# Image Hosting Guide for Cross-Origin Isolated Environment

## Quick Reference

### ✅ Supported Image Sources (Work in Development)

| Service | Proxy Endpoint | Example URL |
|---------|---------------|-------------|
| TimeSafari | `/image-proxy/` | `https://image.timesafari.app/abc123.jpg` |
| Flickr | `/flickr-proxy/` | `https://live.staticflickr.com/123/456.jpg` |
| Imgur | `/imgur-proxy/` | `https://i.imgur.com/example.jpg` |
| GitHub Raw | `/github-proxy/` | `https://raw.githubusercontent.com/user/repo/main/image.png` |
| Unsplash | `/unsplash-proxy/` | `https://images.unsplash.com/photo-123456` |
| Facebook | `/facebook-proxy/` | `https://www.facebook.com/images/groups/...` |
| Medium | `/medium-proxy/` | `https://miro.medium.com/v2/resize:fit:180/...` |
| Meetup | `/meetup-proxy/` | `https://secure.meetupstatic.com/photos/...` |

### ⚠️ Problematic Image Sources (May Not Work in Development)

- Random external websites without CORS headers
- WordPress uploads from arbitrary domains
- Custom CDNs without proper CORS configuration
- Any service that doesn't send `Cross-Origin-Resource-Policy: cross-origin`

## Why This Happens

In development mode, we enable SharedArrayBuffer for fast SQLite operations, which requires:
- `Cross-Origin-Opener-Policy: same-origin`
- `Cross-Origin-Embedder-Policy: require-corp`

These headers create a **cross-origin isolated environment** that blocks resources unless they have proper CORS headers.

## Solutions

### 1. Use Supported Image Hosting Services

**Recommended services that work well:**
- **Imgur**: Free, no registration required, direct links
- **GitHub**: If you have images in repositories
- **Unsplash**: For stock photos
- **TimeSafari Image Server**: For app-specific images

### 2. Add New Image Hosting Proxies

If you frequently use images from a specific domain, add a proxy:

#### Step 1: Add Proxy to `vite.config.common.mts`
```typescript
'/yourservice-proxy': {
  target: 'https://yourservice.com',
  changeOrigin: true,
  secure: true,
  followRedirects: true,
  rewrite: (path) => path.replace(/^\/yourservice-proxy/, ''),
  configure: (proxy) => {
    proxy.on('proxyRes', (proxyRes, req, res) => {
      proxyRes.headers['Access-Control-Allow-Origin'] = '*';
      proxyRes.headers['Access-Control-Allow-Methods'] = 'GET, OPTIONS';
      proxyRes.headers['Cross-Origin-Resource-Policy'] = 'cross-origin';
    });
  }
}
```

#### Step 2: Update Transform Function in `src/libs/util.ts`
```typescript
// Transform YourService URLs to use proxy
if (imageUrl.startsWith("https://yourservice.com/")) {
  const imagePath = imageUrl.replace("https://yourservice.com/", "");
  return `/yourservice-proxy/${imagePath}`;
}
```

### 3. Use Alternative Image Sources

For frequently failing domains, consider:
- Upload images to Imgur or GitHub
- Use a CDN with proper CORS headers
- Host images on your own domain with CORS enabled

## Development vs Production

### Development Mode
- Images from supported services work through proxies
- Unsupported images may fail to load
- Console warnings show which images have issues

### Production Mode
- All images load directly without proxies
- No CORS restrictions in production
- Better performance without proxy overhead

## Testing Image Sources

### Check if an Image Source Works
```bash
# Test in browser console:
fetch('https://example.com/image.jpg', { mode: 'cors' })
  .then(response => console.log('✅ Works:', response.status))
  .catch(error => console.log('❌ Blocked:', error));
```

### Visual Testing
```typescript
import { createTestImageElements } from './libs/test-cors-images';
createTestImageElements(); // Creates visual test panel
```

## Common Error Messages

### `ERR_BLOCKED_BY_RESPONSE.NotSameOriginAfterDefaultedToSameOriginByCoep`
**Cause**: Image source doesn't send required CORS headers
**Solution**: Use a supported image hosting service or add a proxy

### `ERR_NETWORK` or `ERR_INTERNET_DISCONNECTED`
**Cause**: Proxy service is unavailable
**Solution**: Check internet connection or use alternative image source

### Images Load in Production but Not Development
**Cause**: Normal behavior - development has stricter CORS requirements
**Solution**: Use supported image sources for development testing

## Best Practices

### For New Projects
1. Use supported image hosting services from the start
2. Upload user images to Imgur or similar service
3. Host critical images on your own domain with CORS enabled

### For Existing Projects
1. Identify frequently used image domains in console warnings
2. Add proxies for the most common domains
3. Gradually migrate to supported image hosting services

### For User-Generated Content
1. Provide upload functionality to supported services
2. Validate image URLs against supported domains
3. Show helpful error messages for unsupported sources

## Troubleshooting

### Image Not Loading?
1. Check browser console for error messages
2. Verify the domain is in the supported list
3. Test if the image loads in production mode
4. Consider adding a proxy for that domain

### Proxy Not Working?
1. Check if the target service allows proxying
2. Verify CORS headers are being set correctly
3. Test with a simpler image URL from the same domain

### Performance Issues?
1. Proxies add latency in development only
2. Production uses direct image loading
3. Consider using a local image cache for development

## Quick Fixes

### For Immediate Issues
```typescript
// Temporary fallback: disable CORS headers for testing
// In vite.config.common.mts, comment out:
// headers: {
//   'Cross-Origin-Opener-Policy': 'same-origin',
//   'Cross-Origin-Embedder-Policy': 'require-corp'
// },
```
**Note**: This disables SharedArrayBuffer performance benefits.

### For Long-term Solution
- Use supported image hosting services
- Add proxies for frequently used domains
- Migrate critical images to your own CORS-enabled CDN

## Summary

The cross-origin isolated environment is necessary for SharedArrayBuffer performance but requires careful image source management. Use the supported services, add proxies for common domains, and accept that some external images may not work in development mode.

This is a development-only limitation - production deployments work with any image source.