Calcula el último día hábil de acuerdo a los dos últimos digitos de un nit

social_security_date_sql.go

// Este archivo me permite generar el SQL que se inserta en la tabla de social_security_date
// OJO: debe revisarse los festivos del año.
package social_security_date

import (
	"fmt"
	"log"
	"sort"
	"time"
)

const (
	layoutISO = "2006-01-02"
)

var lastDayWithDigits = map[uint8][2]string{
	2:  [...]string{"00", "07"},
	3:  [...]string{"08", "14"},
	4:  [...]string{"15", "21"},
	5:  [...]string{"22", "28"},
	6:  [...]string{"29", "35"},
	7:  [...]string{"36", "42"},
	8:  [...]string{"43", "49"},
	9:  [...]string{"50", "56"},
	10: [...]string{"57", "63"},
	11: [...]string{"64", "69"},
	12: [...]string{"70", "75"},
	13: [...]string{"76", "81"},
	14: [...]string{"82", "87"},
	15: [...]string{"88", "93"},
	16: [...]string{"94", "99"},
}

var holidays = []time.Time{
	parseDate("2021-01-01"),
	parseDate("2021-01-11"),
	parseDate("2021-03-22"),
	parseDate("2021-04-01"),
	parseDate("2021-04-02"),
	parseDate("2021-05-01"),
	parseDate("2021-05-17"),
	parseDate("2021-06-07"),
	parseDate("2021-06-14"),
	parseDate("2021-07-05"),
	parseDate("2021-07-20"),
	parseDate("2021-08-07"),
	parseDate("2021-08-16"),
	parseDate("2021-10-18"),
	parseDate("2021-11-01"),
	parseDate("2021-11-15"),
	parseDate("2021-12-08"),
	parseDate("2021-12-25"),
}

func GetLastBusinessDay(year, month int) {
	date := time.Date(year, time.Month(month), 1, 0, 0, 0, 0, time.UTC)
	keys := make([]int, 0, len(lastDayWithDigits))
	for k := range lastDayWithDigits {
		keys = append(keys, int(k))
	}
	sort.Ints(keys)

	fmt.Println("INSERT INTO social_security_dates (last_two_digits_begins, last_two_digits_ends, business_day, year_date, month_date, last_date) VALUES ")

	for _, k := range keys {
		fmt.Print("(")
		fmt.Printf(`'%s',`, lastDayWithDigits[uint8(k)][0])
		fmt.Printf(`'%s',`, lastDayWithDigits[uint8(k)][1])
		fmt.Printf(`%d,`, k)
		fmt.Printf("%d, %d,", year, month)
		fmt.Printf("'%s'", lastBusinessDay(date, uint8(k), []time.Weekday{time.Saturday, time.Sunday}, holidays).Format(layoutISO))
		fmt.Println("),")
	}

	fmt.Println(";")
}

func parseDate(date string) time.Time {
	r, err := time.Parse(layoutISO, date)
	if err != nil {
		log.Fatalf("parseDate(): no se pudo convertir la fecha: %v", err)
	}

	return r
}

func lastBusinessDay(firstDayOfMonth time.Time, days uint8, daysOff []time.Weekday, holidays []time.Time) time.Time {
	countNonWorkingDays := nonWorkingDays(firstDayOfMonth, days, daysOff, holidays)
	return addDays(firstDayOfMonth, countNonWorkingDays+days-1)
}

func nonWorkingDays(currDate time.Time, days uint8, daysOff []time.Weekday, holidays []time.Time) uint8 {
	var nonWorkingDays uint8
	currDate = removeDays(currDate, 1)
	for days > 0 {
		currDate = addDays(currDate, 1)
		if dayIsDayOff(currDate.Weekday(), daysOff) || daysIsHoliday(currDate, holidays) {
			nonWorkingDays++

			continue
		}

		days--
	}

	return nonWorkingDays
}

// dayIsDayOff identifica si el día es dia de descanso
func dayIsDayOff(day time.Weekday, days []time.Weekday) bool {
	for _, v := range days {
		if day == v {
			return true
		}
	}

	return false
}

// daysIsHoliday identifica se el día es festivo
func daysIsHoliday(day time.Time, holidays []time.Time) bool {
	for _, v := range holidays {
		if day.Equal(v) {
			return true
		}
	}

	return false
}

// addDays agrega días a una fecha y retorna el resultado
func addDays(date time.Time, days uint8) time.Time {
	return date.Add(time.Hour * 24 * time.Duration(days))
}

// removeDays quita días a una fecha y retorna el resultado
func removeDays(date time.Time, days int) time.Time {
	return date.Add(time.Hour * 24 * -time.Duration(days))
}

social_security_last_day.go

package main

import (
	"time"
)

func LastBusinessDay(firstDayOfMonth time.Time, days uint8, daysOff []time.Weekday, holidays []time.Time) time.Time {
	countNonWorkingDays := nonWorkingDays(firstDayOfMonth, days, daysOff, holidays)
	return addDays(firstDayOfMonth, countNonWorkingDays+days-1)
}

func nonWorkingDays(currDate time.Time, days uint8, daysOff []time.Weekday, holidays []time.Time) uint8 {
	var nonWorkingDays uint8
	currDate = removeDays(currDate, 1)
	for days > 0 {
		currDate = addDays(currDate, 1)
		if dayIsDayOff(currDate.Weekday(), daysOff) || daysIsHoliday(currDate, holidays) {
			nonWorkingDays++

			continue
		}

		days--
	}

	return nonWorkingDays
}

// dayIsDayOff identifica si el día es dia de descanso
func dayIsDayOff(day time.Weekday, days []time.Weekday) bool {
	for _, v := range days {
		if day == v {
			return true
		}
	}

	return false
}

// daysIsHoliday identifica se el día es festivo
func daysIsHoliday(day time.Time, holidays []time.Time) bool {
	for _, v := range holidays {
		if day.Equal(v) {
			return true
		}
	}

	return false
}

// addDays agrega días a una fecha y retorna el resultado
func addDays(date time.Time, days uint8) time.Time {
	return date.Add(time.Hour * 24 * time.Duration(days))
}

// removeDays quita días a una fecha y retorna el resultado
func removeDays(date time.Time, days int) time.Time {
	return date.Add(time.Hour * 24 * -time.Duration(days))
}