import type { Option } from ".";
import type { Args, Fn, GenericFn, GenericResolver } from "../HKT";
import type { AssertBool, IsNever, Lazied, Lazied$Get } from "../helpers";

/**
 * A type that represents a value that exists (compared to {@link None}).
 */
export interface Some<T> {
  readonly _tag: "Some";
  readonly value: T;
}
/**
 * {@link Lazied} version of {@link Some}.
 */
export interface SomeL<L extends Lazied> extends Some<Lazied$Get<L>> {}

/**
 * A type that represents a value that does not exist (compared to {@link Some}).
 */
export interface None {
  readonly _tag: "None";
}

/**
 * Wrap a value in a {@link Some}.
 *
 * Sig: `<T>(value: T) => Some<T>`
 */
export type OfSome<T> = Some<T>;

interface OfSomeFnResolver extends GenericResolver<[unknown], Some<unknown>> {
  on1: ([x]: Args<this>) => [[], Some<typeof x>];
}

/**
 * [Fn] Wrap a value in a {@link Some}.
 *
 * Sig: `<T>(value: T) => Some<T>`
 */
export interface OfSomeFn extends GenericFn<OfSomeFnResolver> {
  def: ([o]: Args<this>) => OfSome<typeof o>;
}

/**
 * Check if an {@link Option} is {@link Some}.
 *
 * Sig: `(o: Option<unknown>) => boolean`
 */
export type IsSome<O extends Option<unknown>> = AssertBool<
  IsNever<O> extends true ? never
  : O["_tag"] extends "Some" ? true
  : O["_tag"] extends "None" ? false
  : boolean
>;
/**
 * [Fn] Check if an {@link Option} is {@link Some}.
 *
 * Sig: `(o: Option<unknown>) => boolean`
 */
export interface IsSomeFn extends Fn<[Option<unknown>], boolean> {
  def: ([o]: Args<this>) => IsSome<typeof o>;
}

/**
 * Check if an {@link Option} is {@link None}.
 *
 * Sig: `(o: Option<unknown>) => boolean`
 */
export type IsNone<O extends Option<unknown>> = AssertBool<
  IsNever<O> extends true ? never
  : O["_tag"] extends "None" ? true
  : O["_tag"] extends "Some" ? false
  : boolean
>;
/**
 * [Fn] Check if an {@link Option} is {@link None}.
 *
 * Sig: `(o: Option<unknown>) => boolean`
 */
export interface IsNoneFn extends Fn<[Option<unknown>], boolean> {
  def: ([o]: Args<this>) => IsNone<typeof o>;
}