type t = string | number;
type fn = () => t[];

export function duplicate(matches: t[] | fn, ignoreCase: boolean = false) {
  if (Array.isArray(matches)) return factory(matches, ignoreCase);

  return value => {
    let cb = factory(matches(), ignoreCase);
    return cb(value);
  };
}

function factory(values: t[], ignoreCase: boolean) {
  return value => {
    if (value === undefined || value === null || values.length === 0)
      return true;
    else{
      let flags = ignoreCase ? "i" : "";
      let exp = new RegExp(`^(${value})$`, flags);
      return values.find(o => exp.test(o.toString())) === undefined;
    }
  };
}