# Canvas API Implementation Summary

## What Was Implemented

Your product finder now has a **hierarchical image fallback system** (Canvas API) that automatically serves images with smart fallbacks across multiple directory levels. This eliminates duplicate files and makes it easy to share common elements (like plants, hardware, backgrounds) across products.

## System Architecture

### Three-Layer Approach

1. **Backend (Python/Flask)** - Smart image resolution with fallback logic
2. **Frontend (JavaScript)** - Dynamic image loading using Canvas API endpoints
3. **File Structure** - Hierarchical organization with automatic fallbacks

```
Product Specific → Subtype Shared → Type Shared → Global Shared
```

## What Changed

### New Files Created

1. **`app/blueprints/canvas.py`** - Canvas API Flask blueprint with fallback logic
   - `/api/canvas/<product_code>/<layer>?color=<color>` - Get image with fallback
   - `/api/canvas/<product_code>/info` - Get available layers info
   - `/api/canvas/test` - Test endpoint

2. **`information/CANVAS_API_GUIDE.md`** - Complete technical documentation
3. **`information/CANVAS_API_QUICKSTART.md`** - 5-minute setup guide
4. **`information/CANVAS_DIRECTORY_SETUP.md`** - Directory setup scripts and helpers
5. **`information/FOREGROUND_LAYER_EXAMPLE.md`** - Foreground layer guide (from earlier)
6. **`information/FOREGROUND_QUICKSTART.md`** - Quick foreground guide (from earlier)

### Modified Files

1. **`app/app.py`** - Registered canvas blueprint
2. **`app/static/js/script.js`** - Added Canvas API support
   - `buildCanvasAPIUrl()` - Build API URLs
   - `updateCanvasAPIPreview()` - Update layers using API
   - Updated rendering logic to support Canvas API
3. **`app/static/css/styles.css`** - Added `.layer-foreground` with z-index 5 (from earlier)
4. **`information/LAYERED_IMAGES.md`** - Updated with foreground layer info
5. **`information/products-layered-example.json`** - Added Canvas API example (product #700)

## How It Works

### 1. Directory Structure
```
app/static/images/
├── doors/
│   └── storm/
│       ├── 404/
│       │   └── door-white.png     # Product-specific
│       └── layers/
│           └── hardware.png       # Shared by all storm doors
└── layers/
    └── foreground.png             # Global fallback
```

### 2. Product Configuration
```json
{
  "productCode": "404",
  "imageConfig": {
    "useCanvasAPI": true
  }
}
```

### 3. Automatic Fallback
Request: `/api/canvas/404/hardware`

Searches in order:
1. `/images/doors/storm/404/hardware.png` ← Product-specific
2. `/images/doors/storm/layers/hardware.png` ← Subtype shared ✓ **Found!**
3. `/images/doors/layers/hardware.png` ← Type shared
4. `/images/layers/hardware.png` ← Global

### 4. Frontend Rendering
```javascript
// JavaScript automatically calls Canvas API
const url = buildCanvasAPIUrl('404', 'door', 'white');
// Result: /api/canvas/404/door?color=white

doorLayer.src = url; // Image loads with automatic fallback!
```

## Layering System (Updated)

All 5 layers are now supported:

1. **Base** (z-index: 1) - Background/house/frame
2. **Door** (z-index: 2) - Door/window panel (color variants)
3. **Hardware** (z-index: 3) - Handles, locks, hinges
4. **Overlay** (z-index: 4) - Glass views, decorative overlays
5. **Foreground** (z-index: 5) - Plants, decorations ⭐ **NEW from earlier request**

## Benefits

### ✅ Eliminates Duplication
Before: Each product has own copy of hardware.png
After: One shared hardware.png for all products of that type

### ✅ Smart Fallbacks
Product can have custom image OR inherit from parent levels automatically

### ✅ Easier Maintenance
Update one shared file → affects all products using it

### ✅ Flexible Organization
- Product-specific overrides: `/images/<type>/<subtype>/<code>/`
- Subtype shared: `/images/<type>/<subtype>/layers/`
- Type shared: `/images/<type>/layers/`
- Global fallback: `/images/layers/`

### ✅ Reduced File Size
Example with 10 products sharing hardware + foreground:
- Before: 10 × (100KB + 150KB) = 2.5MB
- After: 1 × (100KB + 150KB) = 250KB
- **Savings: 2.25MB (90% reduction for shared elements)**

## Usage Examples

### Example 1: All Storm Doors Share Hardware
```
/images/doors/storm/layers/hardware.png  ← One file
```
Products 404, 505, 450 all use this automatically!

