using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Runtime.InteropServices;

namespace Masuit.Tools.DateTimeExt
{
	/// <summary>
	/// 日期操作工具类
	/// </summary>
	public static class DateTimeHelper
	{
		/// <summary>
		/// 获取某一年有多少周
		/// </summary>
		/// <param name="_"></param>
		/// <param name="year">年份</param>
		/// <returns>该年周数</returns>
		public static int GetWeekAmount(this DateTime _, int year)
		{
			var end = new DateTime(year, 12, 31); //该年最后一天
			var gc = new GregorianCalendar();
			return gc.GetWeekOfYear(end, CalendarWeekRule.FirstDay, DayOfWeek.Monday); //该年星期数
		}

		/// <summary>
		/// 返回年度第几个星期   默认星期日是第一天
		/// </summary>
		/// <param name="date">时间</param>
		/// <returns>第几周</returns>
		public static int WeekOfYear(this in DateTime date)
		{
			var gc = new GregorianCalendar();
			return gc.GetWeekOfYear(date, CalendarWeekRule.FirstDay, DayOfWeek.Sunday);
		}

		/// <summary>
		/// 返回年度第几个星期
		/// </summary>
		/// <param name="date">时间</param>
		/// <param name="week">一周的开始日期</param>
		/// <returns>第几周</returns>
		public static int WeekOfYear(this in DateTime date, DayOfWeek week)
		{
			var gc = new GregorianCalendar();
			return gc.GetWeekOfYear(date, CalendarWeekRule.FirstDay, week);
		}

		/// <summary>
		/// 得到一年中的某周的起始日和截止日
		/// 年 nYear
		/// 周数 nNumWeek
		/// 周始 out dtWeekStart
		/// 周终 out dtWeekeEnd
		/// </summary>
		/// <param name="_"></param>
		/// <param name="nYear">年份</param>
		/// <param name="nNumWeek">第几周</param>
		/// <param name="dtWeekStart">开始日期</param>
		/// <param name="dtWeekeEnd">结束日期</param>
		public static void GetWeekTime(this DateTime _, int nYear, int nNumWeek, out DateTime dtWeekStart, out DateTime dtWeekeEnd)
		{
			var dt = new DateTime(nYear, 1, 1);
			dt += new TimeSpan((nNumWeek - 1) * 7, 0, 0, 0);
			dtWeekStart = dt.AddDays(-(int)dt.DayOfWeek + (int)DayOfWeek.Monday);
			dtWeekeEnd = dt.AddDays((int)DayOfWeek.Saturday - (int)dt.DayOfWeek + 1);
		}

		/// <summary>
		/// 得到一年中的某周的起始日和截止日    周一到周五  工作日
		/// </summary>
		/// <param name="_"></param>
		/// <param name="nYear">年份</param>
		/// <param name="nNumWeek">第几周</param>
		/// <param name="dtWeekStart">开始日期</param>
		/// <param name="dtWeekeEnd">结束日期</param>
		public static void GetWeekWorkTime(this DateTime _, int nYear, int nNumWeek, out DateTime dtWeekStart, out DateTime dtWeekeEnd)
		{
			var dt = new DateTime(nYear, 1, 1);
			dt += new TimeSpan((nNumWeek - 1) * 7, 0, 0, 0);
			dtWeekStart = dt.AddDays(-(int)dt.DayOfWeek + (int)DayOfWeek.Monday);
			dtWeekeEnd = dt.AddDays((int)DayOfWeek.Saturday - (int)dt.DayOfWeek + 1).AddDays(-2);
		}

		#region P/Invoke 设置本地时间

		[DllImport("kernel32.dll")]
		private static extern bool SetLocalTime(ref SystemTime time);

		[StructLayout(LayoutKind.Sequential)]
		private struct SystemTime
		{
			public short year;
			public short month;
			public short dayOfWeek;
			public short day;
			public short hour;
			public short minute;
			public short second;
			public short milliseconds;
		}

