Replace commons-validator email validation

This isn't quite as strict, but it is a good enough "looks like an
email" check for this purpose.

Author: oschwald

src/main/java/com/maxmind/minfraud/request/Email.java

@@ -13,7 +13,6 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.regex.Pattern;
-import org.apache.commons.validator.routines.EmailValidator;
 
 /**
  * The email information for the transaction.
@@ -340,7 +339,7 @@ public Builder(boolean enableValidation) {
          * @throws IllegalArgumentException when address is not a valid email address.
          */
         public Email.Builder address(String address) {
-            if (enableValidation && !EmailValidator.getInstance().isValid(address)) {
+            if (enableValidation && !isValidEmail(address)) {
                 throw new IllegalArgumentException(
                     "The email address " + address + " is not valid.");
             }
@@ -460,6 +459,34 @@ private String cleanAddress(String address) {
         return localPart + "@" + domain;
     }
 
+    private static boolean isValidEmail(String email) {
+        if (email == null || email.isEmpty()) {
+            return false;
+        }
+
+        // RFC 5321 the forward path limits the mailbox to 254 characters
+        // even though a domain can be 255 and the local part 64
+        if (email.length() > 254) {
+            return false;
+        }
+
+        int atIndex = email.lastIndexOf('@');
+        if (atIndex <= 0) {
+            return false;
+        }
+
+        String localPart = email.substring(0, atIndex);
+        String domainPart = email.substring(atIndex + 1);
+
+        // The local-part has a maximum length of 64 characters.
+        if (localPart.length() > 64) {
+            return false;
+        }
+
+        return isValidDomain(domainPart);
+    }
+
+
     private String cleanDomain(String domain) {
         if (domain == null) {
             return null;

src/test/java/com/maxmind/minfraud/request/EmailTest.java

@@ -4,6 +4,7 @@
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+
 import com.maxmind.minfraud.request.Email.Builder;
 import java.math.BigInteger;
 import java.nio.charset.StandardCharsets;
@@ -244,11 +245,26 @@ private String toMD5(String s) throws NoSuchAlgorithmException {
         return String.format("%032x", i);
     }
 
-    @Test
-    public void testInvalidAddress() {
+    @ParameterizedTest(name = "Run #{index}: email = \"{0}\"")
+    @ValueSource(strings = {
+            "test.com",
+            "test@",
+            "@test.com",
+            "",
+            "  ",
+            "test@test com.com",
+            "test@test_domain.com",
+            "test@-test.com",
+            "test@test-.com",
+            "test@.test.com",
+            "test@test..com",
+            "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa@test.com",
+            "test@aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.com"
+    })
+    void testInvalidAddresses(String invalidAddress) {
         assertThrows(
             IllegalArgumentException.class,
-            () -> new Builder().address("a@test@test.org").build()
+            () -> new Builder().address(invalidAddress).build()
         );
     }