import type { ReadonlyAry } from ".";
import type { Args, GenericFn, GenericResolver } from "../HKT";

/**
 * Build a readonly array from a type.
 *
 * Sig: `<T>(x: T) => ReadonlyArray<T>`
 *
 * @example
 * ```typescript
 * type R1 = OfReadonly<number>;
 * //   ^?: readonly number[]
 * type R2 = OfReadonly<42>;
 * //   ^?: readonly (42 | string)[]
 * ```
 */
export type OfReadonly<T> = readonly T[];

interface Resolver extends GenericResolver<[unknown], ReadonlyAry<unknown>> {
  on1: ([x]: Args<this>) => [[], ReadonlyAry<typeof x>];
}

/**
 * [Fn] Build a readonly array from a type.
 *
 * Sig: `<T>(x: T) => ReadonlyArray<T>`
 */
export default interface OfReadonlyFn extends GenericFn<Resolver> {
  def: ([x]: Args<this>) => OfReadonly<typeof x>;
}