DateTime.copyWith.dart

extension DateTimeX<T extends DateTime> on T {
  DateTime copyWith({
    int year,
    int month,
    int day,
    int hour,
    int minute,
    int second,
    int millisecond,
    int microsecond,
  }) {
    return DateTime(
      year ?? this.year,
      month ?? this.month,
      day ?? this.day,
      hour ?? this.hour,
      minute ?? this.minute,
      second ?? this.second,
      millisecond ?? this.millisecond,
      microsecond ?? this.microsecond,
    );
  }

  /// Last day of this month
  DateTime lastDay() => nextMonths().copyWith(day: 0);

  DateTime lastDaySecond() => nextMonths().copyWith(
    day: 1,
    hour: 0,
    minute: 0,
    second: -1,
    millisecond: 0,
    microsecond: 0,
  );

  /// Last day moment of this month
  ///
  /// Equivalent to first day moment of next month - 1 microsecond
  DateTime lastDayMoment() => nextMonths().copyWith(
      day: 1,
      hour: 0,
      minute: 0,
      second: 0,
      millisecond: 0,
      microsecond: -1,
  );

  DateTime firstDay() => copyWith(day: 1);

  /// First day moment of this month
  DateTime firstDayMoment() => copyWith(
    day: 1,
    hour: 0,
    minute: 0,
    second: 0,
    millisecond: 0,
    microsecond: 0,
  );

  /// Last moment today
  ///
  /// Equivalent to tomorrow first moment - 1 microsecond
  DateTime lastMoment() => copyWith(
    day: day + 1,
    hour: 0,
    minute: 0,
    second: 0,
    millisecond: 0,
    microsecond: -1,
  );

  /// First moment today
  DateTime firstMoment() => copyWith(
    hour: 0,
    minute: 0,
    second: 0,
    millisecond: 0,
    microsecond: 0,
  );

  /// 1234567
  ///       ^
  DateTime firstWeekday([int end]) => copyWith(
    day: day - (DurationX.daysPerWeek) + 1,
  );

  DateTime firstWeekdayMoment([int end]) => copyWith(
    day: day - (DurationX.daysPerWeek) + 1,
    hour: 0,
    minute: 0,
    second: 0,
    millisecond: 0,
    microsecond: 0,
  );

  /// TODO end weekday
  DateTime lastWeekday([int end]) => copyWith(
    day: day + (DurationX.daysPerWeek) - 1,
  );

  /// TODO end weekday
  DateTime lastWeekdayMoment([int end]) => copyWith(
    day: day + (DurationX.daysPerWeek),
    hour: 0,
    minute: 0,
    second: 0,
    millisecond: 0,
    microsecond: -1,
  );

  /// expect(3/31.monthAgo(), 2/29)
  DateTime monthsAgo([int months = 1]) => copyWith(month: month - months).coerceAtMost(copyWith(month: month - months + 1, day: 0));
  /// expect(1/31.nextMonth(), 2/29)
  DateTime nextMonths([int months = 1]) => copyWith(month: month + months).coerceAtMost(copyWith(month: month + months + 1, day: 0));

  DateTime yearsAgo([int years = 1]) => copyWith(year: year - years);
  DateTime nextYears([int years = 1]) => copyWith(year: year + years);

  DateTime weeksAgo([int weeks = 1]) => copyWith(day: day - (weeks * DurationX.daysPerWeek));
  DateTime nextWeeks([int weeks = 1]) => copyWith(day: day + (weeks * DurationX.daysPerWeek));

  DateTime yesterday() => daysAgo();
  DateTime tomorrow() => nextDays();

  DateTime daysAgo([int days = 1]) => copyWith(day: day - days);

  DateTime nextDays([int days = 1]) => copyWith(day: day + days);

  DateTimeRange hours({ bool inclusive = true }) => inclusive
      ? firstMoment().rangeTo(tomorrow().firstMoment(), step: 1.hours)
      : firstMoment().rangeTo(lastMoment(), step: 1.hours);

  /// 1234567
  /// ^
  DateTimeRange weekdays({ bool inclusive = true }) => inclusive
      ? firstMoment().rangeTo(nextWeeks().firstMoment(), step: 1.days)
      : firstMoment().rangeTo(lastWeekdayMoment(), step: 1.days);
}