conditional.ts

interface Conditional<T> {
  then: (expr: () => T) => Conditional<T>;
  fail: (expr: () => T) => Conditional<T>;
  result: () => T | undefined;
}

export default function cond<T>(condition: boolean): Conditional<T> {
  let res: T | undefined;

  return {
    then(expr) {
      if (condition) {
        res = expr();
      }
      return this;
    },
    fail(expr) {
      if (!condition) {
        res = expr();
      }
      return this;
    },
    result: () => res,
  };
}