import { IScheduler } from '../Scheduler';
import { async } from '../scheduler/async';
import { Observable } from '../Observable';
import { isNumeric } from '../util/isNumeric';
import { isScheduler } from '../util/isScheduler';
import { windowTime as higherOrder } from '../operators/windowTime';

/**
 * Branch out the source Observable values as a nested Observable periodically
 * in time.
 *
 * <span class="informal">It's like {@link bufferTime}, but emits a nested
 * Observable instead of an array.</span>
 *
 * <img src="./img/windowTime.png" width="100%">
 *
 * Returns an Observable that emits windows of items it collects from the source
 * Observable. The output Observable starts a new window periodically, as
 * determined by the `windowCreationInterval` argument. It emits each window
 * after a fixed timespan, specified by the `windowTimeSpan` argument. When the
 * source Observable completes or encounters an error, the output Observable
 * emits the current window and propagates the notification from the source
 * Observable. If `windowCreationInterval` is not provided, the output
 * Observable starts a new window when the previous window of duration
 * `windowTimeSpan` completes. If `maxWindowCount` is provided, each window
 * will emit at most fixed number of values. Window will complete immediately
 * after emitting last value and next one still will open as specified by
 * `windowTimeSpan` and `windowCreationInterval` arguments.
 *
 * @example <caption>In every window of 1 second each, emit at most 2 click events</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.windowTime(1000)
 *   .map(win => win.take(2)) // each window has at most 2 emissions
 *   .mergeAll(); // flatten the Observable-of-Observables
 * result.subscribe(x => console.log(x));
 *
 * @example <caption>Every 5 seconds start a window 1 second long, and emit at most 2 click events per window</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.windowTime(1000, 5000)
 *   .map(win => win.take(2)) // each window has at most 2 emissions
 *   .mergeAll(); // flatten the Observable-of-Observables
 * result.subscribe(x => console.log(x));
 *
 * @example <caption>Same as example above but with maxWindowCount instead of take</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.windowTime(1000, 5000, 2) // each window has still at most 2 emissions
 *   .mergeAll(); // flatten the Observable-of-Observables
 * result.subscribe(x => console.log(x));

 * @see {@link window}
 * @see {@link windowCount}
 * @see {@link windowToggle}
 * @see {@link windowWhen}
 * @see {@link bufferTime}
 *
 * @param {number} windowTimeSpan The amount of time to fill each window.
 * @param {number} [windowCreationInterval] The interval at which to start new
 * windows.
 * @param {number} [maxWindowSize=Number.POSITIVE_INFINITY] Max number of
 * values each window can emit before completion.
 * @param {Scheduler} [scheduler=async] The scheduler on which to schedule the
 * intervals that determine window boundaries.
 * @return {Observable<Observable<T>>} An observable of windows, which in turn
 * are Observables.
 * @method windowTime
 * @owner Observable
 */
export function windowTime<T>(this: Observable<T>, windowTimeSpan: number,
                              scheduler?: IScheduler): Observable<Observable<T>>;
export function windowTime<T>(this: Observable<T>, windowTimeSpan: number,
                              windowCreationInterval: number,
                              scheduler?: IScheduler): Observable<Observable<T>>;
export function windowTime<T>(this: Observable<T>, windowTimeSpan: number,
                              windowCreationInterval: number,
                              maxWindowSize: number,
                              scheduler?: IScheduler): Observable<Observable<T>>;

export function windowTime<T>(this: Observable<T>,
                              windowTimeSpan: number): Observable<Observable<T>> {

  let scheduler: IScheduler = async;
  let windowCreationInterval: number = null;
  let maxWindowSize: number = Number.POSITIVE_INFINITY;

  if (isScheduler(arguments[3])) {
    scheduler = arguments[3];
  }

  if (isScheduler(arguments[2])) {
    scheduler = arguments[2];
  } else if (isNumeric(arguments[2])) {
    maxWindowSize = arguments[2];
  }

  if (isScheduler(arguments[1])) {
    scheduler = arguments[1];
  } else if (isNumeric(arguments[1])) {
    windowCreationInterval = arguments[1];
  }

  return higherOrder(windowTimeSpan, windowCreationInterval, maxWindowSize, scheduler)(this) as Observable<Observable<T>>;
}