Credit card validation

baked_in.go

@@ -201,6 +201,7 @@ var (
 		"bic":                           isIsoBicFormat,
 		"semver":                        isSemverFormat,
 		"dns_rfc1035_label":             isDnsRFC1035LabelFormat,
+		"credit_card":                   isCreditCard,
 	}
 )
 
@@ -2436,3 +2437,40 @@ func isDnsRFC1035LabelFormat(fl FieldLevel) bool {
 	val := fl.Field().String()
 	return dnsRegexRFC1035Label.MatchString(val)
 }
+
+func isCreditCard(fl FieldLevel) bool {
+	val := fl.Field().String()
+	var creditCard bytes.Buffer
+	parts := strings.Split(val, " ")
+	for _, part := range parts {
+		if len(part) < 2 {
+			return false
+		}
+		creditCard.WriteString(part)
+	}
+
+	ccDigits := strings.Split(creditCard.String(), "")
+	size := len(ccDigits)
+	if size < 14 || size > 16 {
+		return false
+	}
+
+	sum := 0
+	for i := 0; i < size; i++ {
+		value, err := strconv.Atoi(ccDigits[i])
+		if err != nil {
+			return false
+		}
+		if size%2 == 0 && i%2 == 0 || size%2 == 1 && i%2 == 1 {
+			v := value * 2
+			if v >= 10 {
+				sum += 1 + (v % 10)
+			} else {
+				sum += v
+			}
+		} else {
+			sum += value
+		}
+	}
+	return (sum % 10) == 0
+}

doc.go

@@ -1283,6 +1283,12 @@ More information on https://semver.org/
 
 	Usage: semver
 
+Credit Card
+
+This validates that a string value contains a valid credit card number using Luhn algoritm.
+
+	Usage: credit_card
+
 Alias Validators and Tags
 
 NOTE: When returning an error, the tag returned in "FieldError" will be

validator_test.go

@@ -11460,7 +11460,7 @@ func TestSemverFormatValidation(t *testing.T) {
 		}
 	}
 }
-  
+
 func TestRFC1035LabelFormatValidation(t *testing.T) {
 	tests := []struct {
 		value    string `validate:"dns_rfc1035_label"`
@@ -11611,3 +11611,39 @@ func TestPostCodeByIso3166Alpha2Field_InvalidKind(t *testing.T) {
 	_ = New().Struct(test{"ABC", 123, false})
 	t.Errorf("Didn't panic as expected")
 }
+
+func TestCreditCardFormatValidation(t *testing.T) {
+	tests := []struct {
+		value    string `validate:"credit_card"`
+		tag      string
+		expected bool
+	}{
+		{"4624748233249780", "credit_card", true},
+		{"4624748233349780", "credit_card", false},
+		{"378282246310005", "credit_card", true},
+		{"378282146310005", "credit_card", false},
+		{"4624 7482 3324 9780", "credit_card", true},
+		{"4624 7482 3324  9780", "credit_card", false},
+	}
+
+	validate := New()
+
+	for i, test := range tests {
+		errs := validate.Var(test.value, test.tag)
+
+		if test.expected {
+			if !IsEqual(errs, nil) {
+				t.Fatalf("Index: %d credit_card failed Error: %s", i, errs)
+			}
+		} else {
+			if IsEqual(errs, nil) {
+				t.Fatalf("Index: %d credit_card failed Error: %s", i, errs)
+			} else {
+				val := getError(errs, "", "")
+				if val.Tag() != "credit_card" {
+					t.Fatalf("Index: %d credit_card failed Error: %s", i, errs)
+				}
+			}
+		}
+	}
+}