using System;
using System.Threading;
using System.Globalization;
using System.Collections.Generic;

namespace App
{
    class Program
    {
        static void Main(string[] args)
        {
            Thread.CurrentThread.CurrentCulture = new CultureInfo("pt-BR");
            //Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");

            //Adicionando dias, contemplando apenas os dias úteis.
            DateTime data = DateTime.Now.AddWorkDays(3);

            //Adicionando dias, contemplando apenas dias úteis e definindo uma condição
            //que determina se o dia inicial deve estar contemplado no cálculo.
            //DateTime data = DateTime.Now.AddWorkDays(3, d => d.Hour > 12);

            //Verificando se é ou não feriado.
            DateTime temp = new DateTime(2008, 12, 25);
            Console.WriteLine(temp.IsHoliday());
        }
    }

    public static class CultureInfoHelper
    {
        public static DateTime[] GetHolidays(this CultureInfo value, int year)
        {
            List<DateTime> holidays = new List<DateTime>();
            holidays.Add(new DateTime(year, 12, 25));
            holidays.Add(new DateTime(year, 1, 1));

            switch (value.Name)
            {
                case "pt-BR":
                    holidays.Add(new DateTime(year, 5, 1));   //Dia do Trabalho
                    holidays.Add(new DateTime(year, 7, 9));   //Revolução (Somente SP)
                    holidays.Add(new DateTime(year, 9, 7));   //Independencia do Brasil
                    holidays.Add(new DateTime(year, 11, 2));  //Finados
                    holidays.Add(new DateTime(year, 11, 15)); //Proclamação da República
                    break;
                case "en-US":
                    holidays.Add(new DateTime(year, 7, 4));   //Independencia dos EUA
                    break;
            }

            return holidays.ToArray();
        }
    }

    public static class DateTimeHelper
    {
        public static DateTime AddWorkDays(this DateTime value, int quantityOfDaysToAdd)
        {
            return AddWorkDays(value, quantityOfDaysToAdd, true, Thread.CurrentThread.CurrentCulture.GetHolidays(value.Year));
        }

        public static DateTime AddWorkDays(this DateTime value, int quantityOfDaysToAdd, bool startInCurrentDay)
        {
            return AddWorkDays(value, quantityOfDaysToAdd, startInCurrentDay, Thread.CurrentThread.CurrentCulture.GetHolidays(value.Year));
        }

        public static DateTime AddWorkDays(this DateTime value, int quantityOfDaysToAdd, Predicate<DateTime> conditionToStartInCurrentDay)
        {
            return AddWorkDays(value, quantityOfDaysToAdd, conditionToStartInCurrentDay(value), Thread.CurrentThread.CurrentCulture.GetHolidays(value.Year));
        }

        public static DateTime AddWorkDays(this DateTime value, int quantityOfDaysToAdd, Predicate<DateTime> conditionToStartInCurrentDay, DateTime[] holidays)
        {
            return AddWorkDays(value, quantityOfDaysToAdd, conditionToStartInCurrentDay(value), holidays);
        }

        public static DateTime AddWorkDays(this DateTime value, int quantityOfDaysToAdd, bool startInCurrentDay, DateTime[] holidays)
        {
            if (quantityOfDaysToAdd < 0)
                throw new ArgumentOutOfRangeException("quantityOfDaysToAdd", "A quantidade deve ser maior que 0.");

            if (startInCurrentDay) 
                value = value.AddDays(-1);

            while (quantityOfDaysToAdd >= 0)
            {
                value = value.AddDays(1);

                if (value.IsHoliday(holidays))
                    value = value.AddDays(1);

                if (value.DayOfWeek != DayOfWeek.Sunday && value.DayOfWeek != DayOfWeek.Saturday)
                    quantityOfDaysToAdd--;
            }

            return value;
        }

        public static bool IsHoliday(this DateTime value)
        {
            return IsHoliday(value, Thread.CurrentThread.CurrentCulture.GetHolidays(value.Year));
        }

        public static bool IsHoliday(this DateTime value, DateTime[] holidays)
        {
            if (holidays == null || holidays.Length == 0) 
                return false;

            return Array.Exists<DateTime>(holidays, d => d == value.Date);
        }
    }
}