/**
 * Applicable is a structure that allows a function to be applied inside of the
 * associated concrete structure. For example, `Option` may hold a value of
 * `(a: A) => B` inside of it. An Applicable for Option would allow one to
 * apply the `A` in an `Option<A>` to the function `(a: A) => B` in an
 * `Option<(a: A) => B>`, resulting in an `Option<B>`.
 *
 * @module Applicable
 * @since 2.0.0
 */

import type { $, Hold, Kind } from "./kind.ts";
import type { Combinable } from "./combinable.ts";
import type { Mappable } from "./mappable.ts";
import type { Wrappable } from "./wrappable.ts";

/**
 * The Applicable interface. This interface includes the methods apply, map, and
 * wrap.
 *
 * @since 2.0.0
 */
export interface Applicable<
  U extends Kind,
> extends Mappable<U>, Wrappable<U>, Hold<U> {
  readonly apply: <
    A,
    B = never,
    C = never,
    D = unknown,
    E = unknown,
  >(
    ta: $<U, [A, B, C], [D], [E]>,
  ) => <
    I,
    J = never,
    K = never,
    L = unknown,
  >(
    tfai: $<U, [(value: A) => I, J, K], [L], [E]>,
  ) => $<U, [I, B | J, C | K], [D & L], [E]>;
}

/**
 * Create a Combinable instance for an Applicable structure given a Combinable for the inner type.
 *
 * @example
 * ```ts
 * import * as A from "./applicable.ts";
 * import * as O from "./option.ts";
 * import * as N from "./number.ts";
 *
 * const combinableOption = A.getApplicableCombinable(O.ApplicableOption)(N.CombinableNumberSum);
 *
 * const result = combinableOption.combine(O.some(2))(O.some(3)); // Some(5)
 * ```
 *
 * @since 2.0.0
 */
export function getApplicableCombinable<U extends Kind>(
  { apply, map }: Applicable<U>,
): <A, B = never, C = never, D = unknown, E = unknown>(
  combinable: Combinable<A>,
) => Combinable<$<U, [A, B, C], [D], [E]>> {
  return <A, B = never, C = never, D = unknown, E = unknown>(
    { combine }: Combinable<A>,
  ): Combinable<$<U, [A, B, C], [D], [E]>> => {
    const _map = map(combine);
    return {
      combine: (second) => (first) => apply(first)(_map(second)),
    };
  };
}