// Package perfect is for checking if a number is perfect, abundant or deficient.
package perfect
import (
	"errors"
)
// Classification is a number type representation.
type Classification byte
// Classification types.
const (
	ClassificationDeficient Classification = iota
	ClassificationPerfect
	ClassificationAbundant
)
// ErrOnlyPositive is reported if input is < 1.
var ErrOnlyPositive error = errors.New("input must be positive")
// Classify returs the input number Classification.
func Classify(input int64) (Classification, error) {
	if input < 1 {
		return 0, ErrOnlyPositive
	}
	diff := abliquot(input) - input
	if diff > 0 {
		return ClassificationAbundant, nil
	}
	if diff < 0 {
		return ClassificationDeficient, nil
	}
	return ClassificationPerfect, nil
}
func abliquot(in int64) int64 {
	var sum int64
	for i := 1; int64(i*i) < in; i++ {
		if in%int64(i) == 0 {
			sum += int64(i)
			if int64(i) != in/int64(i) && i != 1 {
				sum += in / int64(i)
			}
		}
	}
	return sum
}