### Example 2: Product 404 Has Custom Foreground
```
/images/doors/storm/404/foreground.png        ← Product 404
/images/doors/storm/layers/foreground.png     ← Products 505, 450
```
Product 404 gets custom, others get shared.

### Example 3: Global Plant Layer
```
/images/layers/foreground-plants.png  ← Used by ALL products
```
Unless a more specific version exists.

## Migration Path

### Phase 1: Keep Existing System (Low Risk)
- Leave current products unchanged
- New products use Canvas API: `"useCanvasAPI": true`
- Both systems work simultaneously

### Phase 2: Identify Duplicates
- Run duplicate file detection scripts
- Find common hardware, foregrounds, bases
- Plan shared directory structure

### Phase 3: Reorganize Files
- Create type/subtype structure
- Move shared files to appropriate `/layers/` directories
- Update product JSON: Add `"useCanvasAPI": true`

### Phase 4: Cleanup
- Remove old duplicate files
- Verify all products load correctly
- Measure storage savings

## API Endpoints Reference

```
GET /api/canvas/<product_code>/<layer>?color=<color>&material=<material>
→ Returns image file with automatic fallback

GET /api/canvas/<product_code>/info
→ Returns metadata about available layers

GET /api/canvas/test
→ Test endpoint to verify API is working
```

## Configuration Options

### Enable Canvas API
```json
{
  "productCode": "404",
  "imageConfig": {
    "useCanvasAPI": true
  }
}
```

### Keep Backward Compatibility (During Migration)
```json
{
  "productCode": "404",
  "imageConfig": {
    "useCanvasAPI": true,
    "layered": true,
    "basePath": "images/products/404/",
    "layers": { /* ... */ }
  }
}
```
If Canvas API fails, falls back to static layered system.

## Testing

### 1. Test API is Working
```
Visit: http://localhost:8080/api/canvas/test
Expected: {"status": "ok"}
```

### 2. Test Specific Image
```
Visit: http://localhost:8080/api/canvas/404/base
Expected: Image file loads
```

### 3. Test Fallback
```
Visit: http://localhost:8080/api/canvas/404/hardware
Check Flask logs to see which path was used
```

### 4. Test Product Info
```
Visit: http://localhost:8080/api/canvas/404/info
Expected: JSON with available layers
```

### 5. Test Product Page
```
Visit product page
Open browser console
Check for Canvas API requests: GET /api/canvas/404/door?color=white
```

## Troubleshooting

### Images not loading?
1. Check Flask logs for which path was searched
2. Visit `/api/canvas/<product_code>/info` to see available layers
3. Verify `"useCanvasAPI": true` in products.json
4. Check directory structure matches type/subtype

### 404 errors?
- File doesn't exist at any fallback level
- Check file naming (lowercase for colors)
- Verify baseType and subType in products.json

### Wrong image showing?
- More specific path overrides generic
- Check fallback priority order
- Verify file exists where you expect

## Documentation Files

- **[CANVAS_API_GUIDE.md](CANVAS_API_GUIDE.md)** - Complete technical guide
- **[CANVAS_API_QUICKSTART.md](CANVAS_API_QUICKSTART.md)** - 5-minute setup
- **[CANVAS_DIRECTORY_SETUP.md](CANVAS_DIRECTORY_SETUP.md)** - Setup scripts
- **[FOREGROUND_LAYER_EXAMPLE.md](FOREGROUND_LAYER_EXAMPLE.md)** - Foreground guide
- **[FOREGROUND_QUICKSTART.md](FOREGROUND_QUICKSTART.md)** - Quick foreground setup
- **[LAYERED_IMAGES.md](LAYERED_IMAGES.md)** - Full layering system

## Next Steps

1. ✅ **Test the API**: Visit `/api/canvas/test`
2. ✅ **Create directory structure**: Use scripts in CANVAS_DIRECTORY_SETUP.md
3. ✅ **Move/organize images**: Place in appropriate fallback levels
4. ✅ **Update products.json**: Add `"useCanvasAPI": true`
5. ✅ **Test products**: Load product pages and verify images
6. ✅ **Optimize**: Run duplicate detection and consolidate files

## Summary

You now have a sophisticated, production-ready image serving system with:

✨ **Smart hierarchical fallbacks**  
✨ **Automatic image resolution**  
✨ **5-layer compositing** (including foreground from earlier)  
✨ **Massive storage savings**  
✨ **Easy maintenance**  
✨ **Flexible organization**  
✨ **Backward compatible**  

The system is fully implemented and ready to use. Start with a few test products, verify it works, then gradually migrate your entire catalog!
