using System;
using System.Collections.Generic;
using System.Linq;

namespace LCU.Api.Internal.DispatcherSharedLib.Utilities;

public static class HolidayHelpers
{
    public static DateTime? HandleHolidays(DateTime? nextRunTime)
    {
        if (nextRunTime != null)
        {
            List<DateTime> holidays = GetHolidays(nextRunTime.Value.Year);
            var today = Convert.ToDateTime(nextRunTime).Date;
            var isHoliday = holidays.Where(x => today == x).Any();

            if (isHoliday)
            {
                nextRunTime = nextRunTime.Value.AddDays(1);
            }
        }
        return nextRunTime;
    }

    private static List<DateTime> GetHolidays(int year)
    {
        List<DateTime> holidays = new List<DateTime>
        {
            GetNewYearsDay(year),
            GetMemorialDay(year),
            GetIndependenceDay(year),
            GetLaborDay(year),
            GetThanksgivingDay(year),
            GetChristmasDay(year)
        };

        return holidays;
    }

    ///<summary> New Years Day - Jan 1st </summary>
    public static DateTime GetNewYearsDay(int year)
    {
        return new DateTime(year, 1, 1).Date;
    }

    ///<summary> Memorial Day - last Monday in May </summary>
    public static DateTime GetMemorialDay(int year)
    {
        DateTime memorialDay = new DateTime(year, 5, 31);
        var dayOfWeek = memorialDay.DayOfWeek;
        while (dayOfWeek != DayOfWeek.Monday)
        {
            memorialDay = memorialDay.AddDays(-1);
            dayOfWeek = memorialDay.DayOfWeek;
        }
        return memorialDay.Date;
    }

    ///<summary> Independence Day - July 4th </summary>
    public static DateTime GetIndependenceDay(int year)
    {
        return new DateTime(year, 7, 4).Date;
    }

    ///<summary> Labor Day -- 1st Monday in September </summary>
    public static DateTime GetLaborDay(int year)
    {
        DateTime laborDay = new DateTime(year, 9, 1);
        var dayOfWeek = laborDay.DayOfWeek;
        while (dayOfWeek != DayOfWeek.Monday)
        {
            laborDay = laborDay.AddDays(1);
            dayOfWeek = laborDay.DayOfWeek;
        }
        return laborDay.Date;
    }

    ///<summary> Thanksgiving Day - 4th Thursday in November </summary>
    public static DateTime GetThanksgivingDay(int year)
    {
        var thanksgiving = (from day in Enumerable.Range(1, 30)
                            where new DateTime(year, 11, day).DayOfWeek == DayOfWeek.Thursday
                            select day).ElementAt(3);
        return new DateTime(year, 11, thanksgiving).Date;
    }

    ///<summary> Christmas Day - Dec 25th </summary>
    public static DateTime GetChristmasDay(int year)
    {
        return new DateTime(year, 12, 25).Date;
    }
}