		/// <summary>
		/// 设置本地计算机系统时间，仅支持Windows系统
		/// </summary>
		/// <param name="dt">DateTime对象</param>
		public static void SetLocalTime(this in DateTime dt)
		{
			SystemTime st;
			st.year = (short)dt.Year;
			st.month = (short)dt.Month;
			st.dayOfWeek = (short)dt.DayOfWeek;
			st.day = (short)dt.Day;
			st.hour = (short)dt.Hour;
			st.minute = (short)dt.Minute;
			st.second = (short)dt.Second;
			st.milliseconds = (short)dt.Millisecond;
			SetLocalTime(ref st);
		}

		#endregion P/Invoke 设置本地时间

		/// <summary>
		/// 返回相对于当前时间的相对天数
		/// </summary>
		/// <param name="dt"></param>
		/// <param name="relativeday">相对天数</param>
		public static string GetDateTime(this in DateTime dt, int relativeday)
		{
			return dt.AddDays(relativeday).ToString("yyyy-MM-dd HH:mm:ss");
		}

		/// <summary>
		/// 返回标准时间格式string
		/// </summary>
		public static string GetDateTimeF(this in DateTime dt) => dt.ToString("yyyy-MM-dd HH:mm:ss:fffffff");

		/// <summary>
		/// 获取该时间相对于1970-01-01T00:00:00Z的秒数
		/// </summary>
		/// <param name="dt"></param>
		/// <returns></returns>
		public static long GetTotalSeconds(this in DateTime dt) => new DateTimeOffset(dt).UtcDateTime.Ticks / 10_000_000L - 62135596800L;

		/// <summary>
		/// 获取该时间相对于1970-01-01T00:00:00Z的毫秒数
		/// </summary>
		/// <param name="dt"></param>
		/// <returns></returns>
		public static long GetTotalMilliseconds(this in DateTime dt) => new DateTimeOffset(dt).UtcDateTime.Ticks / 10000L - 62135596800000L;

		/// <summary>
		/// 获取该时间相对于1970-01-01T00:00:00Z的微秒时间戳
		/// </summary>
		/// <param name="dt"></param>
		/// <returns></returns>
		public static long GetTotalMicroseconds(this in DateTime dt) => (new DateTimeOffset(dt).UtcTicks - 621355968000000000) / 10;

		[DllImport("Kernel32.dll")]
		private static extern bool QueryPerformanceCounter(out long lpPerformanceCount);

		/// <summary>
		/// 获取该时间相对于1970-01-01T00:00:00Z的纳秒时间戳
		/// </summary>
		/// <param name="dt"></param>
		/// <returns></returns>
		public static long GetTotalNanoseconds(this in DateTime dt)
		{
			var ticks = (new DateTimeOffset(dt).UtcTicks - 621355968000000000) * 100;
			if (Environment.OSVersion.Platform == PlatformID.Win32NT)
			{
				QueryPerformanceCounter(out var timestamp);
				return ticks + timestamp % 100;
			}

			return ticks + Stopwatch.GetTimestamp() % 100;
		}

		/// <summary>
		/// 获取该时间相对于1970-01-01T00:00:00Z的分钟数
		/// </summary>
		/// <param name="dt"></param>
		/// <returns></returns>
		public static double GetTotalMinutes(this in DateTime dt) => new DateTimeOffset(dt).Offset.TotalMinutes;

		/// <summary>
		/// 获取该时间相对于1970-01-01T00:00:00Z的小时数
		/// </summary>
		/// <param name="dt"></param>
		/// <returns></returns>
		public static double GetTotalHours(this in DateTime dt) => new DateTimeOffset(dt).Offset.TotalHours;

		/// <summary>
		/// 获取该时间相对于1970-01-01T00:00:00Z的天数
		/// </summary>
		/// <param name="dt"></param>
		/// <returns></returns>
		public static double GetTotalDays(this in DateTime dt) => new DateTimeOffset(dt).Offset.TotalDays;

