settings.facade.ts

@Injectable()
export class SettingsFacade {

  constructor(
    private cashflowCategoryApi: CashflowCategoryApi, 
    private settingsState: SettingsState
  ) { }

  get isUpdating$(): Observable<boolean> {
    return this.settingsState.isUpdating$;
  }

  get cashflowCategories$(): Observable<CashflowCategory[]> {
    // aqui passamos o estado sem projeções
    // pode acontecer que seja necessário combinar dois ou mais observables e expor aos componentes
    return this.settingsState.cashflowCategories$;
  }

  loadCashflowCategories() {
    return this.cashflowCategoryApi.getCashflowCategories()
      .pipe(tap(categories => this.settingsState.cashflowCategories = categories));
  }

  // atualização otimista
  // 1. atualiza a UI state
  // 2. chama a API
  addCashflowCategory(category: CashflowCategory) {
    this.settingsState.addCashflowCategory(category);
    this.cashflowCategoryApi.createCashflowCategory(category)
      .subscribe(
        (addedCategoryWithId: CashflowCategory) => {
          // callback de sucesso - nós temos o id gerado pelo servidor, vamos atualizar o estado
          this.settingsState.updateCashflowCategoryId(category, addedCategoryWithId)
        },
        (error: any) => {
          // callback de erro - nós precisamos reverter a mudança de estado
          this.settingsState.removeCashflowCategory(category);
          console.log(error);
        }
      );
  }

  // atualização pessimista
  // 1. chama a API
  // 2. atualiza a UI state
  updateCashflowCategory(category: CashflowCategory) {
    this.settingsState.isUpdating = true;
    this.cashflowCategoryApi.updateCashflowCategory(category)
      .subscribe(
        () => this.settingsState.updateCashflowCategory(category),
        (error) => console.log(error),
        () => this.settingsState.isUpdating = false;
      );
  }
  
  removeCashflowCategory(category: CashflowCategory) {
    this.settingsState.isUpdating = true;
    this.cashflowCategoryApi.removeCashflowCategory(category)
      .subscribe(
        () => this.settingsState.removeCashflowCategory(category),
        (error) => console.log(error),
        () => this.settingsState.isUpdating = false;
      );
  }
}