/**
 * Some utils for manipulating dates
 *
 * **WARNING** experimental
 */

/**
 * Return the date to local ISO date, like YYYY-mm-dd
 *
 * The date is valid for the same timezone as the date's locale
 *
 * Do not take time into account
 *
 */
const dateToISO = (date) => {
  if (null === date) {
    return null;
  }

  return [
    date.getFullYear(),
    (date.getMonth() + 1).toString().padStart(2, '0'),
    date.getDate().toString().padStart(2, '0')
  ].join('-');
};

/**
 * Return a date object from iso string formatted as YYYY-mm-dd
 *
 * **Experimental**
 */
const ISOToDate = (str) => {
  let
    [year, month, day] = str.split('-');
      
  return new Date(year, month-1, day);
}

/**
 * Return a date object from iso string formatted as YYYY-mm-dd:HH:MM:ss+01:00
 *
 */
const ISOToDatetime = (str) => {
  if (null === str) {
    return null;
  }

  let 
    [cal, times] = str.split('T'),
    [year, month, date] = cal.split('-'),
    [time, timezone] = cal.split(times.charAt(9)),
    [hours, minutes, seconds] = cal.split(':')
  ;

  return new Date(year, month-1, date, hours, minutes, seconds);
}

/**
 * Convert a date to ISO8601, valid for usage in api
 * 
 */
const datetimeToISO = (date) => {
  let cal, time, offset;
  cal = [
    date.getFullYear(),
    (date.getMonth() + 1).toString().padStart(2, '0'),
    date.getDate().toString().padStart(2, '0')
  ].join('-');
  
  time = [
    date.getHours().toString().padStart(2, '0'),
    date.getMinutes().toString().padStart(2, '0'),
    date.getSeconds().toString().padStart(2, '0')
  ].join(':');

  offset = [
    date.getTimezoneOffset() <= 0 ? '+' : '-',
    Math.abs(Math.floor(date.getTimezoneOffset() / 60)).toString().padStart(2, '0'),
    ':',
    Math.abs(date.getTimezoneOffset() % 60).toString().padStart(2, '0'),
  ].join('');
  
  let x = cal + 'T' + time + offset;

  return x;
};

export {
  dateToISO,
  ISOToDate,
  ISOToDatetime,
  datetimeToISO
};