stack/docs/scratchpads/72-graph-visualization.md

Issue #72: Graph Visualization Component

Objective

Create interactive knowledge graph visualization component in Next.js web UI using the graph API from issue #71.

Approach

1. Research and select graph visualization library
2. Follow TDD: Write tests before implementation
3. Create graph visualization component with:
   • Force-directed layout
   • Node sizing based on connections
   • PDA-friendly status colors
   • Click handlers for navigation
   • Zoom/pan controls
   • Layout toggle options
4. Performance test with 500+ nodes
5. Integrate with graph API

Library Selection

Evaluating options:

• react-force-graph: WebGL-based, high performance, good for 500+ nodes
• vis-network: Canvas-based, feature-rich
• d3-force: Low-level, full control but more complex

Decision: react-force-graph-2d

• Best performance for 500+ nodes (WebGL rendering)
• Simple API
• Built-in zoom/pan
• Easy to customize node appearance
• Active maintenance

Progress

• Create scratchpad
• Set up component structure
• Write tests (TDD) - 16 tests, all passing
• Implement basic graph rendering
• Add node sizing logic (based on connection count)
• Add status-based coloring (PDA-friendly colors)
• Implement click handlers (navigation to entry)
• Add layout controls (force, hierarchical, circular)
• Performance testing (supports 500+ nodes)
• Create display page at /knowledge/graph
• Add filters (status, tags, orphans)
• Type checking passes
• Linting passes
• Code review
• QA checks
• Commit and close issue

Testing Strategy

1. Unit tests for graph component
2. Test node rendering
3. Test interaction handlers
4. Test layout switching
5. Performance test with large datasets

PDA-Friendly Colors

From CLAUDE.md:

• 🟢 Active: green-500
• 🔵 Scheduled: blue-500
• ⏸️ Paused: yellow-500
• 💤 Dormant: gray-400
• ⚪ Archived: gray-300

Implementation Summary

Components Created

1. KnowledgeGraphViewer.tsx - Main graph visualization component

   • Force-directed, hierarchical, and circular layout options
   • PDA-friendly status colors (green=published, blue=draft, gray=archived)
   • Node sizing based on connection count
   • Interactive zoom/pan controls
   • Click to navigate to entry
   • Filters: status, tags, orphan visibility
   • Legend panel showing color meanings

2. KnowledgeGraphViewer.test.tsx - Comprehensive test suite

   • 16 tests covering all features
   • 100% test pass rate
   • Performance test with 500+ nodes

3. page.tsx - Display page at /knowledge/graph

API Integration

• Added fetchKnowledgeGraph() to knowledge.ts API client
• Fetches from /api/knowledge/graph endpoint (implemented in issue #71)
• Supports filtering by tags, status, and limit

Libraries Used

• @xyflow/react - Graph rendering and layout
• elkjs - Hierarchical layout algorithm
• Already in package.json, no new dependencies needed

Features Implemented

• ✅ Force-directed layout (default)
• ✅ Hierarchical layout (ELK algorithm)
• ✅ Circular layout
• ✅ Node sizing based on connections (40px - 120px)
• ✅ PDA-friendly colors by status
• ✅ Orphan node detection and highlighting
• ✅ Click to navigate to entry
• ✅ Zoom and pan controls (ReactFlow built-in)
• ✅ MiniMap for navigation
• ✅ Filters: status, tags, show/hide orphans
• ✅ Statistics display (total nodes, edges, orphans)
• ✅ Legend panel
• ✅ Performance tested with 500+ nodes

Notes

• Using @xyflow/react instead of react-force-graph (already in dependencies)
• Memoization implemented for filtered nodes/edges
• Layout calculations are async to prevent UI blocking
• All quality gates passed (tests, typecheck, lint)