dees-catalog/readme.refactoring-summary.md

# WYSIWYG Editor Refactoring Progress Summary

## Latest Updates

### Selection Highlighting Fix ✅
- **Issue**: "Paragraphs are not highlighted consistently, headings are always highlighted"
- **Root Cause**: The `shouldUpdate` method in `dees-wysiwyg-block.ts` was using a generic `.block` selector that would match the first element with that class, not necessarily the correct block element
- **Solution**: Changed the selector to be more specific: `.block.${blockType}` which ensures the correct element is found for each block type
- **Result**: All block types now highlight consistently when selected

### Enter Key Block Creation Fix ✅
- **Issue**: "When pressing enter and jumping to new block then typing something: The cursor is not at the beginning of the new block and there is content"
- **Root Cause**: Block handlers were rendering content with template syntax `${block.content || ''}` in their render methods, which violates the static HTML principle
- **Solution**: 
  - Removed all `${block.content}` from render methods in paragraph, heading, quote, and code block handlers
  - Content is now set programmatically in the setup() method only when needed
  - Fixed `setCursorToStart` and `setCursorToEnd` to always find elements fresh instead of relying on cached `blockElement`
- **Result**: New empty blocks remain truly empty, cursor positioning works correctly

### Backspace Key Deletion Fix ✅
- **Issue**: "After typing in a new block, pressing backspace deletes the whole block instead of just the last character"
- **Root Cause**: 
  1. `getCursorPositionInElement` was using `element.contains()` which doesn't work across Shadow DOM boundaries
  2. The backspace handler was checking `block.content === ''` which only contains the stored content, not the actual DOM content
- **Solution**:
  1. Fixed `getCursorPositionInElement` to use `containsAcrossShadowDOM` for proper Shadow DOM support
  2. Updated backspace handler to get actual content from DOM using `blockComponent.getContent()` instead of relying on stored `block.content`
  3. Added debug logging to track cursor position and content state
- **Result**: Backspace now correctly deletes individual characters instead of the whole block

### Arrow Left Navigation Fix ✅
- **Issue**: "When jumping to the previous block from the beginning of a block with arrow left, the cursor should be at the end of the previous block, not at the start"
- **Root Cause**: Browser's default focus behavior places cursor at the beginning of contenteditable elements, overriding our cursor positioning
- **Solution**: For 'end' position, set up the selection range BEFORE focusing the element:
  1. Create a range pointing to the end of content
  2. Apply the selection
  3. Then focus the element (which preserves the existing selection)
  4. Only use setCursorToEnd for empty blocks
- **Result**: Arrow left navigation now correctly places cursor at the end of the previous block

## 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.