Type-Safe Functional Error Handling using Result Wrappers

type Ok<T> = { readonly success: true; readonly value: T };
type Err<E> = { readonly success: false; readonly error: E };
type Result<T, E> = Ok<T> | Err<E>;
 
function ok<T>(value: T): Ok<T> {
  return { success: true, value };
}
 
function err<E>(error: E): Err<E> {
  return { success: false, error };
}
 
function parsePort(input: string): Result<number, string> {
  const parsed = Number(input);
  if (Number.isNaN(parsed) || parsed < 1 || parsed > 65535) {
    return err(`Invalid port number: '${input}'`);
  }
  return ok(parsed);
}