/**
 * Zero-dependency metrics primitives that render to the Prometheus text
 * exposition format. Counters, gauges and histograms with labels — enough to
 * drive a `/metrics` endpoint or push to any Prometheus-compatible scraper,
 * without pulling a client library.
 */
export type Labels = Record<string, string>;
export declare abstract class Metric {
    readonly name: string;
    readonly help: string;
    readonly labelNames: string[];
    abstract readonly type: 'counter' | 'gauge' | 'histogram';
    constructor(name: string, help: string, labelNames?: string[]);
    abstract render(): string;
    protected header(): string;
}
export declare class Counter extends Metric {
    readonly type: 'counter';
    private readonly series;
    inc(labels?: Labels, value?: number): void;
    render(): string;
}
export declare class Gauge extends Metric {
    readonly type: 'gauge';
    private readonly series;
    private mutate;
    set(value: number, labels?: Labels): void;
    inc(labels?: Labels, value?: number): void;
    dec(labels?: Labels, value?: number): void;
    render(): string;
}
export declare const DEFAULT_BUCKETS: number[];
export declare class Histogram extends Metric {
    readonly type: 'histogram';
    private readonly series;
    readonly buckets: number[];
    constructor(name: string, help: string, labelNames?: string[], buckets?: number[]);
    observe(value: number, labels?: Labels): void;
    render(): string;
}
export interface MetricOptions {
    help?: string;
    labelNames?: string[];
}
/** A collection of metrics that renders them all in Prometheus text format. */
export declare class MetricsRegistry {
    private readonly metrics;
    private getOrCreate;
    counter(name: string, options?: MetricOptions): Counter;
    gauge(name: string, options?: MetricOptions): Gauge;
    histogram(name: string, options?: MetricOptions & {
        buckets?: number[];
    }): Histogram;
    /** Prometheus text exposition (content-type text/plain; version=0.0.4). */
    render(): string;
}