import type { Unawaitable } from '../functions/unawaitable';
export type Callback = (val?: any) => void;
export declare class Queue {
	error_handler?: Callback;
	constructor(error_handler?: Callback);
	/** Is a process ongoing? */
	working: boolean;
	/** Queued callbacks */
	queue: Callback[];
	/** Call next() after call stack resolved */
	next_async(): void;
	/** Call the next callback */
	next(): false | void;
	/** Add a callback */
	add(cb: Callback): number | void;
	/** Get a promise */
	get promise(): Promise<unknown>;
	/** executes callback after queue empty, does not lock queue */
	then(callback: (self: Unawaitable<Queue>) => any): Promise<any>;
}
export default Queue;