Use case to manage viewing Facebook repositories

ViewRepositoriesUseCase.ts

import { Observable, of } from "rxjs";
import { flatMap } from "rxjs/operators";
import { ApiService } from "../data/ApiService";
import { Dao } from "../data/Dao";
import { IRepositroy } from "../data/models/Repository";

export class ViewRepositoriesUseCase {
  private readonly apiService: ApiService;
  private readonly dataDao: Dao;

  constructor(apiSerivce: ApiService, dataDao: Dao) {
    this.apiService = apiSerivce;
    this.dataDao = dataDao;
  }

  public observeItems(): Observable<IRepositroy[]> {
    return this.dataDao.getItems().pipe(
      flatMap(items => {
        if (items.length === 0) {
          return this.fetchMore();
        }
        return of(items);
      })
    );
  }
  public fetchMore(): Observable<IRepositroy[]> {
    return this.apiService.getRepos().pipe(
      flatMap(items => {
        return this.dataDao.addItems(items);
      })
    );
  }
  public async clearItems() {
    await this.dataDao.clearTable();
  }
}