feat: add email validation rule

.gitignore

@@ -88,4 +88,4 @@ fastlane/test_output
 # https://github.com/johnno1962/injectionforxcode
 
 iOSInjectionProject/
-./swiftpm
+.swiftpm/

README.md

@@ -302,6 +302,7 @@ struct RegistrationView: View {
 | `RegexValidationRule` | Pattern matching validation | `RegexValidationRule(pattern: "^\\d{3}-\\d{4}$", error: "Invalid phone format")` |
 | `URLValidationRule` | Validates URL format | `URLValidationRule(error: "Please enter a valid URL")` |
 | `CreditCardValidationRule` | Validates credit card numbers (Luhn algorithm) | `CreditCardValidationRule(error: "Invalid card number")` |
+| `EmailValidationRule` | Validates email format | `EmailValidationRule(error: "Please enter a valid email")` |
 
 ## Custom Validators
 

Sources/ValidatorCore/Classes/Rules/EmailValidationRule.swift

@@ -0,0 +1,38 @@
+//
+// Validator
+// Copyright © 2023 Space Code. All rights reserved.
+//
+
+import Foundation
+
+/// An email validation rule.
+public struct EmailValidationRule: IValidationRule {
+    // MARK: Types
+
+    public typealias Input = String
+
+    // MARK: Properties
+
+    /// The validation error.
+    public let error: IValidationError
+
+    // MARK: Initialization
+
+    public init(error: IValidationError) {
+        self.error = error
+    }
+
+    // MARK: IValidationRule
+
+    public func validate(input: String) -> Bool {
+        let range = NSRange(location: .zero, length: input.count)
+        if let regex = try? NSRegularExpression(
+            // swiftlint:disable:next line_length
+            pattern: "^(?!\\.)(?!.*\\.\\.)[A-Z0-9a-z._%+-]+(?<!\\.)@[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?(?:\\.[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?)*\\.[A-Za-z]{2,64}$",
+            options: [.caseInsensitive]
+        ) {
+            return regex.firstMatch(in: input, range: range) != nil
+        }
+        return false
+    }
+}

Tests/ValidatorCoreTests/UnitTests/Rules/EmailValidationRuleTests.swift

@@ -0,0 +1,326 @@
+//
+// Validator
+// Copyright © 2025 Space Code. All rights reserved.
+//
+
+@testable import ValidatorCore
+import XCTest
+
+final class EmailValidationRuleTests: XCTestCase {
+    var sut: EmailValidationRule!
+
+    override func setUp() {
+        super.setUp()
+        sut = EmailValidationRule(error: "Invalid email")
+    }
+
+    override func tearDown() {
+        sut = nil
+        super.tearDown()
+    }
+
+    // MARK: - Valid Email Tests
+
+    func testValidateWithValidEmail_ReturnsTrue() {
+        // Given
+        let email = "user@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithNumbers_ReturnsTrue() {
+        // Given
+        let email = "user123@example456.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithDots_ReturnsTrue() {
+        // Given
+        let email = "first.last@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithPlus_ReturnsTrue() {
+        // Given
+        let email = "user+tag@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithUnderscore_ReturnsTrue() {
+        // Given
+        let email = "user_name@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithHyphen_ReturnsTrue() {
+        // Given
+        let email = "user@my-domain.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithSubdomain_ReturnsTrue() {
+        // Given
+        let email = "user@mail.example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithLongTLD_ReturnsTrue() {
+        // Given
+        let email = "user@example.museum"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    func testValidateWithValidEmailWithTwoCharacterTLD_ReturnsTrue() {
+        // Given
+        let email = "user@example.io"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    // MARK: - Invalid Email Tests
+
+    func testValidateWithInvalidEmailMissingAtSign_ReturnsFalse() {
+        // Given
+        let email = "invalid.email.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailMissingDomain_ReturnsFalse() {
+        // Given
+        let email = "user@"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailMissingLocalPart_ReturnsFalse() {
+        // Given
+        let email = "@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailMissingTLD_ReturnsFalse() {
+        // Given
+        let email = "user@example"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailMultipleAtSigns_ReturnsFalse() {
+        // Given
+        let email = "user@@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailSpaces_ReturnsFalse() {
+        // Given
+        let email = "user @example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailSpecialCharacters_ReturnsFalse() {
+        // Given
+        let email = "user#name@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailDotAtStart_ReturnsFalse() {
+        // Given
+        let email = ".user@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailDotAtEnd_ReturnsFalse() {
+        // Given
+        let email = "user.@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailConsecutiveDots_ReturnsFalse() {
+        // Given
+        let email = "user..name@example.com"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailTLDTooLong_ReturnsFalse() {
+        // Given
+        let email = "user@example.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklm"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithInvalidEmailSingleCharacterTLD_ReturnsFalse() {
+        // Given
+        let email = "user@example.c"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    // MARK: - Edge Cases
+
+    func testValidateWithEmptyString_ReturnsFalse() {
+        // Given
+        let email = ""
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithOnlyAtSign_ReturnsFalse() {
+        // Given
+        let email = "@"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithOnlyDot_ReturnsFalse() {
+        // Given
+        let email = "."
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithWhitespaceOnly_ReturnsFalse() {
+        // Given
+        let email = "   "
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertFalse(result)
+    }
+
+    func testValidateWithValidEmailWithMaxTLDLength_ReturnsTrue() {
+        // Given
+        let email = "user@example.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghij"
+
+        // When
+        let result = sut.validate(input: email)
+
+        // Then
+        XCTAssertTrue(result)
+    }
+
+    // MARK: - Error Property Tests
+
+    func testErrorPropertyIsSetCorrectly() {
+        // Given
+        let expectedError = "Invalid email"
+
+        // When
+        let actualError = sut.error as? String
+
+        // Then
+        XCTAssertEqual(actualError, expectedError)
+    }
+}