import toInteger from '../_lib/toInteger/index'
import addMilliseconds from '../addMilliseconds/index'
import requiredArgs from '../_lib/requiredArgs/index'

const MILLISECONDS_IN_HOUR = 3600000

/**
 * @name addHours
 * @category Hour Helpers
 * @summary Add the specified number of hours to the given date.
 *
 * @description
 * Add the specified number of hours to the given date.
 *
 * @param {Date|Number} date - the date to be changed
 * @param {Number} amount - the amount of hours to be added. Positive decimals will be rounded using `Math.floor`, decimals less than zero will be rounded using `Math.ceil`.
 * @returns {Date} the new date with the hours added
 * @throws {TypeError} 2 arguments required
 *
 * @example
 * // Add 2 hours to 10 July 2014 23:00:00:
 * const result = addHours(new Date(2014, 6, 10, 23, 0), 2)
 * //=> Fri Jul 11 2014 01:00:00
 */
export default function addHours(
  dirtyDate: Date | number,
  dirtyAmount: number
): Date {
  requiredArgs(2, arguments)

  const amount = toInteger(dirtyAmount)
  return addMilliseconds(dirtyDate, amount * MILLISECONDS_IN_HOUR)
}