1import { Subject } from './Subject';
2import { SchedulerLike } from './types';
3import { queue } from './scheduler/queue';
4import { Subscriber } from './Subscriber';
5import { Subscription } from './Subscription';
6import { ObserveOnSubscriber } from './operators/observeOn';
7import { ObjectUnsubscribedError } from './util/ObjectUnsubscribedError';
8import { SubjectSubscription } from './SubjectSubscription';
9/**
10 * A variant of Subject that "replays" or emits old values to new subscribers.
11 * It buffers a set number of values and will emit those values immediately to
12 * any new subscribers in addition to emitting new values to existing subscribers.
13 *
14 * @class ReplaySubject<T>
15 */
16export class ReplaySubject<T> extends Subject<T> {
17  private _events: (ReplayEvent<T> | T)[] = [];
18  private _bufferSize: number;
19  private _windowTime: number;
20  private _infiniteTimeWindow: boolean = false;
21
22  constructor(bufferSize: number = Number.POSITIVE_INFINITY,
23              windowTime: number = Number.POSITIVE_INFINITY,
24              private scheduler?: SchedulerLike) {
25    super();
26    this._bufferSize = bufferSize < 1 ? 1 : bufferSize;
27    this._windowTime = windowTime < 1 ? 1 : windowTime;
28
29    if (windowTime === Number.POSITIVE_INFINITY) {
30      this._infiniteTimeWindow = true;
31      this.next = this.nextInfiniteTimeWindow;
32    } else {
33      this.next = this.nextTimeWindow;
34    }
35  }
36
37  private nextInfiniteTimeWindow(value: T): void {
38    const _events = this._events;
39    _events.push(value);
40    // Since this method is invoked in every next() call than the buffer
41    // can overgrow the max size only by one item
42    if (_events.length > this._bufferSize) {
43      _events.shift();
44    }
45
46    super.next(value);
47  }
48
49  private nextTimeWindow(value: T): void {
50    this._events.push(new ReplayEvent(this._getNow(), value));
51    this._trimBufferThenGetEvents();
52
53    super.next(value);
54  }
55
56  /** @deprecated This is an internal implementation detail, do not use. */
57  _subscribe(subscriber: Subscriber<T>): Subscription {
58    // When `_infiniteTimeWindow === true` then the buffer is already trimmed
59    const _infiniteTimeWindow = this._infiniteTimeWindow;
60    const _events = _infiniteTimeWindow ? this._events : this._trimBufferThenGetEvents();
61    const scheduler = this.scheduler;
62    const len = _events.length;
63    let subscription: Subscription;
64
65    if (this.closed) {
66      throw new ObjectUnsubscribedError();
67    } else if (this.isStopped || this.hasError) {
68      subscription = Subscription.EMPTY;
69    } else {
70      this.observers.push(subscriber);
71      subscription = new SubjectSubscription(this, subscriber);
72    }
73
74    if (scheduler) {
75      subscriber.add(subscriber = new ObserveOnSubscriber<T>(subscriber, scheduler));
76    }
77
78    if (_infiniteTimeWindow) {
79      for (let i = 0; i < len && !subscriber.closed; i++) {
80        subscriber.next(<T>_events[i]);
81      }
82    } else {
83      for (let i = 0; i < len && !subscriber.closed; i++) {
84        subscriber.next((<ReplayEvent<T>>_events[i]).value);
85      }
86    }
87
88    if (this.hasError) {
89      subscriber.error(this.thrownError);
90    } else if (this.isStopped) {
91      subscriber.complete();
92    }
93
94    return subscription;
95  }
96
97  _getNow(): number {
98    return (this.scheduler || queue).now();
99  }
100
101  private _trimBufferThenGetEvents(): ReplayEvent<T>[] {
102    const now = this._getNow();
103    const _bufferSize = this._bufferSize;
104    const _windowTime = this._windowTime;
105    const _events = <ReplayEvent<T>[]>this._events;
106
107    const eventsCount = _events.length;
108    let spliceCount = 0;
109
110    // Trim events that fall out of the time window.
111    // Start at the front of the list. Break early once
112    // we encounter an event that falls within the window.
113    while (spliceCount < eventsCount) {
114      if ((now - _events[spliceCount].time) < _windowTime) {
115        break;
116      }
117      spliceCount++;
118    }
119
120    if (eventsCount > _bufferSize) {
121      spliceCount = Math.max(spliceCount, eventsCount - _bufferSize);
122    }
123
124    if (spliceCount > 0) {
125      _events.splice(0, spliceCount);
126    }
127
128    return _events;
129  }
130
131}
132
133class ReplayEvent<T> {
134  constructor(public time: number, public value: T) {
135  }
136}
137