namespace Library;

public class Calculations
{
    public static string[] AvailablePeriods(
        TimeSpan[] startTimes,
        int[] durations,
        TimeSpan beginWorkingTime,
        TimeSpan endWorkingTime,
        int consultationTime)
    {
        var busy = new List<(DateTime Start, DateTime End)>();
        for (int i = 0; i < startTimes.Length; i++)
        {
            var start = DateTime.Today.Add(startTimes[i]);
            var end = start.AddMinutes(durations[i]);
            busy.Add((start, end));
        }

        var workStart = DateTime.Today.Add(beginWorkingTime);
        var workEnd = DateTime.Today.Add(endWorkingTime);

        var result = new List<string>();
        var current = workStart;

        while (current.AddMinutes(consultationTime) <= workEnd)
        {
            var slotEnd = current.AddMinutes(consultationTime);

            bool isOverlapping = busy.Any(b =>
                current < b.End && slotEnd > b.Start
            );

            if (!isOverlapping)
            {
                result.Add($"{current:HH:mm}-{slotEnd:HH:mm}");
            }

            current = slotEnd;
        }

        return result.ToArray();
    }
}