import type { Args, Fn } from "../HKT";
import type { List } from "../List";
import type { Assert } from "../helpers";

/**
 * Returns a list of characters of a string.
 *
 * Sig: `(s: string) => List<string>`
 */
export type ToChars<S extends string> = Assert<
  List<string>,
  string extends S ? List<string>
  : S extends `${infer Head}${infer Tail}` ? readonly [Head, ...ToChars<Tail>]
  : readonly []
>;

/**
 * [Fn] Returns a list of characters of a string.
 *
 * Sig: `(s: string) => List<string>`
 */
export default interface ToCharsFn extends Fn<[string], List<string>> {
  def: ([s]: Args<this>) => ToChars<typeof s>;
}