// @ts-ignore - Only used in doc comments
import type { Merge } from "./Merge";
// @ts-ignore - Only used in doc comments
import type MergeFn from "./Merge";
import type { Args, Fn } from "../HKT";

type _Id<O> = { [K in keyof O]: O[K] };

/**
 * Simply merge two objects together without considering optional properties.
 *
 * It is recommended to use to optimize performance when you're sure that
 * the two objects have no optional properties, otherwise use {@link Merge}.
 *
 * Sig: `(l: object, r: object) => object`
 *
 * @example
 * ```typescript
 * type A = { a: number; b: string };
 * type B = { a: boolean; c: string };
 * type R = SimpleMerge<A, B>;
 * //   ^?: { a: boolean; b: string; c: string }
 * ```
 *
 * @see {@link Merge}
 */
export type SimpleMerge<L extends object, R extends object> = _Id<{
  [K in keyof L | keyof R]: K extends keyof R ? R[K]
  : K extends keyof L ? L[K]
  : never;
}>;

/**
 * Fn] Simply merge two objects together without considering optional properties.
 *
 * It is recommended to use to optimize performance when you're sure that
 * the two objects have no optional properties, otherwise use {@link MergeFn}.
 *
 * Sig: `(l: object, r: object) => object`
 *
 * @see {@link MergeFn}
 */
export default interface SimpleMergeFn extends Fn<[object, object], object> {
  def: ([l, r]: Args<this>) => SimpleMerge<typeof l, typeof r>;
}