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'use strict';
import CanceledError from './CanceledError.js';
/**
* A `CancelToken` is an object that can be used to request cancellation of an operation.
*
* @param {Function} executor The executor function.
*
* @returns {CancelToken}
*/
class CancelToken {
constructor(executor) {
if (typeof executor !== 'function') {
throw new TypeError('executor must be a function.');
}
let resolvePromise;
this.promise = new Promise(function promiseExecutor(resolve) {
resolvePromise = resolve;
});
const token = this;
// eslint-disable-next-line func-names
this.promise.then(cancel => {
if (!token._listeners) return;
let i = token._listeners.length;
while (i-- > 0) {
token._listeners[i](cancel);
}
token._listeners = null;
});
// eslint-disable-next-line func-names
this.promise.then = onfulfilled => {
let _resolve;
// eslint-disable-next-line func-names
const promise = new Promise(resolve => {
token.subscribe(resolve);
_resolve = resolve;
}).then(onfulfilled);
promise.cancel = function reject() {
token.unsubscribe(_resolve);
};
return promise;
};
executor(function cancel(message, config, request) {
if (token.reason) {
// Cancellation has already been requested
return;
}
token.reason = new CanceledError(message, config, request);
resolvePromise(token.reason);
});
}
/**
* Throws a `CanceledError` if cancellation has been requested.
*/
throwIfRequested() {
if (this.reason) {
throw this.reason;
}
}
/**
* Subscribe to the cancel signal
*/
subscribe(listener) {
if (this.reason) {
listener(this.reason);
return;
}
if (this._listeners) {
this._listeners.push(listener);
} else {
this._listeners = [listener];
}
}
/**
* Unsubscribe from the cancel signal
*/
unsubscribe(listener) {
if (!this._listeners) {
return;
}
const index = this._listeners.indexOf(listener);
if (index !== -1) {
this._listeners.splice(index, 1);
}
}
/**
* Returns an object that contains a new `CancelToken` and a function that, when called,
* cancels the `CancelToken`.
*/
static source() {
let cancel;
const token = new CancelToken(function executor(c) {
cancel = c;
});
return {
token,
cancel
};
}
}
export default CancelToken;
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