/**
 * MCP Circuit Breaker
 * Implements circuit breaker pattern for external MCP operations
 * Provides fault tolerance and prevents cascading failures
 */
import { EventEmitter } from "events";
import type { CircuitBreakerConfig, CircuitBreakerStats } from "../types/index.js";
export { CircuitBreakerOpenError } from "../types/index.js";
/**
 * MCPCircuitBreaker
 * Implements circuit breaker pattern for fault tolerance
 */
export declare class MCPCircuitBreaker extends EventEmitter {
    private name;
    private state;
    private config;
    private callHistory;
    private lastFailureTime;
    private halfOpenCalls;
    private lastStateChange;
    private cleanupTimer?;
    constructor(name: string, config?: Partial<CircuitBreakerConfig>);
    /**
     * Execute an operation with circuit breaker protection.
     *
     * `operation` is handed a `recordResolvedFailure` callback so it can flag a
     * *resolved* result as a logical failure without throwing. This matters for
     * MCP tool calls: the client does not throw on a protocol error, it
     * resolves with `{ isError: true, ... }`. Before this callback existed,
     * such a call always fell through to the success path below — the breaker
     * could never open for a tool that only ever "fails" by resolving an error
     * result, and callers still need that resolved value returned as-is (not
     * replaced by a thrown transport error). Call `recordResolvedFailure()`
     * from inside `operation` when that resolved value represents a failure;
     * the call is still counted as a normal, non-throwing success from the
     * `Promise.race` below, so this callback is what tells `execute()`
     * otherwise. Callers that never call it see no behavior change.
     */
    execute<T>(operation: (recordResolvedFailure: (reason?: string) => void) => Promise<T>): Promise<T>;
    /**
     * Shared bookkeeping for a failed outcome — a thrown error, or a resolved
     * result the caller flagged via `recordResolvedFailure`. Records the call
     * as a failure, emits `callFailure`, and runs the state transitions that
     * used to live inline in the `catch` block: half-open failure immediately
     * re-opens the circuit; closed checks the failure threshold.
     */
    private recordFailureOutcome;
    /**
     * Record a call in the history
     */
    private recordCall;
    /**
     * Check if failure threshold is exceeded
     */
    private checkFailureThreshold;
    /**
     * Change circuit breaker state
     */
    private changeState;
    /**
     * Race an operation against a timeout, clearing the timer on either
     * outcome. A bare `Promise.race([operation, timeoutPromise])` leaves the
     * timeout's `setTimeout` handle ref'd and pending until it fires even
     * after `operation` already won the race — on the (common) success path
     * that stray timer holds the event loop open for the full timeout
     * duration for no reason.
     */
    private raceWithTimeout;
    /**
     * Clean up old call records
     */
    private cleanupCallHistory;
    /**
     * Get current statistics
     */
    getStats(): CircuitBreakerStats;
    /**
     * Manually reset the circuit breaker
     */
    reset(): void;
    /**
     * Force open the circuit breaker
     */
    forceOpen(reason?: string): void;
    /**
     * Get circuit breaker name
     */
    getName(): string;
    /**
     * Check if circuit is open
     */
    isOpen(): boolean;
    /**
     * Check if circuit is closed
     */
    isClosed(): boolean;
    /**
     * Check if circuit is half-open
     */
    isHalfOpen(): boolean;
    /**
     * Destroy the circuit breaker and clean up resources
     * This method should be called when the circuit breaker is no longer needed
     * to prevent memory leaks from the cleanup timer
     */
    destroy(): void;
}
/**
 * Circuit breaker manager for multiple circuit breakers
 */
export declare class CircuitBreakerManager {
    private breakers;
    /**
     * Get or create a circuit breaker
     */
    getBreaker(name: string, config?: Partial<CircuitBreakerConfig>): MCPCircuitBreaker;
    /**
     * Remove a circuit breaker and clean up its resources
     */
    removeBreaker(name: string): boolean;
    /**
     * Get all circuit breaker names
     */
    getBreakerNames(): string[];
    /**
     * Get statistics for all circuit breakers
     */
    getAllStats(): Record<string, CircuitBreakerStats>;
    /**
     * Reset all circuit breakers
     */
    resetAll(): void;
    /**
     * Get health summary
     */
    getHealthSummary(): {
        totalBreakers: number;
        closedBreakers: number;
        openBreakers: number;
        halfOpenBreakers: number;
        unhealthyBreakers: string[];
    };
    /**
     * Destroy all circuit breakers and clean up their resources
     * This should be called during application shutdown to prevent memory leaks
     */
    destroyAll(): void;
}
export declare const globalCircuitBreakerManager: CircuitBreakerManager;