using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var workingRosterStart = DateTime.Today.AddHours(12);

        var workingRosterEnd = DateTime.Today.AddHours(20);

        var validRanges = GetPartialTurndownAvailableOffsets(workingRosterStart, workingRosterEnd);

        foreach(var k in validRanges)

        {

            Console.WriteLine(string.Format("{0}, {1}", k.Item1.ToString(), k.Item2.ToString()));

        }

        var bidStart = DateTime.Today.AddHours(17);

        var bidEnd = DateTime.Today.AddHours(20);

        var valid = ValidatePartialTurndownWithinPossibleHours(workingRosterStart, workingRosterEnd, bidStart, bidEnd);

        Console.WriteLine(valid);

    }

    public static List<Tuple<DateTime, DateTime>> GetPartialTurndownAvailableOffsets(DateTime start, DateTime end)

    {

        var partialTurndownAvailableOffsets = new List<Tuple<DateTime, DateTime>>();

​

        var scheduledHours = (end - start).TotalHours;

        var partialTurndownBlockSize = 1;

        var minimumPartialTurndownSize = 4;

​

        for (int hour = partialTurndownBlockSize; hour < scheduledHours; hour += partialTurndownBlockSize)

        {

            if (hour >= minimumPartialTurndownSize)

            {

                partialTurndownAvailableOffsets.Add(new (start, start.AddHours(hour)));

                partialTurndownAvailableOffsets.Add(new (end.AddHours(-1 * hour), end));

            }

        }

        return partialTurndownAvailableOffsets;

    }

    private static bool ValidatePartialTurndownWithinPossibleHours(DateTime workingRosterStart, DateTime workingRosterEnd, DateTime bidStartTime, DateTime bidEndTime)

    {

        var offsetList = GetPartialTurndownAvailableOffsets(workingRosterStart, workingRosterEnd);

        return offsetList.Contains(new (bidStartTime, bidEndTime));

    }

}