/**
 * Circuit Breaker Pattern
 *
 * Prevents cascade failures by failing fast when a service is unhealthy.
 * States: CLOSED (normal) → OPEN (failing fast) → HALF_OPEN (testing recovery)
 *
 * @module utils/circuit-breaker
 */
import { VeryfrontError } from "../errors/types.js";
type CircuitState = "CLOSED" | "OPEN" | "HALF_OPEN";
interface CircuitBreakerOptions {
    /** Failures before opening (default: 5) */
    failureThreshold?: number;
    /** Ms to wait before retry (default: 30000) */
    resetTimeoutMs?: number;
    /** Successes to close (default: 3) */
    successThreshold?: number;
    /** Optional name for logging */
    name?: string;
}
/**
 * Thrown when an operation is attempted while the circuit breaker is open.
 *
 * Extends {@link VeryfrontError} so it carries registry slug/status/category
 * and RFC-9457 fields, while remaining `instanceof CircuitBreakerOpen` for
 * existing catch sites.
 */
export declare class CircuitBreakerOpen extends VeryfrontError {
    readonly breakerName: string;
    readonly nextAttemptMs: number;
    constructor(breakerName: string, nextAttemptMs: number);
}
export declare class CircuitBreaker {
    private state;
    private failureCount;
    private successCount;
    private lastFailureTime;
    private halfOpenAttempts;
    private readonly failureThreshold;
    private readonly resetTimeoutMs;
    private readonly successThreshold;
    private readonly breakerName;
    constructor(options?: CircuitBreakerOptions);
    /** Execute operation through circuit breaker. Throws CircuitBreakerOpen if open. */
    execute<T>(operation: () => Promise<T>, options?: {
        isNeutralError?: (error: unknown) => boolean;
    }): Promise<T>;
    private recordSuccess;
    private recordFailure;
    private transitionTo;
    getState(): CircuitState;
    /** Get the last activity time (failure or success) */
    getLastActivityTime(): number;
    /** Update last activity time on use */
    touch(): void;
}
export declare function getCircuitBreaker(name: string, options?: Omit<CircuitBreakerOptions, "name">): CircuitBreaker;
export {};
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