import { type Deferred } from './Deferred';
type PromiseQueueOpts = {
    maxConcurrent: number;
};
export default class PromiseQueue<T> {
    _deferred: Deferred<Array<T>> | null | undefined;
    _maxConcurrent: number;
    _numRunning: number;
    _queue: Array<() => Promise<void>>;
    _runPromise: Promise<Array<T>> | null | undefined;
    _error: unknown;
    _count: number;
    _results: Array<T>;
    _addSubscriptions: Set<() => void>;
    constructor(opts?: PromiseQueueOpts);
    getNumWaiting(): number;
    add(fn: () => Promise<T>): void;
    subscribeToAdd(fn: () => void): () => void;
    run(): Promise<Array<T>>;
    _next(): Promise<void>;
    _runFn(fn: () => unknown): Promise<void>;
    _resetState(): void;
    _done(): void;
}
export {};