using System;
using System.Text;

namespace CommonHelper
{
    public static class ExtDateTime
    {
        /// <summary>
        /// 获取格式化字符串，不带时分秒。格式："yyyy-MM-dd"
        /// </summary>
        /// <param name="dateTime">日期</param>
        public static string ToDateString(this DateTime dateTime)
        {
            return dateTime.ToString("yyyy-MM-dd");
        }

        /// <summary>
        /// 获取格式化字符串，不带时分秒。格式："yyyy-MM-dd"
        /// </summary>
        /// <param name="dateTime">日期</param>
        public static string ToDateString(this DateTime? dateTime)
        {
            if (dateTime == null)
            {
                return string.Empty;
            }
            return ToDateString(dateTime.Value);
        }

        /// <summary>
        /// 获取格式化字符串，不带年月日，格式："HH:mm:ss"
        /// </summary>
        /// <param name="dateTime">日期</param>
        public static string ToTimeString(this DateTime dateTime)
        {
            return dateTime.ToString("HH:mm:ss");
        }

        /// <summary>
        /// 获取格式化字符串，不带年月日，格式："HH:mm:ss"
        /// </summary>
        /// <param name="dateTime">日期</param>
        public static string ToTimeString(this DateTime? dateTime)
        {
            if (dateTime == null)
            {
                return string.Empty;
            }
            return ToTimeString(dateTime.Value);
        }

        /// <summary>
        /// 获取格式化字符串，带毫秒，格式："yyyy-MM-dd HH:mm:ss.fff"
        /// </summary>
        /// <param name="dateTime">日期</param>
        public static string ToMillisecondString(this DateTime dateTime)
        {
            return dateTime.ToString("yyyy-MM-dd HH:mm:ss.fff");
        }

        /// <summary>
        /// 获取格式化字符串，带毫秒，格式："yyyy-MM-dd HH:mm:ss.fff"
        /// </summary>
        /// <param name="dateTime">日期</param>
        public static string ToMillisecondString(this DateTime? dateTime)
        {
            if (dateTime == null)
            {
                return string.Empty;
            }
            return ToMillisecondString(dateTime.Value);
        }

        /// <summary>
        /// 获取格式化字符串，不带时分秒，格式："yyyy年MM月dd日"
        /// </summary>
        /// <param name="dateTime">日期</param>
        public static string ToChineseDateString(this DateTime dateTime)
        {
            return string.Format("{0}年{1}月{2}日", dateTime.Year, dateTime.Month, dateTime.Day);
        }

        /// <summary>
        /// 获取格式化字符串，带时分秒，格式："yyyy年MM月dd日 HH时mm分"
        /// </summary>
        /// <param name="dateTime">日期</param>
        /// <param name="isRemoveSecond">是否移除秒</param>
        public static string ToChineseDateTimeString(this DateTime dateTime, bool isRemoveSecond = false)
        {
            StringBuilder result = new StringBuilder(50);
            result.AppendFormat("{0}年{1}月{2}日", dateTime.Year, dateTime.Month, dateTime.Day);
            result.AppendFormat(" {0}时{1}分", dateTime.Hour, dateTime.Minute);

            if (isRemoveSecond == false)
            {
                result.AppendFormat("{0}秒", dateTime.Second);
            }

            return result.ToString();
        }

        /// <summary>
        /// 获取格式化字符串，带时分秒，格式："yyyy年MM月dd日 HH时mm分"
        /// </summary>
        /// <param name="dateTime">日期</param>
        /// <param name="isRemoveSecond">是否移除秒</param>
        public static string ToChineseDateTimeString(this DateTime? dateTime, bool isRemoveSecond = false)
        {
            if (dateTime == null)
            {
                return string.Empty;
            }

            return ToChineseDateTimeString(dateTime.Value);
        }

        /// <summary>
        ///  返回指定日期起始时间。
        /// </summary>
        /// <param name="dateTime"></param>
        /// <returns></returns>
        public static DateTime StartDateTime(this DateTime dateTime)
        {
            if (dateTime == null)
            {
                throw new ArgumentNullException();
            }

            return new DateTime(dateTime.Year, dateTime.Month, dateTime.Day, 0, 0, 0);
        }
        /// <summary>
        ///  返回指定日期结束时间。
        /// </summary>
        /// <param name="dateTime"></param>
        /// <returns></returns>
        public static DateTime EndDateTime(this DateTime dateTime)
        {
            if (dateTime == null)
            {
                throw new ArgumentNullException();
            }

            return new DateTime(dateTime.Year, dateTime.Month, dateTime.Day, 23, 59, 59);
        }

        /// <summary>
        /// 获取时间戳
        /// </summary>
        /// <param name="dt">时间</param>
        /// <param name="millisecond">是否毫秒级,true毫秒级(默认值)</param>
        /// <returns></returns>
        public static long ToTimestamp(this DateTime dt, bool millisecond = true)
        {
            /*
             * ticks的单位是100纳秒,1 Tick=100纳秒,所以需要除以10000000(秒),10000(毫秒)
             *  s(秒),ms(毫秒),μs(微秒),ns(纳秒),1s=1000ms,1 ms=1000μs,1μs=1000ns
             */

            TimeSpan ts = DateTime.Now - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            if(millisecond)
                return Convert.ToInt64(ts.TotalMilliseconds);
            else
                return Convert.ToInt64(ts.TotalSeconds);
        }

        /// <summary>
        /// 时间戳转换成时间,返回NULL则说明转换失败(如时间戳无效)
        /// </summary>
        /// <param name="timestamp">时间戳</param>
        /// <param name="millisecond">是否毫秒级,true毫秒级(默认值)</param>
        /// <param name="localTime">是否输出本地时间,true本地时间(默认值)</param>
        /// <returns></returns>
        public static DateTime? ToDateTime(this long timestamp, bool millisecond = true)
        {
            try
            {
                if(millisecond)
                    return (new System.DateTime(1970, 1, 1, 0, 0, 0, 0)).AddMilliseconds(timestamp).ToLocalTime();
                else
                    return (new System.DateTime(1970, 1, 1, 0, 0, 0, 0)).AddSeconds(timestamp).ToLocalTime();

            }
            catch
            {
                return null;
            }
        }

        /// <summary>
        /// 时间戳转换成时间
        /// </summary>
        /// <param name="timestamp">时间戳</param>
        /// <param name="millisecond">是否毫秒级,true毫秒级(默认值)</param>
        /// <param name="localTime">是否输出本地时间,true本地时间(默认值)</param>
        /// <returns></returns>
        public static DateTime? ToDateTime(this string timestamp)
        {
            if (long.TryParse(timestamp, out long ts))
            {
                var isM = true;
                if (timestamp.Length == 10)
                    isM = false;
                return ts.ToDateTime(isM);
            }
            return null;
        }
    }
}