using System;

namespace TestInput
{
    public class Tester
    {
        public static bool IsInteger(string p)
        {
            bool result = false;
            int i;

            if (int.TryParse(p, out i))
            {
                result = true;
            }

            return result;
        }

        public static bool IsDate(string p)
        {
            bool result = false;
            DateTime dt;

            if (DateTime.TryParse(p, out dt))
            {
                result = true;
            }

            return result;
        }

        public static int GetDifferenceInYears(DateTime startDate, DateTime endDate)
        {
            //Excel documentation says "COMPLETE calendar years in between dates"
            int years = endDate.Year - startDate.Year;

            if (startDate.Month == endDate.Month &&// if the start month and the end month are the same
                endDate.Day < startDate.Day// AND the end day is less than the start day
                || endDate.Month < startDate.Month)// OR if the end month is less than the start month
            {
                years--;
            }

            return years;
        }

        public static bool IsDateAndLiesInTheFuture(string sDT)
        {
            bool result = false;

            if (IsDate(sDT))
            {
                DateTime dtParsed = DateTime.Parse(sDT);

                if (dtParsed > DateTime.Now)
                {
                    result = true;
                }
            }

            return result;
        }

        public static bool IsDateAndLiesInThePast(string sDT)
        {
            bool result = false;

            if (IsDate(sDT))
            {
                DateTime dtParsed = DateTime.Parse(sDT);

                if (dtParsed < DateTime.Now)
                {
                    result = true;
                }
            }

            return result;
        }

        public static int DaysTillNextBirthday(DateTime dateOfBirth)
        {
            //full days (whole, 24-hr periods) until next birthday...
            int result = 0;
            DateTime dtToday = DateTime.Now;
            DateTime dtNextBirthday = new DateTime(dtToday.Year, dateOfBirth.Month, dateOfBirth.Day);
            TimeSpan tsDifference = dtNextBirthday - dtToday;

            if (tsDifference.Days < 0)
            {
                //already had birthday this year
                tsDifference = dtNextBirthday.AddYears(1) - dtToday;
            }
            result = tsDifference.Days;
            return result;
        }
    }

}