import { EventEmitter } from 'eventemitter3';
import { BrowserInstance, BrowserPoolConfig, Logger } from './types';
/**
 * @file Implements a pool for managing Playwright browser instances.
 * This helps in reusing browser instances to improve performance and control resource usage
 * by limiting the maximum number of concurrent browsers.
 */
/**
 * Manages a pool of Playwright browser instances.
 * This class handles the creation, acquisition, release, and cleanup of browser instances,
 * ensuring efficient reuse and adherence to configured limits (e.g., max size, instance age).
 * It emits events related to pool operations like 'pool:acquire', 'pool:release', 'pool:cleanup'.
 * @extends EventEmitter
 */
export declare class BrowserPool extends EventEmitter {
    private pool;
    private config;
    private logger;
    private cleanupTimer?;
    private isShuttingDown;
    /**
     * Creates an instance of BrowserPool.
     * @param config The configuration object for the browser pool. See {@link BrowserPoolConfig}.
     * @param logger An instance of a logger conforming to the {@link Logger} interface.
     */
    constructor(config: BrowserPoolConfig, logger: Logger);
    /**
     * Acquires a browser instance from the pool.
     * If an idle instance is available, it's reused.
     * If the pool is not full, a new instance is created.
     * If the pool is full and no instances are idle, it waits for one to become available.
     * Emits 'pool:acquire' event when an instance is acquired.
     * @returns A Promise that resolves to an available {@link BrowserInstance}.
     * @throws Error if the pool is shutting down or if waiting for an instance times out.
     */
    acquire(): Promise<BrowserInstance>;
    /**
     * Releases a previously acquired browser instance back to the pool,
     * marking it as available for reuse.
     * Emits 'pool:release' event.
     * @param instance The {@link BrowserInstance} to release.
     */
    release(instance: BrowserInstance): void;
    /**
     * Retrieves statistics about the current state of the browser pool.
     * @returns An object containing:
     *  - `total`: The total number of browser instances currently managed by the pool (both active and idle).
     *  - `inUse`: The number of browser instances currently acquired and in use.
     *  - `available`: The number of idle browser instances available for immediate acquisition.
     *  - `maxSize`: The maximum number of browser instances the pool is configured to allow.
     */
    getStats(): {
        total: number;
        inUse: number;
        available: number;
        maxSize: number;
    };
    /**
     * Periodically cleans up old and unused browser instances from the pool.
     * An instance is considered old if it has not been used for a duration exceeding
     * `config.maxAge` and is not currently in use.
     * This method is typically called by an internal timer.
     * Emits 'pool:cleanup' event with the number of removed instances.
     * @returns A Promise that resolves when the cleanup operation is complete.
     */
    cleanupOldInstances(): Promise<void>;
    /**
     * Shuts down the browser pool.
     * This process involves stopping the cleanup timer and closing all active browser instances
     * managed by the pool. No new instances can be acquired after shutdown is initiated.
     * @returns A Promise that resolves when all browser instances have been closed and resources are freed.
     */
    shutdown(): Promise<void>;
    /**
     * Create a new browser instance
     */
    private createInstance;
    /**
     * Destroy a browser instance
     */
    private destroyInstance;
    /**
     * Wait for an available instance
     */
    private waitForAvailableInstance;
    /**
     * Start the cleanup timer
     */
    private startCleanupTimer;
}
/**
 * Provides a default configuration for the {@link BrowserPool}.
 * This configuration can be used as a base and customized as needed.
 * Key defaults include:
 * - `maxSize`: 5 browser instances.
 * - `maxAge`: 30 minutes for an instance before it's recycled.
 * - `headless`: True (or as per `BROWSER_HEADLESS` env var).
 * - `cleanupInterval`: 5 minutes.
 */
export declare const defaultBrowserPoolConfig: BrowserPoolConfig;
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