const CONFIRM_ATTR = 'data-confirm-message';

const isSubmitControl = (element) => {
  if (!(element instanceof HTMLElement)) {
    return false;
  }
  if (element instanceof HTMLButtonElement) {
    const type = String(element.getAttribute('type') || 'submit').trim().toLowerCase();
    return type === '' || type === 'submit';
  }
  if (element instanceof HTMLInputElement) {
    const type = String(element.type || '').trim().toLowerCase();
    return type === 'submit' || type === 'image';
  }
  return false;
};

const submitterByForm = new Map();

const onClickCapture = (event) => {
  const trigger = event.target instanceof HTMLElement ? event.target.closest('a, button, input') : null;
  if (!(trigger instanceof HTMLElement)) {
    return;
  }

  if (isSubmitControl(trigger)) {
    const form = trigger.form instanceof HTMLFormElement ? trigger.form : null;
    if (form) {
      submitterByForm.set(form, trigger);
    }
    return;
  }

  const confirmMessage = String(trigger.getAttribute(CONFIRM_ATTR) || '').trim();
  if (confirmMessage === '') {
    return;
  }

  if (!window.confirm(confirmMessage)) {
    event.preventDefault();
    event.stopPropagation();
  }
};

const onSubmitCapture = (event) => {
  const form = event.target instanceof HTMLFormElement ? event.target : null;
  if (!(form instanceof HTMLFormElement)) {
    return;
  }

  const submitter = event.submitter instanceof HTMLElement
    ? event.submitter
    : (submitterByForm.get(form) || null);
  submitterByForm.delete(form);

  const submitterMessage = String(submitter?.getAttribute(CONFIRM_ATTR) || '').trim();
  const formMessage = String(form.getAttribute(CONFIRM_ATTR) || '').trim();
  const confirmMessage = submitterMessage !== '' ? submitterMessage : formMessage;

  if (confirmMessage === '') {
    return;
  }
  if (!window.confirm(confirmMessage)) {
    event.preventDefault();
    event.stopPropagation();
  }
};

document.addEventListener('click', onClickCapture, true);
document.addEventListener('submit', onSubmitCapture, true);