		/// <summary>
		/// 返回本年有多少天
		/// </summary>
		/// <param name="_"></param>
		/// <param name="iYear">年份</param>
		/// <returns>本年的天数</returns>
		public static int GetDaysOfYear(this DateTime _, int iYear)
		{
			return IsRuYear(iYear) ? 366 : 365;
		}

		/// <summary>本年有多少天</summary>
		/// <param name="dt">日期</param>
		/// <returns>本天在当年的天数</returns>
		public static int GetDaysOfYear(this in DateTime dt)
		{
			//取得传入参数的年份部分，用来判断是否是闰年
			int n = dt.Year;
			return IsRuYear(n) ? 366 : 365;
		}

		/// <summary>本月有多少天</summary>
		/// <param name="_"></param>
		/// <param name="iYear">年</param>
		/// <param name="month">月</param>
		/// <returns>天数</returns>
		public static int GetDaysOfMonth(this DateTime _, int iYear, int month)
		{
			return month switch
			{
				1 => 31,
				2 => (IsRuYear(iYear) ? 29 : 28),
				3 => 31,
				4 => 30,
				5 => 31,
				6 => 30,
				7 => 31,
				8 => 31,
				9 => 30,
				10 => 31,
				11 => 30,
				12 => 31,
				_ => 0
			};
		}

		/// <summary>本月有多少天</summary>
		/// <param name="dt">日期</param>
		/// <returns>天数</returns>
		public static int GetDaysOfMonth(this in DateTime dt)
		{
			//--利用年月信息，得到当前月的天数信息。
			return dt.Month switch
			{
				1 => 31,
				2 => (IsRuYear(dt.Year) ? 29 : 28),
				3 => 31,
				4 => 30,
				5 => 31,
				6 => 30,
				7 => 31,
				8 => 31,
				9 => 30,
				10 => 31,
				11 => 30,
				12 => 31,
				_ => 0
			};
		}

		/// <summary>返回当前日期的星期名称</summary>
		/// <param name="idt">日期</param>
		/// <returns>星期名称</returns>
		public static string GetWeekNameOfDay(this in DateTime idt)
		{
			return idt.DayOfWeek switch
			{
				DayOfWeek.Monday => "星期一",
				DayOfWeek.Tuesday => "星期二",
				DayOfWeek.Wednesday => "星期三",
				DayOfWeek.Thursday => "星期四",
				DayOfWeek.Friday => "星期五",
				DayOfWeek.Saturday => "星期六",
				DayOfWeek.Sunday => "星期日",
				_ => ""
			};
		}

		/// <summary>判断当前年份是否是闰年，私有函数</summary>
		/// <param name="iYear">年份</param>
		/// <returns>是闰年：True ，不是闰年：False</returns>
		private static bool IsRuYear(int iYear)
		{
			//形式参数为年份
			//例如：2003
			var n = iYear;
			return n % 400 == 0 || n % 4 == 0 && n % 100 != 0;
		}

		/// <summary>
		/// 判断是否为合法日期，必须大于1800年1月1日
		/// </summary>
		/// <param name="strDate">输入日期字符串</param>
		/// <returns>True/False</returns>
		public static bool IsDateTime(this string strDate)
		{
			DateTime.TryParse(strDate, out var result);
			return result.CompareTo(DateTime.Parse("1800-1-1")) > 0;
		}

		/// <summary>
		/// 判断时间是否在区间内
		/// </summary>
		/// <param name="this"></param>
		/// <param name="start">开始</param>
		/// <param name="end">结束</param>
		/// <param name="mode">模式</param>
		/// <returns></returns>
		public static bool In(this in DateTime @this, DateTime start, DateTime end, RangeMode mode = RangeMode.Close)
		{
			return mode switch
			{
				RangeMode.Open => start < @this && end > @this,
				RangeMode.Close => start <= @this && end >= @this,
				RangeMode.OpenClose => start < @this && end >= @this,
				RangeMode.CloseOpen => start <= @this && end > @this,
				_ => throw new ArgumentOutOfRangeException(nameof(mode), mode, null)
			};
		}

