import type { Args, Call0, Call1, Call1W, Fn, Fn0, Fn1, GenericReturn1W, Param0 } from "./HKT";

/**
 * Sig: `<T, OnTrueResult, OnFalseResult>[pred: (x: T) => boolean, onTrue: (x: T) => OnTrueResult, onFalse: (x: T) => OnFalseResult](x: T) => OnTrueResult | OnFalseResult`
 */
export interface IfElse<
  Pred extends Fn1<never, boolean>,
  OnTrue extends Fn0 | Fn1<Param0<Pred>>,
  OnFalse extends Fn0 | Fn1<Param0<Pred>>,
> extends Fn<
    [Param0<Pred>],
    | (OnTrue extends Fn0<infer R> ? R : GenericReturn1W<OnTrue, Param0<Pred>>)
    | (OnFalse extends Fn0<infer R> ? R : GenericReturn1W<OnFalse, Param0<Pred>>)
  > {
  def: ([x]: Args<this>) => Call1<Pred, typeof x> extends true ?
    OnTrue extends Fn0 ?
      Call0<OnTrue>
    : Call1W<OnTrue, typeof x>
  : OnFalse extends Fn0 ? Call0<OnFalse>
  : Call1W<OnFalse, typeof x>;
}