vscode/extensions/tunnel-forwarding/src/deferredPromise.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

export type ValueCallback<T = unknown> = (value: T | Promise<T>) => void;

const enum DeferredOutcome {
	Resolved,
	Rejected
}

/**
 * Copied from src\vs\base\common\async.ts
 */
export class DeferredPromise<T> {

	private completeCallback!: ValueCallback<T>;
	private errorCallback!: (err: unknown) => void;
	private outcome?: { outcome: DeferredOutcome.Rejected; value: any } | { outcome: DeferredOutcome.Resolved; value: T };

	public get isRejected() {
		return this.outcome?.outcome === DeferredOutcome.Rejected;
	}

	public get isResolved() {
		return this.outcome?.outcome === DeferredOutcome.Resolved;
	}

	public get isSettled() {
		return !!this.outcome;
	}

	public get value() {
		return this.outcome?.outcome === DeferredOutcome.Resolved ? this.outcome?.value : undefined;
	}

	public readonly p: Promise<T>;

	constructor() {
		this.p = new Promise<T>((c, e) => {
			this.completeCallback = c;
			this.errorCallback = e;
		});
	}

	public complete(value: T) {
		return new Promise<void>(resolve => {
			this.completeCallback(value);
			this.outcome = { outcome: DeferredOutcome.Resolved, value };
			resolve();
		});
	}

	public error(err: unknown) {
		return new Promise<void>(resolve => {
			this.errorCallback(err);
			this.outcome = { outcome: DeferredOutcome.Rejected, value: err };
			resolve();
		});
	}
}