using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Web;

namespace WebAPI.Models
{
    public class GetWeekList
    {

        #region 根据时间获取当前是第几周

        //如果12月31号与下一年的1月1好在同一个星期则算下一年的第一周
        public int GetWeekIndex(DateTime dTime)
        {
            try
            {
                //确定此时间在一年中的位置(第多少天)
                int dayOfYear = dTime.DayOfYear;

                //当年第一天
                DateTime tempDate = new DateTime(dTime.Year, 1, 1);
                //确定当年第一天是周几
                int tempDayOfWeek = (int)tempDate.DayOfWeek;
                //判断当前一月一号如果是周日(0),则默认为周一
                tempDayOfWeek = tempDayOfWeek == 0 ? 1 : tempDayOfWeek;

                //确定当前日期是星期几
                int index = (int)dTime.DayOfWeek;
                //判断当前日期如果是周日(0),则默认为周一
                index = index == 0 ? 1 : index;

                //当前日期周的范围
                DateTime retStartDay = dTime.AddDays(-(index - 1));
                DateTime retEndDay = dTime.AddDays(7 - index);

                //确定当前日期是第几周
                int weekIndex = (int)Math.Ceiling(((double)dayOfYear + tempDayOfWeek - 1) / 7);

                //对比当前日期周的开始和结束，判定是否跨年第一周
                if (retStartDay.Year < retEndDay.Year)
                {
                    weekIndex = 1;
                }

                return weekIndex;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
            //string retVal = retStartDay.ToString("yyyy/MM/dd") + "～" + retEndDay.ToString("yyyy/MM/dd");

        }
        public int GetWeekIndex(string strDate)
        {
            try
            {
                //需要判断的时间
                DateTime dTime = Convert.ToDateTime(strDate);
                return GetWeekIndex(dTime);
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }

        }
        #endregion

        #region 以周末为每周第一天来计算当前日期所属哪一年第几周
        public string getWeek(DateTime dtime)
        {
            int nowweekindex = 0;
            //定义每周第一天为周末开始
            int[] aweek = new int[] { 0, 1, 2, 3, 4, 5, 6 };
            int weekd = 0;
            string yearmonthweek = "";
            //确定此时间在一年中的位置(第多少天)
            int dayofyear = dtime.DayOfYear;
            //确定此时间在一年中的月份
            int dayofmonth = dtime.Month;
            //确定当年第一天是周几
            //int dayofweek = (int)dtime.DayOfWeek;
            //当年第一天
            DateTime dtfirstday = new DateTime(dtime.Year, 1, 1);
            //确定当年第一天是周几
            int dtfirstdayofweek = (int)dtfirstday.DayOfWeek;
            //DateTime dtlastday = new DateTime(dtime.Year, 12, 31);
            //下一年第一天
            DateTime dtnextyear = new DateTime(dtime.Year + 1, 1, 1);
            //int dtnextyeardayofweek = (int)dtnextyear.DayOfWeek;
            //下一年第一天是周几
            int nextyear = sy(dtnextyear,aweek) - 1;
            DateTime dtlastday1 = new DateTime(dtime.Year, 12, 31 - nextyear);
            if ((int)dtime.DayOfYear - (int)dtfirstday.DayOfYear <= 7 - sy(dtfirstday,aweek))
            {
                nowweekindex = 1;
                yearmonthweek = dtime.Year + "_" + dayofmonth + "_" + nowweekindex;
            }
            else if ((int)dtime.DayOfYear <= (int)dtlastday1.DayOfYear)
            {
                for (int j = 0; j < aweek.Length; j++)
                {
                    if (Convert.ToInt32(aweek[j]) == dtfirstdayofweek)
                    {
                        int b = aweek.Length - (j + 1);
                        int x = (dayofyear - 1) - b;
                        weekd = x / 7;
                        int yushu = x % 7;
                        if (yushu != 0)
                        {
                            nowweekindex = weekd + 2;
                            yearmonthweek = dtime.Year + "_" + dayofmonth + "_" + nowweekindex;
                        }
                        else
                        {
                            nowweekindex = weekd + 1;
                            yearmonthweek = dtime.Year + "_" + dayofmonth + "_" + nowweekindex;
                        }
                    }
                }
            }
            else
            {
                nowweekindex = weekd + 1;
                yearmonthweek = dtime.Year + 1 + "_" + 1 + "_" + nowweekindex;
            }
            return yearmonthweek;
        }
       

