api

cmd/api.go

@@ -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))
+}

lib/validate.go

@@ -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{}
-}

lib/validate_test.go

@@ -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)
-			}
-		})
-	}
-}

validation/validate.go

@@ -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
+}

validation/validate_test.go

@@ -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)
+			}
+		})
+	}
+}