import { EventEmitter } from 'events';
import { PoolState } from './constants.js';
import { PoolOptions } from './pool-options.js';
import type { Callback, PoolConfiguration, PoolFactory } from './types.js';
export declare class Pool<T = any> extends EventEmitter {
    private readonly _options;
    private readonly _factory;
    private _requestQueue;
    private _allResources;
    private _acquiredResources;
    private _idleResources;
    private _creating;
    private _requestsProcessing;
    private _state;
    private _houseKeepTimer;
    private _closeWaitTimer;
    constructor(factory: PoolFactory<T>, config?: PoolConfiguration);
    /**
     * Returns Pool options
     */
    get options(): PoolOptions;
    /**
     * Returns number of resources that are currently acquired
     */
    get acquired(): number;
    /**
     * Returns number of unused resources in the pool
     */
    get available(): number;
    /**
     * Returns number of resources currently creating
     */
    get creating(): number;
    /**
     * Returns number of callers waiting to acquire a resource
     */
    get pending(): number;
    /**
     * Returns number of resources in the pool
     * regardless of whether they are idle or in use
     */
    get size(): number;
    /**
     * Returns state of the pool
     */
    get state(): PoolState;
    /**
     * Starts the pool and begins creating of resources, starts house keeping and any other internal logic.
     * Note: This method is not need to be called. Pool instance will automatically be started when acquire() method is called
     */
    start(): void;
    /**
     * Shuts down the pool and destroys all resources.
     */
    close(callback?: Callback): void;
    close(terminateWait: number, callback?: Callback): void;
    close(force: boolean, callback?: Callback): void;
    closeAsync(): Promise<void>;
    closeAsync(terminateWait: number): Promise<void>;
    closeAsync(force: boolean): Promise<void>;
    /**
     * Acquires `resource` from the pool or create a new one
     */
    acquire(): Promise<T>;
    acquire(callback: Callback): void;
    /**
     * Releases an allocated `resource` and let it back to pool.
     */
    release(resource: T, callback?: Callback): void;
    /**
     * Async version of release().
     */
    releaseAsync(resource: T): Promise<void>;
    /**
     * Releases, destroys and removes any `resource` from `Pool`.
     */
    destroy(resource: T, callback?: Callback): any;
    /**
     * Async version of destroy().
     */
    destroyAsync(resource: T): Promise<void>;
    /**
     * Returns if a `resource` has been acquired from the pool and not yet released or destroyed.
     */
    isAcquired(resource: T): boolean;
    /**
     * Returns if the pool contains a `resource`
     */
    includes(resource: T): boolean;
    private _processNextRequest;
    emit(event: string | symbol, ...args: any[]): boolean;
    /**
     * Creates new resource
     */
    private _createResource;
    private _setHouseKeep;
    private _houseKeep;
    private _ensureMin;
    private _itemSetAcquired;
    private _itemDetach;
    private _itemSetIdle;
    private _itemDestroy;
    private _itemValidate;
}