package time_parse

import (
	"github.com/jinzhu/now"
	"math"
	"net/http"
	"time"
)

var (
	cst *time.Location
)

// China Standard Time Layout
const (
	CSTLayout     = time.DateTime
	CSTDateLayout = time.DateOnly
)

func init() {
	var err error
	if cst, err = time.LoadLocation("Asia/Shanghai"); err != nil {
		cst = time.Local
	}
}

func Now() *now.Now {
	timeFormats := append(append(now.TimeFormats, CSTLayout), CSTDateLayout)

	c := &now.Config{
		WeekStartDay: time.Monday,
		TimeLocation: cst,
		TimeFormats:  timeFormats,
	}

	return c.With(time.Now().In(cst))
}

// RFC3339ToCSTLayout convert rfc3339 value to china standard time layout
// 2020-11-08T08:18:46+08:00 => 2020-11-08 08:18:46
func RFC3339ToCSTLayout(value string) (string, error) {
	ts, err := time.Parse(time.RFC3339, value)
	if err != nil {
		return "", err
	}

	return ts.In(cst).Format(CSTLayout), nil
}

// GetMilliTimestamp 获取CST毫秒时间戳
func GetMilliTimestamp() int64 {
	return time.Now().In(cst).UnixMilli()
}

// GetTimestamp 获取CST时间戳
func GetTimestamp() int64 {
	return time.Now().In(cst).Unix()
}

// CSTLayoutString 格式化时间
// 返回 "2006-01-02 15:04:05" 格式的时间
func CSTLayoutString() string {
	ts := time.Now()
	return ts.In(cst).Format(CSTLayout)
}

// ParseCSTInLocation 格式化时间
func ParseCSTInLocation(date string) (time.Time, error) {
	return time.ParseInLocation(CSTLayout, date, cst)
}

// CSTLayoutStringToUnix 返回 unix 时间戳
// 2020-01-24 21:11:11 => 1579871471
func CSTLayoutStringToUnix(cstLayoutString string) (int64, error) {
	stamp, err := time.ParseInLocation(CSTLayout, cstLayoutString, cst)
	if err != nil {
		return 0, err
	}
	return stamp.Unix(), nil
}

// GMTLayoutString 格式化时间
// 返回 "Mon, 02 Jan 2006 15:04:05 GMT" 格式的时间
func GMTLayoutString() string {
	return time.Now().In(cst).Format(http.TimeFormat)
}

// ParseGMTInLocation 格式化时间
func ParseGMTInLocation(date string) (time.Time, error) {
	return time.ParseInLocation(http.TimeFormat, date, cst)
}

// SubInLocation 计算时间差
func SubInLocation(ts time.Time) float64 {
	return math.Abs(time.Now().In(cst).Sub(ts).Seconds())
}

// GetFirstDateOfMonth 获取传入的时间所在月份的第一天，即某月第一天的0点。如传入time.Now(), 返回当前月份的第一天0点时间。
func GetFirstDateOfMonth(d time.Time) time.Time {
	d = d.AddDate(0, 0, -d.Day()+1)
	return GetStartDayTime(d)
}

// GetLastDateOfMonth 获取传入的时间所在月份的最后一天，即某月最后一天的0点。如传入time.Now(), 返回当前月份的最后一天0点时间。
func GetLastDateOfMonth(d time.Time) time.Time {
	return GetEndDayTime(GetFirstDateOfMonth(d).AddDate(0, 1, -1))
}

// GetStartDayTime 获取某一天的开始时间
func GetStartDayTime(d time.Time) time.Time {
	return time.Date(d.Year(), d.Month(), d.Day(), 0, 0, 0, 0, cst)
}

// GetEndDayTime 获取某一天的结束时间
func GetEndDayTime(d time.Time) time.Time {
	return GetStartDayTime(d).Add(24 * time.Hour).Add(-time.Second)
}

// GetStartYesterdayTime 获取昨天的起始时间
func GetStartYesterdayTime() time.Time {
	d, _ := time.ParseDuration("-24h")
	return GetStartDayTime(time.Now().Add(d))
}

// SubInLocationDays 计算两个日期相差的天数
func SubInLocationDays(t1, t2 time.Time) float64 {
	t1 = time.Date(t1.Year(), t1.Month(), t1.Day(), 0, 0, 0, 0, cst)
	t2 = time.Date(t2.Year(), t2.Month(), t2.Day(), 0, 0, 0, 0, cst)
	return math.Abs(t1.Sub(t2).Hours() / 24)
}