// Copyright (c) Microsoft Corporation. All rights reserved.

// Licensed under the MIT License.

'use strict';

import { CancellationToken } from 'vscode-jsonrpc';

import { createDeferred } from './utils/async';

import * as localize from './utils/localize';

/**

* Error type thrown when canceling.

*/

export class CancellationError extends Error {

constructor() {

super(localize.Common.canceled());

}

}

export namespace Cancellation {

/**

* Races a promise and cancellation. Promise can take a cancellation token too in order to listen to cancellation.

* @param work function returning a promise to race

* @param token token used for cancellation

*/

export function race<T>(work : (token?: CancellationToken) => Promise<T>, token?: CancellationToken) : Promise<T> {

if (token) {

// Use a deferred promise. Resolves when the work finishes

const deferred = createDeferred<T>();

// Cancel the deferred promise when the cancellation happens

token.onCancellationRequested(() => {

if (!deferred.completed) {

deferred.reject(new CancellationError());

}

});

// Might already be canceled

if (token.isCancellationRequested) {

// Just start out as rejected

deferred.reject(new CancellationError());

} else {

// Not canceled yet. When the work finishes

// either resolve our promise or cancel.

work(token)

.then((v) => {

if (!deferred.completed) {

deferred.resolve(v);

}

})

.catch((e) => {

if (!deferred.completed) {

deferred.reject(e);

}

});

}

return deferred.promise;

} else {

// No actual token, just do the original work.

return work();

}

}

/**

* isCanceled returns a boolean indicating if the cancel token has been canceled.

* @param cancelToken

*/

export function isCanceled(cancelToken?: CancellationToken) : boolean {

return cancelToken ? cancelToken.isCancellationRequested : false;

}

/**

* throws a CancellationError if the token is canceled.

* @param cancelToken

*/

export function throwIfCanceled(cancelToken?: CancellationToken) : void {

if (isCanceled(cancelToken)) {

throw new CancellationError();

}

}

}