import { ILogger } from './types';
export type CircuitState = 'closed' | 'open' | 'half-open';
export interface CircuitBreakerOptions {
    failureThreshold: number;
    resetTimeoutMs: number;
    logger: ILogger;
    onStateChange?: (state: CircuitState, failures: number) => void;
}
/**
 * Circuit breaker to prevent cascading failures when the feature flag API is down.
 *
 * States:
 *  - CLOSED: Requests pass through. Failures increment counter.
 *  - OPEN:   Requests are rejected immediately. After resetTimeoutMs, transitions to HALF-OPEN.
 *  - HALF-OPEN: One probe request is allowed. Success → CLOSED, failure → OPEN.
 */
export declare class CircuitBreaker {
    private state;
    private failures;
    private lastFailureTime;
    private readonly options;
    constructor(options: CircuitBreakerOptions);
    getState(): CircuitState;
    getFailures(): number;
    /**
     * Execute a function through the circuit breaker.
     * If the circuit is open, throws immediately.
     * If the circuit is half-open, allows one probe request.
     */
    execute<T>(fn: () => Promise<T>): Promise<T>;
    /**
     * Manually reset the circuit to closed state.
     */
    reset(): void;
    private onSuccess;
    private onFailure;
    private shouldAttemptReset;
    private transitionTo;
}
/**
 * Error thrown when the circuit breaker is open and rejecting requests.
 */
export declare class CircuitOpenError extends Error {
    readonly name = "CircuitOpenError";
    constructor(message: string);
}