import type { Request, Response, NextFunction } from 'express';
import { Registry, Gauge } from 'prom-client';
/**
 * Register the `secret_rotation_previous_set{secret}` gauge on `registry`: 1
 * while a secret's `*_PREVIOUS` rotation value is still set, 0 otherwise. The
 * value is read from api-core's probe registry at scrape time, so it always
 * reflects the live process. Exported so platform (own registry) exposes the
 * identical series; the `SecretRotationPreviousLingering` alert keys on it.
 */
export declare function registerSecretRotationGauge(registry: Registry): Gauge<'secret'>;
/**
 * Express middleware that records request duration and count.
 *
 * Must be registered before route handlers so `res.on('finish')` fires
 * after the response is sent.
 */
export declare function metricsMiddleware(): (req: Request, res: Response, next: NextFunction) => void;
/**
 * Express handler that returns Prometheus metrics in text exposition format.
 */
export declare function metricsHandler(): (_req: Request, res: Response) => Promise<void>;
/**
 * Increment a business counter, creating it on first use.
 *
 * @example
 * ```typescript
 * incCounter('pipelines_generated_total', { provider: 'anthropic' });
 * incCounter('plugin_builds_total', { status: 'completed' });
 * incCounter('quota_threshold_crossed_total', { type: 'aiCalls', tier: 'pro' });
 * incCounter('compliance_violations_found_total', { severity: 'critical' });
 * ```
 */
export declare function incCounter(name: string, labels?: Record<string, string>, value?: number): void;
/**
 * Record an observation on a business histogram, creating it on first use.
 * Use for durations, sizes, anything where percentiles matter.
 *
 * @example
 * ```typescript
 * observe('ai_generation_duration_seconds', { provider: 'anthropic', model: 'sonnet' }, durationSec);
 * observe('plugin_build_duration_seconds', { buildType: 'docker' }, durationSec);
 * ```
 */
export declare function observe(name: string, labels: Record<string, string>, value: number): void;
/**
 * Set the value of a business gauge, creating it on first use. Use for
 * point-in-time observations sampled by a scraper — queue depth, active
 * connection counts, in-flight requests.
 *
 * @example
 * ```typescript
 * setGauge('plugin_queue_jobs', { queue: 'plugin-build', state: 'waiting' }, 12);
 * setGauge('plugin_queue_jobs', { queue: 'plugin-build', state: 'active' }, 3);
 * ```
 */
export declare function setGauge(name: string, labels: Record<string, string>, value: number): void;