import { Observable } from '../Observable';
import { Notification } from '../Notification';
import { dematerialize as higherOrder } from '../operators/dematerialize';

/**
 * Converts an Observable of {@link Notification} objects into the emissions
 * that they represent.
 *
 * <span class="informal">Unwraps {@link Notification} objects as actual `next`,
 * `error` and `complete` emissions. The opposite of {@link materialize}.</span>
 *
 * <img src="./img/dematerialize.png" width="100%">
 *
 * `dematerialize` is assumed to operate an Observable that only emits
 * {@link Notification} objects as `next` emissions, and does not emit any
 * `error`. Such Observable is the output of a `materialize` operation. Those
 * notifications are then unwrapped using the metadata they contain, and emitted
 * as `next`, `error`, and `complete` on the output Observable.
 *
 * Use this operator in conjunction with {@link materialize}.
 *
 * @example <caption>Convert an Observable of Notifications to an actual Observable</caption>
 * var notifA = new Rx.Notification('N', 'A');
 * var notifB = new Rx.Notification('N', 'B');
 * var notifE = new Rx.Notification('E', void 0,
 *   new TypeError('x.toUpperCase is not a function')
 * );
 * var materialized = Rx.Observable.of(notifA, notifB, notifE);
 * var upperCase = materialized.dematerialize();
 * upperCase.subscribe(x => console.log(x), e => console.error(e));
 *
 * // Results in:
 * // A
 * // B
 * // TypeError: x.toUpperCase is not a function
 *
 * @see {@link Notification}
 * @see {@link materialize}
 *
 * @return {Observable} An Observable that emits items and notifications
 * embedded in Notification objects emitted by the source Observable.
 * @method dematerialize
 * @owner Observable
 */
export function dematerialize<T>(this: Observable<Notification<T>>): Observable<T> {
  return higherOrder()(this) as Observable<T>;
}