import type { DebouncedFunc } from 'lodash';
import { Emitter } from './event-emitter';
declare type MaybePromise<T> = T | Promise<T>;
export interface QueueOptions<T> {
    flushInterval?: number;
    onSend?: (items: T[]) => MaybePromise<void | undefined | boolean>;
}
export declare class Queue<T = unknown> extends Emitter {
    readonly flushed: T[];
    readonly queue: Set<T>;
    readonly scheduleSend: DebouncedFunc<() => void>;
    private flushing;
    constructor(options?: QueueOptions<T>);
    add(item: T): void;
    flush(): void;
    get all(): T[];
    reset(): void;
    protected onSend(_items: T[]): MaybePromise<void | undefined | boolean>;
    /**
     * Simplistic promise queue
     * Attempt to deliver all items in the queue, and then clear it.
     * If `this.onSend` returns false, the queue will not be cleared.
     * If `this.onSend` throws, the queue will not be cleared.
     * If we are already flushing, we'll delay the attempt by scheduling another flush.
     */
    send(force?: boolean): void;
}
export {};