import { MongoClient } from 'mongodb';
/** Manages a shared pool of MongoClient instances, reusing connections by URI and pool options. */
export declare class MongoClientWrapper {
    /** Global cache of wrapper instances keyed by URI and pool options. */
    static readonly clients: Map<string, MongoClientWrapper>;
    private readonly cacheKey;
    private readonly client;
    private readonly closeDelay;
    private closeTimer;
    private connected;
    private operationChain;
    private refCount;
    constructor(uri: string, maxPoolSize?: number, closeDelay?: number, cacheKey?: string);
    /**
     * Builds a cache key from connection URI and pool options.
     * @param URI - The MongoDB connection URI
     * @param poolSize - Maximum connection pool size
     * @param closeDelay - Delay in milliseconds before closing idle connections
     */
    static cacheKey(uri: string, poolSize?: number, closeDelay?: number): string;
    /**
     * Gets or creates a cached MongoClientWrapper for the given URI and pool options.
     * @param URI - The MongoDB connection URI
     * @param poolSize - Maximum connection pool size
     * @param closeDelay - Delay in milliseconds before closing idle connections
     * @returns A cached or newly created wrapper instance
     */
    static get(uri: string, poolSize?: number, closeDelay?: number): MongoClientWrapper;
    /** Connects to MongoDB and returns the underlying MongoClient. */
    connect(): Promise<MongoClient>;
    /**
     * Releases a connection reference. The shared client is kept alive and only closed once it
     * has had no references for `closeDelay` ms, so back-to-back operations reuse a single pooled
     * client. A reconnect within that window cancels the pending close. Use `closeDelay: 0` for
     * the legacy behavior of closing immediately on the last release.
     */
    disconnect(): Promise<void>;
    /** Initiates a graceful close of the connection, regardless of outstanding references. */
    initiateClose(): Promise<void>;
    private cancelScheduledClose;
    private closeIfIdle;
    private enqueue;
    private removeFromCache;
    private scheduleClose;
}
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