import type { Args, Fn } from "../HKT";
import type { Nat } from "../Num";
import type { Compare } from "../Num/Compare";
import type { Inc } from "../Num/Int/Inc";
import type { EQ, GT } from "../typeclass/Ord";

/**
 * Create a union of a range of numbers from `From` to `To` (exclusive).
 *
 * Sig: `(from: Nat, to: Nat) => UnionOf<Nat>`
 */
export type RangeOf<From extends Nat, To extends Nat> =
  Compare<From, To> extends GT | EQ ? never
  : From | RangeOf<From extends Nat ? Inc<From> : never, To>;

/**
 * [Fn] Create a union of a range of numbers from `from` to `to` (exclusive).
 *
 * Sig: `(from: Nat, to: Nat) => UnionOf<Nat>`
 */
export default interface RangeOfFn extends Fn<[Nat, Nat], Nat> {
  def: ([from, to]: Args<this>) => RangeOf<typeof from, typeof to>;
}