const isBaseFocusable = (element: Element): boolean => {
  if (element.hasAttribute('disabled')) {
    return false;
  }

  const nodeName = element.nodeName.toLowerCase();
  const validInput = nodeName === 'input' && element.getAttribute('type') !== 'hidden';
  const validAnchor = nodeName === 'a' && element.hasAttribute('href');
  const validAudioVideo = ['audio', 'video'].includes(nodeName) && element.hasAttribute('controls');
  const validImgObject = ['img', 'object'].includes(nodeName) && element.hasAttribute('usemap');
  const validNativelyFocusable = [
    'button',
    'details',
    'embed',
    'iframe',
    'select',
    'textarea',
  ].includes(nodeName);

  const hasTabIndex = element.getAttribute('tabindex') === '0';

  return (
    validInput ||
    validAnchor ||
    validAudioVideo ||
    validImgObject ||
    validNativelyFocusable ||
    hasTabIndex
  );
};

/**
 * Is an element focusable? This function performs various tests to see if the element in question
 * can receive focus via a pointer. Should skip disabled elements as they are not focusable.
 */
export const isMouseFocusable = isBaseFocusable;

/**
 * Is an element focusable? This function performs various tests to see if the element in question
 * can receive focus via the keyboard. Should skip disabled elements as they are not focusable.
 */
export const isKeyboardFocusable = (element: Element): boolean => {
  return isBaseFocusable(element) && element.getAttribute('tabindex') !== '-1';
};

/**
 * @deprecated Use `isMouseFocusable` for mouse events and `isKeyboardFocusable` for keyboard
 * events. `isFocusable` is an alias to `isKeyboardFocusable`
 */
export const isFocusable = isKeyboardFocusable;

/**
 * Get the first focusable element in a container.
 *
 * Returns an array of elements if the first focusable element is a radio group
 */
export const getFirstFocusableElement = (
  container: HTMLElement
): Element[] | HTMLElement | null => {
  const elements = container.querySelectorAll('*');

  for (let i = 0; i < elements.length; i++) {
    const element = elements.item(i);
    if (element && isKeyboardFocusable(element)) {
      if (isRadioInput(element)) {
        const radioGroup = getRadioGroup(container, element);

        return radioGroup.length > 1 ? Array.from(radioGroup) : element;
      }
      return element as HTMLElement;
    }
  }

  return null;
};

const isRadioInput = (element: Element): element is HTMLInputElement => {
  return element.nodeName.toLowerCase() === 'input' && element.getAttribute('type') === 'radio';
};

const getRadioGroup = (
  container: HTMLElement,
  element: HTMLInputElement
): NodeListOf<HTMLInputElement> => {
  return container.querySelectorAll(`input[type="radio"][name="${element.getAttribute('name')}"]`);
};

/**
 * Get the last focusable element in a container.
 *
 * Returns an array of elements if the last focusable element is a radio group
 */
export const getLastFocusableElement = (container: HTMLElement): Element[] | Element | null => {
  const elements = container.querySelectorAll('*');

  for (let i = elements.length - 1; i >= 0; i--) {
    const element = elements.item(i);
    if (element && isKeyboardFocusable(element)) {
      if (isRadioInput(element)) {
        const radioGroup = getRadioGroup(container, element);

        return radioGroup.length > 1 ? Array.from(radioGroup) : element;
      }
      return element as HTMLElement;
    }
  }

  return null;
};