PayrollYearInfo.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using PayrollYear = System.Int32;
using PayperiodNumber = System.Int32;

namespace TAS.SQL_DAL
{
    public class PayrollYearInfo
    {
        // i used the year 1950 because this is the furthest back I could find information
        // about federal payperiods.  the first day of the first pay period in 1950 was
        // 1950/01/08.

        private static Dictionary<PayrollYear, PayrollYearInfo> yearCache = new Dictionary<PayrollYear, PayrollYearInfo>();

        private static DateTime genesis = new DateTime(1950, 1, 8);
        private static int surplusDaysAtGenesis = 7;


        private Dictionary<PayperiodNumber, PayPeriodInfo> periodCache = new Dictionary<PayperiodNumber, PayPeriodInfo>();

        private PayrollYearInfo previousYear;
        private PayrollYearInfo nextYear;

        private PayrollYearInfo(PayrollYear year)
        {
            PayrollYear = year;
        }

        public static PayrollYearInfo GetPayrollYearInfo(PayrollYear year)
        {
            lock (yearCache)
            {
                if (!yearCache.ContainsKey(year))
                    yearCache[year] = new PayrollYearInfo(year);
            }

            return yearCache[year];
        }

        public int PayrollYear { get; private set; }

        public PayrollYearInfo Previous
        {
            get
            {
                if (previousYear == null)
                    previousYear = GetPayrollYearInfo(PayrollYear - 1);

                return previousYear;
            }
        }

        public PayrollYearInfo Next
        {
            get
            {
                if (nextYear == null)
                    nextYear = GetPayrollYearInfo(PayrollYear + 1);

                return nextYear;
            }
        }

        public int YearsSinceGenesis { get { return PayrollYear - genesis.Year; } }
        public int SurplusDays { get { return YearsSinceGenesis + LeapDaysSinceGenesis + surplusDaysAtGenesis; } }
        public int AdditionalPayPeriods { get { return SurplusDays / 14; } }
        public int PayPeriods { get { return Next.ElapsedPayPeriods - ElapsedPayPeriods; } }
        public int DaysSinceGenesis { get { return ElapsedPayPeriods * 14; } }
        public DateTime FirstDayOfPayrollYear { get { return genesis.AddDays(DaysSinceGenesis); } }

        public int LeapDaysSinceGenesis
        {
            get
            {
                return (YearsSinceGenesis + 2) / 4 - (YearsSinceGenesis + 50) / 100 + (YearsSinceGenesis + 350) / 400;
            }
        }

        public int ElapsedPayPeriods
        {
            get
            {
                if (PayrollYear <= 1950) return 0;
                return 26 * YearsSinceGenesis + Previous.AdditionalPayPeriods;
            }
        }
    }
}