cache.decorator.ts

export interface CacheOptions {
  ttl: number;
}
export function Cache(options: CacheOptions) {
  return (target: any, propertyKey: string, descriptor) => {
    const originalFunction = descriptor.value;
    target[`${propertyKey}_cached`] = new ReplaySubject(1, options.ttl);
    descriptor.value = function(…args) {
      const req = originalFunction.apply(this, args).pipe(
        tap((response) => {
          this[`${propertyKey}_cached`].next(response);
        })
      );
      return race(this[`${propertyKey}_cached`], req);
    };
    return descriptor;
  };
}