Add CreditCardValidationRule implementation

Author: ns-vasilev

Sources/ValidatorCore/Classes/Rules/CreditCardValidationRule.swift

@@ -0,0 +1,76 @@
+//
+// Validator
+// Copyright © 2025 Space Code. All rights reserved.
+//
+
+/// A credit card validation rule.
+public struct CreditCardValidationRule: IValidationRule {
+    // MARK: Types
+
+    public enum CardType: String, Sendable, CaseIterable {
+        case visa, masterCard, amex, jcb, unionPay
+    }
+
+    public typealias Input = String
+
+    // MARK: Properties
+
+    public let types: [CardType]
+
+    /// The validation error.
+    public let error: IValidationError
+
+    // MARK: Initialization
+
+    public init(types: [CardType] = CardType.allCases, error: IValidationError) {
+        self.types = types
+        self.error = error
+    }
+
+    // MARK: IValidationRule
+
+    public func validate(input: String) -> Bool {
+        let sanitized = input.replacingOccurrences(of: " ", with: "")
+
+        guard sanitized.allSatisfy(\.isNumber) else { return false }
+
+        guard types.contains(where: { matches(cardNumber: sanitized, type: $0) }) else { return false }
+
+        return isValidLuhn(sanitized)
+    }
+
+    // MARK: Private
+
+    private func matches(cardNumber: String, type: CardType) -> Bool {
+        switch type {
+        case .visa:
+            cardNumber.hasPrefix("4") && (cardNumber.count == 13 || cardNumber.count == 16 || cardNumber.count == 19)
+        case .masterCard:
+            (cardNumber.hasPrefix("51") || cardNumber.hasPrefix("52") ||
+                cardNumber.hasPrefix("53") || cardNumber.hasPrefix("54") ||
+                cardNumber.hasPrefix("55")) && cardNumber.count == 16
+        case .amex:
+            (cardNumber.hasPrefix("34") || cardNumber.hasPrefix("37")) && cardNumber.count == 15
+        case .jcb:
+            (cardNumber.hasPrefix("3528") || cardNumber.hasPrefix("3589")) && cardNumber.count == 16
+        case .unionPay:
+            cardNumber.hasPrefix("62") && (cardNumber.count >= 16 && cardNumber.count <= 19)
+        }
+    }
+
+    private func isValidLuhn(_ cardNumber: String) -> Bool {
+        let reversedDigits = cardNumber.reversed().map { Int(String($0)) ?? 0 }
+        var sum = 0
+
+        for (index, digit) in reversedDigits.enumerated() {
+            if !index.isMultiple(of: 2) {
+                let doubled = digit * 2
+                sum += doubled > 9 ? doubled - 9 : doubled
+            } else {
+                sum += digit
+            }
+        }
+
+        return sum.isMultiple(of: 10)
+    }
+}