import type { ConnectionOptions, SmtpConnection } from "./connection.mjs";
/** Options for the pool layer. A subset of `SmtpDriverOptions`. */
export interface PoolOptions {
	enabled: boolean;
	maxConnections: number;
	maxMessagesPerConnection: number;
	idleTimeoutMs: number;
	disposeGraceMs: number;
	connection: ConnectionOptions;
}
/** A FIFO connection pool with graceful dispose. Fixes the v0 leak: both
*  idle AND in-flight connections are tracked, so `dispose()` can wait on
*  in-flight sends and then quit everything. */
export interface ConnectionPool {
	acquire: () => Promise<SmtpConnection>;
	release: (conn: SmtpConnection, failed?: boolean) => Promise<void>;
	dispose: () => Promise<void>;
	size: () => {
		idle: number;
		inFlight: number;
		waiters: number;
	};
}
export declare function createPool(options: PoolOptions): ConnectionPool;