package validate

import (
	"slices"
	"strconv"
	"strings"
)

type Card struct {
	Pan   string
	Month string
	Year  string
}

type ValidationResult struct {
	Code  int
	Error error
}

func Luhn(pan string) bool {
	if pan == "" {
		return false
	}

	lastIndex := len(pan) - 1

	asDigits := []int{}

	for _, char := range strings.Split(pan, "") {
		digit, err := strconv.Atoi(char)

		if err != nil {
			return false
		}

		asDigits = append(asDigits, digit)
	}

	sum := 0

	// do we really need reversed array?
	for i, digit := range slices.Backward(asDigits[:lastIndex]) {

		if i%2 == len(pan)%2 {
			if digit > 4 {
				sum += 2*digit - 9
			} else {
				sum += 2 * digit
			}
		} else {
			sum += digit
		}

	}

	return asDigits[lastIndex] == (10-(sum%10))%10
}

func Validate(card Card) (bool, ValidationResult) {

	return true, ValidationResult{}
}