# Frontend Performance Optimization Guide

This guide documents all performance optimizations implemented in the Telegram Marketing Agent frontend.

## Overview

The frontend has been optimized for performance across multiple dimensions:
- Initial load time
- Runtime performance
- Memory usage
- Network efficiency
- User experience

## Build Optimizations

### 1. Code Splitting
- Automatic vendor chunks for better caching
- Manual chunks for large libraries (Element Plus, Chart.js)
- Route-based code splitting with lazy loading

### 2. Compression
- Gzip compression for all assets > 10KB
- Brotli compression for better compression ratios
- Image optimization with quality settings

### 3. Asset Optimization
- Proper asset naming for cache busting
- Inline small assets (< 4KB)
- Organized asset directories

## Runtime Optimizations

### 1. Lazy Loading
- **Images**: Intersection Observer-based lazy loading
- **Components**: Dynamic imports with loading/error states
- **Routes**: Lazy-loaded route components

```vue
<!-- Image lazy loading -->
<img v-lazy="imageSrc" :alt="imageAlt">

<!-- Background lazy loading -->
<div v-lazy-bg="backgroundUrl"></div>

<!-- Progressive image loading -->
<img v-progressive="{ lowQuality: thumbUrl, highQuality: fullUrl }">
```

### 2. Virtual Scrolling
For large lists, use the VirtualList component:

```vue
<VirtualList 
  :items="items" 
  :item-height="50"
  v-slot="{ item }"
>
  <div>{{ item.name }}</div>
</VirtualList>
```

### 3. Web Workers
Heavy computations are offloaded to web workers:

```javascript
import { useComputationWorker } from '@/composables/useWebWorker'

const { sort, filter, aggregate, loading, result } = useComputationWorker()

// Sort large dataset
await sort(largeArray)

// Filter data
await filter(items, 'status', 'active')
```

### 4. Debouncing & Throttling
```javascript
import { debounce, throttle } from '@/utils/performance'

// Debounce search input
const search = debounce((query) => {
  // Search logic
}, 300)

// Throttle scroll handler
const handleScroll = throttle(() => {
  // Scroll logic
}, 100)
```

## State Management

### 1. Persisted State
Store state is automatically persisted with debouncing:

```javascript
// In store configuration
export const useUserStore = defineStore('user', {
  persist: {
    paths: ['profile', 'preferences'],
    debounceTime: 1000
  }
})
```

### 2. Memory Management
- WeakMap for object references
- Automatic cleanup on component unmount
- Memory leak detection in development

## Network Optimizations

### 1. Service Worker
- Offline support with cache strategies
- Background sync for failed requests
- Push notifications support

### 2. API Caching
- Cache-first for static data
- Network-first with cache fallback for dynamic data
- Stale-while-revalidate for frequently updated data

### 3. Request Optimization
- Request batching for multiple API calls
- Request deduplication
- Automatic retry with exponential backoff

## Monitoring & Analytics

### 1. Performance Metrics
The app automatically tracks:
- First Contentful Paint (FCP)
- Largest Contentful Paint (LCP)
- First Input Delay (FID)
- Cumulative Layout Shift (CLS)
- Time to Interactive (TTI)

### 2. Error Tracking
- Global error handler
- Source maps for production debugging
- User context in error reports

### 3. User Analytics
- Page view tracking
- User interaction events
- Performance impact analysis

## Best Practices

### 1. Component Development
- Use `shallowRef` for large objects
- Implement `v-memo` for expensive renders
- Use `computed` instead of methods for derived state

### 2. Event Handling
- Use passive event listeners
- Delegate events when possible
- Clean up listeners on unmount

### 3. Asset Loading
- Preload critical resources
- Use resource hints (prefetch, preconnect)
- Implement responsive images

### 4. Bundle Size
- Tree-shake unused code
- Use dynamic imports for optional features
- Monitor bundle size with visualizer

## Development Tools

### 1. Performance Profiling
```bash
# Generate bundle analysis
npm run build -- --report

# Profile runtime performance
window.__PERFORMANCE__.getMetrics()
```

### 2. Lighthouse CI
Run Lighthouse in CI to track performance over time:
```bash
npm run lighthouse
```

### 3. Memory Profiling
Use Chrome DevTools Memory Profiler to identify leaks.

## Configuration Files

### vite.config.optimized.js
Contains all build optimizations including:
- Code splitting configuration
- Compression plugins
- Asset optimization
- Performance hints

### Performance Budget
Target metrics:
- FCP: < 1.8s
- LCP: < 2.5s
- TTI: < 3.8s
- Bundle size: < 500KB (initial)

## Checklist

Before deploying, ensure:
- [ ] Images are optimized and lazy-loaded
- [ ] Large lists use virtual scrolling
- [ ] Heavy computations use web workers
- [ ] API calls are cached appropriately
- [ ] Service worker is registered (production)
- [ ] Performance metrics are within budget
- [ ] No memory leaks detected
- [ ] Bundle size is optimized

## Troubleshooting

### High Memory Usage
1. Check for detached DOM nodes
2. Review event listener cleanup
3. Verify store subscription cleanup

### Slow Initial Load
1. Review bundle splitting
2. Check for blocking resources
3. Verify compression is working

### Poor Runtime Performance
1. Profile with Chrome DevTools
2. Check for unnecessary re-renders
3. Review computed property usage

## Future Optimizations

1. **HTTP/3 Support**: When available
2. **Module Federation**: For micro-frontends
3. **Edge Computing**: For global performance
4. **AI-Powered Prefetching**: Predictive resource loading