality restored immediately

## File Size Comparison

| Metric | Before | After |
|--------|--------|-------|
| Single file | 453 lines | - |
| Largest file | 453 lines | 145 lines |
| Total files | 1 | 12 |
| Average file size | 453 lines | ~70 lines |
| Cyclomatic complexity | High | Low |

## Code Quality Metrics

- ✅ Single Responsibility Principle
- ✅ Dependency Injection ready
- ✅ Easy to mock for testing
- ✅ Clear module boundaries
- ✅ Consistent error handling
- ✅ Comprehensive logging
- ✅ Type-safe throughout

## Conclusion

The refactoring successfully transformed a complex 453-line file into a clean, maintainable architecture with 12 focused modules. Each component has a clear purpose, is independently testable, and follows TypeScript best practices.

**Status**: ✅ Ready for testing
**Risk**: Low (old code preserved for easy rollback)
**Impact**: High (significantly improved maintainability)