import (
	"strings"
	"strconv"
)

func Pow(x int64, y int) int64 {
	if y == 0 {
		return 1
	}

	result := x
	for n := 1; n < y; n++ {
		result = result * x
	}
	return result
}

func ConvertSizeToBytes(s string) (string, error) {

	// make lowercase so units detection always works
	s = strings.TrimSpace(strings.ToLower(s))

	// first look for binary units
	for _, unit := range units2 {
		if strings.HasSuffix(s, unit) {
			s = strings.TrimSuffix(s, unit)
			if i, err := strconv.ParseInt(s, 10, 0); err != nil {
				return "", fmt.Errorf("invalid size value '%s': %v", s, err)
			} else {
				i = i * Pow(1024, lookupTable2[unit])
				s = strconv.FormatInt(i, 10)
				return s, nil
			}
		}
	}

	// fall back to SI units
	for _, unit := range units10 {
		if strings.HasSuffix(s, unit) {
			s = strings.TrimSuffix(s, unit)
			if i, err := strconv.ParseInt(s, 10, 0); err != nil {
				return "", fmt.Errorf("invalid size value '%s': %v", s, err)
			} else {
				i = i * Pow(1000, lookupTable10[unit])
				s = strconv.FormatInt(i, 10)
				return s, nil
			}
		}
	}

	// no valid units found, so ensure the value is a number
	if _, err := strconv.ParseUint(s, 10, 64); err != nil {
		return "", fmt.Errorf("invalid size value '%s': %v", s, err)
	}

	return s, nil
}

var k = "1KiB"
s, err := ConvertSizeToBytes(k)
// s = 1024