		/// <summary>
		///  返回每月的第一天和最后一天
		/// </summary>
		/// <param name="_"></param>
		/// <param name="month">月份</param>
		/// <param name="firstDay">第一天</param>
		/// <param name="lastDay">最后一天</param>
		public static void ReturnDateFormat(this DateTime _, int month, out string firstDay, out string lastDay)
		{
			int year = DateTime.Now.Year + month / 12;
			if (month != 12)
			{
				month %= 12;
			}

			switch (month)
			{
				case 1:
					firstDay = DateTime.Now.ToString($"{year}-0{month}-01");
					lastDay = DateTime.Now.ToString($"{year}-0{month}-31");
					break;

				case 2:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.IsLeapYear(DateTime.Now.Year) ? DateTime.Now.ToString(year + "-0" + month + "-29") : DateTime.Now.ToString(year + "-0" + month + "-28");
					break;

				case 3:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.Now.ToString("yyyy-0" + month + "-31");
					break;

				case 4:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");
					break;

				case 5:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");
					break;

				case 6:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");
					break;

				case 7:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");
					break;

				case 8:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");
					break;

				case 9:
					firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");
					break;

				case 10:
					firstDay = DateTime.Now.ToString(year + "-" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-" + month + "-31");
					break;

				case 11:
					firstDay = DateTime.Now.ToString(year + "-" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-" + month + "-30");
					break;

				default:
					firstDay = DateTime.Now.ToString(year + "-" + month + "-01");
					lastDay = DateTime.Now.ToString(year + "-" + month + "-31");
					break;
			}
		}

		/// <summary>
		/// 返回某年某月最后一天
		/// </summary>
		/// <param name="_"></param>
		/// <param name="year">年份</param>
		/// <param name="month">月份</param>
		/// <returns>日</returns>
		public static int GetMonthLastDate(this DateTime _, int year, int month)
		{
			DateTime lastDay = new DateTime(year, month, new GregorianCalendar().GetDaysInMonth(year, month));
			int day = lastDay.Day;
			return day;
		}

		/// <summary>
		/// 获得一段时间内有多少小时
		/// </summary>
		/// <param name="dtStar">起始时间</param>
		/// <param name="dtEnd">终止时间</param>
		/// <returns>小时差</returns>
		public static string GetTimeDelay(this in DateTime dtStar, DateTime dtEnd)
		{
			long lTicks = (dtEnd.Ticks - dtStar.Ticks) / 10000000;
			string sTemp = (lTicks / 3600).ToString().PadLeft(2, '0') + ":";
			sTemp += (lTicks % 3600 / 60).ToString().PadLeft(2, '0') + ":";
			sTemp += (lTicks % 3600 % 60).ToString().PadLeft(2, '0');
			return sTemp;
		}

		/// <summary>
		/// 获得8位时间整型数字
		/// </summary>
		/// <param name="dt">当前的日期时间对象</param>
		/// <returns>8位时间整型数字</returns>
		public static string GetDateString(this in DateTime dt)
		{
			return dt.Year + dt.Month.ToString().PadLeft(2, '0') + dt.Day.ToString().PadLeft(2, '0');
		}

		/// <summary>
		/// 返回时间差
		/// </summary>
		/// <param name="dateTime1">时间1</param>
		/// <param name="dateTime2">时间2</param>
		/// <returns>时间差</returns>
		public static string DateDiff(this in DateTime dateTime1, in DateTime dateTime2)
		{
			string dateDiff;
			var ts = dateTime2 - dateTime1;
			if (ts.Days >= 1)
			{
				dateDiff = dateTime1.Month + "月" + dateTime1.Day + "日";
			}
			else
			{
				dateDiff = ts.Hours > 1 ? ts.Hours + "小时前" : ts.Minutes + "分钟前";
			}

			return dateDiff;
		}

		/// <summary>
		/// 计算2个时间差
		/// </summary>
		/// <param name="beginTime">开始时间</param>
		/// <param name="endTime">结束时间</param>
		/// <returns>时间差</returns>
		public static string GetDiffTime(this in DateTime beginTime, in DateTime endTime)
		{
			string strResout = string.Empty;

