import type * as P from "@principia/prelude";
import * as HKT from "@principia/prelude/HKT";

import { flow } from "../Function";
import { getLeft, getRight } from "./combinators";
import { none } from "./constructors";
import { map_ } from "./functor";
import { isNone } from "./guards";
import type { URI, V } from "./model";

/*
 * -------------------------------------------
 * Witherable Option
 * -------------------------------------------
 */

export const wither_: P.WitherFn_<[URI], V> = (A) => (wa, f) =>
   isNone(wa) ? A.map_(A.unit(), () => none()) : f(wa.value);

export const wither: P.WitherFn<[URI], V> = (A) => (f) => (wa) => wither_(A)(wa, f);

export const wilt_: P.WiltFn_<[URI], V> = (A) => (wa, f) => {
   const o = map_(
      wa,
      flow(
         f,
         A.map((e) => ({
            left: getLeft(e),
            right: getRight(e)
         }))
      )
   );
   return isNone(o)
      ? A.map_(A.unit(), () => ({
           left: none(),
           right: none()
        }))
      : o.value;
};

export const wilt: P.WiltFn<[URI], V> = (A) => (f) => (wa) => wilt_(A)(wa, f);

export const Witherable: P.Witherable<[URI], V> = HKT.instance({
   wilt_,
   wither_,
   wilt,
   wither
});