/**
 * @license Use of this source code is governed by an MIT-style license that
 * can be found in the LICENSE file at https://github.com/cartant/rxjs-etc
 */

import {
  ConnectableObservable,
  merge,
  MonoTypeOperatorFunction,
  Observable,
  SchedulerLike,
  Subscription,
  timer,
} from "rxjs";

import { debounce, mapTo, publish, startWith, switchMap } from "rxjs/operators";

export function debounceTimeWithinReason<T>(
  debounceDuration: number,
  reasonableDuration: number,
  scheduler?: SchedulerLike
): MonoTypeOperatorFunction<T> {
  return (source) =>
    source.pipe(
      publish(
        (sharedSource) =>
          new Observable<T>((observer) => {
            let reasonableTimer: ConnectableObservable<number>;

            const debounced = sharedSource.pipe(
              debounce(() =>
                merge(timer(debounceDuration, scheduler), reasonableTimer)
              )
            );

            reasonableTimer = debounced.pipe(
              mapTo(undefined),
              startWith(undefined),
              switchMap(() => timer(reasonableDuration, scheduler)),
              publish()
            ) as ConnectableObservable<number>;

            const subscription = new Subscription();
            subscription.add(reasonableTimer.connect());
            subscription.add(debounced.subscribe(observer));
            return subscription;
          })
      )
    );
}