			//获得2时间的时间间隔秒计算
			TimeSpan span = endTime.Subtract(beginTime);
			int sec = Convert.ToInt32(span.TotalSeconds);
			int minutes = 1 * 60;
			int hours = minutes * 60;
			int day = hours * 24;
			int month = day * 30;
			int year = month * 12;

			//提醒时间,到了返回1,否则返回0
			if (sec > year)
			{
				strResout += sec / year + "年";
				sec %= year; //剩余
			}

			if (sec > month)
			{
				strResout += sec / month + "月";
				sec %= month;
			}

			if (sec > day)
			{
				strResout += sec / day + "天";
				sec %= day;
			}

			if (sec > hours)
			{
				strResout += sec / hours + "小时";
				sec %= hours;
			}

			if (sec > minutes)
			{
				strResout += sec / minutes + "分";
				sec %= minutes;
			}

			strResout += sec + "秒";
			return strResout;
		}

		/// <summary>
		/// 根据某个时间段查找在某批时间段中的最大并集
		/// </summary>
		/// <param name="destination"></param>
		/// <param name="sources"></param>
		/// <typeparam name="T"></typeparam>
		/// <returns></returns>
		public static ICollection<T> GetUnionSet<T>(this T destination, List<T> sources) where T : ITimePeriod, new()
		{
			var result = true;
			ICollection<T> frames = new List<T>();

			var timeFrames = sources.Where(frame =>
				!(destination.Start > frame.End || destination.End < frame.Start)).ToList();
			if (timeFrames.Any())
				foreach (var frame in timeFrames)
				{
					frames.Add(frame);
					sources.Remove(frame);
				}

			if (!frames.Any()) return frames;
			var timePeriod = new T()
			{
				End = frames.OrderBy(frame => frame.End).Max(frame => frame.End),
				Start = frames.OrderBy(frame => frame.Start).Min(frame => frame.Start)
			};

			while (result)
			{
				var maxTimeFrame = GetUnionSet<T>(timePeriod, sources);
				if (!maxTimeFrame.Any())
					result = false;
				else
					foreach (var frame in maxTimeFrame)
						frames.Add(frame);
			}

			return frames;
		}

		/// <summary>
		/// 获取一批时间段内存在相互重叠的最大时间段
		/// </summary>
		/// <param name="destination">基础时间段</param>
		/// <param name="sources">一批时间段</param>
		/// <typeparam name="T"></typeparam>
		/// <returns></returns>
		/// <remarks>源数据sources 会受到影响</remarks>
		public static T GetMaxTimePeriod<T>(this T destination, List<T> sources) where T : ITimePeriod, new()
		{
			var list = sources.Select(period => new T()
			{
				End = period.End,
				Start = period.Start,
			}).ToList();

			var timePeriods = GetUnionSet(destination, list);
			return new T()
			{
				End = timePeriods.OrderBy(period => period.End).Max(period => period.End),
				Start = timePeriods.OrderBy(period => period.Start).Min(period => period.Start)
			};
		}
	}

	public interface ITimePeriod
	{
		/// <summary>
		/// 起始时间
		/// </summary>
		public DateTime Start { get; set; }

		/// <summary>
		/// 终止时间
		/// </summary>
		public DateTime End { get; set; }
	}

	/// <summary>
	/// 区间模式
	/// </summary>
	public enum RangeMode
	{
		/// <summary>
		/// 开区间
		/// </summary>
		Open,

		/// <summary>
		/// 闭区间
		/// </summary>
		Close,

		/// <summary>
		/// 左开右闭区间
		/// </summary>
		OpenClose,

		/// <summary>
		/// 左闭右开区间
		/// </summary>
		CloseOpen
	}
}