using System;

public class Program

{

    public static void Main()

    {

        //(bool isDue, bool isOverdue) result1 = ChecklistAuditStatusCalculator.Calculate(new DateTime(2020,01,01), new Date(2020,01,01), (30,0)); // Due 30 days before, Overdue on date

        DateTime now = new DateTime(2020,02,03);

        DateTime due = new DateTime(2020,02,01);

        int dueOffset = 10;

        int overdueOffset = -1;

        Console.WriteLine(ChecklistAuditStatusCalculator.IsDue(now, due, dueOffset, overdueOffset));

        Console.WriteLine(ChecklistAuditStatusCalculator.IsOverdue(now, due, dueOffset, overdueOffset));

    }

}

​

​

​

​

public static class ChecklistAuditStatusCalculator

{

    private static (bool isDue, bool isOverdue) InProgress => (false, false);

    private static (bool isDue, bool isOverdue) Due => (true, false);

    private static (bool isDue, bool isOverdue) Overdue => (false, true);

    public static (bool isDue, bool isOverdue) Calculate(DateTime utcNow, DateTime? dueDate, (int dueOffset, int overdueOffset) offsets) {

        if (dueDate == null) return InProgress;

        DateTime due = dueDate.Value;

​

        // Becomes due if due date and now are the same month, overdue if due is in the past

        if (offsets.dueOffset == 0 && offsets.overdueOffset == 0) {

            if (due < utcNow) return Overdue;

            if (due.Year == utcNow.Year && due.Month == utcNow.Month) return Due;

        }

        else {

            // Becomes due if due date < now plus offset, overdue if due is in the past plus offset

            if (due.AddDays(offsets.overdueOffset*-1) < utcNow) return Overdue;

            if (due.AddDays(offsets.dueOffset*-1) < utcNow) return Due;

        }

​

        return InProgress;

    }

    public static bool IsOverdue(DateTime utcNow, DateTime? dueDate, int dueOffset, int overdueOffset)

    {

        var x = Calculate(utcNow, dueDate, (dueOffset, overdueOffset));

        return x.isOverdue;

    }

    public static bool IsDue(DateTime utcNow, DateTime? dueDate, int dueOffset, int overdueOffset)

    {

        var x = Calculate(utcNow, dueDate, (dueOffset, overdueOffset));

        return x.isDue;

    }

}