using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        DateTime now = new DateTime(2025,2,10,5,0,1);

        DateTime nextdate = new DateTime(2025,2,10,5,0,1);

        bool b;

        int.TryParse("0", out  int unit); // 1 – Sekunden, 2 – Minuten, 3 – Stunden, 4 - Tage, 5 - Woche, 6 - Monate, 7 - Quartal, 8 - Jahr 

​

        int.TryParse("0", out  int interval);

​

        int.TryParse("420", out int endmin);

​

        int.TryParse("900", out int startmin);

​

        int.TryParse("3", out int startday);

​

        int.TryParse("5", out int periode); // 1 – Sekunden, 2 – Minuten, 3 – Stunden, 4 - Tage, 5 - Woche, 6 - Monate, 7 - Quartal, 8 - Jahr 

​

​

​

        switch (unit)

        {

            case 1:

                nextdate = nextdate.AddSeconds(interval);

                break;

            case 2:

                nextdate = nextdate.AddMinutes(interval);

                break;

            case 3:

                nextdate = nextdate.AddHours(interval);

                break;

            case 4:

                nextdate = nextdate.AddDays(interval);

                break;

            case 5:

                nextdate = nextdate.AddDays(interval * 7);

                break;

            case 6:                                

                nextdate = nextdate.AddMonths(interval); 

                break;

            case 7:

                nextdate = nextdate.AddMonths(interval * 3);

                break;

            case 8:                                

                nextdate = nextdate.AddYears(interval);

                break;

            default:

                nextdate = DateTime.MaxValue;

                break;

        }

​

        switch (periode)

        {

            case 4:

                if (nextdate > now.Date.AddMinutes(endmin))

                {

                    nextdate = now.Date.AddDays(1).AddMinutes(startmin);

                    b = true;

                }

​

                break;

            case 5:

                int c = CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(now, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

                int nc = CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(nextdate, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

                if (nc > c)

                {

                    int nday = (int)now.DayOfWeek;

                    if (nday == 0) nday = 7;

                    nextdate = now.AddDays(7 - nday).AddDays(startday); //???

                    b = true;

                }

                Console.WriteLine(c);

                Console.WriteLine(nc);

                break;

            case 6:

​

                if (nextdate.Month > now.Month)

                {

                    nextdate = nextdate.AddDays(startday).AddMinutes(startmin); //AddMonths(1)

                    b = true;

                }

​

                break;

            case 7:

                if ((int)((nextdate.Month + 2) / 3) > (int)((now.Month + 2) / 3))

                {                                        

                    int nmonth = ((int)(((now.Month + 2) / 3) + 1) * 3 - 2) % 12;

                    int nyear = DateTime.Now.Year;

                    if (nmonth == 1) nyear++;

                    nextdate = new DateTime(nyear,nmonth,startday).AddMinutes(startmin);

                    b = true;

                }

                break;

            case 8:

                if (nextdate.Year > now.Year)

                {

                    nextdate = nextdate.AddYears(1).AddDays(startday).AddMinutes(startmin);

                    b = true;

                }

​

                break;

            default:

                nextdate = DateTime.MaxValue;

                break;

        }

        Console.WriteLine(nextdate);

        /*DateTime now = new DateTime(2025,2,12);

        DateTime nextdate = DateTime.MaxValue;

        //nextdate = nextdate.AddDays(7);

         int c = CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(now, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

         int nc = CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(nextdate, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);      

        if (nc > c)

        {

            int nday = (int)now.DayOfWeek;

            Console.WriteLine(nday);

            if (nday == 0) nday = 7;

            nextdate = now.AddDays(7 - nday).AddDays(3);

        }    

        Console.WriteLine(c);

        Console.WriteLine(nc);

        Console.WriteLine(nextdate);*/

    }

}