let handleError: (() => boolean) | undefined;
let lastTime = 0;

function createExpBackoffTimer(step: number) {
  let count = 1;
  return function (reset?: boolean) {
    // Reset call
    if (reset) {
      count = 1;
      return 0;
    }
    // Calculate next timeout
    const timeout = Math.pow(2, count - 1);
    if (count < 5) count += 1;
    return timeout * step;
  };
}

const nextErrorTimeout = createExpBackoffTimer(5000);

function postError(message: string) {
  if (handleError && !handleError()) return;
  window.postMessage(
    {
      source: '@devtools-page',
      type: 'ERROR',
      message: message,
    },
    '*',
  );
}

function catchErrors(e: ErrorEvent) {
  if (
    (window.devToolsOptions && !window.devToolsOptions.shouldCatchErrors) ||
    e.timeStamp - lastTime < nextErrorTimeout()
  ) {
    return;
  }
  lastTime = e.timeStamp;
  nextErrorTimeout(true);
  postError(e.message);
}

export default function notifyErrors(onError?: () => boolean) {
  handleError = onError;
  window.addEventListener('error', catchErrors, false);
}