# WYSIWYG Editor Refactoring Progress Summary

## Completed Phases

### Phase 1: Infrastructure ✅
- Created modular block handler architecture
- Implemented `IBlockHandler` interface and `BaseBlockHandler` class
- Created `BlockRegistry` for dynamic block type registration
- Set up proper file structure under `blocks/` directory

### Phase 2: Proof of Concept ✅
- Successfully migrated divider block as the simplest example
- Validated the architecture works correctly
- Established patterns for block migration

### Phase 3: Text Blocks ✅
- **Paragraph Block**: Full editing support with text splitting, selection handling, and cursor tracking
- **Heading Blocks**: All three heading levels (h1, h2, h3) with unified handler
- **Quote Block**: Italic styling with border, full editing capabilities
- **Code Block**: Monospace font, tab handling, plain text paste support
- **List Block**: Bullet/numbered lists with proper list item management

## Key Achievements

### 1. Preserved Critical Knowledge
- **Static Rendering**: Blocks use `innerHTML` in `firstUpdated` to prevent focus loss during typing
- **Shadow DOM Selection**: Implemented `containsAcrossShadowDOM` utility for proper selection detection
- **Cursor Position Tracking**: All editable blocks track cursor position across multiple events
- **Content Splitting**: HTML-aware splitting using Range API preserves formatting
- **Focus Management**: Microtask-based focus restoration ensures reliable cursor placement

### 2. Enhanced Architecture
- Each block type is now self-contained in its own file
- Block handlers are dynamically registered and loaded
- Common functionality is shared through base classes
- Styles are co-located with their block handlers

### 3. Maintained Functionality
- All keyboard navigation works (arrows, backspace, delete, enter)
- Text selection across Shadow DOM boundaries functions correctly
- Block merging and splitting behave as before
- IME (Input Method Editor) support is preserved
- Formatting shortcuts (Cmd/Ctrl+B/I/U/K) continue to work

## Code Organization

```
ts_web/elements/wysiwyg/
├── dees-wysiwyg-block.ts (simplified main component)
├── wysiwyg.selection.ts (Shadow DOM selection utilities)
├── wysiwyg.blockregistration.ts (handler registration)
└── blocks/
    ├── index.ts (exports and registry)
    ├── block.base.ts (base handler interface)
    ├── decorative/
    │   └── divider.block.ts
    └── text/
        ├── paragraph.block.ts
        ├── heading.block.ts
        ├── quote.block.ts
        ├── code.block.ts
        └── list.block.ts
```

## Next Steps

### Phase 4: Media Blocks (In Progress)
- Image block with upload/drag-drop support
- YouTube block with video embedding
- Attachment block for file uploads

### Phase 5: Content Blocks
- Markdown block with preview toggle
- HTML block with raw HTML editing

### Phase 6: Cleanup
- Remove old code from main component
- Optimize bundle size
- Update documentation

## Technical Improvements

1. **Modularity**: Each block type is now completely self-contained
2. **Extensibility**: New blocks can be added by creating a handler and registering it
3. **Maintainability**: Files are smaller and focused on single responsibilities
4. **Type Safety**: Strong TypeScript interfaces ensure consistent implementation
5. **Performance**: No degradation in performance; potential for lazy loading in future

## Migration Pattern

For future block migrations, follow this pattern:

1. Create block handler extending `BaseBlockHandler`
2. Implement required methods: `render()`, `setup()`, `getStyles()`
3. Add helper methods for cursor/content management
4. Handle Shadow DOM selection properly using utilities
5. Register handler in `wysiwyg.blockregistration.ts`
6. Test all interactions (typing, selection, navigation)

The refactoring has been successful in making the codebase more maintainable while preserving all the hard-won functionality and edge case handling from the original implementation.