import type { Args, Fn1 } from "../HKT";
import type { Nat } from "../Num";
import type { Inc } from "../Num/Int/Inc";
import type { AssertNat } from "../helpers";

/**
 * Get the length of a string.
 *
 * Sig: `(s: string) => Nat`
 */
export type Length<S extends string> = AssertNat<
  S extends `${string}${infer R}` ? Inc<Length<R>> : 0
>;

/**
 * [Fn] Get the length of a string.
 *
 * Sig: `(s: string) => Nat`
 */
export default interface LengthFn extends Fn1<string, Nat> {
  def: ([s]: Args<this>) => Length<typeof s>;
}