refactor(server): event emits (#10648)

* refactor(server): event emits

* refactor: change default priority to 0

server/src/utils/events.ts

@@ -0,0 +1,33 @@
+import { ModuleRef, Reflector } from '@nestjs/core';
+import _ from 'lodash';
+import { HandlerOptions } from 'src/decorators';
+import { EmitEvent, EmitEventHandler, IEventRepository, OnEvents, events } from 'src/interfaces/event.interface';
+import { Metadata } from 'src/middleware/auth.guard';
+import { services } from 'src/services';
+
+export const setupEventHandlers = (moduleRef: ModuleRef) => {
+  const reflector = moduleRef.get(Reflector, { strict: false });
+  const repository = moduleRef.get<IEventRepository>(IEventRepository);
+  const handlers: Array<{ event: EmitEvent; handler: EmitEventHandler<EmitEvent>; priority: number }> = [];
+
+  // discovery
+  for (const Service of services) {
+    const instance = moduleRef.get<OnEvents>(Service);
+    for (const event of events) {
+      const handler = instance[event] as EmitEventHandler<typeof event>;
+      if (typeof handler !== 'function') {
+        continue;
+      }
+
+      const options = reflector.get<HandlerOptions>(Metadata.EVENT_HANDLER_OPTIONS, handler);
+      const priority = options?.priority || 0;
+
+      handlers.push({ event, handler: handler.bind(instance), priority });
+    }
+  }
+
+  // register by priority
+  for (const { event, handler } of _.orderBy(handlers, ['priority'], ['asc'])) {
+    repository.on(event, handler);
+  }
+};