/**
* In-process EventBus implementation using Node.js EventEmitter.
* Maintains a ring buffer for replay on SSE reconnect.
*/
import { EventEmitter } from 'node:events';
import type { BacklogEvent, BacklogEventCallback, EventBus } from './event-bus.js';
const RING_BUFFER_SIZE = 1000;
const EVENT_NAME = 'backlog';
export class LocalEventBus implements EventBus {
private emitter = new EventEmitter();
private seq = 0;
private buffer: BacklogEvent[] = [];
constructor() {
this.emitter.setMaxListeners(100);
}
emit(event: Omit<BacklogEvent, 'seq'>): void {
const full: BacklogEvent = { ...event, seq: ++this.seq };
// Ring buffer: drop oldest when full
if (this.buffer.length >= RING_BUFFER_SIZE) {
this.buffer.shift();
}
this.buffer.push(full);
this.emitter.emit(EVENT_NAME, full);
}
subscribe(callback: BacklogEventCallback): void {
this.emitter.on(EVENT_NAME, callback);
}
unsubscribe(callback: BacklogEventCallback): void {
this.emitter.off(EVENT_NAME, callback);
}
replaySince(seq: number): BacklogEvent[] {
return this.buffer.filter(e => e.seq > seq);
}
}
