import type { Option, Some } from ".";
import type { Args, GenericFn, GenericResolver } from "../HKT";
import type { AssertUnknown } from "../helpers";

/**
 * Get the inner value of an {@link Option} if it is {@link Some}, otherwise return `never`.
 *
 * Type safety is **not guaranteed**.
 *
 * Sig: `<T>(o: Option<T>) => T`
 */
export type Unwrap<O extends Option<unknown>> = AssertUnknown<O extends Some<infer T> ? T : never>;

interface Resolver extends GenericResolver<[Option<unknown>], unknown> {
  on1: ([o]: Args<this>) => [[], typeof o extends Option<infer T> ? T : never];
}

/**
 * [Fn] Get the inner value of an {@link Option} if it is {@link Some}, otherwise return `never`.
 *
 * Type safety is **not guaranteed**.
 *
 * Sig: `<T>(o: Option<T>) => T`
 */
export default interface UnwrapFn extends GenericFn<Resolver> {
  def: ([o]: Args<this>) => Unwrap<typeof o>;
}