/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict
 */

export type Check<+T> = (val: mixed, name?: string) => Error | T;
export type InferCheckType<T> = T extends Check<infer U> ? U : empty;

type Msg = (value: mixed, name?: string) => string;
type PrimitiveChecker<+T> = (message?: Msg) => Check<T>;

declare export const string: PrimitiveChecker<string>;

declare export const nullish: PrimitiveChecker<null | void>;

declare export const optional: <T>(Check<T>) => Check<void | T>;

declare export const boolean: PrimitiveChecker<boolean>;

declare export const number: PrimitiveChecker<number>;

declare export const func: <T: Function>(msg?: Msg) => Check<T>;

declare export const literal: <T: string | number | boolean>(
  T,
  msg?: Msg,
) => Check<T>;

declare export const array: <T>(
  Check<T>,
  msg?: Msg,
) => Check<$ReadOnlyArray<T>>;

type ObjOfChecks<T: { +[string]: Check<mixed> }> = $ReadOnly<{
  [K in keyof T]: InferCheckType<T[K]>,
}>;

declare export const object: <T: { +[string]: Check<mixed> }>(
  T,
  msg?: Msg,
) => Check<ObjOfChecks<T>>;

declare export const objectOf: <T>(
  Check<T>,
  message?: Msg,
) => Check<{ +[string]: T }>;

declare export const unionOf: <A, B>(
  a: Check<A>,
  b: Check<B>,
  message?: Msg,
) => Check<A | B>;

declare export const unionOf3: <A, B, C>(
  a: Check<A>,
  b: Check<B>,
  c: Check<C>,
  message?: Msg,
) => Check<A | B | C>;

declare export const unionOf4: <A, B, C, D>(
  a: Check<A>,
  b: Check<B>,
  c: Check<C>,
  d: Check<D>,
  message?: Msg,
) => Check<A | B | C | D>;

declare export const logAndDefault: <T>(
  check: Check<T>,
  value: mixed,
  def: T,
  name?: string,
) => T;