From c9b4eefce2cfb0401e19f4a4b8afb9ab55ead117 Mon Sep 17 00:00:00 2001
From: Grzegorz Kielak <grzegorz@kielak.me>
Date: Tue, 2 Jan 2024 10:33:42 +0100
Subject: [PATCH] feat: allow to overwrite event id strategy

---
 src/event-bus.ts                              | 18 +++++++--------
 src/helpers/default-event-id-provider.ts      | 20 ++++++++++++++++
 src/helpers/default-get-event-id.ts           | 23 -------------------
 .../events/event-id-provider.interface.ts     | 10 ++++++++
 src/interfaces/index.ts                       |  1 +
 5 files changed, 40 insertions(+), 32 deletions(-)
 create mode 100644 src/helpers/default-event-id-provider.ts
 delete mode 100644 src/helpers/default-get-event-id.ts
 create mode 100644 src/interfaces/events/event-id-provider.interface.ts

diff --git a/src/event-bus.ts b/src/event-bus.ts
index 2a6c08d2..d721f759 100644
--- a/src/event-bus.ts
+++ b/src/event-bus.ts
@@ -5,12 +5,10 @@ import { catchError, filter, mergeMap } from 'rxjs/operators';
 import { CommandBus } from './command-bus';
 import { EVENTS_HANDLER_METADATA, SAGA_METADATA } from './decorators/constants';
 import { InvalidSagaException } from './exceptions';
-import {
-  defaultGetEventId,
-  defaultReflectEventId,
-} from './helpers/default-get-event-id';
+import { defaultEventIdProvider } from './helpers/default-event-id-provider';
 import { DefaultPubSub } from './helpers/default-pubsub';
 import {
+  EventIdProvider,
   ICommand,
   IEvent,
   IEventBus,
@@ -31,7 +29,7 @@ export class EventBus<EventBase extends IEvent = IEvent>
   extends ObservableBus<EventBase>
   implements IEventBus<EventBase>, OnModuleDestroy
 {
-  protected getEventId: (event: EventBase) => string | null;
+  public eventIdProvider: EventIdProvider<EventBase>;
   protected readonly subscriptions: Subscription[];
 
   private _publisher: IEventPublisher<EventBase>;
@@ -44,7 +42,7 @@ export class EventBus<EventBase extends IEvent = IEvent>
   ) {
     super();
     this.subscriptions = [];
-    this.getEventId = defaultGetEventId;
+    this.eventIdProvider = defaultEventIdProvider;
     this.useDefaultPublisher();
   }
 
@@ -146,13 +144,15 @@ export class EventBus<EventBase extends IEvent = IEvent>
     events.map((event) =>
       this.bind(
         instance as IEventHandler<EventBase>,
-        defaultReflectEventId(event),
+        this.eventIdProvider.reflectEventId(event),
       ),
     );
   }
 
   protected ofEventId(id: string) {
-    return this.subject$.pipe(filter((event) => this.getEventId(event) === id));
+    return this.subject$.pipe(
+      filter((event) => this.eventIdProvider.getEventId(event) === id),
+    );
   }
 
   protected registerSaga(saga: ISaga<EventBase>) {
@@ -191,7 +191,7 @@ export class EventBus<EventBase extends IEvent = IEvent>
 
   private reflectEvents(
     handler: EventHandlerType<EventBase>,
-  ): FunctionConstructor[] {
+  ): Array<Type<EventBase>> {
     return Reflect.getMetadata(EVENTS_HANDLER_METADATA, handler);
   }
 
diff --git a/src/helpers/default-event-id-provider.ts b/src/helpers/default-event-id-provider.ts
new file mode 100644
index 00000000..b2dcf7dc
--- /dev/null
+++ b/src/helpers/default-event-id-provider.ts
@@ -0,0 +1,20 @@
+import { IEvent } from '../interfaces';
+import { EVENT_METADATA } from '../decorators/constants';
+import { Type } from '@nestjs/common';
+import { EventIdProvider } from '../interfaces';
+
+class DefaultEventIdProvider<EventBase extends IEvent = IEvent>
+  implements EventIdProvider<EventBase>
+{
+  getEventId(event: EventBase): string | null {
+    const { constructor } = Object.getPrototypeOf(event);
+
+    return this.reflectEventId(constructor);
+  }
+
+  reflectEventId(event: Type<EventBase>): string | null {
+    return Reflect.getMetadata(EVENT_METADATA, event)?.id ?? null;
+  }
+}
+
+export const defaultEventIdProvider = new DefaultEventIdProvider();
diff --git a/src/helpers/default-get-event-id.ts b/src/helpers/default-get-event-id.ts
deleted file mode 100644
index 361de41b..00000000
--- a/src/helpers/default-get-event-id.ts
+++ /dev/null
@@ -1,23 +0,0 @@
-import { IEvent } from '../interfaces';
-import { EVENT_METADATA } from '../decorators/constants';
-import { Type } from '@nestjs/common';
-
-/**
- * Null if the published class is not connected to any handler
- * @param event
- * @returns
- */
-export const defaultGetEventId = <EventBase extends IEvent = IEvent>(
-  event: EventBase,
-): string => {
-  const { constructor } = Object.getPrototypeOf(event);
-  return Reflect.getMetadata(EVENT_METADATA, constructor)?.id ?? null;
-};
-
-export const defaultReflectEventId = <
-  EventBase extends Type<IEvent> = Type<IEvent>,
->(
-  event: EventBase,
-): string => {
-  return Reflect.getMetadata(EVENT_METADATA, event).id;
-};
diff --git a/src/interfaces/events/event-id-provider.interface.ts b/src/interfaces/events/event-id-provider.interface.ts
new file mode 100644
index 00000000..76fdf9cc
--- /dev/null
+++ b/src/interfaces/events/event-id-provider.interface.ts
@@ -0,0 +1,10 @@
+import { IEvent } from './event.interface';
+import { Type } from '@nestjs/common';
+
+export interface EventIdProvider<EventBase extends IEvent = IEvent> {
+  /**
+   * Null if the published class is not connected to any handler
+   */
+  getEventId(event: EventBase): string | null;
+  reflectEventId(event: Type<EventBase>): string | null;
+}
diff --git a/src/interfaces/index.ts b/src/interfaces/index.ts
index a9df2105..081411e5 100644
--- a/src/interfaces/index.ts
+++ b/src/interfaces/index.ts
@@ -7,6 +7,7 @@ export * from './events/event-handler.interface';
 export * from './events/event-publisher.interface';
 export * from './events/event.interface';
 export * from './events/message-source.interface';
+export * from './events/event-id-provider.interface';
 export * from './exceptions/unhandled-exception-info.interface';
 export * from './exceptions/unhandled-exception-publisher.interface';
 export * from './queries/query-bus.interface';