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

/**
 * @name subHours
 * @category Hour Helpers
 * @summary Subtract the specified number of hours from the given date.
 *
 * @description
 * Subtract the specified number of hours from the given date.
 *
 * ### v2.0.0 breaking changes:
 *
 * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
 *
 * @param {Date|Number} date - the date to be changed
 * @param {Number} amount - the amount of hours to be subtracted. 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 subtracted
 * @throws {TypeError} 2 arguments required
 *
 * @example
 * // Subtract 2 hours from 11 July 2014 01:00:00:
 * const result = subHours(new Date(2014, 6, 11, 1, 0), 2)
 * //=> Thu Jul 10 2014 23:00:00
 */
export default function subHours(dirtyDate: Date | number, dirtyAmount: number) {
  requiredArgs(2, arguments)

  const amount = toInteger(dirtyAmount)
  return addHours(dirtyDate, -amount)
}