using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Globalization;

namespace EasyDevCore.Common
{
    /// <summary>
    /// DateTime extension helper
    /// </summary>
    public static class DateTimeExtensions
    {
        /// <summary>
        /// Parses by format.
        /// </summary>
        /// <param name="input">The input.</param>
        /// <param name="format">The format.</param>
        /// <returns></returns>
        public static DateTime ParseByFormat(this DateTime input, string format)
        {
            return DateTime.ParseExact(input.ToString(format), format, System.Globalization.CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Determines whether this instance is expired.
        /// </summary>
        /// <param name="input">The input.</param>
        /// <returns>
        ///   <c>true</c> if the specified input is expired; otherwise, <c>false</c>.
        /// </returns>
        public static bool IsExpired(this DateTime? input)
        {
            return input != null && input.Value > DateTime.Now;
        }

        /// <summary>
        /// Determines whether this instance is expired.
        /// </summary>
        /// <param name="input">The input.</param>
        /// <returns>
        ///   <c>true</c> if the specified input is expired; otherwise, <c>false</c>.
        /// </returns>
        public static bool IsExpired(this DateTime input)
        {
            return input > DateTime.Now;
        }
            
        /// <summary>
        /// Gets the week of month.
        /// </summary>
        /// <param name="time">The time.</param>
        /// <returns></returns>
        public static int GetWeekOfMonth(this DateTime time)
        {
            DateTime first = new DateTime(time.Year, time.Month, 1);
            return time.GetWeekOfYear() - first.GetWeekOfYear() + 1;
        }

        /// <summary>
        /// Gets the week of year.
        /// </summary>
        /// <param name="time">The time.</param>
        /// <returns></returns>
        public static int GetWeekOfYear(this DateTime time)
        {
            return new GregorianCalendar().GetWeekOfYear(time, CalendarWeekRule.FirstDay, DayOfWeek.Sunday);
        }

    }
}