Migrate EventsHandler

Author: CarsonF

src/core/events/constants.ts

@@ -1,9 +1,4 @@
-import { type ID } from '~/common';
-
 export const EVENT_METADATA = '__event__';
-export const EVENTS_HANDLER_METADATA = '__eventsHandler__';
-
-export type EventHandlerMetadata = Map<ID, Priority>;
 
 /**
  * Higher goes first.

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

@@ -1,4 +1,3 @@
-import { DiscoveryService } from '@golevelup/nestjs-discovery';
 import { Injectable, type OnApplicationBootstrap } from '@nestjs/common';
 import {
   type FnLike,
@@ -8,13 +7,10 @@ import {
 } from '@seedcompany/common';
 import { stripIndent } from 'common-tags';
 import { type ID, ServerException } from '~/common';
+import { MetadataDiscovery } from '~/core/discovery';
 import { ILogger, Logger } from '../logger';
-import {
-  EVENT_METADATA,
-  type EventHandlerMetadata,
-  EVENTS_HANDLER_METADATA,
-} from './constants';
-import { type IEventHandler } from './event-handler.decorator';
+import { EVENT_METADATA } from './constants';
+import { EventsHandler, type IEventHandler } from './event-handler.decorator';
 
 /**
  * An event bus for internal use.
@@ -30,7 +26,7 @@ export class SyncEventBus implements IEventBus, OnApplicationBootstrap {
   private listenerMap: Record<ID, FnLike[]> = {};
 
   constructor(
-    private readonly discovery: DiscoveryService,
+    private readonly discovery: MetadataDiscovery,
     @Logger('event-bus') private readonly logger: ILogger,
   ) {}
 
@@ -59,15 +55,14 @@ export class SyncEventBus implements IEventBus, OnApplicationBootstrap {
   }
 
   async onApplicationBootstrap() {
-    const discovered =
-      await this.discovery.providersWithMetaAtKey<EventHandlerMetadata>(
-        EVENTS_HANDLER_METADATA,
-      );
+    const discovered = this.discovery
+      .discover(EventsHandler)
+      .classes<IEventHandler<any>>();
 
     if (process.env.NODE_ENV !== 'production') {
       const defined = new Set<string>();
       for (const entry of discovered) {
-        const name = entry.discoveredClass.name;
+        const name = entry.instance.constructor.name;
         if (defined.has(name)) {
           throw new ServerException(stripIndent`
             Event handler "${name}" has already been defined.
@@ -78,10 +73,9 @@ export class SyncEventBus implements IEventBus, OnApplicationBootstrap {
       }
     }
 
-    const flat = discovered.flatMap((entry) => {
-      const instance = entry.discoveredClass.instance as IEventHandler<any>;
+    const flat = discovered.flatMap(({ instance, meta }) => {
       const handler = instance.handle.bind(instance);
-      return [...entry.meta].map(([id, priority]) => ({
+      return [...meta].map(([id, priority]) => ({
         id,
         priority,
         handler,

src/core/events/event-handler.decorator.ts

@@ -1,12 +1,8 @@
 import { type Type } from '@nestjs/common';
+import { createMetadataDecorator } from '@seedcompany/nest';
 import { nanoid } from 'nanoid';
 import { type ID } from '~/common';
-import {
-  EVENT_METADATA,
-  type EventHandlerMetadata,
-  EVENTS_HANDLER_METADATA,
-  type Priority,
-} from './constants';
+import { EVENT_METADATA, type Priority } from './constants';
 
 /**
  * Subscribe to these given events.
@@ -25,10 +21,10 @@ import {
  * )
  * ```
  */
-export const EventsHandler =
-  (...events: Array<Type | [...Type[], Priority]>): ClassDecorator =>
-  (target) => {
-    const metadata: EventHandlerMetadata = new Map<ID, Priority>();
+export const EventsHandler = createMetadataDecorator({
+  types: ['class'],
+  setter: (...events: Array<Type | [...Type[], Priority]>) => {
+    const metadata = new Map<ID, Priority>();
 
     for (const arg of events) {
       let priority: Priority = 0;
@@ -45,8 +41,9 @@ export const EventsHandler =
       }
     }
 
-    Reflect.defineMetadata(EVENTS_HANDLER_METADATA, metadata, target);
-  };
+    return metadata;
+  },
+});
 
 // eslint-disable-next-line @typescript-eslint/naming-convention
 export interface IEventHandler<T> {