import type { CacheConfig, CacheEntry } from "../types.js";
/**
* Simple in-memory cache for resource data
* Implements LRU (Least Recently Used) eviction policy
*/
export class ResourceCache {
private cache: Map<string, CacheEntry>;
private config: CacheConfig;
private accessOrder: string[]; // Track access order for LRU
constructor(config: CacheConfig) {
this.cache = new Map();
this.config = config;
this.accessOrder = [];
}
/**
* Get cached data if available and not expired
*/
get<T>(key: string): T | null {
if (!this.config.enabled) {
return null;
}
const entry = this.cache.get(key);
if (!entry) {
return null;
}
// Check if expired
if (Date.now() > entry.expiresAt) {
this.delete(key);
return null;
}
// Update access order (move to end = most recently used)
this.updateAccessOrder(key);
return entry.data as T;
}
/**
* Store data in cache
*/
set<T>(key: string, data: T): void {
if (!this.config.enabled) {
return;
}
const now = Date.now();
const entry: CacheEntry<T> = {
data,
timestamp: now,
expiresAt: now + this.config.ttlSeconds * 1000,
};
// Evict if at max capacity
if (this.cache.size >= this.config.maxEntries && !this.cache.has(key)) {
this.evictLRU();
}
this.cache.set(key, entry);
this.updateAccessOrder(key);
}
/**
* Delete specific cache entry
*/
delete(key: string): void {
this.cache.delete(key);
this.accessOrder = this.accessOrder.filter(k => k !== key);
}
/**
* Clear all cache entries
*/
clear(): void {
this.cache.clear();
this.accessOrder = [];
}
/**
* Check if key exists and is valid
*/
has(key: string): boolean {
return this.get(key) !== null;
}
/**
* Get cache statistics
*/
getStats(): {
size: number;
maxSize: number;
enabled: boolean;
ttlSeconds: number;
} {
return {
size: this.cache.size,
maxSize: this.config.maxEntries,
enabled: this.config.enabled,
ttlSeconds: this.config.ttlSeconds,
};
}
/**
* Update access order for LRU tracking
*/
private updateAccessOrder(key: string): void {
// Remove from current position
this.accessOrder = this.accessOrder.filter(k => k !== key);
// Add to end (most recently used)
this.accessOrder.push(key);
}
/**
* Evict least recently used entry
*/
private evictLRU(): void {
if (this.accessOrder.length === 0) {
return;
}
// First item is least recently used
const lruKey = this.accessOrder[0];
this.delete(lruKey);
}
/**
* Remove all expired entries
*/
pruneExpired(): void {
const now = Date.now();
const expiredKeys: string[] = [];
this.cache.forEach((entry, key) => {
if (now > entry.expiresAt) {
expiredKeys.push(key);
}
});
expiredKeys.forEach(key => this.delete(key));
}
}
