1import { async } from '../scheduler/async';
2import { isDate } from '../util/isDate';
3import { Operator } from '../Operator';
4import { Subscriber } from '../Subscriber';
5import { Subscription } from '../Subscription';
6import { Notification } from '../Notification';
7import { Observable } from '../Observable';
8import { MonoTypeOperatorFunction, PartialObserver, SchedulerAction, SchedulerLike, TeardownLogic } from '../types';
9
10/**
11 * Delays the emission of items from the source Observable by a given timeout or
12 * until a given Date.
13 *
14 * <span class="informal">Time shifts each item by some specified amount of
15 * milliseconds.</span>
16 *
17 * ![](delay.png)
18 *
19 * If the delay argument is a Number, this operator time shifts the source
20 * Observable by that amount of time expressed in milliseconds. The relative
21 * time intervals between the values are preserved.
22 *
23 * If the delay argument is a Date, this operator time shifts the start of the
24 * Observable execution until the given date occurs.
25 *
26 * ## Examples
27 * Delay each click by one second
28 * ```ts
29 * import { fromEvent } from 'rxjs';
30 * import { delay } from 'rxjs/operators';
31 *
32 * const clicks = fromEvent(document, 'click');
33 * const delayedClicks = clicks.pipe(delay(1000)); // each click emitted after 1 second
34 * delayedClicks.subscribe(x => console.log(x));
35 * ```
36 *
37 * Delay all clicks until a future date happens
38 * ```ts
39 * import { fromEvent } from 'rxjs';
40 * import { delay } from 'rxjs/operators';
41 *
42 * const clicks = fromEvent(document, 'click');
43 * const date = new Date('March 15, 2050 12:00:00'); // in the future
44 * const delayedClicks = clicks.pipe(delay(date)); // click emitted only after that date
45 * delayedClicks.subscribe(x => console.log(x));
46 * ```
47 *
48 * @see {@link debounceTime}
49 * @see {@link delayWhen}
50 *
51 * @param {number|Date} delay The delay duration in milliseconds (a `number`) or
52 * a `Date` until which the emission of the source items is delayed.
53 * @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for
54 * managing the timers that handle the time-shift for each item.
55 * @return {Observable} An Observable that delays the emissions of the source
56 * Observable by the specified timeout or Date.
57 * @method delay
58 * @owner Observable
59 */
60export function delay<T>(delay: number|Date,
61                         scheduler: SchedulerLike = async): MonoTypeOperatorFunction<T> {
62  const absoluteDelay = isDate(delay);
63  const delayFor = absoluteDelay ? (+delay - scheduler.now()) : Math.abs(<number>delay);
64  return (source: Observable<T>) => source.lift(new DelayOperator(delayFor, scheduler));
65}
66
67class DelayOperator<T> implements Operator<T, T> {
68  constructor(private delay: number,
69              private scheduler: SchedulerLike) {
70  }
71
72  call(subscriber: Subscriber<T>, source: any): TeardownLogic {
73    return source.subscribe(new DelaySubscriber(subscriber, this.delay, this.scheduler));
74  }
75}
76
77interface DelayState<T> {
78  source: DelaySubscriber<T>;
79  destination: PartialObserver<T>;
80  scheduler: SchedulerLike;
81}
82
83/**
84 * We need this JSDoc comment for affecting ESDoc.
85 * @ignore
86 * @extends {Ignored}
87 */
88class DelaySubscriber<T> extends Subscriber<T> {
89  private queue: Array<DelayMessage<T>> = [];
90  private active: boolean = false;
91  private errored: boolean = false;
92
93  private static dispatch<T>(this: SchedulerAction<DelayState<T>>, state: DelayState<T>): void {
94    const source = state.source;
95    const queue = source.queue;
96    const scheduler = state.scheduler;
97    const destination = state.destination;
98
99    while (queue.length > 0 && (queue[0].time - scheduler.now()) <= 0) {
100      queue.shift().notification.observe(destination);
101    }
102
103    if (queue.length > 0) {
104      const delay = Math.max(0, queue[0].time - scheduler.now());
105      this.schedule(state, delay);
106    } else {
107      this.unsubscribe();
108      source.active = false;
109    }
110  }
111
112  constructor(destination: Subscriber<T>,
113              private delay: number,
114              private scheduler: SchedulerLike) {
115    super(destination);
116  }
117
118  private _schedule(scheduler: SchedulerLike): void {
119    this.active = true;
120    const destination = this.destination as Subscription;
121    destination.add(scheduler.schedule<DelayState<T>>(DelaySubscriber.dispatch, this.delay, {
122      source: this, destination: this.destination, scheduler: scheduler
123    }));
124  }
125
126  private scheduleNotification(notification: Notification<T>): void {
127    if (this.errored === true) {
128      return;
129    }
130
131    const scheduler = this.scheduler;
132    const message = new DelayMessage(scheduler.now() + this.delay, notification);
133    this.queue.push(message);
134
135    if (this.active === false) {
136      this._schedule(scheduler);
137    }
138  }
139
140  protected _next(value: T) {
141    this.scheduleNotification(Notification.createNext(value));
142  }
143
144  protected _error(err: any) {
145    this.errored = true;
146    this.queue = [];
147    this.destination.error(err);
148    this.unsubscribe();
149  }
150
151  protected _complete() {
152    this.scheduleNotification(Notification.createComplete());
153    this.unsubscribe();
154  }
155}
156
157class DelayMessage<T> {
158  constructor(public readonly time: number,
159              public readonly notification: Notification<T>) {
160  }
161}
162