import { Client } from '@modelcontextprotocol/sdk/client/index.js';
/**
 * Represents a pooled connection to an MCP server
 */
export interface PooledConnection {
    url: string;
    transport: 'stdio' | 'http' | 'websocket' | 'tcp' | 'auto';
    client: Client;
    connectedAt: Date;
    lastUsed: Date;
    useCount: number;
    healthy: boolean;
    metadata?: Record<string, any>;
}
/**
 * Configuration for connection pool
 */
export interface ConnectionPoolConfig {
    maxConnections?: number;
    connectionTTL?: number;
    idleTimeout?: number;
    healthCheckInterval?: number;
    retryAttempts?: number;
    retryDelay?: number;
}
/**
 * Connection pool for managing MCP client connections
 * Handles connection reuse, health checks, and automatic transport negotiation
 */
export declare class MCPConnectionPool {
    private connections;
    private config;
    private healthCheckTimer?;
    private cleanupTimer?;
    constructor(config?: ConnectionPoolConfig);
    /**
     * Get or create a client connection
     * @param url The server URL
     * @param transport Optional transport type (auto-negotiates if not specified)
     * @returns The MCP client
     */
    getClient(url: string, transport?: 'stdio' | 'http' | 'websocket' | 'tcp' | 'auto'): Promise<Client>;
    /**
     * Create a new connection with auto-negotiation
     */
    private createConnection;
    /**
     * Create a transport based on type
     */
    private createTransport;
    /**
     * Detect transport type from URL
     */
    private detectTransport;
    /**
     * Get next transport to try in fallback sequence
     */
    private getNextTransport;
    /**
     * Extract headers from URL parameters
     */
    private extractHeaders;
    /**
     * Remove a connection from the pool
     */
    private removeConnection;
    /**
     * Evict the least recently used connection
     */
    private evictLeastRecentlyUsed;
    /**
     * Perform health check on a connection
     */
    private checkHealth;
    /**
     * Start maintenance tasks (health checks and cleanup)
     */
    private startMaintenanceTasks;
    /**
     * Get connection key for caching
     */
    private getConnectionKey;
    /**
     * Get count of active connections (those recently used)
     */
    private getActiveConnectionCount;
    /**
     * Get pool statistics
     */
    getStats(): {
        totalConnections: number;
        healthyConnections: number;
        unhealthyConnections: number;
        activeConnections: number;
        idleConnections: number;
        connectionsByTransport: Record<string, number>;
        connectionsByUseCount: Array<{
            url: string;
            useCount: number;
            ageMs: number;
        }>;
        averageUseCount: number;
    };
    /**
     * Close all connections and stop maintenance tasks
     */
    close(): Promise<void>;
}
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