using System;

namespace HRM.BO
{
    public struct DateDifferenceInYearsMonthDays
    {
        private readonly int years;
        private readonly int months;
        private readonly int days;
        private readonly int hours;
        private readonly int minutes;
        private readonly int seconds;
        private readonly int milliseconds;

        public DateDifferenceInYearsMonthDays(int years, int months, int days, int hours, int minutes, int seconds,
            int milliseconds)
        {
            this.years = years;
            this.months = months;
            this.days = days;
            this.hours = hours;
            this.minutes = minutes;
            this.seconds = seconds;
            this.milliseconds = milliseconds;
        }

        public int Years
        {
            get { return years; }
        }

        public int Months
        {
            get { return months; }
        }

        public int Days
        {
            get { return days; }
        }

        public int Hours
        {
            get { return hours; }
        }

        public int Minutes
        {
            get { return minutes; }
        }

        public int Seconds
        {
            get { return seconds; }
        }

        public int Milliseconds
        {
            get { return milliseconds; }
        }

        enum Phase
        {
            Years,
            Months,
            Days,
            Done
        }

        public static DateDifferenceInYearsMonthDays CompareDates(DateTime date1, DateTime date2)
        {
            if (date2 < date1)
            {
                DateTime sub = date1;
                date1 = date2;
                date2 = sub;
            }

            DateTime current = date2;
            int years = 0;
            int months = 0;
            int days = 0;

            Phase phase = Phase.Years;
            DateDifferenceInYearsMonthDays span = new DateDifferenceInYearsMonthDays();

            while (phase != Phase.Done)
            {
                switch (phase)
                {
                    case Phase.Years:
                        if (current.Year == 1 || current.AddYears(-1) < date1)
                        {
                            phase = Phase.Months;
                        }
                        else
                        {
                            current = current.AddYears(-1);
                            years++;
                        }

                        break;
                    case Phase.Months:
                        if (current.AddMonths(-1) < date1)
                        {
                            phase = Phase.Days;
                        }
                        else
                        {
                            current = current.AddMonths(-1);
                            months++;
                        }

                        break;
                    case Phase.Days:
                        if (current.AddDays(-1) < date1)
                        {
                            days++;
                            TimeSpan timespan = current - date1;
                            span = new DateDifferenceInYearsMonthDays(years, months, days, timespan.Hours,
                                timespan.Minutes, timespan.Seconds, timespan.Milliseconds);
                            phase = Phase.Done;
                        }
                        else
                        {
                            current = current.AddDays(-1);
                            days++;
                        }

                        break;
                }
            }

            return span;
        }
    }
}