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

import type { ReadonlyRecord, URI, V } from "./model";

/*
 * -------------------------------------------
 * Functor Record
 * -------------------------------------------
 */

/**
 * ```haskell
 * mapWithIndex_ :: (FunctorWithIndex f, Index k) => (f a, ((k, a) -> b)) -> f b
 * ```
 *
 * Map a record passing the keys to the iterating function
 *
 * @category FunctorWithIndex
 * @since 1.0.0
 */
export const mapWithIndex_ = <N extends string, A, B>(
   fa: ReadonlyRecord<N, A>,
   f: (k: N, a: A) => B
): ReadonlyRecord<N, B> => {
   const out = {} as Record<N, B>;
   const keys = Object.keys(fa);
   for (let i = 0; i < keys.length; i++) {
      const k = keys[i] as keyof typeof fa;
      out[k] = f(k, fa[k]);
   }
   return out;
};

/**
 * ```haskell
 * mapWithIndex_ :: (FunctorWithIndex f, Index k) => ((k, a) -> b) -> f a -> f b
 * ```
 *
 * Map a record passing the keys to the iterating function
 *
 * @category FunctorWithIndex
 * @since 1.0.0
 */
export const mapWithIndex = <N extends string, A, B>(f: (k: N, a: A) => B) => (
   fa: ReadonlyRecord<N, A>
): ReadonlyRecord<N, B> => mapWithIndex_(fa, f);

/**
 * ```haskell
 * map_ :: Functor f => (f a, (a -> b)) -> f b
 * ```
 *
 * Map a record passing the values to the iterating function
 *
 * @category Functor
 * @since 1.0.0
 */
export const map_ = <N extends string, A, B>(fa: ReadonlyRecord<N, A>, f: (a: A) => B): ReadonlyRecord<N, B> =>
   mapWithIndex_(fa, (_, a) => f(a));

/**
 * ```haskell
 * map :: Functor f => (a -> b) -> f a -> f b
 * ```
 *
 * Map a record passing the values to the iterating function
 *
 * @category Functor
 * @since 1.0.0
 */
export const map = <A, B>(f: (a: A) => B) => <N extends string>(fa: ReadonlyRecord<N, A>): ReadonlyRecord<N, B> =>
   map_(fa, f);

export const Functor: P.Functor<[URI], V> = HKT.instance({
   map,
   map_: map_
});

export const FunctorWithIndex: P.FunctorWithIndex<[URI], V> = HKT.instance({
   ...Functor,
   mapWithIndex,
   mapWithIndex_: mapWithIndex_
});