import { getExplicitRole } from '../../commons/aria';

/**
 * A map from HTML tag names to a boolean which reflects whether it is
 * appropriate for scrollable elements found in the focus order.
 */
const VALID_TAG_NAMES_FOR_SCROLLABLE_REGIONS = {
  ARTICLE: true,
  ASIDE: true,
  NAV: true,
  SECTION: true
};

/**
 * A map from each landmark role to a boolean which reflects whether it is
 * appropriate for scrollable elements found in the focus order.
 */
const VALID_ROLES_FOR_SCROLLABLE_REGIONS = {
  application: true,
  banner: false,
  complementary: true,
  contentinfo: true,
  form: true,
  main: true,
  navigation: true,
  region: true,
  search: false
};

/**
 * @param {HTMLElement} node
 * @return {Boolean} Whether the element has a tag appropriate for a scrollable
 *		 region.
 */
function validScrollableTagName(node) {
  // Some elements with nonsensical roles will pass this check, but should be
  // flagged by other checks.
  const nodeName = node.nodeName.toUpperCase();
  return VALID_TAG_NAMES_FOR_SCROLLABLE_REGIONS[nodeName] || false;
}

/**
 * @param {HTMLElement} node
 * @return {Boolean} Whether the node has a role appropriate for a scrollable
 *		 region.
 */
function validScrollableRole(node, options) {
  var role = getExplicitRole(node);
  if (!role) {
    return false;
  }
  return (
    VALID_ROLES_FOR_SCROLLABLE_REGIONS[role] ||
    options.roles.includes(role) ||
    false
  );
}

/**
 * Check if the element has a valid scrollable role or tag.
 *
 * @memberof checks
 * @param {HTMLElement} node
 * @return {Boolean} True if the elements role or tag name is a valid scrollable region. False otherwise.
 */
function validScrollableSemanticsEvaluate(node, options) {
  return validScrollableRole(node, options) || validScrollableTagName(node);
}

export default validScrollableSemanticsEvaluate;