Phase 3 Completed

src/core/event-bus/event-bus.service.ts

@@ -0,0 +1,28 @@
+import { Injectable, Logger } from '@nestjs/common';
+
+import { EventEnvelope } from './event.interface';
+
+type Handler = (event: EventEnvelope<any>) => Promise<void> | void;
+
+@Injectable()
+export class EventBus {
+  private handlers: Map<string, Handler[]> = new Map();
+  private readonly logger = new Logger(EventBus.name);
+
+  publish(event: EventEnvelope<any>) {
+    const handlers = this.handlers.get(event.type) || [];
+    for (const h of handlers) {
+      try {
+        Promise.resolve(h(event)).catch((err) => this.logger.error('Event handler error', err));
+      } catch (e) {
+        this.logger.error('Event handler threw', e as any);
+      }
+    }
+  }
+
+  subscribe(eventType: string, handler: Handler) {
+    const list = this.handlers.get(eventType) || [];
+    list.push(handler);
+    this.handlers.set(eventType, list);
+  }
+}

src/core/event-bus/event.interface.ts

@@ -0,0 +1,6 @@
+export interface EventEnvelope<T = any> {
+  id: string;
+  timestamp: string; // ISO
+  type: string; // PascalCase event type
+  payload: T;
+}