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* EventBus - 事件总线核心实现
*
* 设计模式：事件驱动架构 (EDA)
* 来源：2026-04-09 23:00 小时学习
*/
const EventEmitter = require('events');
const crypto = require('crypto');
/**
* 事件 Schema 验证器
*/
class EventValidator {
constructor(schemaRegistry = {}) {
this.schemaRegistry = schemaRegistry;
}
registerSchema(eventName, schema) {
this.schemaRegistry[eventName] = schema;
}
validate(eventName, payload) {
const schema = this.schemaRegistry[eventName];
if (!schema) return true; // 无 schema 则跳过验证
// 简单类型检查
for (const [key, type] of Object.entries(schema)) {
if (payload[key] === undefined && schema.required?.includes(key)) {
throw new Error(`Missing required field: ${key}`);
}
if (payload[key] !== undefined && typeof payload[key] !== type) {
throw new Error(`Invalid type for ${key}: expected ${type}, got ${typeof payload[key]}`);
}
}
return true;
}
}
/**
* 事件总线
*/
class EventBus extends EventEmitter {
constructor(options = {}) {
super();
this.eventHistory = [];
this.maxHistorySize = options.maxHistorySize || 1000;
this.validator = new EventValidator();
this.middlewareChain = [];
this.subscribers = new Map();
}
/**
* 注册事件 Schema
*/
registerSchema(eventName, schema) {
this.validator.registerSchema(eventName, schema);
}
/**
* 注册中间件
*/
use(middleware) {
this.middlewareChain.push(middleware);
}
/**
* 订阅事件
*/
subscribe(eventName, handler, options = {}) {
const subscriberId = crypto.randomBytes(8).toString('hex');
const subscriber = {
id: subscriberId,
handler,
priority: options.priority || 0,
filter: options.filter || null,
once: options.once || false
};
if (!this.subscribers.has(eventName)) {
this.subscribers.set(eventName, []);
}
this.subscribers.get(eventName).push(subscriber);
// 按优先级排序
this.subscribers.get(eventName).sort((a, b) => b.priority - a.priority);
return subscriberId;
}
/**
* 取消订阅
*/
unsubscribe(eventName, subscriberId) {
Iif (!this.subscribers.has(eventName)) return false;
const subscribers = this.subscribers.get(eventName);
const index = subscribers.findIndex(s => s.id === subscriberId);
Eif (index !== -1) {
subscribers.splice(index, 1);
return true;
}
return false;
}
/**
* 发布事件
*/
async publish(eventName, payload = {}, metadata = {}) {
const eventId = crypto.randomBytes(16).toString('hex');
const timestamp = Date.now();
const event = {
id: eventId,
name: eventName,
payload,
metadata: {
timestamp,
correlationId: metadata.correlationId || eventId,
causationId: metadata.causationId || null,
retryCount: metadata.retryCount || 0
},
timestamp
};
// 验证事件
try {
this.validator.validate(eventName, payload);
} catch (error) {
throw new Error(`Event validation failed: ${error.message}`);
}
// 执行中间件链
let shouldContinue = true;
for (const middleware of this.middlewareChain) {
try {
const result = await middleware(event);
if (result === false) {
shouldContinue = false;
break;
}
} catch (error) {
console.error(`Middleware error: ${error.message}`);
}
}
Iif (!shouldContinue) {
return { eventId, status: 'skipped', reason: 'middleware_blocked' };
}
// 记录到历史
this._addToHistory(event);
// 通知订阅者
const subscribers = this.subscribers.get(eventName) || [];
const results = [];
for (const subscriber of subscribers) {
// 应用过滤器
if (subscriber.filter && !subscriber.filter(payload)) {
continue;
}
try {
const result = await subscriber.handler(event);
results.push({ subscriberId: subscriber.id, result, status: 'success' });
// 处理 once 订阅
if (subscriber.once) {
this.unsubscribe(eventName, subscriber.id);
}
} catch (error) {
results.push({ subscriberId: subscriber.id, error: error.message, status: 'failed' });
}
}
// 发出原生事件（兼容 Node.js EventEmitter）
super.emit(eventName, event);
return {
eventId,
status: 'published',
timestamp,
subscriberResults: results
};
}
/**
* 添加到历史记录
*/
_addToHistory(event) {
this.eventHistory.push(event);
if (this.eventHistory.length > this.maxHistorySize) {
this.eventHistory.shift();
}
}
/**
* 获取事件历史
*/
getHistory(limit = 100, eventName = null) {
let history = this.eventHistory;
if (eventName) {
history = history.filter(e => e.name === eventName);
}
return history.slice(-limit);
}
/**
* 清空历史
*/
clearHistory() {
this.eventHistory = [];
}
/**
* 获取订阅者统计
*/
getSubscriberStats() {
const stats = {};
for (const [eventName, subscribers] of this.subscribers.entries()) {
stats[eventName] = subscribers.length;
}
return stats;
}
}
module.exports = { EventBus, EventValidator };
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