var getISOYear = require('../get_iso_year/index.js')
var setISOYear = require('../set_iso_year/index.js')

/**
 * @category ISO Week-Numbering Year Helpers
 * @summary Add the specified number of ISO week-numbering years to the given date.
 *
 * @description
 * Add the specified number of ISO week-numbering years to the given date.
 *
 * ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
 *
 * @param {Date|String|Number} date - the date to be changed
 * @param {Number} amount - the amount of ISO week-numbering years to be added
 * @returns {Date} the new date with the ISO week-numbering years added
 *
 * @example
 * // Add 5 ISO week-numbering years to 2 July 2010:
 * var result = addISOYears(new Date(2010, 6, 2), 5)
 * //=> Fri Jun 26 2015 00:00:00
 */
function addISOYears (dirtyDate, dirtyAmount) {
  var amount = Number(dirtyAmount)
  return setISOYear(dirtyDate, getISOYear(dirtyDate) + amount)
}

module.exports = addISOYears