using Microsoft.CodeAnalysis.CSharp.Syntax;
using System;
using System.Collections.Generic;
using System.Text;

namespace Bowin.Common.Utility
{
    public static class DateHelper
    {
        public static DateTime GetYearMonthStartDate(int yearMonth)
        {
            return DateTime.ParseExact(yearMonth.ToString() + "01", "yyyyMMdd", null);
        }
        public static string FormatYearMonth(int yearMonth, string formatString)
        {
            return GetYearMonthStartDate(yearMonth).ToString(formatString);
        }
        public static bool IsYearMonthBetween(int yearMonth, int fromMonth, int toMonth)
        {
            var yearMonthDate = GetYearMonthStartDate(yearMonth);
            var fromDate = new DateTime(DateTime.Today.Year, fromMonth, 1);
            DateTime toDate;
            if (toMonth >= fromMonth)
            {
                toDate = new DateTime(DateTime.Today.Year, toMonth, 1);
            }
            else
            {
                toDate = new DateTime(DateTime.Today.Year + 1, toMonth, 1);
            }

            return yearMonthDate >= fromDate && yearMonthDate <= toDate;
        }

        public static double GetYearSpan(DateTime fromDate, DateTime toDate)
        {
            double yearSpanBase = toDate.Year - fromDate.Year;
            double toDateYearDays = DateTime.IsLeapYear(toDate.Year) ? 366 : 365;
            DateTime toYearBase;
            if (fromDate.Month == 2 && fromDate.Day > DateTime.DaysInMonth(toDate.Year, 2))
            {
                toYearBase = new DateTime(toDate.Year, 2, DateTime.DaysInMonth(toDate.Year, 2));
            }
            else
            {
                toYearBase = new DateTime(toDate.Year, fromDate.Month, fromDate.Day);
            }

            return yearSpanBase + (toDate.Subtract(toYearBase).TotalDays / toDateYearDays);
        }

        public static int YearMonthAdd(int yearMonth, int addMonths)
        {
            return GetYearMonthStartDate(yearMonth).AddMonths(addMonths).ToYearMonth();
        }
        public static int? YearMonthAdd(int? yearMonth, int addMonths)
        {
            if (yearMonth.HasValue)
            {
                return YearMonthAdd(yearMonth.Value, addMonths);
            }
            else
            {
                return null;
            }
        }

        public static int ToYearMonth(this DateTime dateTime)
        {
            return dateTime.Year * 100 + dateTime.Month;
        }

        /// <summary>
        /// 计算两个时间相差的月数
        /// </summary>
        /// <param name="statrDate"></param>
        /// <param name="endDate"></param>
        /// <returns></returns>
        public static int DiffMonth(DateTime statrDate, DateTime endDate)
        {
            return (endDate.Year * 12 + endDate.Month - statrDate.Year * 12 - statrDate.Month);
        }

    }
}