/**
 * Helper function to pluck out a dataset JSON key
 *
 * @param {Object} obj An object with JSON strings as values
 * @param {string} keyName The key to pluck from the object
 * @return {Object} An object with keyName as key and parsed JSON as value
 */
const pluckJsonKey = (obj, keyName) => (obj[keyName] ? { [keyName]: JSON.parse(obj[keyName]) } : {});

/**
 * Helper function to get the tracking attribute values from a DOM element
 * and return them mapped to a trackingData object
 *
 * @param {HTMLElement} el An HTML element to inspect, for example
 * @return {Object}
 */
const getTrackingDataObject = el => {
  const { dataset } = el;
  const href = el.getAttribute('href') || el.getAttribute('formAction');
  const defaultServices = { amplitude: true, ga: true };

  const trackingDataObject = {
    href,
    isSameTabLink: Boolean(href && el.getAttribute('target') !== '_blank'),
    trackingData: {
      services: (dataset.trackingServices && JSON.parse(dataset.trackingServices)) || defaultServices,
      ...pluckJsonKey(dataset, 'track'),
      ...pluckJsonKey(dataset, 'page'),
      ...pluckJsonKey(dataset, 'identify'),
    },
  };

  return trackingDataObject;
};

export { getTrackingDataObject };