package humanize

import (
	"strconv"
	"strings"
)

// Place commas after every three orders of magnitude.
func Comma(v int64) string {
	sign := ""
	if v < 0 {
		sign = "-"
		v = 0 - v
	}

	parts := []string{"", "", "", "", "", "", "", "", ""}
	j := len(parts) - 1

	for v > 999 {
		parts[j] = strconv.FormatInt(v%1000, 10)
		switch len(parts[j]) {
		case 2:
			parts[j] = "0" + parts[j]
		case 1:
			parts[j] = "00" + parts[j]
		}
		v = v / 1000
		j--
	}
	parts[j] = strconv.Itoa(int(v))
	return sign + strings.Join(parts[j:len(parts)], ",")
}