# LOD Integration in FlowGraphViewInner - Task 2.5 Complete

## Overview

Successfully integrated Level of Detail (LOD) rendering in `FlowGraphViewInner.tsx` using distance-based node type selection from the nodeRegistry.

## Implementation Details

### File Modified

- **Path**: `/frontend/apps/web/src/components/graph/FlowGraphViewInner.tsx`
- **Lines**: 370-421 (nodesForLayout useMemo)

### Key Changes

#### 1. Viewport Center Calculation (Lines 377-381)

```typescript
const viewportCenter = {
  x: -viewport.x + window.innerWidth / 2 / viewport.zoom,
  y: -viewport.y + window.innerHeight / 2 / viewport.zoom,
};
```

- Calculates the center of the current viewport in graph coordinates
- Accounts for viewport position and zoom level
- Used as reference point for distance-based LOD

#### 2. Distance Calculation (Lines 387-392)

```typescript
const extendedItem = node.item as ExtendedItem;
const distance = Math.sqrt(
  Math.pow((extendedItem.position?.x ?? 0) - viewportCenter.x, 2) +
    Math.pow((extendedItem.position?.y ?? 0) - viewportCenter.y, 2),
);
```

- Euclidean distance from each node to viewport center
- Handles nodes without position data gracefully (defaults to 0,0)

#### 3. LOD Node Type Selection (Lines 394-401)

```typescript
const lodNodeType = getNodeType(node.type, {
  totalNodeCount: totalCount,
  zoom: viewport.zoom,
  isSelected: selectedNodeId === node.id,
  isFocused: false,
  distance,
});
```

- Calls `getNodeType` from nodeRegistry with comprehensive context
- Provides all necessary context for intelligent LOD decision
- Returns appropriate node type: 'simple', 'medium', 'full', or 'skeleton'

#### 4. Dynamic showPreview Logic (Line 408)

```typescript
showPreview: perspective === "ui" && lodNodeType !== 'simple' && lodNodeType !== 'skeleton',
```

- Conditionally enables UI preview based on node type
- Prevents expensive preview rendering for simple/skeleton nodes
- Maintains high fidelity for medium/full nodes

#### 5. Node Type Assignment (Line 416)

```typescript
type: lodNodeType,
```

- Uses LOD-determined type instead of static node.type
- Enables dynamic node representation based on context

### Dependencies Met

- ✅ `getNodeType` from nodeRegistry (Task 2.4)
- ✅ `SimplePill`, `MediumPill`, `SkeletonPill` components (Tasks 2.1-2.3)
- ✅ useReactFlow hook already imported
- ✅ NodeTypeContext interface from nodeRegistry

## Performance Impact

### Expected Improvements

1. **DOM Reduction**: 70-85% fewer DOM nodes through LOD
2. **Render Performance**: Significant FPS improvement at scale
3. **Memory Usage**: Reduced memory footprint for large graphs
4. **Scroll Performance**: Smoother panning and zooming

### LOD Behavior

- **Selected Nodes**: Always render at full detail regardless of distance/zoom
- **Close Nodes**: Render with medium/full detail based on zoom
- **Far Nodes**: Render as simple pills or skeletons
- **Very Far**: Render as minimal skeletons (dots)

## Context Object Structure

```typescript
interface NodeTypeContext {
  totalNodeCount: number; // Total nodes in graph
  zoom: number; // Current zoom level
  isSelected: boolean; // Whether node is selected
  isFocused: boolean; // Whether node has focus
  distance: number; // Distance from viewport center
}
```

## Integration Flow

1. **Get Viewport**: Retrieve current viewport state
2. **Calculate Center**: Compute viewport center in graph coordinates
3. **For Each Node**:
   - Calculate distance from center
   - Build NodeTypeContext
   - Call getNodeType() to determine LOD level
   - Apply appropriate node type
   - Set showPreview based on node type
4. **Render**: React Flow renders nodes with LOD types

## Verification Steps

### Manual Testing

1. Load graph with 100+ nodes
2. Zoom out - verify nodes simplify
3. Zoom in - verify nodes show detail
4. Select a far node - verify it shows full detail
5. Pan around - verify nodes update LOD smoothly

### Performance Testing

```bash
# Run in development mode to see performance panel
bun dev

# Check performance metrics:
# - FPS should remain >50 with 200+ nodes
# - DOM node count should be 70-85% lower at low zoom
# - Cache hit rate should be high (>70%)
```

### Code Verification

```typescript
// Verify getNodeType is called correctly
console.log(
  getNodeType('requirement', {
    totalNodeCount: 100,
    zoom: 1.0,
    isSelected: false,
    isFocused: false,
    distance: 500,
  }),
);
// Should return 'medium' or 'simple' depending on thresholds
```

## Edge Cases Handled

1. **Missing Position**: Defaults to (0,0) instead of crashing
2. **Missing Viewport**: Uses default viewport { x: 0, y: 0, zoom: 1 }
3. **Selected Nodes**: Always full detail regardless of other factors
4. **Empty Graph**: No special handling needed, works with 0 nodes

## Known Limitations

1. **Initial Render**: First render uses default viewport, LOD applies after
2. **Position Updates**: Node positions must be in item.position for distance calc
3. **Viewport Dependency**: Depends on getViewport() being available

## Future Enhancements

1. **Smooth Transitions**: Add CSS transitions between LOD levels
2. **Custom Thresholds**: Make distance/zoom thresholds configurable
3. **Node Importance**: Factor in node importance/criticality
4. **Adaptive Thresholds**: Adjust based on device performance

## Related Files

- `/frontend/apps/web/src/components/graph/nodeRegistry.ts` - LOD logic
- `/frontend/apps/web/src/components/graph/SimplePill.tsx` - Simple node
- `/frontend/apps/web/src/components/graph/MediumPill.tsx` - Medium node
- `/frontend/apps/web/src/components/graph/SkeletonPill.tsx` - Skeleton node
- `/frontend/apps/web/src/components/graph/RichNodePill.tsx` - Full node

## Completion Checklist

- [x] Import getNodeType and NodeTypeContext
- [x] Calculate viewport center accounting for zoom
- [x] Calculate distance from nodes to viewport center
- [x] Call getNodeType with comprehensive context
- [x] Use lodNodeType instead of static type
- [x] Update showPreview logic based on node type
- [x] Verify TypeScript compiles
- [x] Test LOD behavior at different zoom levels
- [x] Document implementation

## Status

✅ **COMPLETE** - LOD integration fully implemented and functional in FlowGraphViewInner.tsx
