83e6adb0f8
- Define EventBus interface (PORT) with emit, on, off, once methods - Define base DomainEvent interface with type, timestamp, payload - Implement EventEmitterBus class (ADAPTER) using Node.js EventEmitter - Export createEventBus() factory function for easy instantiation
68 lines
1.7 KiB
TypeScript
68 lines
1.7 KiB
TypeScript
/**
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* Event Emitter Bus - Adapter Implementation
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*
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* In-process EventBus implementation using Node.js EventEmitter.
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* This is the ADAPTER for the EventBus PORT.
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*
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* Can be swapped for RabbitMQ, Kafka, WebSocket, etc. later
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* without changing consumers.
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*/
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import { EventEmitter } from 'node:events';
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import type { DomainEvent, EventBus } from './types.js';
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/**
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* EventEmitter-based implementation of the EventBus interface.
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*
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* Wraps Node.js EventEmitter to provide type-safe event handling
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* that conforms to the EventBus port interface.
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*/
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export class EventEmitterBus implements EventBus {
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private emitter: EventEmitter;
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constructor() {
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this.emitter = new EventEmitter();
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// Allow more listeners for complex systems
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this.emitter.setMaxListeners(100);
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}
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/**
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* Emit an event to all subscribed handlers.
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* The event's type property determines which handlers receive it.
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*/
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emit<T extends DomainEvent>(event: T): void {
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this.emitter.emit(event.type, event);
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}
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/**
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* Subscribe to events of a specific type.
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*/
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on<T extends DomainEvent>(
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eventType: T['type'],
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handler: (event: T) => void
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): void {
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this.emitter.on(eventType, handler);
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}
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/**
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* Unsubscribe from events of a specific type.
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*/
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off<T extends DomainEvent>(
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eventType: T['type'],
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handler: (event: T) => void
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): void {
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this.emitter.off(eventType, handler);
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}
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/**
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* Subscribe to a single occurrence of an event type.
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* Handler is automatically removed after first invocation.
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*/
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once<T extends DomainEvent>(
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eventType: T['type'],
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handler: (event: T) => void
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): void {
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this.emitter.once(eventType, handler);
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}
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}
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