95 lines
1.6 KiB
Go
95 lines
1.6 KiB
Go
package validation
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import (
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"errors"
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"slices"
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"strconv"
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"strings"
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"time"
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)
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type Card struct {
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Pan string
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Month string
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Year string
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}
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type ValidationResult struct {
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Code int
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Error error
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}
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var ErrValid = ValidationResult{0, errors.New("the card is valid")}
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var ErrInvalidPAN = ValidationResult{1, errors.New("invalid PAN")}
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var ErrInvalidYear = ValidationResult{2, errors.New("invalid year")}
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var ErrInvalidMonth = ValidationResult{3, errors.New("invalid month")}
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var ErrExpire = ValidationResult{4, errors.New("expired card")}
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func Luhn(pan string) bool {
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if pan == "" {
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return false
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}
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lastIndex := len(pan) - 1
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asDigits := []int{}
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for _, char := range strings.Split(pan, "") {
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digit, err := strconv.Atoi(char)
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if err != nil {
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return false
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}
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asDigits = append(asDigits, digit)
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}
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sum := 0
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// do we really need reversed iteration?
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for i, digit := range slices.Backward(asDigits[:lastIndex]) {
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if i%2 == len(pan)%2 {
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if digit > 4 {
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sum += 2*digit - 9
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} else {
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sum += 2 * digit
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}
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} else {
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sum += digit
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}
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}
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return asDigits[lastIndex] == (10-(sum%10))%10
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}
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func Validate(card Card) ValidationResult {
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if !Luhn(card.Pan) {
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return ErrInvalidPAN
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}
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year, yearErr := strconv.Atoi(card.Year)
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if yearErr != nil || len(card.Year) != 2 {
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return ErrInvalidYear
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}
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month, monthErr := strconv.Atoi(card.Month)
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if monthErr != nil || len(card.Month) != 2 || month > 12 || month < 1 {
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return ErrInvalidMonth
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}
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now := time.Now()
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// not sure about time zones
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cardExpire := time.Date(year+2000, time.Month(month), 1, 0, 0, 0, 0, time.UTC)
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if now.After(cardExpire) {
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return ErrExpire
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}
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return ErrValid
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}
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