import type { List } from ".";
import type { Concat } from "./Concat";
import type { Args, Cons, Fn } from "../HKT";
import type { Broaden } from "../helpers";
import type { Semigroup, TypeClass$$Semigroup } from "../typeclass";

declare module "../typeclass/Semigroup" {
  interface SemigroupImpl {
    List: ImplSemigroupForGeneric<List, List$$Semigroup$$Relaxer, List$$Semigroup$$Builder>;
  }
}

interface List$$Semigroup$$Relaxer extends Fn<[List<unknown>], List<Cons<unknown>>> {
  def: ([xs]: Args<this>) => List<Broaden<(typeof xs)[number]>>;
}

interface List$$Semigroup$$Builder
  extends Fn<[List<Cons<unknown>>], List$$Semigroup<Cons<unknown>>> {
  def: ([xsCons]: Args<this>) => List$$Semigroup<(typeof xsCons)[number]>;
}

/**
 * Implementation of the {@link Semigroup} type class for {@link List}.
 */
export interface List$$Semigroup<T> extends TypeClass$$Semigroup<List<T>> {
  Concat: List$$Semigroup$ConcatFn<T>;
}

/**
 * [Fn] Concatenate two {@link List}s holding the same type.
 *
 * Sig: `<T>(xs: List<T>, ys: List<T>) => List<T>`
 */
interface List$$Semigroup$ConcatFn<T> extends Fn<[List<T>, List<T>], List<T>> {
  def: ([xs, ys]: Args<this>) => Concat<typeof xs, typeof ys>;
}