# Cache Manager Module

**Intelligent Caching for API Responses and Computed Values**

The Cache Manager Module provides a comprehensive caching system with multiple storage backends and caching strategies.

---

## Features

- **Memory Cache** - Fast in-memory caching
- **IndexedDB Cache** - Persistent browser storage
- **Cache Strategies** - Multiple caching strategies (cache-first, network-first, stale-while-revalidate, etc.)
- **Cache Invalidation** - Pattern-based cache invalidation
- **Cache Warming** - Preload cache values
- **Cache Analytics** - Track cache performance
- **Integration with RequestDeduplicator** - Works with LiveComponent request deduplication

---

## Quick Start

### Basic Usage

```javascript
import { CacheManager, CacheStrategy } from './modules/cache-manager/index.js';

// Create cache manager
const cache = CacheManager.create({
    defaultStrategy: CacheStrategy.STALE_WHILE_REVALIDATE,
    defaultTTL: 3600000 // 1 hour
});

// Get or set value
const data = await cache.getOrSet('users', async () => {
    const response = await fetch('/api/users');
    return await response.json();
});

// Get from cache
const cached = await cache.get('users');

// Set in cache
await cache.set('users', data, { ttl: 1800000 }); // 30 minutes
```

### Module System Integration

```html
<!-- Enable global cache manager -->
<script type="module">
    import { init } from './modules/cache-manager/index.js';
    
    init({
        defaultStrategy: 'stale-while-revalidate',
        enableIndexedDB: true
    });
</script>

<!-- Access globally -->
<script>
    // Get or set
    const data = await window.CacheManager.getOrSet('key', async () => {
        return await fetch('/api/data').then(r => r.json());
    });
</script>
```

---

## API Reference

### CacheManager.create(config)

Create a new CacheManager instance.

**Parameters**:
- `config.defaultStrategy` - Default caching strategy
- `config.defaultTTL` - Default time-to-live in milliseconds
- `config.maxMemorySize` - Maximum items in memory cache
- `config.enableIndexedDB` - Enable IndexedDB persistence
- `config.indexedDBName` - IndexedDB database name
- `config.enableAnalytics` - Enable cache analytics

**Example**:
```javascript
const cache = CacheManager.create({
    defaultStrategy: CacheStrategy.STALE_WHILE_REVALIDATE,
    defaultTTL: 3600000,
    maxMemorySize: 100,
    enableIndexedDB: true
});
```

### cache.get(key, options)

Get value from cache.

**Parameters**:
- `key` - Cache key
- `options.strategy` - Caching strategy override
- `options.ttl` - Time-to-live override

**Returns**: `Promise<any | null>`

### cache.set(key, value, options)

Set value in cache.

**Parameters**:
- `key` - Cache key
- `value` - Value to cache
- `options.strategy` - Caching strategy
- `options.ttl` - Time-to-live

**Returns**: `Promise<void>`

### cache.getOrSet(key, computeFn, options)

Get value from cache or compute and cache it.

**Parameters**:
- `key` - Cache key
- `computeFn` - Function to compute value if not cached
- `options` - Cache options

**Returns**: `Promise<any>`

**Example**:
```javascript
const users = await cache.getOrSet('users', async () => {
    const response = await fetch('/api/users');
    return await response.json();
}, { ttl: 1800000 });
```

### cache.delete(key)

Delete value from cache.

**Parameters**:
- `key` - Cache key

**Returns**: `Promise<void>`

### cache.clear()

Clear all cache.

**Returns**: `Promise<void>`

### cache.invalidate(pattern)

Invalidate cache entries matching a pattern.

**Parameters**:
- `pattern` - String, RegExp, or function

**Returns**: `Promise<void>`

**Example**:
```javascript
// Invalidate all user-related cache
await cache.invalidate('user:');

// Invalidate with regex
await cache.invalidate(/^user:\d+$/);

// Invalidate with function
await cache.invalidate(key => key.startsWith('user:'));
```

### cache.warm(keys, computeFn)

Warm cache by preloading values.

**Parameters**:
- `keys` - Array of cache keys
- `computeFn` - Function to compute value for each key

**Returns**: `Promise<void>`

**Example**:
```javascript
await cache.warm(['user:1', 'user:2', 'user:3'], async (key) => {
    const userId = key.split(':')[1];
    const response = await fetch(`/api/users/${userId}`);
    return await response.json();
});
```

### cache.getAnalytics()

Get cache performance analytics.

