declare const counter: <A extends number | bigint>(key: MetricKey.MetricKey.Counter<A>) => MetricHook.Counter<A>

declare const frequency: (_key: MetricKey.MetricKey.Frequency) => MetricHook.Frequency

declare const gauge: {
  (key: MetricKey.MetricKey.Gauge<number>, startAt: number): MetricHook.Gauge<number>
  (key: MetricKey.MetricKey.Gauge<bigint>, startAt: bigint): MetricHook.Gauge<bigint>
}

declare const histogram: (key: MetricKey.MetricKey.Histogram) => MetricHook.Histogram

declare const make: <In, Out>(options: {
  readonly get: LazyArg<Out>
  readonly update: (input: In) => void
  readonly modify: (input: In) => void
}) => MetricHook<In, Out>

declare const summary: (key: MetricKey.MetricKey.Summary) => MetricHook.Summary

export interface MetricHook<in In, out Out> extends MetricHook.Variance<In, Out>, Pipeable {
  get(): Out
  update(input: In): void
  modify(input: In): void
}

declare const MetricHookTypeId: unique symbol

type MetricHookTypeId = typeof MetricHookTypeId

export interface Variance<in In, out Out> {
  readonly [MetricHookTypeId]: {
    readonly _In: Types.Contravariant<In>
    readonly _Out: Types.Covariant<Out>
  }
}

type Root = MetricHook<any, MetricState.MetricState.Untyped>

type Untyped = MetricHook<any, any>

type Counter<A> = MetricHook<A, MetricState.MetricState.Counter<A>>

type Gauge<A> = MetricHook<A, MetricState.MetricState.Gauge<A>>

type Frequency = MetricHook<string, MetricState.MetricState.Frequency>

type Histogram = MetricHook<number, MetricState.MetricState.Histogram>

type Summary = MetricHook<readonly [number, number], MetricState.MetricState.Summary>

declare const onModify: {
  <In, Out>(f: (input: In) => void): (self: MetricHook<In, Out>) => MetricHook<In, Out>
  <In, Out>(self: MetricHook<In, Out>, f: (input: In) => void): MetricHook<In, Out>
}

declare const onUpdate: {
  <In, Out>(f: (input: In) => void): (self: MetricHook<In, Out>) => MetricHook<In, Out>
  <In, Out>(self: MetricHook<In, Out>, f: (input: In) => void): MetricHook<In, Out>
}