import type { Args, GenericFn, GenericResolver } from "../HKT";
import type { Eq, IsPropertyKeyLiteral } from "../helpers";

/**
 * Omit properties from an object.
 *
 * Sig: `<K extends keyof O, O extends object>(k: K, o: O) => object`
 */
// We do not use the built-in `Omit` type because it does not keep the readonly modifier.
export type Omit<K extends keyof O, O> = {
  [P in keyof O as P extends K ? never : P]: O[P];
};

interface Resolver extends GenericResolver<[PropertyKey, object], object> {
  on1_: ([k]: Args<this>) => [[{ readonly [P in typeof k]: any }], object];
  on_1: ([, o]: Args<this>) => [[keyof typeof o], object];
  on11: ([k, o]: Args<this>) => typeof k extends PropertyKey ?
    [
      [],
      IsPropertyKeyLiteral<typeof k> extends true ?
        { [P in keyof typeof o as P extends typeof k ? never : P]: (typeof o)[P] } extends infer R ?
          Eq<R, typeof o> extends true ?
            typeof o
          : R
        : never
      : object,
    ]
  : never;
}

/**
 * [Fn] Omit properties from an object.
 *
 * Sig: `<K extends keyof O, O extends object>(k: K, o: O) => object`
 */
export default interface OmitFn extends GenericFn<Resolver> {
  def: ([k, o]: Args<this>) => {
    [P in keyof typeof o as P extends typeof k ? never : P]: (typeof o)[P];
  };
}