package webutility
  
  import (
  	"fmt"

  	"strings"

  	"time"
  )
  
  const (
  	YYYYMMDD_sl = "2006/01/02"
  	YYYYMMDD_ds = "2006-01-02"
  	YYYYMMDD_dt = "2006.01.02."
  
  	DDMMYYYY_sl = "02/01/2006"
  	DDMMYYYY_ds = "02-01-2006"
  	DDMMYYYY_dt = "02.01.2006."
  
  	YYYYMMDD_HHMMSS_sl = "2006/01/02 15:04:05"
  	YYYYMMDD_HHMMSS_ds = "2006-01-02 15:04:05"
  	YYYYMMDD_HHMMSS_dt = "2006.01.02. 15:04:05"
  
  	DDMMYYYY_HHMMSS_sl = "02/01/2006 15:04:05"
  	DDMMYYYY_HHMMSS_ds = "02-01-2006 15:04:05"
  	DDMMYYYY_HHMMSS_dt = "02.01.2006. 15:04:05"
  )

  var (
  	regularYear = [12]int64{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
  	leapYear    = [12]int64{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
  )

  func Systime() int64 {
  	return time.Now().Unix()
  }
  
  func DateToEpoch(date, format string) int64 {
  	t, err := time.Parse(format, date)
  	if err != nil {
  		fmt.Println(err.Error())
  		return 0
  	}
  	return t.Unix()
  }
  
  func EpochToDate(e int64, format string) string {
  	return time.Unix(e, 0).Format(format)
  }

  
  func EpochToDayMonthYear(timestamp int64) (d, m, y int64) {
  	datestring := EpochToDate(timestamp, DDMMYYYY_sl)
  	parts := strings.Split(datestring, "/")
  	d = StringToInt64(parts[0])
  	m = StringToInt64(parts[1])
  	y = StringToInt64(parts[2])
  	return d, m, y
  }
  
  func DaysInMonth(year, month int64) int64 {
  	if month < 1 || month > 12 {
  		return 0
  	}
  	if IsLeapYear(year) {
  		return leapYear[month-1]
  	}
  	return regularYear[month-1]
  }
  
  func IsLeapYear(year int64) bool {
  	return year%4 == 0 && !((year%100 == 0) && (year%400 != 0))
  }

  
  // FirstDayOfNextMonthEpoch ...
  func FirstDayOfNextMonthEpoch(e int64) int64 {
  	d, m, y := EpochToDayMonthYear(e)
  	m++
  	if m > 12 {
  		m = 1
  		y++
  	}
  	d = 1
  
  	date := fmt.Sprintf("%02d/%02d/%d", d, m, y)
  
  	return DateToEpoch(date, DDMMYYYY_sl)
  }