// `lodash/debounce` has a non-trivial implementation which can lead to
// [flaky spec errors][1]. This mock simply makes `debounce` calls synchronous.
//
// In the future we could enhance this by injecting some test values in
// the function passed to it. See [this issue][2] for more information.
//
// [1]: https://gitlab.com/gitlab-org/gitlab/-/issues/212532
// [2]: https://gitlab.com/gitlab-org/gitlab/-/issues/213378
// Further reference: https://github.com/facebook/jest/issues/3465

export default (fn) => {
  let id;
  const debouncedFn = jest.fn(function run(...args) {
    // this is calculated in runtime so beforeAll hook works in tests
    const timeout = global.JEST_DEBOUNCE_THROTTLE_TIMEOUT;
    if (timeout) {
      id = setTimeout(() => {
        fn.apply(this, args);
      }, timeout);
    } else {
      fn.apply(this, args);
    }
  });
  debouncedFn.cancel = jest.fn(() => {
    clearTimeout(id);
  });
  debouncedFn.flush = jest.fn(() => {
    const errorMessage =
      "The .flush() method returned by lodash.debounce is not yet implemented/mocked by the mock in 'spec/frontend/__mocks__/lodash/debounce.js'.";

    throw new Error(errorMessage);
  });

  return debouncedFn;
};