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Greg 2025-01-31 21:08:14 +02:00
parent 06198ced9a
commit 95c9a72779
5 changed files with 243 additions and 122 deletions
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46
cmd/api.go
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@ -0,0 +1,46 @@
package main
import (
"encoding/json"
"log"
"net/http"
"git.tertyshy.dev/cards/validation"
)
type ValidatePayload struct {
Pan string `json:"pan"`
Month string `json:"month"`
Year string `json:"year"`
}
type ValidationResponse struct {
Status int `json:"status"`
Error string `json:"error"`
}
func validate(w http.ResponseWriter, r *http.Request) {
var payload ValidatePayload
var response ValidationResponse
decoder := json.NewDecoder(r.Body)
err := decoder.Decode(&payload)
if err != nil {
response = ValidationResponse{
-1,
err.Error(),
}
} else {
result := validation.Validate(validation.Card{payload.Pan, payload.Month, payload.Year})
response = ValidationResponse{result.Code, result.Error.Error()}
}
// todo: correct response type and code
json.NewEncoder(w).Encode(response)
}
func main() {
http.HandleFunc("POST /validate", validate)
log.Fatal(http.ListenAndServe(":8080", nil))
}

62
lib/validate.go
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@ -1,62 +0,0 @@
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{}
}

60
lib/validate_test.go
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@ -1,60 +0,0 @@
package validate
import "testing"
func TestLuhn(t *testing.T) {
tests := []struct {
name string
pan string
want bool
}{
{
"Mastercard",
"5555555555554444",
true,
},
{
"Visa",
"4111111111111111",
true,
},
{
"example from wiki",
"17893729974",
true,
},
{
"another example",
"79927398713",
true,
},
{
"worong check digit",
"17893729975",
false,
},
{
"off by one error",
"27893729974",
false,
},
{
"empty",
"",
false,
},
{
"not a digit",
"27893a29974",
false,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got := Luhn(tt.pan)
if got != tt.want {
t.Errorf("Luhn(%s) = %v, want %v", tt.name, got, tt.want)
}
})
}
}

95
validation/validate.go Normal file
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@ -0,0 +1,95 @@
package validation
import (
"errors"
"slices"
"strconv"
"strings"
"time"
)
type Card struct {
Pan string
Month string
Year string
}
type ValidationResult struct {
Code int
Error error
}
var ErrValid = ValidationResult{0, errors.New("the card is valid")}
var ErrInvalidPAN = ValidationResult{1, errors.New("invalid PAN")}
var ErrInvalidYear = ValidationResult{2, errors.New("invalid year")}
var ErrInvalidMonth = ValidationResult{3, errors.New("invalid month")}
var ErrExpire = ValidationResult{4, errors.New("expired card")}
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 iteration?
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) ValidationResult {
if !Luhn(card.Pan) {
return ErrInvalidPAN
}
year, yearErr := strconv.Atoi(card.Year)
if yearErr != nil || len(card.Year) != 2 {
return ErrInvalidYear
}
month, monthErr := strconv.Atoi(card.Month)
if monthErr != nil || len(card.Month) != 2 || month > 12 || month < 1 {
return ErrInvalidMonth
}
now := time.Now()
// not sure about time zones
cardExpire := time.Date(year+2000, time.Month(month), 1, 0, 0, 0, 0, time.UTC)
if now.After(cardExpire) {
return ErrExpire
}
return ErrValid
}

102
validation/validate_test.go Normal file
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@ -0,0 +1,102 @@
package validation
import "testing"
func TestLuhn(t *testing.T) {
tests := []struct {
name string
pan string
want bool
}{
{
"Mastercard",
"5555555555554444",
true,
},
{
"Visa",
"4111111111111111",
true,
},
{
"example from wiki",
"17893729974",
true,
},
{
"another example",
"79927398713",
true,
},
{
"worong check digit",
"17893729975",
false,
},
{
"off by one error",
"27893729974",
false,
},
{
"empty",
"",
false,
},
{
"not a digit",
"27893a29974",
false,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got := Luhn(tt.pan)
if got != tt.want {
t.Errorf("Luhn(%s) = %v, want %v", tt.name, got, tt.want)
}
})
}
}
func TestValidate(t *testing.T) {
tests := []struct {
name string
card Card
result ValidationResult
}{
{
"simple valid card",
Card{"4111111111111111", "09", "30"},
ErrValid,
},
{
"invalid PAN",
Card{"4111111111111114", "10", "26"},
ErrInvalidPAN,
},
{
"invalid year",
Card{"4111111111111111", "10", "2"},
ErrInvalidYear,
},
{
"invalid month",
Card{"4111111111111111", "13", "27"},
ErrInvalidMonth,
},
{
"expired",
Card{"4111111111111111", "10", "20"},
ErrExpire,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got := Validate(tt.card)
if got != tt.result {
t.Errorf("Validate() = %v, want %v", got, tt.result)
}
})
}
}