refactor

readme.refactoring-summary.md

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+# 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.