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import { CancellationAggregate } from "./CancellationAggregate";
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import { ICancellation, IDestroyable } from "./interfaces";
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import { argumentNotNull, destroyed } from "./safe";
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export class Cancellation implements ICancellation {
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private _reason: any;
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private _cbs: Array<(e: any) => void> | undefined;
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constructor(action: (cancel: (e?: any) => void) => void) {
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argumentNotNull(action, "action");
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action(this._cancel.bind(this));
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}
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isSupported(): boolean {
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return true;
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}
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throwIfRequested(): void {
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if (this._reason)
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throw this._reason;
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}
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isRequested(): boolean {
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return !!this._reason;
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}
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register(cb: (e: any) => void): IDestroyable {
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argumentNotNull(cb, "cb");
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if (this._reason) {
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cb(this._reason);
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return destroyed;
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} else {
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if (!this._cbs)
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this._cbs = [cb];
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else
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this._cbs.push(cb);
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const me = this;
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return {
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destroy() {
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me._unregister(cb);
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}
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};
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}
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}
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private _unregister(cb: any) {
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if (this._cbs) {
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const i = this._cbs.indexOf(cb);
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if (i >= 0)
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this._cbs.splice(i, 1);
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}
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}
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private _cancel(reason: any) {
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if (this._reason)
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return;
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this._reason = (reason = reason || new Error("Operation cancelled"));
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if (this._cbs) {
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this._cbs.forEach(cb => cb(reason));
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this._cbs = undefined;
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}
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}
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static readonly none: ICancellation = {
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isSupported(): boolean {
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return false;
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},
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throwIfRequested(): void {
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},
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isRequested(): boolean {
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return false;
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},
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register(_cb: (e: any) => void): IDestroyable {
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return destroyed;
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}
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};
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/**
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* Combines multiple cancellation tokens to the single aggregated token.
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*
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* Aggregated token will be considered as signalled when some tokens are
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* signalled. The cancellation callback can be registered with the `register`
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* method, it will be fired once with the first signalled token, all other
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* tokens will be ignored.
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*
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* The tokens which don't support cancellation are filtered out, if there are
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* no tokens left in the list the method returns `Cancellation.none`.
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*
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* @param args The list of cancellation tokens to combine
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* @returns
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*/
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static combine(...args: ICancellation[]) {
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const tokens = args.filter(ct => ct.isSupported());
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return tokens.length > 1 ?
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new CancellationAggregate(tokens) :
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tokens.length == 1 ? tokens[0] :
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this.none;
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}
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}
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