dspace-angular/src/app/core/data/remote-data.ts

import { Observable } from "rxjs";

export enum RemoteDataState {
  RequestPending,
  ResponsePending,
  Failed,
  Success
}

/**
 * A class to represent the state of a remote resource
 */
export class RemoteData<T> {
  constructor(
    public self: string,
    private requestPending: Observable<boolean>,
    private responsePending: Observable<boolean>,
    private isSuccessFul: Observable<boolean>,
    public errorMessage: Observable<string>,
    public payload: Observable<T>
  ) {
  }

  get state(): Observable<RemoteDataState> {
    return Observable.combineLatest(
      this.requestPending,
      this.responsePending,
      this.isSuccessFul,
      (requestPending, responsePending, isSuccessFul) => {
        if (requestPending) {
          return RemoteDataState.RequestPending
        }
        else if (responsePending) {
          return RemoteDataState.ResponsePending
        }
        else if (!isSuccessFul) {
          return RemoteDataState.Failed
        }
        else {
          return RemoteDataState.Success
        }
      }
    ).distinctUntilChanged();
  }

  get isRequestPending(): Observable<boolean> {
    return this.state
      .map(state => state == RemoteDataState.RequestPending)
      .distinctUntilChanged();
  }

  get isResponsePending(): Observable<boolean> {
    return this.state
      .map(state => state == RemoteDataState.ResponsePending)
      .distinctUntilChanged();
  }

  get isLoading(): Observable<boolean> {
    return this.state
      .map(state => {
        return state == RemoteDataState.RequestPending
          || state === RemoteDataState.ResponsePending
      })
      .distinctUntilChanged();
  }

  get hasFailed(): Observable<boolean> {
    return this.state
      .map(state => state == RemoteDataState.Failed)
      .distinctUntilChanged();
  }

  get hasSucceeded(): Observable<boolean> {
    return this.state
      .map(state => state == RemoteDataState.Success)
      .distinctUntilChanged();
  }

}