@difizen/magent-core/src/common/async-model.ts

import { Deferred, injectable } from '@difizen/mana-app';

@injectable()
export abstract class DeferredModel<T = any> {
  ready: Promise<T>;
  protected readyDeferred: Deferred<T> = new Deferred<T>();

  constructor() {
    this.ready = this.readyDeferred.promise;
  }
}

@injectable()
export abstract class AsyncModel<T = any, O = any> {
  ready: Promise<T>;
  protected readyDeferred: Deferred<T> = new Deferred<T>();

  constructor() {
    this.ready = this.readyDeferred.promise;
  }

  initialize(option: O) {
    setImmediate(() => {
      if (this.shouldInitFromMeta(option)) {
        this.fromMeta(option);
      } else {
        this.fetchInfo(option);
      }
    });
  }

  abstract shouldInitFromMeta(option: O): boolean;

  protected fromMeta(option: O) {
    this.readyDeferred.resolve(this as unknown as T);
  }

  abstract fetchInfo(option: O): Promise<void>;
}