        public static int sy(DateTime dtime, int[] aweek)
        {
            int midnum = 0;
            int midof = (int)dtime.DayOfWeek;
            for (int i = 0; i < aweek.Length; i++)
            {
                if (Convert.ToInt32(aweek[i]) == midof)
                {
                    midnum = i;
                }
            }
            return midnum + 1;
        }
        #endregion

        public  string GetCodeDateStr(DateTime dtime)
        {
            DateTime currentTime = dtime;
            var year = GetOfYear(currentTime);
            var week = GetWeekOfYear(currentTime);
            var weekStr = week < 10 ? $"0{week}" : week.ToString();
            var dateStr = $"{year}{weekStr}{getWeekOfDay(dtime)}"; ;
            return dateStr;
        }
        private static int GetOfYear(DateTime dt)
        {
            var OfYear =int.Parse(dt.Year.ToString().ToCharArray()[3].ToString());
            GregorianCalendar gc = new GregorianCalendar();
            //判断当前日期是否是12月份
            int dayofmonth = dt.Month;
            //判断当前日期是第几周
            int dayofweek = gc.GetWeekOfYear(dt, CalendarWeekRule.FirstDay, DayOfWeek.Sunday);
            //下一年的第一天
            DateTime dtfirstday = new DateTime(dt.Year + 1, 1, 1);
            //确定下一年第一天是周几
            int dtfirstdayofweek = (int)dtfirstday.DayOfWeek;
            //判断下一年第一天不为周日且当前日期为本年第12月且当前日期为本年第53周
            if (dtfirstdayofweek != 0 && dayofmonth == 12 && dayofweek == 53)
            {
                OfYear = OfYear + 1;  //加一年
            }
            else
            {
                OfYear = int.Parse(dt.Year.ToString().ToCharArray()[3].ToString());
            }
            return OfYear;
        }
        private static int GetWeekOfYear(DateTime dt)
        {
            int weekOfYear = 1;
            GregorianCalendar gc = new GregorianCalendar();
            //判断当前日期是否是12月份
            int dayofmonth = dt.Month;
            //判断当前日期是第几周
            int dayofweek=gc.GetWeekOfYear(dt, CalendarWeekRule.FirstDay, DayOfWeek.Sunday);
            //下一年的第一天
            DateTime dtfirstday = new DateTime(dt.Year+1, 1, 1);
            //确定下一年第一天是周几
            int dtfirstdayofweek = (int)dtfirstday.DayOfWeek;
            //判断下一年第一天不为周日且当前日期为本年第12月且当前日期为本年第53周
            if (dtfirstdayofweek != 0&& dayofmonth == 12&&dayofweek ==53)
            {
                weekOfYear = 1;  //下一年第一周
            }
            else 
            {
                 weekOfYear = gc.GetWeekOfYear(dt, CalendarWeekRule.FirstDay, DayOfWeek.Sunday);
            }
            return weekOfYear;
        }
        public static int getWeekOfDay(DateTime dtime)
        {
            int DayinWeek = 0;
            string week = dtime.DayOfWeek.ToString();
            switch (week)
            {
                case "Monday":
                    DayinWeek = 2;
                    break;
                case "Tuesday":
                    DayinWeek = 3;
                    break;
                case "Wednesday":
                    DayinWeek = 4;
                    break;
                case "Thursday":
                    DayinWeek = 5;
                    break;
                case "Friday":
                    DayinWeek = 6;
                    break;
                case "Saturday":
                    DayinWeek = 7;
                    break;
                case "Sunday":
                    DayinWeek = 1;
                    break;
            }
            return DayinWeek;
        }
    }
}