/**
* LRU 缓存实现
*/
import { ICacheItem, ICacheStats, ICacheConfig } from '../types';
export class LRUCache<K, V> {
private cache = new Map<K, ICacheItem<V>>();
private config: ICacheConfig;
// 统计信息
private stats = {
hits: 0,
misses: 0
};
constructor(config: Partial<ICacheConfig> = {}) {
this.config = {
maxSize: 1000,
defaultTtl: 5 * 60 * 1000, // 5 分钟
enableStats: true,
...config,
};
}
/**
* 获取缓存值
*/
get(key: K): V | null {
const item = this.cache.get(key);
if (!item) {
if (this.config.enableStats) {
this.stats.misses++;
}
return null;
}
// 检查 TTL
const now = Date.now();
if (now - item.timestamp > item.ttl) {
this.cache.delete(key);
if (this.config.enableStats) {
this.stats.misses++;
}
return null;
}
// 更新 lastAccess
item.lastAccess = now;
if (this.config.enableStats) {
this.stats.hits++;
}
return item.data;
}
/**
* 设置缓存值
*/
set(key: K, value: V, ttl?: number): void {
// 如果达到最大容量，删除最久未使用的项
if (this.cache.size >= this.config.maxSize) {
const oldestKey = this.findOldestKey();
if (oldestKey !== undefined) {
this.cache.delete(oldestKey);
}
}
const now = Date.now();
const item: ICacheItem<V> = {
data: value,
timestamp: now,
ttl: ttl ?? this.config.defaultTtl,
lastAccess: now,
};
this.cache.set(key, item);
}
/**
* 删除缓存项
*/
delete(key: K): boolean {
return this.cache.delete(key);
}
/**
* 清空所有缓存
*/
clear(): void {
this.cache.clear();
}
/**
* 清理过期缓存项
*/
cleanup(): number {
const now = Date.now();
const keysToDelete: K[] = [];
for (const [key, item] of this.cache.entries()) {
if (now - item.timestamp > item.ttl) {
keysToDelete.push(key);
}
}
for (const key of keysToDelete) {
this.cache.delete(key);
}
return keysToDelete.length;
}
/**
* 获取缓存统计信息
*/
getStats(): ICacheStats {
const size = this.cache.size;
const maxSize = this.config.maxSize;
const total = this.stats.hits + this.stats.misses;
// 估算内存使用量（简化）
let memoryUsage = 0;
for (const item of this.cache.values()) {
memoryUsage += JSON.stringify(item).length;
}
return {
size,
maxSize,
hits: this.stats.hits,
misses: this.stats.misses,
hitRate: total > 0 ? this.stats.hits / total : 0,
memoryUsage,
};
}
/**
* 重置统计信息
*/
resetStats(): void {
this.stats.hits = 0;
this.stats.misses = 0;
}
/**
* 获取当前缓存大小
*/
get size(): number {
return this.cache.size;
}
/**
* 查找最久未使用的键
*/
private findOldestKey(): K | undefined {
let oldestKey: K | undefined;
let oldestTime = Infinity;
for (const [key, item] of this.cache.entries()) {
if (item.lastAccess < oldestTime) {
oldestTime = item.lastAccess;
oldestKey = key;
}
}
return oldestKey;
}
}
