import type { Result } from ".";
import type { Ok } from "./core";
import type { Args, GenericFn, GenericResolver } from "../HKT";
import type { AssertUnknown } from "../helpers";

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

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

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