package utime

import (
	"github.com/jinzhu/now"
	"time"
)

const (
	Day          = 86400
	Layout       = "2006-01-02 15:04:05"
	LayoutDay    = "2006-01-02"
	LayoutDay2   = "20060102"
	LayoutMonth  = "2006-01"
	LayoutMinute = "2006-01-02 15:04"
)

// 获取时间所在周的第一天（周一) 00:00:00，和最后一天（周日）23:59:59
func WeekStartEnd(date time.Time) (start, end time.Time) {
	w := 0
	week := date.Weekday()
	if week == time.Sunday {
		w = 7
	} else {
		w = int(week)
	}
	startTmp := date.AddDate(0, 0, -w+1)
	endTmp := date.AddDate(0, 0, 7-w)

	start = time.Date(startTmp.Year(), startTmp.Month(), startTmp.Day(), 0, 0, 0, 0, startTmp.Location())
	end = time.Date(endTmp.Year(), endTmp.Month(), endTmp.Day(), 23, 59, 59, 999, endTmp.Location())
	return
}

// 当天开始结束
func DayStartEnd(date time.Time) (start, end time.Time) {
	start = time.Date(date.Year(), date.Month(), date.Day(), 0, 0, 0, 0, date.Location())
	end = time.Date(date.Year(), date.Month(), date.Day(), 23, 59, 59, 999, date.Location())
	return
}

// 获取时间所在月的第一天（1号) 00:00:00，和最后一天23:59:59
func MonthStartEnd(date time.Time) (start, end time.Time) {
	start = time.Date(date.Year(), date.Month(), 1, 0, 0, 0, 0, date.Location())
	lastDay := now.New(start).EndOfMonth().Day()
	end = time.Date(date.Year(), date.Month(), lastDay, 23, 59, 59, 999999999, date.Location())
	return
}

// 增加年/月
// 因为golang原生的Time.AddDate增加月份的时候有bug
func AddDate(t time.Time, years int, months int) time.Time {
	year, month, day := t.Date()
	hour, min, sec := t.Clock()

	// firstDayOfMonthAfterAddDate: years 年，months 月后的 那个月份的1号
	firstDayOfMonthAfterAddDate := time.Date(year+years, month+time.Month(months), 1,
		hour, min, sec, t.Nanosecond(), t.Location())
	// firstDayOfMonthAfterAddDate 月份的最后一天
	lastDay := now.New(firstDayOfMonthAfterAddDate).EndOfMonth().Day()

	// 如果 t 的天 > lastDay，则设置为lastDay
	// 如：t 为 2020-03-31 12:00:00 +0800，增加1个月，为4月31号
	// 但是4月没有31号，则设置为4月最后一天lastDay（30号）
	if day > lastDay {
		day = lastDay
	}

	return time.Date(year+years, month+time.Month(months), day,
		hour, min, sec, t.Nanosecond(), t.Location())
}