**Returns**: `CacheAnalytics`

**Example**:
```javascript
const analytics = cache.getAnalytics();
console.log(`Hit rate: ${analytics.hitRate}%`);
console.log(`Hits: ${analytics.hits}, Misses: ${analytics.misses}`);
```

---

## Cache Strategies

### Cache-First

Use cache if available, otherwise fetch.

```javascript
const data = await cache.getOrSet('key', fetchData, {
    strategy: CacheStrategy.CACHE_FIRST
});
```

### Network-First

Try network first, fallback to cache.

```javascript
const data = await cache.getOrSet('key', fetchData, {
    strategy: CacheStrategy.NETWORK_FIRST
});
```

### Stale-While-Revalidate

Return cache immediately, update in background.

```javascript
const data = await cache.getOrSet('key', fetchData, {
    strategy: CacheStrategy.STALE_WHILE_REVALIDATE
});
```

### Network-Only

Always fetch from network, never use cache.

```javascript
const data = await cache.getOrSet('key', fetchData, {
    strategy: CacheStrategy.NETWORK_ONLY
});
```

### Cache-Only

Only use cache, never fetch from network.

```javascript
const data = await cache.get('key', {
    strategy: CacheStrategy.CACHE_ONLY
});
```

---

## Integration with RequestDeduplicator

```javascript
import { CacheManager } from './modules/cache-manager/index.js';
import { RequestDeduplicator } from './modules/livecomponent/RequestDeduplicator.js';

const cache = CacheManager.create();
const deduplicator = new RequestDeduplicator();

// Use cache with request deduplication
async function fetchWithCache(url) {
    return await cache.getOrSet(url, async () => {
        // Check for pending request
        const pending = deduplicator.getPendingRequest('api', 'GET', { url });
        if (pending) {
            return await pending;
        }
        
        // Make request
        const promise = fetch(url).then(r => r.json());
        deduplicator.registerPendingRequest('api', 'GET', { url }, promise);
        
        return await promise;
    });
}
```

---

## Use Cases

### API Response Caching

```javascript
const cache = CacheManager.create({
    defaultStrategy: CacheStrategy.STALE_WHILE_REVALIDATE,
    defaultTTL: 300000 // 5 minutes
});

async function getUsers() {
    return await cache.getOrSet('api:users', async () => {
        const response = await fetch('/api/users');
        return await response.json();
    });
}
```

### Computed Value Caching

```javascript
const cache = CacheManager.create();

function expensiveComputation(input) {
    // Expensive operation
    return input * 2;
}

async function getComputedValue(input) {
    const key = `computed:${input}`;
    return await cache.getOrSet(key, () => expensiveComputation(input), {
        ttl: 3600000 // Cache for 1 hour
    });
}
```

### Cache Invalidation

```javascript
// Invalidate all user-related cache when user updates
async function updateUser(userId, data) {
    await fetch(`/api/users/${userId}`, {
        method: 'PUT',
        body: JSON.stringify(data)
    });
    
    // Invalidate related cache
    await cache.invalidate(`user:${userId}`);
    await cache.invalidate('users:list');
}
```

### Cache Warming

```javascript
// Warm cache on page load
async function warmCache() {
    await cache.warm(['user:1', 'user:2', 'user:3'], async (key) => {
        const userId = key.split(':')[1];
        const response = await fetch(`/api/users/${userId}`);
        return await response.json();
    });
}
```

---

## Best Practices

1. **Choose Appropriate Strategy** - Use cache-first for static data, network-first for dynamic data
2. **Set Appropriate TTL** - Balance freshness with performance
3. **Invalidate on Updates** - Clear cache when data changes
4. **Use Cache Warming** - Preload frequently accessed data
5. **Monitor Analytics** - Track cache performance and adjust strategy

---

## Browser Support

- **Chrome/Edge**: 90+
- **Firefox**: 88+
- **Safari**: 14+
- **Mobile**: iOS 14+, Android Chrome 90+

**Required Features**:
- ES2020 JavaScript
- IndexedDB (for persistent cache)
- Promise support

---

**Next**: Continue with Phase 3 modules →