import { showValue } from '..';
import { expected, success } from '../result';
import { create, Codec } from '../runtype';
import { parenthesize } from '../show';

export interface KeyOf<TObject extends Object> extends Codec<keyof TObject> {
  readonly tag: 'keyOf';
  readonly keys: Set<string>;
}

export function KeyOf<TObject extends Object>(object: TObject): KeyOf<TObject> {
  const keys = new Set(Object.keys(object));
  const name = [...keys]
    .sort()
    .map(k => showValue(k))
    .join(` | `);
  return create<KeyOf<TObject>>(
    'keyOf',
    value =>
      keys.has(typeof value === 'number' ? value.toString() : (value as any))
        ? success(value as any)
        : expected(name, value),
    {
      keys,
      show: needsParens => parenthesize(name, needsParens),
    },
  );
}