queryable-promise.ts

export class QueryablePromise<T> implements Promise<T> {
	private readonly promise: Promise<T>;
	private _isPending: boolean = true;
	private _isRejected: boolean = false;
	private _isFulfilled: boolean = false;

	public get isPending(): boolean { return this._isPending; };
	public get isRejected(): boolean { return this._isRejected; };
	public get isFulfilled(): boolean { return this._isFulfilled; };

	public constructor(promise: Promise<T>) {
		this.promise =
			promise
				.then(value => {
					this._isFulfilled = true;
					return value;
				})
				.catch(reason => {
					this._isRejected = true;
					return reason;
				})
				.finally(() => {
					this._isPending = false;
				});
	}

	then<TResult1 = T, TResult2 = never>(
		onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>,
		onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>
	): Promise<TResult1 | TResult2> {
		return this.promise.then(onfulfilled, onrejected);
	}
	
	catch<TResult = never>(onrejected?: (reason: any) => TResult | PromiseLike<TResult>): Promise<T | TResult> {
		return this.promise.catch(onrejected);
	}

	[Symbol.toStringTag]: string;
	finally(onfinally?: () => void): Promise<T> {
		return this.promise.finally(onfinally);
	}

	toString = () =>
		`isPending: ${this.isPending}\n` +
		`isRejected: ${this.isRejected}\n` +
		`isFulfilled: ${this.isFulfilled}`;
}