45 lines
1.3 KiB
TypeScript
45 lines
1.3 KiB
TypeScript
// Copyright 2017-2020 @polkadot/rpc-core authors & contributors
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// SPDX-License-Identifier: Apache-2.0
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import type { ConnectableObservable, MonoTypeOperatorFunction, TeardownLogic } from '@polkadot/x-rxjs';
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import { asapScheduler, Observable, Subscription } from '@polkadot/x-rxjs';
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/** @internal */
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export function refCountDelay <T> (delay = 1750): MonoTypeOperatorFunction<T> {
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return (source: Observable<T>): Observable<T> => {
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// state: 0 = disconnected, 1 = disconnecting, 2 = connecting, 3 = connected
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let [state, refCount, connection, scheduler] = [0, 0, Subscription.EMPTY, Subscription.EMPTY];
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return new Observable((ob): TeardownLogic => {
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source.subscribe(ob);
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if (refCount++ === 0) {
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if (state === 1) {
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scheduler.unsubscribe();
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} else {
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connection = (source as ConnectableObservable<T>).connect();
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}
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state = 3;
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}
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return (): void => {
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if (--refCount === 0) {
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if (state === 2) {
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state = 0;
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scheduler.unsubscribe();
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} else {
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// state === 3
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state = 1;
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scheduler = asapScheduler.schedule((): void => {
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state = 0;
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connection.unsubscribe();
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}, delay);
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}
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}
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};
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});
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};
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}
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